[Federal Register Volume 64, Number 166 (Friday, August 27, 1999)]
[Proposed Rules]
[Pages 46976-47016]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-21913]
[[Page 46975]]
_______________________________________________________________________
Part II
Environmental Protection Agency
_______________________________________________________________________
40 CFR Part 197
Environmental Radiation Protection Standards for Yucca Mountain,
Nevada; Proposed Rule
Federal Register / Vol. 64, No. 166 / Friday, August 27, 1999 /
Proposed Rules
[[Page 46976]]
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 197
[FRL-6427-5]
RIN 2060-AG14
Environmental Radiation Protection Standards for Yucca Mountain,
Nevada
AGENCY: Environmental Protection Agency.
ACTION: Proposed rule.
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SUMMARY: We, the Environmental Protection Agency (EPA), are proposing
public health and safety standards for radioactive material stored or
disposed of in the potential repository at Yucca Mountain, Nevada.
Section 801 of the Energy Policy Act of 1992 (EnPA) directed the
Administrator of EPA to develop these standards. The EnPA also required
EPA to contract with the National Academy of Sciences (NAS) to conduct
a study to provide findings and recommendations on reasonable standards
for protection of the public health and safety. On August 1, 1995, NAS
released its report (the NAS Report) entitled, ``Technical Bases for
Yucca Mountain Standards.'' We have taken the NAS Report into
consideration as directed by the EnPA.
After we finalize these standards, the Nuclear Regulatory
Commission (NRC or ``the Commission'') will incorporate them into its
licensing regulations. The Department of Energy (DOE or ``the
Department'') will be responsible for demonstrating compliance with
these standards. The Commission will use its licensing regulations to
determine whether the Department has demonstrated compliance with our
standards prior to receiving the necessary licenses to store or dispose
of radioactive material in Yucca Mountain.
DATES: Comments. We must receive your comments at the address given
below on or before November 26, 1999 to assure their consideration.
Hearings. We will hold public hearings upon today's action in
Amargosa Valley, Nevada, Las Vegas, Nevada, and Washington, DC. The
dates will be announced in the Federal Register as soon as they are
determined.
ADDRESSES: Comments. Send two copies of your comments to the Central
Docket Section (6102), ATTN: Docket A-95-12, U.S. Environmental
Protection Agency, 401 M Street, SW, Washington, D.C. 20460-0001.
Documents relevant to the rulemaking. Materials relevant to this
rulemaking are contained in: (1) Docket No. A-95-12, located in Room M-
1500 (first floor in Waterside Mall near the Washington Information
Center), U.S. Environmental Protection Agency, 401 M Street, SW,
Washington, DC 20460-0001; (2) an information file in the Government
Publications Section, Dickinson Library, University of Nevada-Las
Vegas, 4504 Maryland Parkway, Las Vegas, Nevada 89154; and (3) an
information file in the Public Library in Amargosa Valley, Nevada
89020.
Background documents for this action. We have prepared additional
documents that provide more detailed technical background in support of
these proposed standards. You may obtain copies of the draft background
information document (BID), the draft economic impact evaluation, and
the Executive Summary of the NAS Report by requesting them in writing
from the Office of Radiation and Indoor Air (6602J), U.S. Environmental
Protection Agency, Washington, DC 20460-0001. We have also placed these
documents into the docket and information files. You may also find them
on our Internet site for Yucca Mountain (see the Additional Docket and
Electronic Information section later in this notice).
FOR FURTHER INFORMATION CONTACT: Ray Clark, Office of Radiation and
Indoor Air, U.S. Environmental Protection Agency, Washington, D.C.
20460-0001; telephone 202-564-9300.
SUPPLEMENTARY INFORMATION:
Who Will Be Regulated by These Standards?
The Department is the only entity directly regulated by these
standards. To utilize the Yucca Mountain repository, DOE must obtain
licensing approval from NRC. Thus, DOE will be subject to our standards
which NRC will implement through its licensing proceedings. The NRC is
only affected because, under the Energy Policy Act of 1992 (EnPA, Pub.
L. 102-486), it must modify its licensing requirements, as necessary,
to be consistent with our final standards.
Additional Docket and Electronic Information
When may I examine docket information? You may inspect the
Washington, D.C. docket (phone 202-260-7548) on weekdays (8 a.m.-5:30
p.m.). As provided in 40 CFR part 2, the docket personnel may charge a
reasonable fee for photocopying docket materials.
The information file located in the University of Nevada-Las Vegas,
Government Publications Section (702-895-3409) may be inspected when
classes are in session, Monday through Thursday (9 a.m.-8 p.m.), Friday
(9 a.m.-6 p.m.), Saturday (9 a.m.-9 p.m.), and Sunday (11 a.m.-8 p.m.).
However, since the hours vary based upon the academic calendar, you
should call ahead to be certain of the time.
The information file in the Public Library in Amargosa Valley,
Nevada (phone 775-372-5340) may be inspected Monday through Thursday
(11 a.m.-7 p.m.) and Friday (9 a.m.-5 p.m.). The library is closed from
12:30 p.m.-1 p.m. each day. It is also closed Saturday and Sunday.
Can information be accessed by telephone or the Internet? Yes, we
have established a toll-free information line that is accessible 24
hours per day. By dialing 800-331-9477, you can listen to a brief
update describing our rulemaking activities for Yucca Mountain, leave a
message requesting that your name and address be added to the Yucca
Mountain mailing list, or request that an EPA staff person return your
call. You can also find information on the World Wide Web at http://
www.epa.gov/radiation/yucca.
Acronyms
There are many acronyms used in this notice. They are listed below
for your reference and convenience.
ALARA--as low as reasonably achievable
BID--background information document
CAA--Clean Air Act
CEDE--committed effective dose equivalent
CG--critical group
DOE--U.S. Department of Energy
EIS--environmental impact statement
EnPA--Energy Policy Act of 1992
EPA--U.S. Environmental Protection Agency
GCD--greater confinement disposal
HLW--high-level radioactive waste
IAEA--International Atomic Energy Agency
ICRP--International Commission on Radiological Protection
LLW--low-level radioactive waste
MCL--maximum contaminant level
MCLG--maximum contaminant level goal
NAS--National Academy of Sciences
NCRP--National Council on Radiation Protection and Measurements
NEPA--National Environmental Policy Act
NESHAPs--National Emission Standards for Hazardous Air Pollutants
NID--negligible incremental dose
NIR--negligible incremental risk
NRC--U.S. Nuclear Regulatory Commission
[[Page 46977]]
NRDC--Natural Resources Defense Council
NTS--Nevada Test Site
NTTAA--National Technology Transfer and Advancement Act
NWPA--Nuclear Waste Policy Act of 1982
NWPAA--Nuclear Waste Policy Amendments Act of 1987
OMB--Office of Management and Budget
RCRA--Resource Conservation and Recovery Act
RME--reasonable maximum exposure
RMEI--reasonably maximally exposed individual
SDWA--Safe Drinking Water Act
SNF--spent nuclear fuel
TDS--total dissolved solids
UIC--underground injection control
UMRA--Unfunded Mandates Reform Act of 1995
USDW--underground source of drinking water
WIPP LWA--Waste Isolation Pilot Plant Land Withdrawal Act of 1992
Outline of Proposed Action
I. What Led up to Today's Action?
II. Background Information
II.A. What Are the Sources of Radioactive Waste?
II.B. What Types of Health Effects Can Radiation Cause?
II.C. What Are the Major Features of the Geology of Yucca
Mountain and the Disposal System?
II.D. Background on and Summary of the NAS Report
II.D.1. What Were the NAS Findings and Recommendations?
II.D.2. How Has the Public Participated in Our Review of the NAS
Report?
II.D.3. What Were the Public Comments on the NAS Report?
III. What Are We Proposing Today?
III.A. What Is the Proposed Standard for Storage of the Waste?
(Proposed Subpart A)
III.B. What Is the Standard for Protection of Individuals?
(Proposed Secs. 197.20 and 197.25)
III.B.1. Should the Limit Be on Dose or Risk?
III.B.2. What Should the Level of Protection Be?
III.B.3. What Factors Can Lead to Radiation Exposure?
III.B.4. Who Will Be Representative of the Exposed Population?
III.B.5. How Will the General Population Be Protected?
III.B.6. What Should Be Assumed About the Future Biosphere?
III.B.7. How Far Into the Future Is It Reasonable To Project
Disposal System Performance?
III.C. What Are the Requirements for Performance Assessments and
Determinations of Compliance? (Proposed Secs. 197.20, 197.25, and
197.35)
III.C.1. What Limits Are There on Factors Included in the
Performance Assessments?
III.C.2. Is Expert Opinion Allowed?
III.C.3. What Level of Expectation Is Required for NRC To
Determine Compliance?
III.D. Are There Qualitative Requirements To Help Assure
Protection?
III.E. What Is the Standard for Human Intrusion? (Proposed
Sec. 197.25)
III.F. How Will Ground Water Be Protected? (Proposed
Sec. 197.35)
III.F.1. Is the Storage or Disposal of Radioactive Material in
the Yucca Mountain Repository Underground Injection?
III.F.2. Does the Class-IV Well Ban Apply?
III.F.3. Which Ground Water Should Be Protected?
III.F.4. How Far Into the Future Should Compliance Be Projected?
III.F.5. How Will the Point of Compliance Be Identified?
III.F.6. Where Will the Point of Compliance Be Located?
IV. Specific Questions for Public Comment
V. Regulatory Analyses
V.A. Executive Order 12866
V.B. Executive Order 12875
V.C. Executive Order 12898
V.D. Executive Order 13045
V.E. Executive Order 13084
V.F. National Technology Transfer and Advancement Act
V.G. Paperwork Reduction Act
V.H. Regulatory Flexibility Act/Small Business Regulatory
Enforcement Fairness Act of 1996
V.I. Unfunded Mandates Reform Act
I. What Led up to Today's Action?
Spent nuclear fuel (SNF) and high-level radioactive waste (HLW)
have been produced since the 1940s, mainly as a result of commercial
power production and defense activities. Since then, the proper
disposal of these wastes has been the responsibility of the Federal
government. The Nuclear Waste Policy Act of 1982 (NWPA, Pub. L. 97-425)
formalized the current Federal program for the disposal of SNF and HLW
by:
(1) Making DOE responsible for siting, building, and operating an
underground geologic repository for the disposal of SNF and HLW;
(2) Directing us to set generally applicable environmental
radiation protection standards based upon authority established under
other laws; and
(3) Requiring NRC to implement our standards by incorporating them
into its licensing requirements for SNF and HLW repositories.
Those responsibilities are generally maintained under the EnPA.
Thus, NRC will implement the standards that we are proposing today, and
DOE will submit a license application to NRC. The Commission will then
determine whether DOE has met the standards and whether to issue an
operating license for Yucca Mountain. We anticipate that NRC will
require compliance with all of the applicable provisions of 40 CFR part
197 prior to allowing receipt of radioactive material onto the Yucca
Mountain site.
In 1985, we established generic standards for the management,
storage, and disposal of SNF, HLW, and transuranic radioactive waste.
These standards are found in 40 CFR part 191 (50 FR 38066, September
19, 1985). The term ``generic'' meant that the standards applied to any
applicable facilities in the United States, including Yucca Mountain,
Nevada. In 1987, the U.S. Court of Appeals for the First Circuit
invalidated the disposal standards and remanded them to us (NRDC v.
EPA, 824 F.2d 1258 (1st Cir. 1987)). Also in 1987, the Nuclear Waste
Policy Amendments Act (NWPAA, Pub. L. 100-203) amended the NWPA by,
among other actions, selecting Yucca Mountain, Nevada as the only
potential site to be characterized.
In October 1992, the Waste Isolation Pilot Plant Land Withdrawal
Act (WIPP LWA, Pub. L. 102-579) and the EnPA became law. The statutes
changed our obligations concerning certain radiation standards. The
WIPP LWA:
(1) Reinstated the 40 CFR part 191 disposal standards except those
that were the specific subject of the remand by the First Circuit;
(2) Required us to issue standards to replace those that were the
subject of judicial remand; and
(3) Exempted the Yucca Mountain site from the 40 CFR part 191
disposal standards. We issued the final disposal standards in 40 CFR
part 191 on December 20, 1993 (58 FR 66398) to address the judicial
remand.
The EnPA gave us the responsibility to set public health and safety
radiation standards for Yucca Mountain. Specifically, section 801(a)(1)
of the EnPA directed us to ``promulgate, by rule, public health and
safety standards for the protection of the public from releases from
radioactive materials stored or disposed of in the repository at the
Yucca Mountain site.'' The EnPA also directed us to contract with NAS
to give us findings and recommendations on reasonable standards for
protection of public health and safety. Moreover, the statute provided
that our standards shall be the only such standards applicable to the
Yucca Mountain site and are to be based upon and consistent with NAS'
findings and recommendations. On August 1, 1995, NAS released its
report, ``Technical Bases for Yucca Mountain Standards'' (the NAS
Report).
[[Page 46978]]
II. Background Information
II.A. What Are the Sources of Radioactive Waste?
Radioactive wastes are the result of using nuclear fuel and other
radioactive material. Today's action proposes standards pertaining to
SNF, HLW, and other radioactive waste (these are collectively referred
to after this as ``radioactive material'' or ``waste'') which may be
stored or disposed of in the Yucca Mountain repository. (When storage
or disposal are discussed in this notice in reference to Yucca
Mountain, it is to be understood that no decision has been made
regarding the acceptability of Yucca Mountain for storage or disposal.
To save space and excessive repetition, the description of Yucca
Mountain as a ``potential'' repository will not be used but is
intended.) These standards do not apply to facilities other than those
related to Yucca Mountain.
Once enough uranium or other fissionable material in nuclear
reactor fuel has been consumed through nuclear reactions, it is no
longer useful. The product is known as ``spent'' nuclear fuel (SNF).
Sources of SNF include:
(1) Commercial nuclear power plants;
(2) Government-sponsored research and development programs in
universities and industry;
(3) Experimental reactors, such as, liquid metal fast breeder
reactors and high-temperature gas-cooled reactors;
(4) Federal Government-controlled, nuclear-weapons production
reactors;
(5) Naval and other Department of Defense reactors; and
(6) U.S.-owned, foreign SNF.
Spent nuclear fuel can be dissolved in a chemical process called
``reprocessing,'' which is used to recover desired radionuclides.
Radionuclides which are not recovered become part of the acidic liquid
wastes that DOE plans to convert into various types of solid materials.
The highly radioactive liquid or solid wastes from reprocessing SNF are
called HLW. If SNF is not reprocessed prior to disposal, it becomes the
waste form without further modification. The only commercial
reprocessing facility to operate in the United States, the Nuclear Fuel
Services Plant in West Valley, New York, closed in 1972. Since that
time, no commercial SNF has been reprocessed in the United States. In
1992, DOE decided to phase out reprocessing of its SNF which supported
the defense nuclear weapons and propulsion programs.
Where are the wastes stored now? Today, most SNF is stored in water
pools or above-ground in dry concrete or steel canisters at more than
70 commercial nuclear-power reactor sites across the Nation. High-level
waste is stored underground in steel tanks at four Federal facilities
in Idaho, Washington, South Carolina, and New York.
What types of wastes will be placed into Yucca Mountain? We
anticipate that most of the waste in Yucca Mountain will be SNF and
solidified HLW (in the rest of this notice, HLW will refer to
solidified HLW unless otherwise noted). Under current NRC regulations
(10 CFR 60.135), liquid HLW will have to be solidified, through
processes such as vitrification (mixing the waste into glass), since
non-solid waste forms would not be allowed to be stored or disposed of
in Yucca Mountain. The Department estimates that by the year 2010,
about 64,000 metric tons of SNF and 284,000 cubic meters (containing
450 million curies of radioactivity) of HLW in predisposal form and
2,600 cubic meters (containing 189 million curies) of the disposable
form of HLW will be in storage (DOE/RW-0006, Rev. 12, December 1996).
We are aware that other radioactive materials might be stored or
disposed of in the Yucca Mountain repository. These materials include
highly radioactive low-level waste (LLW), known as greater-than-Class-C
waste, and excess plutonium or other fissile materials resulting from
the dismantlement of nuclear weapons. In the future, other types of
radioactive materials could be identified for storage or disposal.
Since the plans for the disposal of these materials have not been
finalized, their impact upon the design and performance of the disposal
system has not been analyzed by NRC or DOE. However, whatever types of
radioactive materials are finally disposed of in Yucca Mountain, the
disposal system must comply with these standards.
II.B. What Types of Health Effects Can Radiation Cause?
Ionizing radiation can cause a variety of health effects. These
effects are classified as either ``non-stochastic'' or ``stochastic.''
Non-stochastic effects are those for which the damage increases with
increasing exposure, such as destruction of cells or reddening of the
skin. They are seen in cases of exposures to large amounts of
radiation. Stochastic effects are associated with long-term exposure to
low levels of radiation. Their type or severity does not depend upon
the amount of exposure. Instead, the chance that an effect, for
example, cancer, will occur is assumed to increase with increasing
exposure.
The three categories of stochastic effects are cancer, mutations,
and teratogenic effects. Cancers caused by radiation are
indistinguishable from those occurring from other causes. Cancers
caused by radiation have been observed in humans. However, the risk of
cancer at the exposure levels normally encountered by members of the
public must be estimated using indirect evidence, that is,
extrapolation from higher doses.1
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\1\ The general term ``dose'' is used to mean the dose
equivalent, effective dose equivalent, or committed effective dose
equivalent, depending upon the surrounding text. When precision is
necessary, the exact term is used.
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Mutations, the second category of stochastic effects, are created
in the reproductive cells of exposed individuals and are transmitted to
their descendants. The severity of hereditary effects can range from
inconsequential to fatal. Although hereditary effects have been
observed in animal studies at relatively high doses, hereditary effects
in humans exposed to relatively small amounts of radiation have not
been confirmed statistically in epidemiological studies. Finally, we
assume that at low levels of exposure, the probability of incurring
either cancer or hereditary effects increases as the dose increases and
that there is no lower threshold, that is, a linear, non-threshold,
dose-response relationship (this is discussed below in more detail).
Teratogenic effects, the third category of stochastic effects, can
occur following exposure of fetuses. We believe that the fetus is more
sensitive than adults to the induction of cancer by radiation. The
fetus also is subject to various radiation-induced, physical
malformations such as small brain size (microencephaly), small head
size (microcephaly), eye malformations and slow growth prior to birth.
Recent studies have focused upon the apparently increased risk of
severe mental retardation as measured by the intelligence quotient.
These studies indicate that the sensitivity of the fetus is greatest
during 8 to 15 weeks following conception, and continues, at a lower
level, between 16 and 25 weeks.2 Although we do not know
exactly how mental retardation is related to dose, it is prudent to
assume that there is a linear, non-threshold, dose-response
relationship between these effects and the dose delivered to the fetus
during the 8- to 15-week period.
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\2\ Health Effects of Exposure to Low Levels of Ionizing
Radiation, National Academy Press, Washington, D.C., 1990.
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The NAS published its reviews of human health risks from exposure
to low levels of ionizing radiation in a
[[Page 46979]]
series of reports between 1972 and 1990. However, scientists still do
not agree upon how best to estimate the probability of cancer occurring
as a result of the doses encountered by members of the public
3 because these effects must be estimated based upon the
effects observed at higher doses (such as effects seen in the survivors
of the Hiroshima and Nagasaki atomic bombs). The linear model for
estimating effects has been endorsed by many organizations, including
NAS, the International Commission on Radiological Protection (ICRP),
the United Nations Scientific Committee on the Effects of Atomic
Radiation, and the National Radiological Protection Board of the United
Kingdom.
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\3\ The risk of interest is not at or near zero dose, but that
due to small increments of dose above the pre-existing background
level. Background in the U.S. is typically about 3 millisievert
(mSv), that is, 300 millirem (mrem), effective dose equivalent per
year, or 0.2 Sv (20 rem) in a lifetime. Approximately two-thirds of
this dose is due to radon, and the balance comes from cosmic,
terrestrial, and internal sources of exposure.
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Over the past decade, the scientific community has performed an
extensive reevaluation of the doses and effects in the Hiroshima and
Nagasaki survivors. These studies have resulted in increased estimates
(roughly threefold between 1972 and 1990) of the extrapolated risk of
cancer arising from exposure to environmental levels of radiation, that
is, background levels of radiation. Nonetheless, the estimated number
of health effects induced by small incremental doses of radiation above
natural background levels remains small compared with the total number
of fatal cancers that occur from other causes. In addition, because
cancers are the same as those resulting from other causes, identifying
them in human epidemiological studies may never be possible. This
difficulty in identifying stochastic radiation effects does not mean
that such effects do not occur. However, there is the possibility that
effects do not occur as a result of these small doses, that is, there
might be an exposure level below which there is no additional risk
above the risk that is posed by natural background radiation.
Sufficient data to prove either possibility scientifically is lacking.
As a result, we believe that the best approach is to assume that the
risk of cancer increases linearly starting at zero dose. That is, any
increase in exposure to ionizing radiation results in a constant and
proportionate increase in the potential for developing cancer.
The NAS Report stated that radiation causes about five cancers for
every severe hereditary disorder. Also, NAS concluded that nonfatal
cancers are more common than fatal cancers. Despite this, the NAS cited
an ICRP study which judged that non-fatal cancers contribute less to
overall health impact than fatal cancers ``because of their lesser
severity in the affected individuals.'' (NAS Report pp. 37-39). Our
risk estimates for exposure of the population to low-dose-rate
radiation is based upon fatal cancers rather than all cancers.
For radiation-protection purposes, we estimate (using a linear,
non-threshold, dose-response model) an average risk for a member of the
U.S. population of 5.75 in 100 (5.75 x 10-2) fatal cancers
per sievert (Sv) 4 (5.75 x 10-4 fatal cancers
per rem) delivered at low dose rates.5 (For example, if
100,000 people randomly chosen from the U.S. population were each given
a uniform dose of 1 millisievert (mSv) (0.1 rem) to the entire body at
a low rate, approximately five to six people are assumed to die of
cancer during their remaining lifetimes because of that exposure. This
is in addition to the roughly 20,000 fatal cancers that would occur in
the same population from other causes.) The risk of fatal childhood
cancer, resulting from exposure while in the fetal stage, is about 3 in
100 (3 x 10-2) per Sv (that is, 3 x 10-4
effects per rem). The risk of severe hereditary effects in offspring is
estimated to be about 1 x 10-2 per Sv (1 x
10-4 effects per rem).6 The risk of severe mental
retardation from doses to a fetus is estimated to be greater per unit
dose than the risk of cancer in the general population.7
However, the period of increased sensitivity is much shorter. Hence, at
a constant exposure rate, fatal cancer risk in the general population
remains the dominant factor.
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\4\ The traditional unit for dose equivalent has been the rem.
The unit ``sievert'' (Sv), a unit in the International System of
Units which was adopted in 1979 by the General Conference on Weights
and Measures, is now in general use throughout the world. One
sievert is equal to 100 rem. The prefix ``milli'' (m) means one-
thousandth. The individual-protection limit being proposed today may
be expressed in either unit.
\5\ ``Low dose rates'' here refer to dose rates on the order of
or less than those from background radiation.
\6\ The risk of severe hereditary effects in the first two
generations, for exposure of the reproductive part of the population
(with both parents exposed), is estimated to be 5 x
10-3 per Sv (5 x 10-5 per rem). For all
generations, the risk is estimated to be 1.2 x 10-2 per
Sv (1.2 x 10-4 per rem). For exposure of the entire
population, which includes individuals past the age of normal child-
bearing, each estimate is reduced to 40% of the cited value.
\7\ Assuming a linear, non-threshold dose response, estimated
risk for mental retardation due to exposure during the 8th through
15th week of gestation is 4 x 10-1 per Sv (4 x
10-3 per rem); under the same assumption, the estimated
risk from the 16th to 25th week is 1 x 10-1 per Sv (1
x 10-3 per rem).
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We note that there is, of course, uncertainty in our risk
estimates. A recent uncertainty analysis published by the National
Council on Radiation Protection and Measurements (NCRP Report 126)
estimated that the actual risk of cancer from whole-body exposure to
low doses of radiation could be between 1.5 times higher and 4.8 times
lower (at the 90-percent confidence level) than our basic estimate of
5.75 x 10-2 per Sv (5.75 x 10-4 per rem).
Further, existing epidemiological data does not rule out the existence
of a threshold. If there is a threshold, exposures below that level
would pose no additional risk above the risk that is posed by natural
background radiation. The risks of genetic abnormalities and mental
retardation are less well known than those for cancer and, thus, may
include a greater degree of uncertainty. However, in spite of
uncertainties in the data and its analysis, estimates of the risks from
exposure to low levels of ionizing radiation are more clearly known
than those for virtually any other environmental carcinogen.
II.C. What Are the Major Features of the Geology of Yucca Mountain and
the Disposal System?
The geology. The Yucca Mountain site is located in southwestern
Nevada approximately 90 miles northwest of Las Vegas. The eastern part
of the site is on the Nevada Test Site, the northwestern part of the
site is on the Nellis Air Force Range, and the southwestern part of the
site is on Bureau of Land Management land. The area has a desert
climate with topography typical of the Basin and Range province. See
the BID for more information.
Yucca Mountain is made of layers of ashfalls from volcanic
eruptions which happened more than 10 million years ago. The ash
consolidated into a rock type called ``tuff'' which has varying degrees
of compaction and fracturing depending upon the degree of ``welding''
caused by temperature and pressure when the ash was deposited. Regional
geologic forces have tilted the tuff layers and formed Yucca Mountain's
crest (Yucca Mountain's shape is actually a ridge rather than a peak).
Below the tuff is carbonate rock. The carbonate rock was formed from
sediments laid down at the bottom of ancient seas which existed in the
area.
There are two general hydrologic zones within and below Yucca
Mountain. The upper zone is called the ``unsaturated zone'' because the
pore
[[Page 46980]]
spaces and fractures within the rock are not filled entirely with
water. Below the unsaturated zone, beginning at the water table, is the
``saturated zone'' in which the pores and fractures are filled
completely with water. Fractures in both zones could act as pathways
which allow for faster contaminant transport than would the pores. The
Department plans to build the repository in the unsaturated zone about
300 meters below the surface and about 300 to 500 meters above the
current water table.
There are two major aquifers in the saturated zone under Yucca
Mountain. The upper one is in tuff, while the lower one is in carbonate
rock. Regional ground water in the vicinity of Yucca Mountain is
believed to flow generally in a south-southwesterly direction. The
aquifers are more fully discussed in the BID.
The disposal system. The NAS Report described the current
conception of the potential disposal system as a system of engineered
barriers for the disposal of radioactive waste located in the geologic
setting of Yucca Mountain (NAS Report pp. 23-27). Entry into the
repository for waste emplacement would be on gradually downward sloping
ramps which enter the side of Yucca Mountain. The NWPAA limits the
capacity of the repository to 70,000 metric tons of SNF and HLW.
Current DOE plans project that about 90 percent (by mass) would be
commercial SNF and 10 percent defense HLW. Within 100 years after
starting to put waste in place, the repository would be sealed by
backfilling the tunnels, closing the opening to each of the tunnels,
and sealing the entrance ramps and shafts.
We expect the engineered barrier system to consist of at least the
waste form (that is, SNF assemblies or borosilicate glass containing
the HLW), internal stabilizers for the SNF assemblies, the waste
packages holding the waste, and backfill in the space between the waste
packages and adjacent host rock. Spent nuclear fuel assemblies are
comprised of uranium oxide, fission products, fuel cladding, and
support hardware, all of which will be radioactive. (see the What are
the Sources of Radioactive Waste? section above.)
II.D. Background on and Summary of the NAS Report
Section 801(a)(2) of the EnPA directed us to contract with NAS to
conduct a study to provide findings and recommendations on reasonable
standards for protection of public health and safety. Section 801(a)(2)
of the EnPA specifically called for NAS to address the following three
issues:
(A) whether a health-based standard based upon doses to individual
members of the public from releases to the accessible environment (as
that term is defined in the regulations contained in subpart B of part
191 of title 40, Code of Federal Regulations, as in effect on November
18, 1985) will provide a reasonable standard for protection of the
health and safety of the general public;
(B) whether it is reasonable to assume that a system for post-
closure oversight of the repository can be developed, based upon active
institutional controls, that will prevent an unreasonable risk of
breaching the repository's engineered or geologic barriers or
increasing the exposure of individual members of the public to
radiation beyond allowable limits; and
(C) whether it is possible to make scientifically supportable
predictions of the probability that the repository's engineered or
geologic barriers will be breached as a result of human intrusion over
a period of 10,000 years.
On August 1, 1995, NAS submitted to us its report entitled
``Technical Bases for Yucca Mountain Standards.'' The NAS Report is
available for review in the dockets and information file described
earlier. You can order the Report from the National Academy Press by
calling 800-624-6242 or on the World Wide Web at http://www.nap.edu/
bookstore/isbn/0309052890.html#title.
II.D.1. What Were the NAS Findings and Recommendations?
The NAS Report provided a number of conclusions and
recommendations. (The EnPA used the term ``findings,'' however, the NAS
Report used the term ``conclusions.'')
Conclusions. The conclusions in the Executive Summary of the NAS
Report (pp. 1-14) were:
(a) ``that an individual-risk standard would protect public health,
given the particular characteristics of the site, provided that policy
makers and the public are prepared to accept that very low radiation
doses pose a negligibly small risk'' [later termed ``negligible
incremental risk'']. This is the response to the issue identified in
section 801(a)(2)(A) of the EnPA;
(b) that the Yucca Mountain-related ``physical and geologic
processes are sufficiently quantifiable and the related uncertainties
sufficiently boundable that the performance can be assessed over time
frames during which the geologic system is relatively stable or varies
in a boundable manner;''
(c) ``that it is not possible to predict on the basis of scientific
analyses the societal factors required for an exposure scenario.
Specifying exposure scenarios therefore requires a policy decision that
is appropriately made in a rulemaking process conducted by EPA;''
(d) ``that it is not reasonable to assume that a system for post-
closure oversight of the repository can be developed, based on active
institutional controls, that will prevent an unreasonable risk of
breaching the repository's engineered barriers or increasing the
exposure of individual members of the public to radiation beyond
allowable limits.'' This is the response to the issue identified in
section 801(a)(2)(B) of the EnPA;
(e) ``that it is not possible to make scientifically supportable
predictions of the probability that a repository's engineered or
geologic barriers will be breached as a result of human intrusion over
a period of 10,000 years.'' This is the response to the issue
identified in section 801(a)(2)(C) of the EnPA; and
(f) ``that there is no scientific basis for incorporating the ALARA
[as low as reasonably achievable] principle into the EPA standard or
USNRC [U.S. Nuclear Regulatory Commission] regulations for the
repository.''
Recommendations. The recommendations in the Executive Summary of
the NAS Report were:
(a) ``the use of a standard that sets a limit on the risk to
individuals of adverse health effects from releases from the
repository;''
(b) ``that the critical-group approach be used'' (see the Who Will
Be Representative of the Exposed Population? section later in this
notice);
(c) ``that compliance assessment be conducted for the time when the
greatest risk occurs, within the limits imposed by long-term stability
of the geologic environment;'' and,
(d) ``that the estimated risk calculated from the assumed intrusion
scenario be no greater than the risk limit adopted for the undisturbed-
repository case because a repository that is suitable for safe long-
term disposal should be able to continue to provide acceptable waste
isolation after some type of intrusion.''
Other Conclusions and Recommendations. There were other conclusions
and recommendations in addition to those summarized in the Executive
Summary. Most were related to or supported those presented in the
Executive Summary.
II.D.2. How Has the Public Participated in Our Review of the NAS
Report?
We are committed to providing ample opportunity for public
participation in our Yucca Mountain rulemaking activities. We announced
the first opportunity for public participation on September 11, 1995 in
the Federal
[[Page 46981]]
Register (60 FR 47172) where we requested comments upon the NAS Report
and announced the times and locations of three public meetings. Along
with the general request for public comments, we asked five questions:
(1) did the Report sufficiently answer the questions posed in the
EnPA;
(2) was there sufficient rationale to support the NAS' findings and
conclusions;
(3) do provisions other than those found in NAS' findings and
conclusions need to be included in the EPA standards;
(4) are any of NAS' findings or conclusions inappropriate or
inaccurate regarding Yucca Mountain; and
(5) would the cost of imposing the findings and recommendations be
justifiable when compared with the benefits provided?
We held the public meetings to inform the public of our role, to
outline the issues associated with setting standards for Yucca
Mountain, and to seek comments upon the NAS Report. The meetings were
held on September 20, 1995, in Amargosa Valley, Nevada; on September
21, 1995, in Las Vegas, Nevada; and on September 27, 1995, in
Washington, DC. We also have established several other information
sources and given directions, in the ADDRESSES and Additional Docket
and Electronic Information sections earlier in this notice, on how to
access them.
II.D.3. What Were the Public Comments on the NAS Report?
We received comments regarding the NAS Report both orally and in
writing at the public meetings and in response to the September 11,
1995, Federal Register notice, respectively. All written comments are
in the docket and information files. The oral comments were summarized
in a separate document, copies of which are also in the docket and
information files.
Some commenters believed that the NAS inadequately supported its
conclusion that there is no scientific basis for including the ``as low
as reasonably achievable'' (ALARA) principle and subsystem requirements
in the standards and, therefore, that we should include them in the
proposed standards. The ALARA principle is a radiation-protection
concept which states that exposures to radiation should be kept as low
as can be done taking into account the costs and benefits of exposure
reduction methods. ``Subsystem requirements'' refers to regulation of
individual components of the overall disposal system. Other comments
indicated that there was inadequate rationale to support NAS' concept
of negligible incremental risk (NIR). The NIR concept is based upon an
NCRP concept known as ``negligible incremental dose'' (NID, discussed
in more detail later in this notice) which was described by NAS ``as a
level of effective dose that can, for radiation protection purposes, be
dismissed from consideration'' (NAS Report pp. 59-60). Commenters also
stated that they did not support the NAS'' rejection of a collective-
dose standard. Comments were divided upon requiring quantitative or
qualitative assessment of human intrusion.
With regard to the three questions posed in the EnPA: (1) There
were mixed responses upon whether a standard to protect individuals
could adequately protect the general public; (2) there was nearly
unanimous agreement that active institutional controls cannot prevent a
breach of the repository; and (3) there was nearly unanimous agreement
that it is impossible to predict the probability of future human
intrusion into the repository.
Commenters also expressed views related to a number of other
issues. The majority favored:
(1) A standard expressed in terms of dose;
(2) The highest level of protection possible;
(3) Measuring compliance at the time of peak risk of the maximally
exposed individual;
(4) A reference biosphere to be specified by EPA;
(5) Including other local sources of man-made radiation in
determining an acceptable level of protection;
(6) Protection equal to that specified for WIPP, that is, that in
40 CFR part 191 (WIPP is a geologic disposal system in New Mexico for
defense-related transuranic waste but, unlike Yucca Mountain, WIPP is
subject to our generic radioactive-waste standards codified at 40 CFR
part 191; see also 61 FR 5224, February 9, 1996);
(7) Using a collective-dose limit to restrict exposure to the
general population while ignoring the NIR concept;
(8) Including assurance requirements; and
(9) Including ground water protection requirements.
We have taken into consideration all comments received during
preparation of these proposed standards. If you submitted comments in
response to the September 11, 1995, Federal Register notice or at the
September 1995 public hearings, you should submit additional comments
in response to today's notice to convey any concerns or views about
this proposal.
III. What Are We Proposing Today?
We are proposing, and requesting comment upon, public health and
safety standards governing the storage and disposal of SNF, HLW, and
other radioactive material in the repository at Yucca Mountain, Nevada.
We are also announcing a public comment period and public hearings to
gather comments upon the proposal.
As noted earlier, section 801(a)(1) of the EnPA gave us rulemaking
authority to set ``public health and safety standards for the
protection of the public from releases from radioactive materials
stored or disposed of in the repository at the Yucca Mountain site.''
The statute also directed us to develop standards ``based upon and
consistent with the findings and recommendations of the National
Academy of Sciences.'' Section 801(a)(2) of the EnPA directed us to
contract with NAS to conduct a study to provide findings and
recommendations on reasonable standards for protection of the public
health and safety. Because the EnPA called for us to act ``based upon
and consistent with'' the NAS findings, a major issue in this
rulemaking is whether we are bound to follow the NAS determinations
without exception or whether we have discretionary decision-making
authority.
As a practical matter, the difficulty of this issue is reduced
because some of the findings and recommendations in the NAS Report are
expressed in a non-binding manner. In other words, NAS stated its
findings and recommendations as starting points for the rulemaking
process or recognized those that involve public policy issues that are
more properly addressed in this public rulemaking proceeding. However,
the Report also contains some findings and recommendations stated in
relatively definite terms. It is these issues that most squarely
present the question of whether we are to treat the views of NAS as
binding.
Whether the EnPA binds us to following exactly the NAS findings and
recommendations is a question that warrants close attention at this
stage of the rulemaking because it affects the scope of our rulemaking.
If we are required to follow every view expressed in the NAS Report,
any such issue would be treated as addressed conclusively by NAS. We
would not need to entertain public comment upon the affected issues
since the outcome would be predetermined.
[[Page 46982]]
We believe that the EnPA does not bind us absolutely to follow the
NAS Report. Instead, we have used the NAS Report as the starting point
for this rulemaking. Today's proposal is based upon and consistent with
the findings and recommendations of NAS. We have developed this
proposal guided by the findings and recommendations of NAS because of
the special role given NAS by Congress and the scientific expertise of
NAS. However, the entirety of our proposed standards for the Yucca
Mountain disposal system is the subject of this rulemaking. We do not
intend to treat the views expressed by NAS as necessarily dictating the
outcome of this rulemaking, thereby foreclosing public scrutiny of
important issues. For the reasons described below, we believe this
proposed interpretation of the EnPA is consistent with the statute and
prudent in that it avoids potential Constitutional issues. Further,
this proposed interpretation supports an important EPA policy
objective--ensuring an opportunity for public input upon all aspects of
the issues presented in this rulemaking.
Section 801(a)(2) of the EnPA required a study by NAS that provides
``findings and recommendations on reasonable standards for protection
of the public health and safety.'' While this section of the EnPA calls
for NAS to address three specific issues, Congress did not place any
restrictions upon other issues NAS could address. The report of the
Congressional conferees underscored that ``the National Academy of
Sciences would not be precluded from addressing additional questions or
issues related to the appropriate standards for radiation protection at
Yucca Mountain beyond those that are specified.'' (H.R. Rep. No. 1018,
102nd Cong., 2d Sess. 391 (1992)). Thus, given the potentially
unlimited scope of the NAS inquiry under the statute, NAS could have
provided findings and recommendations that would dictate literally all
aspects of the public health and safety standards for Yucca Mountain,
rendering our function a ministerial one.
Section 801(a)(1) of the EnPA plainly gave EPA the authority to
issue, by rulemaking, public health and safety standards for Yucca
Mountain. If at the same time that Congress gave NAS the authority to
provide findings and recommendations on any issues related to the Yucca
Mountain public health and safety standards, Congress also intended
that NAS' findings and recommendations be binding upon us, then
Congress would have effectively delegated to NAS a standard-setting
authority that overrides our delegated rulemaking authority. Carried to
its logical conclusion, under this view of the statute, NAS would have
authority to establish the public health and safety standards, and to
do so without a public rulemaking process. Then the direction for EPA
to set standards ``by rule'' would be unnecessary or relatively
meaningless. This tension in the statute can be reasonably resolved by
interpreting the NAS' findings and recommendations as non-binding, but
highly influential, expert guidance to inform our rulemaking.
Thus, we do not believe the statute forces our rulemaking to adopt
mechanically the NAS' recommendations as standards. If it did, the
statutory provisions would allow us to consider only those issues that
NAS did not address. Further, the provisions calling for us to use
standard rulemaking procedures in issuing the standards would be
unnecessary to reach results that NAS already established.
The report of the conferees also indicates that Congress did not
intend to limit our rulemaking discretion. The Conference Report
provides that Congress intended NAS to provide ``expert scientific
guidance'' on the issues involved in our rulemaking and that Congress
did not intend for NAS to establish the specific standards:
The Conferees do not intend for the National Academy of
Sciences, in making its recommendations, to establish specific
standards for protection of the public but rather to provide expert
scientific guidance on the issues involved in establishing those
standards. Under the provisions of section 801, the authority and
responsibility to establish the standards, pursuant to rulemaking,
would remain with the Administrator, as is the case under existing
law. The provisions of section 801 are not intended to limit the
Administrator's discretion in the exercise of his authority related
to public health and safety issues. (H.R. Rep. No. 1018 at p. 391)
Our proposed interpretation of the EnPA as not limiting the issues
for consideration in this rulemaking is consistent with the views we
expressed to Congress during deliberations over the legislation. The
Chairman of the Senate Subcommittee on Nuclear Regulation requested our
views of the bill reported out of conference. The Deputy Administrator
of EPA indicated that the NAS Report would provide helpful input.
Moreover, EPA's Deputy Administrator pointed to the language, cited
above, stating the intent of the conferees not to limit our rulemaking
discretion and assured Congress that any standards for radioactive
materials that we ultimately issue would be the subject of public
comment and involvement and would fully protect human health and the
environment. (138 Cong. Rec. S33,955 (daily ed. October 8, 1992)).
Our proposed interpretation also is consistent with the role that
both NAS and Congress understood NAS would fulfill. During the
Congressional deliberations over the legislation, NAS informed Congress
that while it would conduct the study, it would not assume a standard-
setting role because that is properly the responsibility of government
officials. (138 Cong. Rec. S33,953 (October 8, 1992)).
Our proposed interpretation of the NAS Report also avoids
implicating potentially significant Constitutional issues. Construing
the EnPA as delegating to NAS the responsibility to determine the
health and safety standards at Yucca Mountain may violate the
Appointments Clause of the Constitution (Art. II, sec. 2, cl. 2), which
imposes restrictions against giving Federal governmental authority to
persons not appointed in compliance with that Clause. In addition, the
Constitution places restrictions arising under the separation of powers
doctrine upon the delegation of governmental authority to persons not
part of the Federal government. We are not concluding, at this time,
that an alternative interpretation would necessarily run afoul of
Constitutional limits. However, we believe it is reasonable both to
assume that Congress intended to avoid these issues when it adopted
section 801 of the EnPA and to interpret the EnPA accordingly.
In summary, we do not believe we must, in this rulemaking, adopt
all of the positions advanced by NAS. At the same time, the statute
does give NAS a special role. As noted, the NAS' findings and
recommendations have been the starting point for this rulemaking and
our proposal is consonant with those findings and recommendations. In
fact, the NAS Report influenced us heavily during the development of
this proposed rule. We have included many of the findings and
recommendations in whole in today's proposal, and we intend to continue
to weigh the NAS Report heavily throughout the course of this
rulemaking. We will tend to give greatest weight to the judgments of
NAS about issues having a strong scientific component, the area where
NAS has its greatest expertise. In addition, we will reach final
determinations that are congruent with the NAS analysis whenever we can
do so without departing from the Congressional delegation of authority
to us to
[[Page 46983]]
promulgate, by rule, public health and safety standards for protection
of the public, which we believe requires the consideration of public
comment and our own expertise and discretion.
We request public comment upon how we should view and weigh the
NAS' findings and recommendations in this rulemaking. Public commenters
should also address this issue in the context of the specific issues
presented in this rulemaking. Commenters should indicate whether we
have given proper consideration to the NAS' findings and
recommendations, whether we should give them more or less weight, and
what the resulting outcome should be.
The following sections describe our proposed public health and
safety standards for Yucca Mountain and the considerations which
underlie the set of standards we are proposing today. The next section
addresses the storage portion of the proposed standards. All of the
other sections pertain to the disposal portion of the standards.
III.A. What Is the Proposed Standard for Storage of the Waste?
(Proposed Subpart A)
Section 801(a)(1) of the EnPA calls for EPA's public health and
safety standards to apply to radioactive materials ``stored or disposed
of in the repository at the Yucca Mountain site.'' (The repository is
the mined portion of the facility constructed underground within the
Yucca Mountain site. Hereafter, the term ``repository'' refers to the
Yucca Mountain repository.) The EnPA differentiates between waste that
is ``stored'' and waste that is ``disposed,'' although it indicates
that we must issue standards that apply to both types of activity.
Congress was not clear regarding its intended use of the word
``stored'' in this context. Also, NAS did not address the issue of
storage (see proposed Secs. 197.2 and 197.12 for our proposed
definitions of ``storage'' and ``disposal''). The Yucca Mountain
repository currently is conceived to be a disposal facility, not a
storage facility, but that could change. Therefore, we propose to
interpret this language as directing us to develop standards that apply
to waste that DOE either stores or disposes of in the Yucca Mountain
repository. The public health and safety standards we issue under
section 801 of the EnPA would, therefore, apply to waste inside of the
repository, whether it is there for storage or disposal.
The Department will also handle and might store radioactive
material aboveground (that is, outside the repository). Those
activities are covered by our previously promulgated standards for
management and storage, codified at subpart A of 40 CFR part 191. The
40 CFR part 191 standards require that DOE manage and store SNF, HLW,
and transuranic radioactive wastes at a site, such as Yucca Mountain,
in a manner that provides a reasonable expectation that the annual dose
equivalent to any member of the public in the general environment will
not exceed 25 millirem (mrem) to the whole body. This is the standard
which DOE must meet for WIPP and the greater confinement disposal (GCD)
facility. (The GCD facility is a group of 120-feet deep boreholes
located within the Nevada Test Site (NTS) which contains disposed
transuranic wastes.)
The storage standards in 40 CFR 191.03(a) are stated in terms of an
older dose-calculation method and are set at an annual whole-body-dose
limit of 25 mrem/yr. The proposed storage standards for Yucca Mountain
use a modern dose-calculation method known as ``committed effective
dose equivalent'' (CEDE).8 Even though today's proposal uses
the modern method of dose calculation, we believe that the proposed
dose level essentially maintains a similar risk level as in 40 CFR
191.03(a) at the time of its promulgation (see the discussion of the
different dose-calculation methods in the What Should the Level of
Protection Be? section later in this notice). The difference between
these dose calculation procedures presents a problem in combining the
doses for regulatory purposes. However, we have begun a rulemaking to
amend both 40 CFR Parts 190 and 191. That rulemaking would update these
limits to the CEDE methodology. We anticipate that we will finalize the
amendments to parts 190 and 191 prior to the finalization of this
rulemaking. If that does not occur, we would need to address the
calculation of doses under the two methods in another fashion. For
example, we could require that the doses occurring as a result of
activities outside the repository be converted into annual CEDE for
purposes of determining compliance with the storage standard. We
request comments upon such an approach.
---------------------------------------------------------------------------
\8\ The term ``committed effective dose'' in this rulemaking has
the same meaning as the term ``committed effective dose equivalent''
which was used prior to the publication of ICRP Publication No. 60.
It is used here since the term is less complicated and more compact.
Also, the use of ``committed effective dose'' is consistent with
subpart B of 40 CFR part 191 (58 FR 66398, 66402, December 20,
1993).
---------------------------------------------------------------------------
Section 801 of the EnPA specifically provides that the standards
that we issue shall be the only ``such standards'' that apply at Yucca
Mountain. Thus, the statute provides that the EnPA is the exclusive
authority for ``such standards'' and, in turn, replaces our generally
applicable standards for radiation protection to the extent that
section 801 requires site-specific standards. Otherwise, our generic
standards are not affected. As noted, we propose to interpret the scope
of section 801 as applying to both storage and disposal of waste in the
repository. Thus, waste inside the repository would be subject to the
standards proposed in today's notice. Our generic standards in subpart
A of 40 CFR part 191 will apply to waste outside of the repository.
Using this interpretation, we have considered the differences
between the conditions covered by the storage standards in 40 CFR
191.03(a) and the conditions which could affect storage in the Yucca
Mountain repository. The most significant difference is that the
storage in Yucca Mountain would be underground whereas most storage
covered under 40 CFR part 191 is aboveground. Otherwise, the technical
situations we anticipate under both the existing generic standards and
the proposed Yucca Mountain standards are essentially the same. Also,
one of our goals in issuing 40 CFR parts 190 and 191 was to bring the
entire uranium fuel cycle under consistent EPA standards. Therefore, we
are proposing that the part 197 standards continue the coverage of the
uranium fuel cycle because SNF, a large part of the waste planned for
emplacement in Yucca Mountain, is part of that fuel cycle. Therefore,
we are proposing to extend a similar level of protection as in the 1985
version of subpart A of 40 CFR part 191. In other words, under the part
197 storage standards, exposures of members of the public from waste
storage inside the repository would be combined with exposures
occurring as a result of storage outside the repository but within the
Yucca Mountain site. The total dose could be no greater than 150
microsieverts (Sv) (15 mrem) CEDE per year (CEDE/yr).
Our application of subpart A of 40 CFR part 191 to storage
activities outside of the repository at the Yucca Mountain site is
supported by the WIPP LWA. Section 8 of the WIPP LWA excludes Yucca
Mountain from our generic disposal standards but not from the generic
management and storage standards found in subpart A of 40 CFR part 191.
If we finalize the proposed interpretation of section 801 of the EnPA
as applying to radioactive material stored or disposed of in the
repository, we would apply subpart A of 40 CFR part 191 to the storage
activities outside of the repository at the site without further public
notice.
[[Page 46984]]
We request comment upon our proposed interpretation that section
801 of the EnPA directs us to develop new standards that apply only to
radioactive materials stored in the repository. We also request public
comment upon whether we should instead construe section 801 of the EnPA
as providing for the establishment of new storage standards, rather
than applying the existing storage standards in 40 CFR part 191 to
storage, or handling, of radioactive materials at the Yucca Mountain
site prior to their movement into the repository. If we decide, based
upon the alternative interpretation of section 801, to promulgate new
storage standards for the site, we anticipate that we would adopt
standards essentially the same as those in 40 CFR 191.03(a). Thus, we
request public comment upon whether we should develop and adopt in this
rulemaking, under section 801 of the EnPA, new standards for management
and storage activities at the site, and request comments upon the
adoption of such standards based upon those in 40 CFR 191.03(a).
III.B. What Is the Standard for Protection of Individuals? (Proposed
Secs. 197.20 and 197.25)
III.B.1. Should the Limit Be on Dose or Risk?
Although a standard for limiting exposure of people to radiation
can take many forms, NAS narrowed its final considerations to risk and
dose, that is, a risk-based or dose--based standard. The numeric level
of the proposed standard for protecting individual members of the
public from radioactive materials disposed of in the Yucca Mountain
disposal system is addressed in the What Should the Level of Protection
Be? section later in this notice. The discussion here explains why we
selected a dose-based standard rather than a risk-based standard, as
recommended by NAS.
Two forms of radiation exposure can occur depending upon the
location of the source relative to the body `` internal and external.
Internal exposures occur when a person inhales or ingests contaminated
air, food, water, or soil. External exposures occur because a person is
near a radionuclide which is emitting X-rays, gamma rays, beta
particles, or neutrons. ``Dose'' is a measure of the amount of
radiation received by individuals resulting from exposure to
radionuclides. ``Risk'' is the probability of an individual incurring
an adverse health effect from exposure to radiation. The NAS defined
``risk'' as the product of two parameters: (1) the probability of an
individual receiving a dose, and (2) the probability of incurring a
health effect because of that dose (NAS Report p. 42). This rulemaking
takes both of these factors into account. (The probability of an
individual receiving a dose is part of the performance assessment and
is discussed in the What Are the Requirements for Performance
Assessments and Determinations of Compliance? section later in this
notice.) As mentioned in the previous section, these standards state
radiation risk estimates as the probability of an individual developing
a fatal cancer, since fatal cancers are the greatest harm to
individuals from low-dose-rate radiation (NAS pp. 37-39).
Section 801(a)(1) of the EnPA directed that our standards for Yucca
Mountain ``shall prescribe the maximum annual effective dose equivalent
to individual members of the public from releases to the accessible
environment from radioactive materials stored or disposed of in the
repository....'' At the same time, the EnPA calls for us to issue our
standards ``based upon and consistent with'' the findings and
recommendations of NAS. The NAS recommended that we adopt a standard
expressed as risk rather than the dose standard that Congress
prescribed. The NAS offered two reasons for its recommendation. First,
a risk-based standard is advantageous relative to a dose-based standard
because it ``would not have to be revised in subsequent rulemakings if
advances in scientific knowledge reveal that the dose-response
relationship is different from that envisaged today'' (NAS Report p.
64). Second, a standard in the form of risk more readily enables the
public to comprehend and compare the standard with human-health risks
from other sources.
We have reviewed and evaluated the merits of a risk-based standard
as recommended by NAS. However, we are proposing a dose-based standard
for the following reasons. First, both national and international
radiation protection guidelines developed by bodies of non-governmental
radiation experts, such as ICRP and NCRP, generally have recommended
that radiation standards be established in terms of dose. Also,
national and international radiation standards, including the
individual-protection requirements in 40 CFR part 191, are established
almost solely in terms of dose or concentration, not risk. Therefore, a
risk-based standard will not allow a convenient comparison with the
numerous existing radiation guidelines and standards that are stated in
terms of dose.
Second, we have an established methodology for calculating dose
that is described in Federal Guidance Reports Nos. 11 and 12 (Federal
Guidance). The development of this methodology was a combined effort of
many Federal agencies involved in radiation protection and has become
Federal policy. The guidance provides a consistent methodology for
calculating doses for regulatory purposes. By contrast, there is
currently no Federal Guidance Report, in final form, for calculating
risk from radiation exposure.
Third, we have based the proposed dose-based standard upon the risk
of developing a fatal cancer as a result of that level of exposure
based upon a linear, non-threshold, dose-response relationship. We
would establish a risk-based standard in the same manner. Thus, a risk-
based standard, like a dose-based standard, depends upon current
knowledge and assumptions about the chance of developing fatal cancer
from a particular exposure level. Dose and risk are closely related;
one can be converted to the other simply by using the appropriate
factor. Therefore, both dose- and risk-based standards are based upon
scientific assumptions that could change and no matter how it is
expressed, the standard is based upon risk.
Finally, section 801(a)(1) of the EnPA specifically calls for a
dose-based standard. Most commenters supported this by asking for a
dose-based standard rather than a risk-based standard.
Accordingly, we are proposing a standard expressed as a limit on
dose. We are requesting comments upon the proposed form of the
standard, including whether the standard should be expressed as risk.
III.B.2. What Should the Level of Protection Be?
As noted previously, section 801(a)(1) of the EnPA calls for our
Yucca Mountain standards to ``prescribe the maximum annual effective
dose equivalent to individual members of the public from releases of
radioactive materials.'' Development of the individual-protection
standard requires us to evaluate and specify several factors. These
factors include the level of protection, who the standards should
protect, and how long the standards should provide protection.
Determining the appropriate dose level is ultimately a question of both
science and public policy. The NAS stated in its Report: ``The level of
protection established by a standard is a statement of the level of the
risk that is acceptable to society. Whether posed as ``How safe is safe
enough?'' or as ``What is an acceptable
[[Page 46985]]
level?'', the question is not solvable by science'' (NAS Report p. 49).
We seek to find answers to these questions for the Yucca Mountain
disposal system through this rulemaking.
We considered the NAS findings and recommendations in our
determination of the CEDE level that would be adequately protective of
human health. We also reviewed established EPA standards and guidance,
other Federal agencies' actions for both radiation and non-radiation-
related actions, and other countries' regulations. In addition, we
evaluated guidance on dose limits provided by National and
international, non-governmental, advisory groups of radiation experts.
The NAS recommended a range of risk levels that we could use as a
reasonable starting point in this rulemaking (NAS Report p. 5). The
range of annual risk of fatal cancer suggested by NAS was 1 chance in
100,000 (1 x 10-\5\) to 1 chance in 1,000,000 (1 x
10-\6\) (this corresponds to a range of 20 to 2 mrem CEDE/
yr). The NAS based its recommendation upon its review and evaluation of
our actions, other Federal actions, guidelines developed by National
and international groups, and regulations of other countries. For these
standards, we are proposing a limit of 150 Sv (15 mrem) CEDE/
yr. This limit corresponds approximately to an annual risk of 7 chances
in 1,000,000 (7 x 10-\6\)--within the range that NAS
recommended as a starting point for consideration.
Table 1 below lists the dose limits of other current EPA and NRC
regulations (adapted from NAS Report p. 50). Today's proposed standard
of 150 Sv (15 mrem) CEDE/yr is within the range of these
established standards. Further, it is consistent with the individual-
protection standard at 40 CFR 191.15 in our generic disposal standards
which limits the annual CEDE to 150 Sv (15 mrem)/yr.
Table 1.--Current EPA and NRC Dose Limits on Various Environmental
Concerns
------------------------------------------------------------------------
Environmental concern Limit*
------------------------------------------------------------------------
Low-Level Waste (10 CFR part 61)....... 250 Sv (25 mrem)/yr
License Termination (10 CFR part 20)... 25 mrem TEDE**/yr
Uranium Fuel Cycle (40 CFR part 190)... 25 mrem/yr
Generic Standard for Management and 25 mrem/yr
Storage of SNF and HLW (40 CFR 191.03).
Generic Individual-Dose Standard for 150 Sv (15 mrem) CEDE/
Disposal of SNF and HLW (40 CFR yr
191.15).
National Emission Standards for 10 mrem CEDE/yr
Hazardous Air Pollutants (40 CFR part
61, subparts H and I).
SNF and HLW Disposal Limit for 4 mrem/yr for man-made beta-
Underground Sources of Drinking Water and photon-emitting
(40 CFR 191.24). radionuclides
------------------------------------------------------------------------
*Unless otherwise noted, only whole-body dose limits are listed; there
may also be other requirements for any particular environmental
concern. The 25-mrem/yr, whole-body-dose limit established in 1985 is
essentially equivalent to the risk associated with today's dose rate
of 150 Sv (15 mrem) CEDE/yr (58 FR 66402, December 20, 1993).
**TEDE (total effective dose equivalent) is NRC's term for CEDE. This
regulation was not included in the NAS Report.
We note that, except for 40 CFR 191.15, 40 CFR part 61, and 10 CFR
part 20, the dose limits in Table 1 are stated in terms of an old dose
system. For example, the annual limits in 40 CFR 191.03(a) are 25 mrem
for the whole body, 75 mrem for the thyroid, or 25 mrem for any other
organ (only the whole-body limit is listed in Table 1). We established
these dose levels in 1985 (50 FR 38085, September 19, 1985) under a
different system for calculating doses than the more recent rulemakings
that use the CEDE concept. We estimate that the 25-mrem/yr, whole-body-
dose limit established in 1985 is essentially equivalent to the risk
associated with today's proposed limit of 150 Sv (15 mrem)
CEDE/yr (58 FR 66398, 66402, December 20, 1993).
In addition, the proposed 150-Sv (15 mrem)-CEDE/yr limit
in today's proposal is consistent with other current standards. For
example, our limits on radiation exposure through the air is part of
the set of limits for pollutant releases known as the National Emission
Standards for Hazardous Air Pollutants (NESHAPs, 40 CFR part 61). Since
our NESHAPs limit of 10 mrem/yr covers radionuclide releases into only
the air, the 150 Sv (15 mrem) CEDE/yr standard being proposed
for 40 CFR part 197 is consistent with the NESHAPs limit because it
applies to all potential pathways, that is, the dose limit is higher
but includes other pathways in the analysis.
In summary, based upon our review of the guidance, regulations, and
standards cited above, and the NAS Report, we are proposing a standard
of 150 Sv (15 mrem) CEDE/yr for the Yucca Mountain disposal
system. We request comment upon the reasonableness of this level of
protection.
III.B.3. What Factors Can Lead to Radiation Exposure?
Protection of the public from exposure to radioactive pollutants
requires knowledge and understanding of three factors: the source of
the radiation, the pathways leading to exposure, and the recipients of
the radiation. This section provides a discussion of the source of
radiation and pathways of exposure. The following two sections discuss
the recipients of the dose. The development of standards to protect
public health and safety from radionuclides released from waste
disposed of in the Yucca Mountain disposal system must include
consideration of the sources of radiation and pathways which could lead
to exposure of humans. The mechanisms of exposure are the basis of an
analysis called the performance assessment. The performance assessment
is the quantitative analysis of the projected behavior of the disposal
system.
Source. The waste disposed of in Yucca Mountain will contain many
different radionuclides including unconsumed uranium, fission products
(for example, cesium-137 and strontium-90), and transuranic elements
(for example, plutonium and americium).
The inventory of radionuclides over time will depend upon the type
and amount of radionuclides originally disposed of in the disposal
system, the half-lives of the radionuclides, and the amount of any
radionuclides formed from the decay of parent radionuclides (see the
BID). In the time frame of tens-to hundreds-of-thousands of years, most
[[Page 46986]]
radionuclides initially present in SNF and HLW will decay to
essentially no radioactivity. Therefore, the waste will eventually have
radiologic characteristics similar to a large uranium ore body (see the
BID).
To delay the movement of radionuclides into the biosphere, DOE
plans to use multiple barriers. These barriers would be man-made
(engineered) and natural based upon the design of, and conditions in
and around, the disposal system.
Engineered barriers must be designed to delay release of
radionuclides from the repository. For example, an engineered barrier
could be the waste form. The Department plans to convert liquid HLW
derived from reprocessing of SNF into a solid by entraining the
radionuclides into a matrix of borosilicate glass; NRC will likely
consider this an engineered barrier. The molten glass then would be
poured into and hardened in a second man-made barrier, a metal
container (see the BID). In addition, it is possible to have other man-
made barriers in the repository to serve as part of the disposal system
(see the BID).
Natural barriers at Yucca Mountain also could slow the movement of
radionuclides into the accessible environment. For instance, the
Department plans to construct the repository in a layer of tuff located
above the water table. The relative dryness of the tuff around the
repository would limit the amount of water which comes into contact
with the waste. It also would retard the future movement of
radionuclides from the waste into the underlying aquifer. Any
radioactive material that dissolved into infiltrating water,
originating as surface precipitation, still would have to be moved to
the saturated zone. Minerals, such as zeolites, contained within the
tuff beneath the repository could act as molecular filters and ion-
exchange agents for some of the released radionuclides, thereby slowing
their movement. Such minerals also could limit the amount of water that
contacts the waste and could help retard the movement of radionuclides
from the waste to the water table. This mechanism would be most
effective if flow was predominantly through the pores in the rock, also
known as the matrix (see the BID).
Pathways. Once radionuclides have left the waste packages, they
could be carried by water or air and reach the public. Upon release
from the waste packages, most radionuclides will be carried by ground
water away from the repository. However, those in a gaseous form, such
as carbon-14 (\14\C) in the form of carbon dioxide, will be carried by
air moving through the mountain.
Movement via water. Radionuclides will not be moved into the water
table instantaneously. The length of time it takes depends partly upon
how much the water moves via fractures or through the matrix of the
rock. Once radionuclides reach the saturated zone, they would move away
from the disposal system in the direction of ground water flow.
There are currently no perennial rivers or lakes adjacent to Yucca
Mountain to further transport contaminants. Therefore, based upon
current knowledge and conditions, ground water and its usage will
likely be the main pathway leading to exposure of humans. Current
knowledge suggests that the two major ways that people would use the
contaminated ground water are: (1) drinking and domestic uses; and (2)
agricultural uses (see the BID). In other words, radionuclides that
reach the public could deliver a dose if an individual: (1) Drinks
contaminated ground water or uses it directly for other household uses;
(2) drinks other liquids containing contaminated water; (3) eats food
products processed using contaminated water; (4) eats vegetables or
meat raised using contaminated water, or (5) is otherwise exposed as a
result of immersion in contaminated water or air or inhalation of wind-
driven particulates left following the evaporation of the water.
Movement via air. Some radionuclides could be carried by moving
air. The largest known source of potential movement by air in Yucca
Mountain is carbon dioxide containing \14\C. Airborne radionuclides
might move through the tuff overlying the repository and exit into the
atmosphere following release from the waste package. Once the
radioactive gas enters the atmosphere, it would disperse. This
dispersion would probably be global and, therefore, become greatly
diluted. The major pathway for exposure of people by \14\C is the
uptake of radioactive carbon dioxide by plants that humans subsequently
eat (see the BID).
III.B.4. Who Will Be Representative of the Exposed Population?
To determine whether the Yucca Mountain disposal system complies
with the standard, it will be necessary for DOE to calculate the dose
to some individual or group of individuals exposed to releases from the
repository and compare the calculated dose with the limit established
in the standard. The standard must specify, therefore, the individual
or group of individuals for whom the dose calculation is to be made.
The NAS definition of critical group. The NAS Report recommended
that we base the standards for protection of individuals upon risk
incurred by a critical group (CG). The CG would be the group of people
which, based upon cautious, but reasonable, assumptions, has the
highest risk of incurring health effects due to releases from the
disposal system. The ICRP introduced the concept of a CG in order to
account for the variation of dose which may occur in a population due
to differences in age, size, metabolism, habits, and environment. In
other words, the ICRP recommends the use of a group of people because
individuals might have personal traits which make them much more or
less vulnerable to releases of radiation than the average within a
small group of the most highly exposed individuals. The ICRP defines
the CG as a relatively homogeneous group of people whose location and
habits are such that they represent those individuals expected to
receive the highest doses as a result of the discharge of
radionuclides. The NAS adapted the CG concept to a risk framework for
the development of an individual-risk standard and recommended the
following description of the CG (NAS Report p. 53):
The critical group for risk should be representative of those
individuals in the population who, based on cautious, but
reasonable, assumptions, have the highest risk resulting from
repository releases. The group should be small enough to be
relatively homogeneous with respect to diet and other aspects of
behavior that affect risks. The critical group includes the
individuals at maximum risk and is homogeneous with respect to risk.
A group can be considered homogeneous if the distribution of
individual risk within the group lies within a total range of a
factor of ten and the ratio of the mean of individual risks in the
group to the standard is less than or equal to one-tenth. If the
ratio of the mean group risk to the standard is greater than or
equal to one, the range of risk within the group must be within a
factor of 3 for the group to be considered homogeneous. For groups
with ratios of mean group risk to the standard between one-tenth and
one, homogeneity requires a range of risk interpolated between these
limits.
The NAS also recommended that the CG risk calculated for purposes
of comparison with the risk limit established in the standard is the
average of the risks of all the members in the group. Using the average
risk avoids the problem of the outcome being unduly influenced by
unusual habits of individuals within the group.
The NAS indicated that in order to select a CG, the person or
persons likely
[[Page 46987]]
to be at highest risk from among the larger, exposed population must be
specified. To accomplish this, one must make assumptions about the
nature of human activities, lifestyles, and pathways that affect the
level of exposure. The set of circumstances that affects the dose
received, such as where people live, what they eat and drink, and other
lifestyle characteristics, is a very important part of the exposure
scenario. Many human behavior factors important to assessing repository
performance vary over periods that are short in comparison with the
compliance period proposed for these standards. The past several
centuries have seen radical changes in human technology and behavior,
many of which were not reasonably predictable. Given this potential for
rapid change, we believe that it is not possible to know what patterns
of human activity and changes in human biology might occur thousands of
years from now. For the purpose of compliance with the standard,
therefore, we are proposing that it is appropriate to use many of the
current characteristics of members of the public in the vicinity of
Yucca Mountain in the compliance assessments required by these
standards (see the What Should Be Assumed About the Future Biosphere?
section later in this notice).
The NAS Report presented two illustrative approaches for
formulating an exposure scenario for determining compliance. The NAS
also clearly stated that there might be other methods to reach the same
objective (NAS Report p. 100). One approach, described in Appendix C of
the NAS Report, A Probabilistic Critical Group, used statistical
methods and probabilities to characterize a CG. The second, The
Subsistence-Farmer Critical Group, described in Appendix D, identified
a subsistence farmer as a principal representative of the CG.
The NAS probabilistic critical group. Appendix C of the NAS Report
described a ``probabilistic critical group.'' This section describes
the contents of Appendix C of the NAS Report.
The NAS probabilistic CG approach would require use of a
theoretical population distribution which we would, or require DOE to,
develop by using a mathematical method known as ``Monte Carlo.'' The
Monte Carlo method is a mechanism to randomly select values of
parameters which have a range of possible values. The parameters would
be present-day environmental parameters, including soil quality, land
slope, growing season, depth to the aquifer, and population
distribution and lifestyles. The individuals who comprise the CG may
represent a variety of economic lifestyles and activities. The analysis
would then use the variability of those parameters in the region around
Yucca Mountain to arrive at the theoretical population for the
calculation of radiation exposure. This theoretical population would
then, according to NAS, be combined with Monte Carlo simulations of the
distribution of contaminated ground water in time and space (NAS Report
p. 148). According to NAS, each simulation would generate a plume path
which could be overlain on a map of potential farm density or water use
to determine a potential exposure area. Each of these potential plume
paths is known as a ``realization.'' Values for parameters, including
well depths, rates of water use, food sources, and consumption rates,
are determined by sampling from the parameter-value distributions. For
each plume realization of the contamination in the aquifer, the results
of the exposure simulations are combined to give a spatial distribution
of maximum exposures for the locations likely to be inhabited. This
approach would use a large number of simulations of plume realizations
to identify critical subgroups with the highest risk. It would then be
used to calculate the arithmetic average of the risk of all critical
subgroups over all plume realizations to estimate the risk for the CG.
In determining compliance, the Commission would compare this estimate
with the risk limit in the standard.
We considered proposing the probabilistic CG approach but are not
doing so for the following reasons. First, there is no relevant
experience in applying the probabilistic CG approach. Second, the
approach is very complex and difficult to implement in a manner that
assures it would meet the requirements of defining a CG. Third, we are
concerned that this approach does not appear to identify clearly who is
being protected. Finally, a significant majority of the comments that
we have received upon the NAS Report opposes the probabilistic CG
approach.
The NAS subsistence-farmer critical group. The approach in Appendix
D of the NAS Report specified one or more subsistence farmers as the
CG. It made assumptions designed to define the farmer at maximum risk
to be included in the CG. This section describes the contents of
Appendix D of the NAS Report.
The subsistence-farmer CG is a definable, highly exposed segment of
the larger, exposed population. The subsistence farmer would be assumed
to: (1) be a person with eating habits and response to doses of
radiation that would be average for present-day people and (2) obtain
all potable water and grow all of his or her own food using water
withdrawn from the aquifer contaminated with radionuclides from the
disposal system. The water used by this CG would be withdrawn at a
location downgradient from and outside the footprint of the repository
at the point of maximum potential concentration of ground water
contamination, provided that no natural geologic features preclude
drilling for water at that location. (The footprint of the repository
is the circumscription of the outermost, original emplacement locations
of the waste.)
Concentrations of radionuclides in the extracted ground water may
be smaller than in undisturbed ground water due to pumping; this
possibility could be used when evaluating exposures (NAS Report p.
155). As a result of uncertainty, there will be probabilistic
distributions of radionuclide concentrations, as they vary in time and
space in the aquifer outside the repository footprint, which are the
input variables needed to estimate the risk. The radionuclide
distributions in the aquifers, in turn, depend upon the performance of
the components of the natural and engineered barrier systems.
Projections of their performance also contain uncertainty and likely
will be subject to probabilistic assessment. Any assessment of the
potential doses from the repository, therefore, must consider the
probability of processes and events that influence eventual
concentrations of radionuclides in aquifers supplying water to the CG.
Overall, the ``expected'' risk for the average member of this CG
would be about one-half that of the most-exposed subsistence farmer
(NAS Report p. 158). This average risk to the members of the CG would
be compared with the standard selected for compliance.
We considered proposing that the protected individual(s) be the
subsistence-farmer CG. The CG concept has been utilized within the U.S.
in various ways. The NRC uses the CG concept in assessing compliance
with NRC standards for radionuclide releases from nuclear facilities.
For example, the Commission uses the CG concept in: (1) licensing
actions involving dose calculations under 10 CFR part 40, appendix A;
(2) its radiological criteria for license termination of all NRC-
licensed facilities at 10 CFR part 20, subpart E; and (3) its draft
guidance for LLW disposal under 10 CFR part 61. The State of Washington
recently
[[Page 46988]]
implemented the CG concept in actions relating to U.S. Ecology's LLW
site at Hanford, and the State of Texas endorses CG in its
decommissioning standards. Also, a great deal of international guidance
exists that discusses the use of CG. The ICRP endorses CG, and has
recommended the CG concept in numerous documents, both recent and
dating back as far as 1977. Canada, Sweden, Switzerland, and the United
Kingdom are among those individual nations that have adopted the CG
methodology for radioactive waste storage and disposal.
We prefer an approach to exposure assessment that is consistent
with other Agency programs (Guidance on Risk Characterization for Risk
Managers and Risk Assessors, Deputy Administrator F. Henry Habicht II,
February 26, 1992) and which we believe provides a level of protection
substantially equivalent to that which would be achieved by the CG
concept.
Our proposal for the protection of individuals. Most of our
programs use an approach for the development of exposure scenarios that
involves determining the high-end range of doses or exposures.
Conceptually, this range is that above the 90th percentile of the
entire (either measured or estimated) distribution of potential doses
within the exposed population. Conversely, the NESHAPs program for
radionuclides and the individual-protection requirements in the generic
SNF and HLW disposal standards at 40 CFR 191.15 require calculation of
the individual dose for a person assumed to reside at a location where
that person would receive the highest dose. However, other Agency
programs use a different approach to protect individuals by using
``reasonable, maximum exposure'' (RME) conditions. The National
Contingency Plan describes an approach to be used for the RME scenario
to protect individuals as ``a product of factors, such as concentration
and exposure frequency and duration, that are an appropriate mix of
values that reflect averages and 95th percentile distributions'' (55 FR
8666, 8710, March 8, 1990). In the past, we have defined ``reasonable
maximum'' to mean potential exposures that are likely to occur. The
method for calculating the RME is to estimate the high-end range of
possible exposures by identifying the factors which have the greatest
effect upon the size of the dose, and using maximum or nearly maximum
values for one or a few of these factors, leaving the others at their
average values (57 FR 22888, 22922, May 29, 1992). In this approach, we
select a hypothetical individual who would be representative of the
most highly exposed individuals. We call this individual the reasonably
maximally exposed individual (RMEI). To be effective, the RMEI approach
must avoid incompatible combinations of parameter values, such as, low
body weight used in combination with high intakes.
Thus, we intend for this procedure to project doses that are within
a reasonably expected range rather than projecting the most extreme
case. However, the procedure is also meant to identify an individual
dose which is well above the average dose in the exposed population.
The ultimate goal and purpose is to estimate a level of exposure that
is protective of the vast majority of individuals at a site, but is
still within a reasonable range of potential exposures.
For the preceding reasons, we are proposing the RMEI concept as our
preferred approach instead of the CG approach. The United States and
other countries have used the concept of a hypothetical individual to
represent future populations in radioactive-waste management programs.
This is consistent with widespread practice, current and historical, of
estimating dose and risk to highly exposed individuals even when the
exposure habits of future people cannot be specified or accurately
calculated, as in this case where doses must be projected for very long
periods. The approach is straightforward and relatively simple to
understand. We believe that this approach provides protection similar
to that afforded by the NAS recommendation to use a CG. The RMEI model
uses a series of assumptions about the lifestyle of a hypothetical
individual. The desired degree of conservatism can be built into the
model through choices of assumed values of RME parameters. However,
these values would be within certain limits since we are proposing to
require the use of Yucca Mountain-specific characteristics in choosing
those parameters and their values. In subpart B of 40 CFR part 197, we
propose a framework of assumptions for NRC to incorporate into its
implementing regulations.
Our proposed RMEI would be representative of a future population
group termed ``rural-residential.'' The CEDE received by this RMEI
would be calculated by DOE using cautious, but reasonable, exposure
parameters and parameter-value ranges. The projected CEDE would be used
by NRC in the determination of compliance with the proposed standards.
We believe that the results obtained by using this approach would be
similar to those which would be obtained by using the subsistence-
farmer CG approach put forth in Appendix D of the NAS Report. In both
cases, the objective is to determine the magnitude of the potential
exposure using reasonable, not extreme, assumptions. Under the proposed
standards, the RMEI will have food and water intake rates, diet, and
physiology like that of individuals currently living in the
downgradient direction of flow of the ground water passing under Yucca
Mountain. The Department will perform the dose calculation to estimate
exposure resulting from releases from the waste into the accessible
environment based upon the assumption of present-day conditions in the
vicinity of Yucca Mountain. Presently, we expect the ground water
pathway to be the most significant pathway for exposure from
radionuclides that are transported from the repository. Our initial
evaluation of potential exposure pathways from the disposal system to
the RMEI suggests that the dominant fraction of the dose incurred by
the RMEI likely will be from ingestion of food irrigated with
contaminated water (see the BID). It is possible, however, that another
exposure pathway will be determined by DOE and NRC to be more
significant for radiation exposure. Consequently, DOE and NRC must
consider and evaluate all potentially significant exposure pathways in
the performance assessment. As a result of the performance assessment,
there will be a distribution of the highest potential doses incurred by
the RMEI. We are proposing that the mean or median value (whichever is
higher) of that distribution be used by NRC to determine compliance
with the individual-protection standard. We request comments upon this
method of determining compliance with the individual-protection
standard.
We are also requesting comments upon the alternative of adopting
the CG approach rather than the RMEI. Comments supporting the CG
approach should address the level of detail EPA's rule should include
on the parameters of the CG.
Exposure scenario for the RMEI. A major part of the exposure
scenario is the location of the RMEI. In preparing to propose a
location for the RMEI, we collected and evaluated information on the
natural geologic and hydrologic features, such as topography, geologic
structure, aquifer depth, aquifer quality, and the quantity of ground
water, that may preclude drilling for water at a specific location.
Based upon these factors and the current understanding of ground water
flow in the area of Yucca
[[Page 46989]]
Mountain, it appears that an individual could reside anywhere along the
projected radionuclide flow path extending from Forty-Mile Wash,
approximately five kilometers (km) from the proposed repository
location, to the southwestern part of the Town of Amargosa Valley,
Nevada, where the ground water is close to the land surface and where
most of the farming in the area is done. However, an individual's
ability to reside at any particular point along that path depends upon
that individual's purpose and available resources. To explore these
variations, we developed the four scenarios described below. We present
our evaluation of factors associated with these scenarios more fully in
the BID. We welcome comment upon the appropriateness of each of these
scenarios and upon our preferred scenario. In developing scenarios, we
assumed that the level of technology and economic considerations
affecting population distributions and life styles in the future are
the same as today (for more detail, see the What Should Be Assumed
about the Future Biosphere? section below).
The RMEI in the first scenario is a subsistence (low technology)
farmer. Such an individual would have continuous exposure to
radionuclides in water, air, and soil which are arriving through all
exposure pathways. The RMEI's location and habits would be generally
consistent with historical locations of Native Americans and early
settlements in Amargosa Valley and influenced heavily by easy access to
water, that is, where the water table is near the surface
(approximately 30-40 km away from the disposal system). In addition,
all of the RMEI's water and food would come from contaminated sources.
We did not choose this option because we believe that such a scenario
is overly conservative given the site-specific characteristics of the
area and reasonable consideration of the lifestyles of individuals in
that area.
In the second scenario, we considered using a commercial farmer as
the RMEI. We evaluated economic factors and current and potential
future technologies which could be economically viable. There are areas
in the vicinity of Yucca Mountain which are currently being farmed
commercially or could be economically farmed based upon reasonable
assumptions, current technology, and experience in other arid parts of
the western United States. The exposure pathways in this scenario would
be the same as those used for the subsistence-farmer scenario. We did
not choose this as our preferred scenario since we believe that
commercial farming would not be representative of the general
population and would not be likely in areas other than where there is
currently such farming, approximately 30 kilometers from the disposal
system.
The third scenario, selected as our preferred approach, involves a
rural-residential RMEI. We assume that the rural-residential RMEI is
exposed through the same general pathways as the subsistence farmer.
However, this RMEI would not be a full-time farmer but would do
personal gardening and earn income from other sources of work in the
area. We assume further that all of the drinking water (two liters per
day) and some of the food consumed by the RMEI is from the local area.
The consumption of two liters per day of drinking water is a high value
since people consume water from outside sources, such as commercial
products. Similarly, we assume that local food production will use
radioactively contaminated water coming from the disposal system. We
believe this lifestyle is similar to that of most people living in
Amargosa Valley today.
The fourth scenario which we considered is domestic use of an
underground source of drinking water (USDW) by a community living near
the repository site. A USDW is essentially an aquifer which is large
enough to supply or could supply a public water system (the full
definition is in 40 CFR 144.3). Based upon current water usage in the
arid western United States, a public water supply inside of the current
NTS could exist since a community would have greater resources to
access and recover water than would most individuals. Such a community
water supply would have characteristics similar to DOE's water wells J-
12 and J-13. These wells have supplied water needs (including human
consumption) since the early 1960s for the Federal government. While we
consider such a scenario possible, it could be less protective than the
rural-residential scenario because it would not protect individuals
from the ingestion of contaminated home-grown food. Also, we consider
this scenario less representative of current conditions for most people
in the vicinity of Yucca Mountain.
Location of the RMEI. The location of the RMEI is a basic part of
the exposure scenario. We considered locations within a region
occupying an area bordering Forty-Mile Wash, within a few kilometers of
the repository site, to the southwestern border of the Town of Amargosa
Valley. This region, which we believe is hydrologically downgradient
from Yucca Mountain, can be considered as three general subareas.
The first subarea occupies the land south from near Yucca Mountain
to the vicinity of U.S. Route 95. This subarea has deep ground water
(up to about 300 meters) which is accessed by Federally owned wells
used for DOE activities associated with Yucca Mountain and the NTS.
This land is currently under government control and ownership. In
addition, the likelihood of small or economically viable agricultural
activities in this area is questionable when the depth to the water
table is taken into consideration.
The next subarea borders the first and extends several kilometers
south of U.S. Route 95. The northern portion of the Town of Amargosa
Valley, including the businesses at the intersection of U.S. Route 95
and Nevada State Route 373 (Lathrop Wells), is included in this
subarea. This subarea currently includes about 15 residents and no
agricultural activities, although abandoned irrigation wells exist (see
the BID). The depth to water in this area ranges from slightly more
than 100 to about 60 meters. The U.S. Natural Resource Conservation
Service has designated the types of soils in this area as suitable for
rangeland and wildlife habitat.
The third subarea borders the second and covers the remainder of
the Town of Amargosa Valley. This subarea is the closest downgradient
location to Yucca Mountain with perennial agricultural activity. The
depth to ground water is relatively shallow--approximately 50 to 15
meters. The agriculture consists of both personal gardens and
commercial activities. The commercial agriculture is a mainstay of the
local economy. Commercial farms produce crops, livestock, and dairy
products for either local consumption or for transport out of the
region. Most of the residents of the Town of Amargosa Valley are within
this subarea, as are the community center, school, clinic, library,
post office, and sheriff's office. The population consists of all age
groups.
Based upon these considerations of the subareas, we propose that
the intersection of U.S. Route 95 and Nevada State Route 373, known as
Lathrop Wells, is a likely location for the RMEI. In this example, we
do not consider it probable that the rural-residential RMEI would
occupy locations significantly north of U.S. Route 95. We make this
assumption mainly because the rough terrain and increasing depth to
ground water nearer to Yucca Mountain would likely discourage
settlement by individuals because access to water is more difficult
than it would be a few kilometers
[[Page 46990]]
farther south. Also, there are currently several residents and
businesses near this location whose source of water is the underlying
aquifer (which we understand flows from under Yucca Mountain).
Therefore, we believe that it is reasonable to assume that individuals
could reside near this intersection in the future.
Farming occurs today farther south, in the southwestern portion of
the Town of Amargosa Valley in an area near the California border and
west of Nevada State Route 373. However, soil conditions in the
vicinity of Lathrop Wells are similar to those in southwestern Amargosa
Valley. Therefore, it should be feasible for the RMEI to grow some of
his or her own food, including a grazing cow, using a fraction of the
water recovered but not used for household purposes. Larger-scale food
production at Lathrop Wells is unlikely because of the cost of
recovering sufficient water. To supplement the gardening and grazing,
we propose that it is also reasonable to assume that the RMEI would
obtain much of his or her food from the local area.
Finally, we believe that a rural-residential RMEI near Lathrop
Wells would be among the most highly exposed individuals in the
downgradient direction from Yucca Mountain. We believe that this is
true even though individuals residing closer to the repository (where
the ground water is at a greater depth) could be consuming higher
concentrations of radionuclides in their drinking water. Because of the
significant cost of finding and withdrawing the ground water, we
further believe that individuals living nearer the repository are
unlikely to withdraw water from the significantly greater depth and in
the much larger quantities needed for farming activities. Based upon
our analyses of potential pathways of exposure, discussed above, we
believe that irrigation would be the most likely pathway for most of
the dose from the most soluble, least retarded radionuclides (such as
technetium-99 and iodine-129). The percentage of the dose that results
from irrigation would depend upon the assumptions about the fraction of
all food assumed to be consumed by the RMEI from gardening or other
crops grown using contaminated water. We also are proposing that
protection of a rural-residential RMEI would be protective of the
general population (see the How Will the General Population Be
Protected? section below).
Our identification of Lathrop Wells as a potential location of the
RMEI is based upon a review of available, site-specific information. Of
course, DOE and NRC must consider other, more appropriate locations
based upon additional data which DOE or others may develop later, but
the selection of that other location must be based upon the same
considerations used for this example. For example, if DOE subsequently
determines that the direction of ground water flow is different than we
have assumed, DOE and NRC must choose the location, at the same
distance from the center of the repository footprint as the original
point of compliance, where the highest radionuclide concentrations
occur.
As stated earlier, the method of calculating the RME is to select
average values for most parameters except one or a few which are set at
their maximum, that is, high-end, values. We believe that the Lathrop
Wells location and a consumption rate of two liters per day of drinking
water from the plume of contamination represent high-end values for two
of these factors. The Commission may identify additional parameters for
which to assign high-end values in projecting the dose to the RMEI. To
the extent possible, NRC should use site-specific information for any
remaining factors. For example, NRC should use the most accurate
projections of the amount of contaminated food that would be ingested
in the future. Projections might be based upon surveys which indicate
the percentage of the total diet of Amargosa Valley residents which is
from food grown in the Amargosa Valley area.
We particularly request comment upon whether:
(1) Based upon the above criteria, there is now sufficient
information for us to adequately support a choice for the RMEI location
in the final rule or should we leave that determination to NRC in their
licensing process based upon our criteria;
(2) Another location in one of the three subareas identified
previously should be the location of the RMEI; and
(3) Lathrop Wells and an ingestion rate of two liters per day of
drinking water are appropriate high-end values for parameters to be
used to project the RME. We also request comment upon the potential
approaches and assumptions for the exposure scenario to be used for
calculating the dose incurred by the RMEI.
III.B.5. How Will the General Population be Protected?
In section 801(a)(2)(A) of the EnPA, Congress asked whether an
individual-protection standard could also protect the general
population. In response, the NAS concluded that an individual-
protection standard could provide such protection for the case of the
proposed Yucca Mountain repository. The NAS premised this conclusion
upon the condition that the public and policymakers would accept the
idea that extremely small individual radiation doses spread out over
large populations pose a risk that is negligible (NAS Report p. 57).
The NAS refers to this concept as ``negligible incremental risk'' (NAS
Report p. 59). Earlier, we described our proposed individual-protection
standard for the RMEI which would establish the highest allowable
radiation dose. This section of the notice raises another question--
should we also adopt a standard to limit the possible widespread
exposure of whole populations to extremely small individual doses?
In discussing the feasibility of protecting the general population
from releases of radionuclides from Yucca Mountain, NAS considered the
potential for the release of gaseous radionuclides. The NAS Report
explained how the release of carbon dioxide gas containing \14\ C from
the Yucca Mountain disposal system might expose a large population:
Global populations might be affected because radionuclide
releases from a repository can in theory be diffused throughout a
very large and dispersed population. In the case of Yucca Mountain,
the likely pathway leading to widely dispersed radionuclides is via
the atmosphere beginning with release of carbon dioxide gas
containing the carbon-14 (\14\ C) radioactive isotope which might
escape from the waste canisters. (NAS Report p. 7)
On page 61 of its Report, NAS estimated that the average dose to
members of the global population, based upon this scenario, to be 0.003
Sv/year (0.0003 mrem/yr) and equated that to an annual risk of
fatal cancer of 1.5 in 10 billion (1.5 x 10-10).
The NAS relied upon the recommendations of the NCRP in its report
titled ``Limitation of Exposure to Ionizing Radiation'' (NCRP Report
No. 116) to support their claim that such doses are negligibly small.
In this report, the NCRP stated that a radiation dose of less than 10
Sv (1 mrem)/yr for any source or practice would represent a
``negligible incremental dose.'' The NCRP endorsed the assumption that
there is some radiation risk for every radiation exposure. Further,
they explained that there are great uncertainties in trying to
understand the meaning of radiation effects upon populations,
especially when these effects are calculated by summing extremely small
individual doses among huge populations. Agreeing with this
[[Page 46991]]
concept, the NAS preferred to use risk instead of dose. The NAS then
estimated the risk level associated with the NCRP's NID level of 10
Sv/yr and adopted the term ``negligible incremental risk.''
The NAS then proposed this NIR level as the starting point for a
process to establish a risk level for individuals that would be
``negligible.''
For different reasons, we provisionally agree with the NAS that an
individual-risk standard can adequately protect the general population
near Yucca Mountain. Our agreement is based upon the particular
characteristics of the Yucca Mountain site. We emphasize that our view
relates to the specific circumstances associated only with Yucca
Mountain. We are not proposing to adopt either an NID or NIR level. We
are concerned that such an approach is not appropriate in all
circumstances. Again, our proposed determination that an individual-
risk standard is adequate to protect both the local and general
population is based upon considerations unique to the Yucca Mountain
site--it is not a general policy judgment by us upon other uses of the
concept of NID or NIR.
We considered the NAS suggestion to adopt a general NIR level but
have not done so because of reservations regarding the reasoning and
analysis employed by NAS. As noted above, NAS referred to the NID level
of 10 Sv (1 mrem)/yr per source or practice recommended by the
NCRP. The International Atomic Energy Agency (IAEA) has made similar
recommendations regarding exemptions in its Safety Series No. 89,
``Principles for the Exemption of Radiation Sources and Practices from
Regulatory Control.'' The IAEA has recommended that individual doses
not exceed 10 Sv (1 mrem)/yr from each exempt practice. The
IAEA's recommendations relate to criteria for exempting whole sources
or practices, such as waste disposal or recycling generally, not
whether radiation doses from a portion of a given practice, such as the
release of gases from a specific geologic repository, may be considered
negligible. Finally, the IAEA's recommendations intend their exemption
to be for sources and practices ``which are inherently safe.'' It is
not clear that the low individual doses or risks projected from gaseous
releases from the Yucca Mountain repository should be considered on
their own as a ``source'' or ``practice'' or that such a source or
practice should be considered inherently safe. Also, we believe it to
be inappropriate to not calculate a radiation dose merely because the
dose rate from a particular source is small.
Further, we are not sure it is appropriate to apply the NIR concept
to consideration of population dose. A recent NCRP report questions the
application of the negligible incremental dose (NID) concept to
consideration of population doses. According to NCRP Report No. 121:
``A concept such as the NID (Negligible Incremental Dose) provides a
legitimate lower limit below which action to further reduce individual
dose is unwarranted, but it is not necessarily a legitimate cut-off
dose level for the calculation of collective dose. Collective dose
addresses societal risk while the NID and related concepts address
individual risk.'' Based upon this, we think it would be inappropriate
to use the negligible incremental dose or risk concept to evaluate
whether an individual-protection standard adequately protects the
general population.
Although we do not advocate use of the NID concept, we acknowledge
that the extremely low levels of individual risk and dose cited by NAS
as being associated with the release of \14\ C from Yucca Mountain are
many orders of magnitude below the levels at which we have regulated in
other circumstances. For example, we used the following policies under
the pre-1990 Clean Air Act (CAA) hazardous air pollution control
program: (1) provide public health protection for the greatest number
of persons possible based upon a lifetime (70 years) risk level no
higher than approximately 1 x 10-6 for an individual, and
(2) limit the maximum, individual-lifetime, estimated risk to no higher
than 1 in 10,000 (1 x 10-4) (54 FR 51654, 51655, December
15, 1989). Even though we adopted this approach in a different policy
context, it provides insight into how we have dealt with similar risk-
management issues in a regulatory context. In 1990, Congress amended
the CAA to require us to develop technology-based standards to reduce
emissions. At the same time, Congress authorized us to delete
categories of sources from regulation if no source in that category
could cause a lifetime risk of cancer exceeding 1 x 10-6 for
the most-exposed individual in the population. The risk over an
individual's lifetime from exposure to gaseous \14\ C released from the
Yucca Mountain repository, as estimated by NAS, would be about 100
times lower than 10-6. This particular risk level is
extremely low and well below the risk level that we generally regulate.
The disposal standards in 40 CFR part 191 include release limits
(or containment requirements) to protect populations and an individual-
protection standard. We rejected adopting only an individual-protection
standard in those standards because of a concern that an individual-
dose limitation alone might encourage selection of disposal sites that
relied upon dilution of radionuclides at the expense of increased
overall population exposures. Specifically, we were concerned that, in
the absence of release limits, ``disposal sites near bodies of surface
water or large sources of ground water might be preferred--which the
Agency believes is an inappropriate policy that would usually increase
overall population exposures'' (50 FR 38066, 38078, September 19,
1985). For example, it is possible to have a site that could meet the
150 Sv (15 mrem)-CEDE/yr individual-protection standard while
still having large numbers of people being exposed to radiation levels
just below the standard. This scenario could result in significant
numbers of calculated health effects for each generation exposed and
very large numbers of calculated health effects over the regulatory
period. We believe that the policy embodied in the generic 40 CFR part
191 disposal standards is sound. The provisions in 40 CFR part 191,
which could apply to a variety of potential disposal sites, should
discourage reliance upon dilution of radionuclides in the general
environment as a disposal method.
However, the potential for large-scale dilution of radionuclides,
through ground water and into surface water, as modeled in the
supporting analyses for 40 CFR part 191, does not exist at Yucca
Mountain, thereby minimizing the need for the kind of population-
protection requirements found in 40 CFR part 191. Rather, DOE plans to
locate the Yucca Mountain repository in an unsaturated rock formation
with limited amounts of infiltrating water passing through it and into
the underlying tuff aquifer. (``Unsaturated'' means that the rock could
absorb more water than it is holding.) That aquifer is, in turn, within
a ground water system which discharges into arid areas having high
evaporation rates and very little surface water. In other words, we
believe that the characteristics of the saturated zone under Yucca
Mountain are such that dilution from other sources will be limited and
the aquifer does not discharge into any large bodies of surface water.
Therefore, our basis for inclusion of a population-protection
requirement in 40 CFR part 191 does not appear to apply to the
development of site-specific standards for Yucca Mountain.
[[Page 46992]]
In addition, we based the release limits in 40 CFR part 191 partly
upon technology and partly upon risk levels which we believed to be
acceptably small. The technology basis for the release limits was based
upon assessments of repository performance of several generic disposal
systems, including one located in tuff. In finalizing 40 CFR part 191,
we stated:
[T]he rule cannot be interpreted as setting precedents for
``acceptable risk'' levels to future generations that should not be
exceeded regardless of the circumstances. Instead, because of a
number of unique circumstances, the Agency has been able to develop
standards for the management and disposal of these wastes that are
both reasonably achievable . . . and that limit risks to levels that
the Agency believes are clearly acceptably small. (50 FR 38066,
38070, September 19, 1985)
We developed these standards during the siting process mandated by the
NWPA in the 1980s. The inclusion of release limits pointed to the
importance of considering population doses during site selection. We
established the standards at a level that appeared to be reasonably
achievable for several types of rocks or geologic media and which would
keep risks to future populations acceptably small. The assessments we
performed in support of these generally applicable standards, however,
did not include a gaseous-release pathway similar to that described by
NAS for \14\ C because no one foresaw the potential importance of that
pathway at that time. In fact, according to the generic analyses we
performed in support of 40 CFR part 191, the unsaturated site in tuff
was generally more protective, in terms of limiting total releases,
than the other geologic media we evaluated.
For these reasons, we do not believe that these generic analyses
and conclusions supporting the development of release limits in 40 CFR
part 191 are appropriate for judging the need for population-risk
limits or the acceptability of population risks from releases from
wastes in the Yucca Mountain disposal system. We are proposing to find
that the individual-protection standard is sufficient to protect public
health based upon the unique characteristics of the area around the
Yucca Mountain site.
In summary, we are proposing to adopt an individual-protection
standard for Yucca Mountain that will limit the annual radiation dose
incurred by the RMEI to 150 Sv (15 mrem) CEDE. At the same
time, we are not proposing to adopt a separate limit on radiation
releases for the purpose of protecting the general population, but we
are recommending that collective dose be estimated and considered (see
the following paragraph). We based this decision upon several factors.
The first factor is the NAS projection of extremely small doses to
individuals resulting from air releases from Yucca Mountain. That dose
level is well below the risk corresponding to our proposed individual-
protection standard for Yucca Mountain. It is also well below the level
that we have regulated in the past through other regulations. Further,
while we decline to establish a general NIR level, we do agree with NAS
that estimating the number of health effects resulting from a 0.0003
mrem/yr dose rate, in addition to the dose rate from background
radiation, in the general population is uncertain and controversial.
The second major factor is that, based upon current and site-specific
conditions near Yucca Mountain, there is not likely to be great
dilution resulting in exposure of a large population. In addition, we
are proposing additional ground water protection standards that would
establish specific limits to protect users of ground water and ground
water as a resource. Finally, we are still proposing to require that
all of the pathways, including air and ground water, would be analyzed
by DOE and considered by NRC under the individual-protection standard.
We request comment upon this approach. Commenters who disagree with
this approach should specifically address why it is inappropriate for
the Yucca Mountain disposal system and make suggestions about how we
might reasonably address this issue.
While we are not proposing to adopt additional regulatory
requirements for collective exposures of the general population from
releases from the Yucca Mountain disposal system, we urge DOE to
examine design alternatives for the disposal system, for the purpose of
reducing potential risk to the general population, in the National
Environmental Policy Act (NEPA) process for Yucca Mountain. We received
public comments, in response to our request for comments regarding the
NAS Report, noting that DOE had already proposed, in its Notice of
Intent to prepare a NEPA-prescribed environmental impact statement
(EIS) for Yucca Mountain, to evaluate technical alternatives (60 FR
40167, August 7, 1995). In other words, DOE has previously proposed to
evaluate technical alternatives as part of its waste containment and
isolation strategy for Yucca Mountain (DOE, ``Strategy for Waste
Containment and Isolation for the Yucca Mountain Site,'' Preliminary
Review Draft, October 9, 1995). Thus, we recommend that DOE incorporate
these or similar considerations into its NEPA process to assess the
effectiveness of design alternatives to mitigate population exposures.
The following language provides context to the approach we consider
appropriate for calculating population exposure in the NEPA process. We
recommend that DOE calculate the collective dose without truncation and
with full consideration of the appropriate factors. This recommendation
is supported by a recent NCRP report upon the principles and
application of a collective dose in radiation protection (NCRP Report
No. 121). The NCRP advocated the use of collective dose for
optimization of protection and provided guidance on future exposures
from long-lived radionuclides, the situation that will likely exist at
Yucca Mountain:
The most reasonable risk assessment that can be made for such
situations is to calculate potential individual doses for a range of
scenarios in order to: (1) evaluate protective measures and (2) to
try to place some boundaries on estimates of future individual
risks. For the few very long-lived radionuclides that are
metabolically regulated in the body and more or less uniformly
distributed within the biosphere (e.g., \14\ C and \129\ I), future
average individual doses may be estimated from total quantities in
the environment. . . . (NCRP Report No. 121, pp. 57-58)
III.B.6. What Should Be Assumed About the Future Biosphere?
We propose to require DOE and NRC to use the biosphere assumptions
described in this section in all analyses of repository performance,
including the performance assessment for determining compliance with
the individual-protection standard, the assessment for determining
compliance with the ground water standards, and the human-intrusion
analysis. Projecting biosphere conditions necessitates making
assumptions, many of which are very uncertain and may not be boundable.
The NAS stated:
In view of the almost unlimited possible future states of
society and of the significance of these states to future risk and
dose, . . . we have recommended that a particular set of assumptions
be used about the biosphere (including, for example, how and where
people get their food and water) for compliance calculations . . .
we recommend the use of assumptions that reflect current
technologies and living patterns. (NAS Report p. 122)
The NAS also stated:
. . . unlike our conclusion about the earth science and geologic
. . . factors described [earlier], we believe that it is not
possible to
[[Page 46993]]
predict on the basis of scientific analyses the societal factors
that must be specified in a far-future exposure scenario. . . . Any
particular scenario about the future of human society near Yucca
Mountain . . . should not be interpreted as reflecting conditions
that eventually will occur. Although we recognize the burden on
regulators to avoid regulations that are arbitrary, we know of no
scientific method for identifying these [exposure] scenarios. (NAS
Report p. 96)
We agree with the NAS on this point and propose that speculation
concerning some characteristics of the future should not be the focus
of the compliance determination process. Instead, we believe that it
would be more appropriate to assume that those characteristics will be
the same as they are today. No one should interpret this assumption so
literally that only current residences and lifestyles of individuals
living in the area on the day of promulgation of this part can be
considered. Rather, we intend that, based upon current knowledge, DOE
and NRC may use those characteristics in combinations in a cautious,
but reasonable, manner as input into the Yucca Mountain performance
projections. Future characteristics which NRC and DOE may assume to be
the same as they are today include the level of human knowledge and
technical capability (including medical), human physiology and
nutritional needs, general lifestyles of the population, and potential
pathways through the biosphere leading to radiation exposure of humans.
Also, we propose that it is inappropriate to speculate upon extreme
changes in the number of residents, but that consideration should be
given to changes in population near the location of the RMEI.
In concert with the NAS Report, we also propose not to allow the
assumption that conditions in the future will be the same as present
conditions for geologic, hydrologic, and climatic conditions. We are
proposing this because we believe the parameter values in the
performance assessment which relate to these conditions can be
reasonably bounded. We propose to require that these conditions be
varied within reasonable bounds over the compliance period and request
comment upon this proposed approach.
III.B.7. How Far Into the Future Is It Reasonable To Project Disposal
System Performance?
The NAS recommended that the time over which compliance should be
assessed, that is, the compliance period, should be ``the time when the
greatest risk occurs, within the limits imposed by long-term stability
of the geologic environment'' (NAS Report p. 7). The NAS stated that it
based this recommendation upon technical, not policy, considerations.
However, we believe the selection of the compliance period necessarily
involves both technical and policy considerations. For example, NAS
stated that we might choose to establish similar policies for managing
risks ``from disposal of both long-lived hazardous nonradioactive
materials and radioactive materials'' (NAS Report p. 56). As NAS
recognized, we must consider, in this rulemaking, both the technical
and policy issues associated with establishing the appropriate
compliance period for the performance assessment of the Yucca Mountain
disposal system.
We request public comment upon two alternatives for the compliance
period for the individual-protection standard. One alternative is to
adopt a compliance period that is the time to peak dose within the
period of geologic stability. The second alternative is to adopt a time
period during which the repository must meet the disposal standards.
For the reasons described below, we believe that the second alternative
is preferable. Therefore, we are proposing that the peak dose within
10,000 years after disposal must comply with the individual-protection
standard. Also, the EPA-preferred approach would require calculation of
the peak dose within the period of geologic stability. It does not,
however, apply a quantitative limit after 10,000 years. The intent of
examining disposal system performance after 10,000 years is to estimate
the long-term performance of the disposal system to see if dramatic
changes in the performance of the disposal system could be anticipated.
We would require DOE to include the results and bases of the additional
analysis in the EIS for Yucca Mountain as an indicator of the future
performance of the disposal system. This analysis also would serve as
another source of information for decisionmakers in making both design
and licensing decisions. However, NRC is not to use the additional
analysis in determining compliance with proposed Sec. 197.20.
The principal tool used to assess compliance with the individual-
protection standard is a quantitative performance assessment. This
method relies upon modeling of the potential processes and events
leading to releases of radionuclides from the disposal system,
subsequent radionuclide transport, and consequences upon health. To
consider compliance for any length of time, several facets of knowledge
and technical capability are necessary. First, the scientific
understanding of the relevant, potential processes and events leading
to releases must be sufficient to allow a quantitative estimate of
projected repository performance. Second, adequate analytical methods
and numerical tools must exist to incorporate this understanding into a
quantitative assessment of compliance. Third, scientific understanding,
data, and analytical methods must be adequately developed to allow
evaluation of performance with sufficient robustness to judge
compliance with reasonable expectation over the regulatory period.
Finally, the analyses must be able to produce estimated results in a
form capable of comparison with the standards.
The NAS evaluated these requirements for Yucca Mountain and
concluded that those aspects of disposal system and waste behavior that
depend upon physical and geologic properties can be estimated within
reasonable limits of uncertainty. Also, NAS believed that these
properties and processes are sufficiently understood and boundable over
the long periods at issue to make such calculations possible and
meaningful. The NAS acknowledged that these factors cannot be
calculated precisely, but concluded that there is a substantial
scientific basis for making such calculations. The NAS concluded that
by taking uncertainties and natural variabilities into account, it
would be possible to estimate, for example, the concentration of
radionuclides in ground water at different locations and the times of
gaseous releases. Second, NAS concluded that the mathematical and
numerical tools necessary to evaluate repository performance are
available or could be developed as part of the standard-setting or
compliance-determination processes. Third, NAS concluded that: ``So
long as the geologic regime remains relatively stable, it should be
possible to assess the maximum risks with reasonable assurance'' (NAS
Report p. 69). The NAS used the term ``geologic stability'' to describe
the situation where geologic processes, such as earthquakes and
erosion, that could affect the performance assessment of the Yucca
Mountain site are active (not static) and are expected to occur. Based
upon the use of the terms ``stable'' and ``boundable'' throughout the
NAS Report, one can infer that NAS applied the term ``geologic
stability'' or ``stable'' to the situation where the rate of processes
and numeric range of individual physical properties could be bounded
with reasonable certainty. The
[[Page 46994]]
subsequent use of the term ``stable'' will not imply static conditions
or processes. Rather, it will describe the properties and processes
that can be bounded. Finally, NAS found that the established procedures
of risk analysis should enable the results of each performance
simulation of the disposal system to be combined into a single estimate
for comparison with the standard.
Time to peak dose within the period of geologic stability. The NAS
recommended that the compliance period for the Yucca Mountain disposal
system be the time to peak risk within the long-term stability of the
geologic environment. Since the time to peak risk is generally the time
to peak dose, subsequent discussion of the NAS findings will refer to
the time to peak dose. The ``peak dose'' is the mean value of the range
of the highest potential annual doses, as determined by the performance
assessment, incurred by the RMEI within the compliance period. The NAS
based its recommendation to use the time to peak dose upon its review
of:
(1) The technical analyses supporting 40 CFR part 191;
(2) Information derived from current performance assessments of the
Yucca Mountain disposal system; and (3) The geologic and physical
processes that could affect the release and transport of radionuclides
to the biosphere.
The 40 CFR part 191 standards contain a compliance period of 10,000
years. There were three reasons that we set this time frame:
(1) After that time, there is concern that the uncertainties in
compliance assessment become unacceptably large (50 FR 38066, 38076,
September 19, 1985);
(2) There are likely to be no exceptionally large geologic changes
during that time (47 FR 58196, 58199, December 29, 1982); and
(3) Using time frames of less than 10,000 years does not allow for
valid comparisons among potential sites. For example, for 1,000 years,
all of the generic sites analyzed appeared to contain the waste
approximately equally because of long ground water travel times at
well-selected sites (47 FR 58196, 58199, December 29, 1982).
One purpose of geologic disposal is to provide long-term barriers
to the movement of radionuclides into the biosphere (NAS Report p. 19).
As described earlier, the Department plans to locate the Yucca Mountain
repository in tuff about 300 meters above the local water table. When
nongaseous radionuclides are released from the waste packages, they
most likely will be transported by rain water that moves from the
surface both horizontally within individual tuff layers and vertically
downward, through fractures in the tuff layers, toward the underlying
aquifer. Once the radionuclides reach the aquifer, they will be carried
away from the repository in the direction of ground water flow. The
most probable route for exposing humans to radiation resulting from
releases from the Yucca Mountain disposal system is via withdrawal of
contaminated water for local use. In the case of Yucca Mountain, DOE
estimates that most radionuclides would not reach currently populated
areas within 10,000 years (see the BID).
While this finding alone seems to indicate that the compliance
period for Yucca Mountain should be longer than 10,000 years to be
protective, NAS concluded that the need to consider the exposures when
they are calculated to occur must be weighed against the problem of
cumulative uncertainty. As noted above, exposures could occur over
tens-to hundreds-of-thousands of years. However, as the compliance
period is extended to such lengths, uncertainty increases and the
resulting projected doses are increasingly meaningless from a policy
perspective. The NAS stated that there are significant uncertainties in
a performance assessment and that the overall uncertainty increases
with time. Even so, NAS found that, ``. . . there is no scientific
basis for limiting the time period of the individual-risk standard to
10,000 years or any other value'' (NAS Report p. 55). Estimates by NRC
and DOE related to the Yucca Mountain disposal system have indicated
wide differences in estimates of the time that radionuclides may take
to reach the biosphere and cause the peak dose to occur (see the BID).
However, while the results have indicated that the time to peak dose
may vary anywhere from a few tens-of-thousands to hundreds-of-thousands
of years, the estimated values of the peak doses, while separated in
time, are similar in magnitude (see the BID). These estimates differ
because the analysts used different assumptions and conceptual models
for flow and transport of radionuclides through the Yucca Mountain
unsaturated zone. We believe that this situation will exist
independently of the compliance-period issue. The NAS also stated that
data and analyses of some of the factors that are uncertain at one time
might be more certain at a later time. For example, there is
uncertainty as to how many waste packages might fail in the near term.
However, at some later time in the distant future, the uncertainty is
very small because when enough time has passed, all of the packages
will fail (NAS Report p. 72). Also, NAS stated that many of the
uncertainties in parameter values describing the geologic system are
not due to the length of time but rather to the difficulty in
estimating values of site characteristics which vary across the site.
We believe that these difficulties are always present and that analysts
must consider them in the compliance assessment for any period chosen
(NAS Report p.72).
As NAS noted, evaluating compliance with the 40 CFR part 197
standards depends upon being able to:
(1) Understand and model radionuclide-transport processes and the
processes and events that might lead to transport;
(2) Use appropriate analytical methods to determine the levels of
human exposure;
(3) Quantify or bound the probabilities of the processes and
events, including the related uncertainties; and
(4) State the results in a form capable of being compared with the
standards.
The NAS reviewed how radionuclides might enter the biosphere in
order to determine the feasibility of evaluating them in a compliance
assessment. In addition, to determine whether the modifying processes
should also be evaluated in a compliance assessment, NAS analyzed the
geologic and physical processes that could modify the properties of the
contaminant-containing media and processes by which radionuclides are
moved.
The radionuclide-transport processes evaluated by NAS included:
(1) Release from the waste form;
(2) Transport from canisters into the near-field (near the waste
canisters) unsaturated zone;
(3) Gas-phase transport from the unsaturated zone into the
atmosphere around Yucca Mountain;
(4) Atmospheric circulation leading to dispersal of gaseous
radionuclides in the global atmosphere;
(5) Aqueous-phase transport from the unsaturated zone to the water
table; and
(6) Transport of radionuclides through the saturated zone beneath
the repository to other locations from which water may be extracted by
humans or ultimately reach the surface at a discharge area (NAS Report
pp. 85-90).
The NAS concluded that these processes are ``sufficiently
quantifiable and the uncertainties are sufficiently boundable that they
can be included in performance assessments that extend over time frames
corresponding to those over which the geologic system is relatively
stable or varies in a boundable
[[Page 46995]]
manner'' (NAS Report p. 85). The NAS concluded that the ``geologic
record suggests that this time frame is on the order of about one
million years'' (NAS Report pp. 9 and 85). Likewise, NAS concluded that
the probabilities and consequences of these processes and events that
could modify the way in which radionuclides are moved in the vicinity
of Yucca Mountain, including climate change, seismic activity, and
volcanic eruptions, ``are sufficiently boundable so that these factors
can be included in performance assessments that extend over periods on
the order of about one million years'' (NAS Report p. 91).
Thus, NAS recommended, on a technical basis, that the compliance
period for the protection of the individual should extend to the time
of the peak dose during the period in which geologic processes are
stable or boundable. This would require determining compliance and
licensing the disposal system on the basis of projections of
performance over tens- to hundreds-of-thousands of years into the
future. We believe that such an approach is not practical for Yucca
Mountain.
As noted earlier, NAS concluded that ``there is no scientific basis
for limiting the time period of the individual-risk standard to 10,000
years or any other value.'' Nevertheless, there is still considerable
uncertainty as to whether current modeling capability allows
development and validation of computer models that will provide
sufficiently meaningful projections over a time frame up to tens-of-
thousands to hundreds-of-thousands of years. Simply because such models
can provide projections for those time periods does not mean those
projections are either meaningful for decisionmakers or accurate.
Furthermore, we are not aware of a policy basis that we could use to
determine the level of proof or confidence necessary to determine
compliance based upon projections of hundreds-of-thousands of years
into the future. While NAS indicated that analyses of the performance
of the Yucca Mountain disposal system dealing with the far future can
be bounded, a large and cumulative amount of uncertainty is associated
with those numerical projections. Setting a strict numerical standard
at a level of risk acceptable today for the period of geologic
stability would tend to ignore this cumulative uncertainty. For
example, if the performance assessment indicates that the peak dose
occurs 600,000 years in the future at an annual CEDE that has an
uncertainty range of 0.1 mrem to 10,000 mrem, does that indicate that
the disposal system is safe or unsafe and should NRC license it or not?
In light of the cumulative uncertainty for calculations over an
extremely long time, it may be more appropriate to consider, in a
regulatory decisionmaking, assessments of disposal system performance
over such time in a qualitative manner. We request comments upon the
reasonableness of adopting the NAS-recommended compliance period or
some other approach in lieu of the 10,000-year compliance period which
we favor and describe below. We also seek comment upon whether the NAS-
recommended compliance period can be implemented in a reasonable manner
and how that could be done.
A 10,000-year compliance period (proposed Sec. 197.20). As noted
earlier, the selection of the compliance period for the individual-
protection standard involves both technical and policy considerations.
It is our responsibility to weigh both during this rulemaking. In
addition to the technical guidance provided in the NAS Report, we have
considered several policy and technical factors that NAS did not fully
address.
First, as suggested by NAS, we evaluated the policies for managing
risks from the disposal of both long-lived, hazardous, nonradioactive
materials and radioactive materials. Second, we evaluated consistency
with both 40 CFR part 191 and the issue of consistent time periods for
the protection of ground water resources and public health. Third, we
considered the issue of uncertainty in predicting dose over the very
long periods contemplated in the alternative of peak dose within the
period of geologic stability. Finally, we reviewed the feasibility of
implementing the alternative of peak risk within the period of geologic
stability, as recommended by NAS. As a result of these considerations,
we are proposing a 10,000-year compliance period with a quantitative
limit and a requirement to calculate the peak dose, using performance
assessments, if the peak dose occurs after 10,000 years. Under our
proposal, the performance assessment results for the post-10,000-year
period must be made part of the public record by DOE including it in
the EIS for Yucca Mountain.
In its discussion of the policy issues associated with the
selection of the time period for compliance, NAS suggested that we
might choose to establish consistent risk-management policies for long-
lived, hazardous, nonradioactive materials and radioactive materials.
We previously addressed the 10,000-year compliance period in the
regulation of hazardous waste subject to land-disposal restrictions.
Land disposal, as defined in 40 CFR 268.2(c), includes, but is not
limited to, any placement of hazardous waste in land-based units such
as landfills, surface impoundments, and injection wells. Facilities may
seek an exemption by demonstrating that there will be no migration of
hazardous constituents from the disposal unit for as long as the waste
remains hazardous (40 CFR 268.6). We have interpreted the phrase ``for
as long as the waste remains hazardous'' to mean that the no-migration
demonstration shows that hazardous constituents will not exceed
acceptable concentration levels for as long as the constituents retain
the potential to harm human health and the environment. This period may
include not only the operating phase of the facility, but also what may
be an extensive period after facility closure. With respect to
injection wells, we have specifically required a demonstration that the
injected fluid will not migrate within 10,000 years (40 CFR 148.20(a)).
We chose the 10,000-year performance period referenced in our guidance
upon no-migration petitions, in part, to be equal to time periods cited
in draft or final DOE, NRC, and EPA regulations (10 CFR 960, 10 CFR 60,
or 40 CFR 191, respectively) governing siting, licensing, and releases
from HLW disposal systems. With respect to other land-based units
regulated under the Resource Conservation and Recovery Act (RCRA)
hazardous-waste regulations, we concluded that the compliance period is
specific to the waste and site under consideration. For example, for
the WIPP no-migration petition, we found that ``it is not particularly
useful to extend this model beyond 10,000 years into the future.* * *
[However, t]he agency does believe * * * that modeling over a 10,000-
year period provides a useful tool in assessing the long-term stability
of the repository and the potential for migration of hazardous
constituents'' (55 FR 13068, 13073, April 6, 1990).
Second, the individual-protection requirements in 40 CFR part 191
(58 FR 66398, 66414, December 20, 1993) have a compliance period of
10,000 years. The part 191 standards apply to the same types of waste
and type of disposal system as proposed for Yucca Mountain. However, as
we explained in the What Led up to Today's Action? section earlier in
this notice, by statute the part 191 requirements do not apply to Yucca
Mountain. If we finally adopt the 10,000-year compliance period, it
would require the same compliance period for
[[Page 46996]]
the Yucca Mountain disposal system as for other disposal systems
subject to 40 CFR part 191. Such a requirement would be consistent with
40 CFR part 191, which we deem appropriate since both sets of standards
apply to the same types of waste.
Third, we are concerned that there might be large uncertainty in
projecting human exposure due to releases from the repository over
extremely long periods. We agree with the NAS conclusion that it is
possible to evaluate the performance of the Yucca Mountain disposal
system and the lithosphere within certain bounds for relatively long
periods. However, we believe that NAS might not have fully addressed
two aspects of uncertainty.
One of the aspects of uncertainty relates to the impact of long-
term natural changes in climate and its effect upon choosing an
appropriate RMEI. For extremely long periods, major changes in the
global climate, for example, a transition to a glacial climate, could
occur (see the BID). However, over the next 10,000 years, the biosphere
in the Yucca Mountain area will probably remain, in general, similar to
present-day conditions due to the rain-shadow effect of the Sierra
Nevada Mountains, which lie to the west of Yucca Mountain (see the
BID). For the longer periods contemplated for the alternative of time
to peak dose, the global climate regime is virtually certain to pass
through several glacial-interglacial cycles, with the majority of time
spent in the glacial state (NAS Report p. 91). These longer periods
would require the specification of exposure scenarios that would not be
based upon current knowledge or cautious, but reasonable, assumptions,
but rather upon potentially arbitrary assumptions. The NAS indicated
that it knew of no scientific basis for identifying such scenarios (NAS
Report p. 96). It is for these reasons that such extremely long-term
calculations are useful only as indicators, rather than accurate
predictors, of the long-term performance of the Yucca Mountain disposal
system (IAEA TECDOC-767, 1994).
The other aspect of uncertainty concerns the range of possible
biosphere conditions and human behavior. It is necessary to make
certain assumptions regarding the biosphere, even for the 10,000-year
alternative, because the period of 10,000 years represents a very long
compliance period for current-day assessments to project performance.
For example, it is twice as long as recorded human history (see the
What Should Be Assumed About the Future Biosphere? section earlier in
this notice). For periods approaching the 1,000,000 years that NAS
contemplated under the peak-dose alternative, even human evolutionary
changes become possible. Thus, reliable modeling of human exposure may
be untenable and regulation to the time of peak dose within the period
of geologic stability could become arbitrary.
Fourth, many international geologic disposal programs use a 10,000-
year regulatory compliance period as a requirement.
Finally, an additional complication associated with the time to
peak dose within the period of geologic stability is that it could lead
to a period of regulation that has never been implemented in a national
or international radiation regulatory program. Focusing upon a 10,000-
year compliance period forces more emphasis upon those features over
which man can exert some control, such as repository design and
engineered barriers. It is unlikely that over much longer time frames
that any engineered barrier will be effective. Those features, the
geologic barriers, and their interactions define the waste isolation
capability of the disposal system. By focusing upon an analysis of the
features that man can influence or dictate at the site, it may be
possible to influence the timing and magnitude of the peak dose, even
over times longer than 10,000 years.
Thus, we request comment upon our proposal of a 10,000-year
compliance period to judge compliance with proposed Sec. 197.20 and our
proposal to require consideration of the peak dose, using performance
assessments, if it occurs after 10,000 years. Again, after 10,000
years, we would not require the calculated level to comply with a
specific numerical standard but we would require its consideration as
an indicator of longer-term performance and be included in the EIS for
Yucca Mountain.
We also request comment upon the appropriateness of a 10,000-year
compliance period for the individual-protection standard. Commenters
should address the issues that we should consider in determining the
appropriate compliance period. We also specifically request comments
upon whether the NAS' recommendation of the time to peak dose within
the period of geologic stability can be implemented reasonably and, if
so, how that could be done.
III.C. What Are the Requirements for Performance Assessments and
Determinations of Compliance? (Proposed Secs. 197.20, 197.25, and
197.35)
III.C.1. What Limits Are there on Factors Included in the Performance
Assessments?
The Commission is responsible for deciding whether or not to
license the Yucca Mountain disposal system. It must make that decision
based largely upon whether DOE has demonstrated compliance with our
standards in 40 CFR part 197. Under the proposed 40 CFR part 197, the
quantitative analysis underlying that decision will be a performance
assessment (the proposed definition of ``performance assessment'' is in
Sec. 197.12). We are proposing that performance assessments be a
requirement of licensing. The EnPA requires that the Commission modify
its technical requirements for licensing the disposal system to be
consistent with our final 40 CFR part 197 standards. Therefore, our
standards would require DOE to complete a performance assessment prior
to applying for a license and would require NRC to determine, taking
into consideration that performance assessment, whether the disposal
system's projected performance complies with Sec. 197.20.
We also are proposing, consistent with the performance assessment
requirements in 40 CFR part 191:
(1) To exclude from performance assessments those natural processes
and events whose likelihood of occurrence is so small that they are
very unlikely;
(2) That such performance assessments need not include categories
of processes or events that DOE and NRC estimate to have less than a 1
in 10,000 (1 x 10-4) chance of occurring during the 10,000
years after disposal. Probabilities below this level are associated
with events such as the appearance of new volcanoes outside of known
areas of volcanic activity or a cataclysmic meteor impact in the area
of the repository. We believe there is little or no benefit to public
health or the environment from trying to regulate the effects of such
very unlikely events; and
(3) That the performance assessment need not evaluate, in detail,
the releases from processes, events, and sequences of processes and
events estimated to have a likelihood of occurrence greater than 1 x
10-4 of occurring during the 10,000 years following
disposal, if there is a reasonable expectation that the time to, or the
magnitude of, the peak dose would not be changed significantly by such
omissions. As necessary, the Commission may provide specific
[[Page 46997]]
guidance upon scenario selection and characterization to assure that
processes or events are not excluded inappropriately.
A related issue upon which we request comment is if there is a
period of the geologic record which we should require DOE and NRC to
use to calculate the probability of processes and events occurring. The
probability of a geologic event, such as an earthquake, occurring in
the future typically comes from evidence of previous events which is
preserved in, and can be dated by using, the geologic record. We
believe that the geologic record is best preserved in the relatively
recent past.
We are also proposing to require that DOE and NRC use quantitative
assessments to determine compliance with the human-intrusion and ground
water protection standards (see the What Is the Standard for Human
Intrusion? and How Will Ground Water Be Protected? Sections later in
this notice). The human-intrusion analysis would require a separate
assessment of the effects of human intrusion upon the resilience of the
Yucca Mountain disposal system. Following the recommendation of NAS, we
intend the analysis to be an assessment of the disposal system's
isolation capability following a single, stylized, human intrusion. The
analysis required to determine compliance with the ground water
protection standards applies only to undisturbed performance.
We are proposing to allow the exclusion of unlikely natural events
from both the ground water and human-intrusion assessments. The
approach for the ground water protection requirements is consistent
with subpart C of 40 CFR part 191, ``Environmental Standards for
Ground-Water Protection'' while the approach for the human-intrusion
assessment is consistent with the NAS recommendation (see the What Is
the Standard for Human Intrusion? section later in this notice). We
request public comment upon whether this approach is appropriate for
Yucca Mountain.
III.C.2. Is Expert Opinion Allowed?
The quantitative requirements in proposed subpart B of part 197
require:
(1) Evaluation of processes, events, and sequences of processes and
events leading to radionuclide releases from the disposal system;
(2) Estimation of the resulting doses or radionuclide
concentrations; and
(3) Estimation of the likelihood of the resulting doses or
radionuclide concentrations.
The likelihood of the processes, events, and sequences of processes
and events occurring should be estimated by DOE and NRC based upon
current scientific knowledge of previous occurrences. However, it is
likely that there will be processes, events, and sequences of processes
and events which have not occurred or occurred too infrequently to be
statistically significant. This situation will require the use of
expert opinion, for example, scientific and engineering expertise, to
arrive at cautious, but reasonable, estimates of the probability of
future occurrence. Also, there likely will be many other areas where
DOE could use expert opinion, for example, when there are multiple
models applicable to the performance assessment or human-intrusion
analysis, or significant uncertainties in the variation of parameter
values.
There are two commonly used methods for the gathering of expert
opinion, namely, expert judgment and expert elicitation. Expert
judgment is typically obtained informally from one or more individuals
and is noted by the person(s) seeking the judgment in documentation
used to support the activity. In contrast, expert elicitation is a
formal, structured, and thoroughly documented process. Whether it is
appropriate to conduct an expert elicitation depends upon the issue
under consideration.
We have considered setting guidelines for the use of expert
elicitation. The type of guidelines we considered could include one or
all of the following requirements when expert elicitation is used: (1)
the Commission needs to consider the source and use of the information
so gathered; (2) we would expect the Commission to assure that, to the
extent possible, experts with both expertise appropriate for the
subject matter and independence from DOE will be on the expert
elicitation panel consulted to judge the validity and adequacy of the
model(s) or value(s) for use in a compliance assessment; and (3) when
DOE presents information to the expert elicitation panel, it should do
so in a public meeting, and qualified experts, such as representatives
of the State, should be given an opportunity to present information.
If we were to set any requirement, we would have to consider
whether NRC may allow DOE to use expert elicitations, which did not
follow these rules but were completed prior to the effective date of
part 197, for the purpose of determining compliance with the provisions
of part 197. We believe that it would probably be an unnecessary use of
time and resources to require such work to be repeated or not be used
if the Commission judges them to be acceptable.
We request comment upon whether it is appropriate for us to set
guidelines for the use of expert opinion in this standard and, if so,
what those guidelines should be.
III.C.3. What Level of Expectation Is Required for NRC To Determine
Compliance?
While the provisions in this rule establish minimum requirements
for implementation of the disposal standards, NRC may establish
requirements that are more stringent. As mentioned in the previous
section, we are proposing the concept of ``reasonable expectation'' to
reflect our intent regarding the level of ``proof'' necessary for NRC
to determine whether the projected performance of the Yucca Mountain
disposal system complies with the standards (see proposed Secs. 197.20,
197.25, and 197.35). We intend for this term to convey our position and
intent that unequivocal numerical proof of compliance is neither
necessary nor likely to be obtainable. The NRC has used a similar
qualitative test, ``reasonable assurance,'' for many years in its
regulations. However, the NRC regulations are focused upon engineered
systems with relatively short lifetimes, for example, nuclear power
reactors. We believe that for very long-term projections, involving the
interaction of natural systems with the engineered system and the
uncertainties associated with the long time periods involved, a
different approach may be more appropriate.
Therefore, we are proposing to require that the test of disposal
system compliance be a ``reasonable expectation'' that the standards
will be met. In carrying out performance assessments under a
``reasonable expectation'' approach, all parameters that significantly
affect performance would be identified and included in the assessments.
The distribution of values for these parameters would be made to the
limits of confidence possible for the expected conditions in the
natural and engineered barriers and the inherent uncertainties involved
in estimating those values. Selecting parameter values for quantitative
performance assessments would focus upon the full range of defensible
and reasonable parameter distributions rather than focusing only upon
the tails of the distributions as is more commonly done under the
``reasonable assurance'' approach. The ``reasonable expectation''
approach also would not exclude important parameters from the
assessments because they are difficult to
[[Page 46998]]
quantify to a high degree of confidence. Some parameters, such as
corrosion rates for metal container components, may be quantified with
a high degree of accuracy and precision. Others, such as the amount of
water entering a waste emplacement drift and dripping onto a waste
package, cannot be quantified with a high degree of accuracy and
precision, but are very important to a realistic assessment of
performance. Overestimating or underestimating the values of
parameters, or ignoring the positive effects upon performance for other
processes and parameters because they cannot be precisely estimated,
would essentially result in the performance assessments actually being
analyses of extreme performance scenarios. These extreme assessments
have a high probability of being unrealistic or of such low probability
that they would not represent the range of likely performance for the
disposal system.
We note that if the compliance period for the individual-protection
standard extended to the time of peak dose within the period of
geologic stability (which NAS estimated to be one million years for the
Yucca Mountain site), this test would allow for decreasing confidence
in the numerical results of the performance assessments as the
compliance period increases beyond 10,000 years. For example, this
means that the weight of evidence necessary, based upon reasonable
expectation, for a compliance period of 10,000 years would be greater
than that required for a compliance period of hundreds of thousands of
years.
III.D. Are There Qualitative Requirements To Help assure Protection?
In addition to the quantitative limits in the standards, we
considered several qualitative principles called ``assurance
requirements.'' We considered including such requirements because of
the uncertainties that exist in projecting the effects of releases from
radioactive waste over long periods. The intent for such assurance
requirements would be to add confidence that the Yucca Mountain
disposal system will achieve the level of protection proposed in the
quantitative standards. This is the same approach that we require in 40
CFR part 191 and would provide similar protection regarding Yucca
Mountain. The NAS also recognized the need for protection beyond that
provided by the disposal system when it addressed institutional
controls in its Report (NAS Report p. 11).
The assurance requirements we considered included the use of
passive and active institutional controls, monitoring, the use of
multiple barriers to isolate waste, and the ability to locate and
remove the waste after disposal. In 40 CFR part 191, there is a sixth
assurance requirement, 40 CFR 191.14(e), which we consider to be
inappropriate for the Yucca site. The purpose of that requirement is to
avoid sites where there are resources that might increase the
likelihood of human intrusion. Congress specifically designated the
Yucca Mountain site for characterization, so avoiding sites close to
resources is not relevant in this instance. Further, the EnPA
specifically dictates that we establish standards for the Yucca
Mountain site so the intent of influencing site selection does not
apply here.
We recognize that no one can accurately project the increase of
protection brought by these assurance requirements. Under 40 CFR part
191, which we promulgated under the authority of the Atomic Energy Act
of 1954, as amended (42 U.S.C. 2022), NRC is exempted from the
assurance requirements because it included equivalent provisions in 10
CFR part 60, the NRC regulations which implement 40 CFR part 191. The
EnPA requires NRC to modify its technical requirements and criteria to
be consistent with our standards for Yucca Mountain. We request comment
upon whether it is appropriate for us to establish assurance
requirements in 40 CFR part 197, and if so, what those requirements
should be.
III.E. What Is the Standard for Human Intrusion? (Proposed Sec. 197.25)
Previous standards and regulations for radioactive waste disposal,
for example, 40 CFR part 191 for SNF and HLW and 10 CFR part 61 for
LLW, included consideration of inadvertent human intrusion which could
affect the release rate from, and the resultant quantity of
radionuclides leaving, a disposal system.
In section 801(a)(2)(B) of the EnPA, Congress inquired about
whether active institutional controls could effectively stop human
intrusion into the Yucca Mountain disposal system (see Background on
and Summary of the NAS Report section earlier in this notice). In its
Report, NAS concluded that the answer to this question was ``no'' (NAS
Report p. 11). The NAS reasoned that an answer of ``yes'' would require
assumptions that active institutional controls will endure and that
future generations are willing to dedicate resources for this purpose
for a period longer than recorded human history. In support of its
opinion, NAS stated, ``that there is no scientific basis for making
projections over the long term of either the social [or]
institutional...status of future societies' (NAS Report p. 106).
It was NAS' opinion that human intrusion is plausible at Yucca
Mountain and that the standards should, therefore, include
consideration of the effects of human intrusion. In order to assess the
effects of human intrusion, one must determine the probability of its
occurrence sometime in the future and the consequences of that
intrusion. Whether it is possible to predict the probability or
frequency of human intrusion in a scientifically supportable manner was
the third and final question posed by Congress in the EnPA (section
801(a)(2)(C)). The NAS concluded ``that there is no technical basis for
predicting either the nature or the frequency of occurrence of
intrusions' and that although accurate prediction of the frequency of
human intrusion is not possible, calculations can project potential
consequences of assumed human-intrusion events (NAS Report p. 106). The
NAS thus recommended that we assume that an intrusion will occur and
that we specify an intrusion scenario for DOE and NRC to use to
evaluate the ``resilience'' of the repository. The NAS stated: ``The
key performance issue is whether repository performance would be
substantially degraded as a consequence of an inadvertent
intrusion....'' (NAS Report p. 121).
In following that recommendation, we are proposing a single-
borehole intrusion scenario based upon Yucca Mountain-specific
conditions. The intended purpose of analyzing this scenario ``...is to
examine the site-and design-related aspects of repository performance
under an assumed intrusion scenario to inform a qualitative judgment''
(NAS Report p. 111). The assessment would result in a calculated RMEI
dose arriving through the pathway created by the assumed borehole (with
no other releases included). Consistent with the NAS Report, we also
are proposing ``that the conditional risk as a result of the assumed
intrusion scenario should be no greater than the risk levels that would
be acceptable for the undisturbed-repository case'' (NAS Report p.
113). We are proposing to interpret the NAS'' term ``undisturbed'' to
mean that the Yucca Mountain disposal system is not disturbed by human
intrusion but could be disturbed by other processes or events which are
likely to occur.
We also are proposing that the human-intrusion analysis of
repository
[[Page 46999]]
performance use the same methods and RME characteristics for the
performance assessment as those required for the individual-protection
standard, with two exceptions. Those exceptions are that the human-
intrusion analysis would exclude unlikely natural events and that the
analysis would only address the releases occurring through the borehole
(see the What Are the Requirements for Performance Assessments and
Determinations of Compliance? section earlier in this notice).
Concerning intentional intrusion, NAS concluded that: ``We also
considered intentional intrusion...but concluded that it makes no
sense...to try to protect against the risks arising from the conscious
activities of future human societies'' (NAS Report p. 114). We agree
with this conclusion and propose to find it acceptable to exclude long-
term or deliberate, as opposed to acute and inadvertent, human
disturbance of the disposal system from the human-intrusion analysis on
the theory that society could retain at least some general knowledge of
the disposal system and, therefore, would know that such actions could
be dangerous. The proposed human-intrusion scenario, therefore,
includes only an acute, inadvertent intrusion.
Description of the proposed human-intrusion scenario. To develop an
appropriate scenario, we reviewed information about known resources and
geologic characteristics of the Yucca Mountain site associated with
past and current drilling for resources in the area surrounding Yucca
Mountain that could have an effect upon the type of proposed human-
intrusion scenario (see the BID). Based upon this examination, we are
proposing to adopt the NAS-suggested starting point for a human-
intrusion scenario. That scenario is a single, stylized intrusion
through the repository to the underlying aquifer based upon current
drilling practices. The proposed scenario presumes that the intrusion
occurs because of exploratory drilling for water. There are a number of
reasons why people in the future could be drilling within the
repository area, e.g., archeological pursuits, mineral exploration, or
geological investigations. However, we believe that drilling for water
is, for regulatory purposes, the best example of an intrusion scenario.
The choice of exploratory drilling for water is not a prediction that
this type of intrusion will occur or that it will occur on the surface
slopes overlying the repository but it is necessary to fulfill the NAS'
consideration that a borehole ``of specified diameter [is] drilled from
the surface through a canister of waste to the underlying aquifer''
(NAS Report p. 111). Exploratory drilling for water, using current
technology, essentially fixes the diameter of the borehole and drilling
from the surface necessarily places the drill rig somewhere above the
repository, but not necessarily on the crest of Yucca Mountain. For
purposes of determining compliance with the human-intrusion standard,
DOE must calculate the CEDE incurred by the RMEI using only releases
through the pathway created by the assumed borehole (with no other
releases included).
Under our proposal, NRC would specify when the intrusion would
occur based upon the earliest time that current technology and
practices could lead to waste package penetration. However, it must not
occur sooner than the cessation of active institutional controls (see
the Are There Qualitative Requirements To Help Assure Protection?
section earlier in this notice). In general, we believe that the time
frame for the drilling intrusion should be within the period that a
small percentage of the waste packages have failed but before
significant migration of radionuclides from the engineered barrier
system has occurred since, based upon our understanding of drilling
practices, this would be about the earliest time that impact with a
waste package would not be recognized by a driller. Our review of
information about drilling and experiences of drillers indicates that
special efforts, for example, changing to a specialized drill bit,
would likely be necessary to penetrate intact, nondegraded waste
packages of the type DOE plans to use. As stated earlier, NRC would
determine the timing as part of the licensing process. The Department's
waste-package performance estimates indicate that a waste package would
be recognizable to a driller for at least thousands of years (see the
BID).
This is consistent with NAS' example scenario (NAS Report pp. 111-
112). It requires evaluation of a single, nearly vertical borehole from
the surface that breaches the repository, passes through a degraded
waste package, and reaches the water table. We also are proposing that
careful sealing of the borehole does not occur, but that natural
processes gradually modify the transport characteristics within the
borehole. In determining compliance, we are proposing that it is
appropriate to assume that the result is no more severe than the
creation of a ground water flow path from the crest of Yucca Mountain
through the repository and into the ground water table. By proposing
this single-borehole, single-waste-package scenario, we are not
suggesting that other forms or types of human intrusion, or that
intrusion as a result of a resource other than water, will not occur.
For example, we know of different drilling techniques such as slanted,
horizontal, and robotic which, in theory, could result in more
penetrated waste packages. However, we do not believe that more complex
scenarios would provide more information about the resilience of the
repository than would the proposed scenario.
We also considered use of a human-intrusion scenario consistent
with that required in EPA's criteria for certifying WIPP (40 CFR part
194). These criteria required DOE to identify the rate of resource
drilling in the area surrounding the WIPP for the past 100 years
(approximately the period of recorded history for drilling events in
the area). DOE was required to then use this drilling rate in its
performance assessment to determine the number of intrusions into the
repository over the 10,000-year regulatory period. We considered this
approach appropriate for the WIPP facility given the considerable
amount of drilling in the vicinity of the site. We chose not to propose
this approach for the Yucca Mountain facility given the recommendation
in the NAS Report. We request comment upon the reasonableness of the
proposed human-intrusion scenario, and whether an approach similar to
that used for WIPP is more appropriate.
As noted earlier, we are proposing to use the same RME descriptors
for this analysis and scenario as in the assessment for compliance with
the individual-protection standard. While one could postulate that an
individual occupies a location above the repository footprint in the
future and is impacted by radioactive material brought to the surface
during an intrusion event, the level of exposure of such an individual
would be independent of whether the repository performs acceptably when
breached by human intrusion in the manner prescribed in the proposed
scenario. Movement of waste to the surface as a result of human
intrusion is an acute action with the resulting exposure being a direct
consequence of that action. Thus, we propose to interpret the NAS-
recommended test of ``resilience'' to be a longer-term test as measured
by exposures caused by releases which occur gradually through the
borehole, not suddenly as with direct removal. In addition, the effects
of direct removal depend upon the specific parameters involved with the
drilling and not upon the containment
[[Page 47000]]
characteristics of the disposal system. We also are proposing that the
test of the resilience of the repository system be the dose incurred by
the same RMEI as determined for the individual-protection standard.
This is consistent with the NAS' recommendation.
We request comment upon how much the human-intrusion analysis will
add to protection of public health. Also, given current drilling
practice in the vicinity of Yucca Mountain, we seek comment upon
whether our proposed, stylized, human-intrusion scenario is reasonable.
Time frame for the analysis. We are considering two approaches to
determine how far into the future that the human-intrusion analyses
will be required to project doses. In the first approach, which is
proposed in Secs. 197.25 and 197.26, we would require the peak dose
during the first 10,000 years, as a result of human intrusion, to be
less than 150 Sv/yr (15 mrem/yr). In the second approach, DOE
would calculate the earliest time that the engineered barrier system
would degrade sufficiently that current drilling techniques could lead
to complete waste package penetration without recognition by the
drillers. If that intrusion can happen within 10,000 years, then DOE
must do an analysis which projects the peak dose that would occur as a
result of the intrusion within 10,000 years. That dose would have to be
less than 150 Sv/yr (15 mrem/yr) for the site to be licensed,
considering reasonable expectation. If the undetected intrusion could
not occur until after 10,000 years, then DOE would still do the
analysis, however the results would not be part of the licensing
process but would be included in the Yucca Mountain EIS. This approach
mirrors the way that the 10,000-year and post-10,000-year analyses are
proposed in the individual-protection standard. This approach has the
advantage of encouraging DOE to use a robust engineered design. We
request comment upon the appropriateness of using either of these
alternatives.
III.F. How Will Ground Water Be Protected? (Proposed Sec. 197.35)
Ground water is a valuable resource with many potential uses. Our
proposed ground water protection standards would protect ground water
that is being used or might be used as drinking water by restricting
potential future contamination. Water from the aquifer which flows
beneath Yucca Mountain is currently being used as a source of drinking
water 20 to 30 km south of Yucca Mountain in the communities directly
protected by the individual-protection standard. It is also a potential
source of drinking water for more distant communities and,
theoretically, could supply drinking water for several hundred thousand
people. For these reasons, we believe it is a resource that needs to be
protected. Therefore, we are proposing to protect the ground water to
the same level as the maximum contaminant levels (MCLs) for
radionuclides which we have established under the authority of the Safe
Drinking Water Act (SDWA). This is also consistent with our policy for
ground water protection as stated in ``Protecting the Nation's Ground
Water: EPA's Strategy for the 1990s'' (``the Strategy,'' EPA 21Z-1020,
July 1991). In addition to drinking water, ground water may be a source
of radiation exposure when used for irrigation, stock watering, food
preparation, showering, or when incorporated into various industrial
processes. Ground water contamination is also of concern to us because
of potential adverse impacts upon ecosystems, particularly sensitive or
endangered ecosystems.
Today's proposal utilizes the current MCLs, but the MCLs might
change in the final rule. The Agency recognizes that the current MCLs
are based upon the best scientific knowledge regarding the relationship
between radiation exposure and risk that existed in 1975 when the MCLs
were developed. Scientific understanding has evolved since 1975 and we
are working to update the existing MCLs based upon a number of factors,
including: the current understanding of the risk of developing a fatal
cancer from exposure to radiation; pertinent risk management factors,
e.g., information about treatment technologies and analytical methods;
and applicable statutory requirements. Particularly relevant statutory
requirements, in this context, are the requirements that MCLs be set as
closely as feasible to the Maximum Contaminant Level Goal (MCLG) (SDWA
section 1412(b)(4)(B)) and that revised drinking water regulations
provide for equivalent or greater human health protection than the
regulations they replace (SDWA section 1412(b)(9)). The Agency's
preliminary efforts indicate that, for the radionuclides of concern at
Yucca Mountain, the concentration values for those MCLs are probably
not likely to change significantly. However, if those revisions to the
MCLs are finalized prior to finalization of the part 197 standards, we
plan to adopt those MCLs into the final part 197 standards. If part 197
is finalized first, the MCLs being proposed today would be maintained.
We believe that this approach is necessary to provide stability for NRC
and DOE in the licensing process. The uncertainty involved in not
knowing when a change would occur and what form that change would take
could delay the licensing proceeding. We request public comment upon
this approach. If you do not consider the proposed approach
appropriate, please provide an alternative and rationale.
In July 1991, we issued the Strategy cited above in order to guide
future EPA and State activities in ground water protection and cleanup.
The Strategy presents an effective approach for protecting the Nation's
ground water resources. Our policies, programs, and resource
allocations reflect this approach. It guides EPA, State and local
governments, and other parties in carrying out ground water protection
programs. In addition, our ``Final Comprehensive State Ground-Water
Protection Program Guidance'' provides guidance to States for
establishing a coordinated approach to their ground water protection.
The key element of our ground water protection strategy is the
overall goal of preventing adverse effects upon human health and the
environment by protecting the environmental integrity of the Nation's
ground water resources. We believe that it is important to protect
ground water to ensure that the Nation's currently used and potential
USDWs are preserved for present and future generations. Also, we
believe that it is important to protect ground water to ensure that
where it interacts with surface water it does not interfere with the
attainment of surface-water-quality standards. These standards are
necessary to protect human health and the integrity of ecosystems.
Our Strategy also recognizes, however, that our efforts to protect
ground water must take into consideration the use, value, and
vulnerability of the resource, as well as social and economic values.
In carrying out our programs, we use MCLs, established under the SDWA,
as reference points for water-resource protection efforts when the
ground water in question is a potential source of drinking water.
Pursuant to section 1412 of the SDWA, we issued the National Primary
Drinking Water Regulations for contaminants in drinking water which may
cause an adverse effect upon the health of persons and which are known
or anticipated to occur in public water systems (see 40 CFR parts 141
and 142). These regulations specify either MCLs or treatment techniques
and contain ``criteria and procedures to assure a
[[Page 47001]]
supply of drinking water which dependably complies'' with such MCLs
(see SDWA Sec. 1401). The relevant MCLs, for water containing less than
10,000 milligrams per liter (mg/L) of total dissolved solids (TDS) and
assuming an ingestion rate of 2 L of water per day, are:
(1) 5 picocuries per liter (pCi/L) for combined radium-226 and
radium-228;
(2) 15 pCi/L for gross alpha; and
(3) 4 mrem/yr for combined beta particle and photon radiation from
man-made radionuclides.
We employ MCLs to protect ground water in numerous regulatory
programs. This approach is reflected in our regulations pertaining to
hazardous-waste disposal (40 CFR part 264), municipal-waste disposal
(40 CFR parts 257 and 258), underground injection control (UIC) (40 CFR
parts 144, 146, and 148), generic SNF, HLW, and transuranic radioactive
waste disposal (40 CFR part 191), and uranium mill tailings disposal
(40 CFR part 192). These Agency programs have demonstrated that such
protection is scientifically and technically achievable, within the
constraints applied in each of these regulations (``Progress In Ground
Water Protection and Restoration,'' EPA 440/6-90-001).
Most ground water in the United States moves slowly, in the range
of five to 50 feet per year. This means that a large amount of a
contaminant can enter an aquifer and remain undetected until it affects
a water well or surface-water body. Contaminants in ground water,
unlike those in other environmental media like air or surface water,
can move with relatively little mixing or dispersion, so concentrations
can remain relatively high. Moreover, because ground water is below the
Earth's surface and ``out of sight,'' its contamination is far more
difficult to monitor or remove than is contamination in air, surface
water, or soil. These plumes of contaminants move slowly through
aquifers and may be present for many years, sometimes for decades or
longer, potentially making the resource unusable for extended periods
of time. Because an individual plume may underlie only a small part of
the land surface, it can be difficult to detect by aquiferwide or
regional monitoring. In addition, for periods spanning thousands of
years, monitoring is unlikely to continue, avoidance of the
contamination may be difficult, and the area affected may become large.
These factors are part of the reason that our policy emphasizes
prevention of ground water pollution.
Regarding this rulemaking, NAS clearly identified the ground water
pathway as one of the significant pathways of exposure in the vicinity
of the Yucca Mountain site (NAS Report pp. 52 and 81). The NAS also
recognized that ground water modeling for the Yucca Mountain site is
complex, involving both fracture and matrix flow and, as a result, that
there is uncertainty regarding which model or models to use in the
analysis:
Because of the fractured nature of the tuff aquifer below Yucca
Mountain, some uncertainty exists regarding the appropriate
mathematical and numerical models required to simulate advective
transport....[E]ven with residual uncertainties, it should be
possible to generate quantitative (possibly bounding) estimates of
radionuclide travel times and spatial distributions and
concentrations of plumes accessible to a potential critical group.
(NAS Report p. 90)
The basis of NRC's determination of compliance with the ground-
water protection standards will be DOE projections in the license
application of potential future contaminant concentrations that will
inevitably contain uncertainty. An important cause of uncertainty, as
recognized above by NAS, is the choice of conceptual site models. To
illustrate, the conceptual models used for Yucca Mountain can differ
fundamentally, that is, water can be presumed to flow through either
pores in the rock or conduits through the rock, such as discrete
fractures or a network of fractures that may act as preferential
pathways for faster ground water flow, or a combination of the two. To
further complicate the situation, any of these flow scenarios, with the
possible exception of flow through conduits, can occur at Yucca
Mountain whether the rock is completely saturated with water or not.
We believe that adequate data and the choice of models will be
critical to any compliance calculation or determination. The NAS has
examined the use of ground-water flow and contaminant-transport models
in regulatory applications (``Ground Water Models: Scientific and
Regulatory Applications,'' 1990). In that report, NAS concluded that
data inadequacy is an impediment to the use of unsaturated fracture
flow models for Yucca Mountain. However, NAS noted that data inadequacy
was also an impediment to using models that assume the pores in the
rock are either saturated or unsaturated or that assume flow through
fractures that are completely filled with water. However, despite the
recognition of the importance of the choice of the site conceptual
model, the Agency believes that the need for sufficient quantity,
types, and quality of data to adequately analyze the site, because of
its hydrogeologic complexity, is even more important. In other words,
the complexity of the ground water flow system requires adequate site
characterization to justify the choice of the conceptual flow model.
The choice of modeling approaches to address the ground water
system in the area of Yucca Mountain, based upon the conceptual model
of the site developed from site characterization activities, is
important to characterize contaminant migration, particularly the
mixing of water, contaminated with radionuclides from breached waste
packages, with uncontaminated water. The extent of the dilution
afforded by mixing contaminated water with other ground water moving
through the rocks below the repository but above the water table and
the dispersion of the plume of contamination within the saturated zone
as the ground water system carries radionuclides downgradient are
critical elements of the dose assessments.
At one end of a spectrum of approaches to modeling the site ground
water system is the assumption that the system can be modeled based
upon flow through pores over the area of total system assessments (tens
of square kilometers). At the other extreme is the assumption that
radionuclides are carried through fast-flow, fracture pathways in the
unsaturated zone separately from uncontaminated ground water also
passing through the repository footprint. Those radionuclides then are
assumed to be carried through the saturated zone in fractures that
allow little or no dispersion within, or mixing with, uncontaminated
water in the saturated zone. This is essentially ``pipe flow'' from the
repository to the receptor. Although the flow of ground water at the
site is influenced strongly by fractures, which should be reflected in
the models, we believe that it is unreasonable to assume that no mixing
with uncontaminated ground water would occur along the radionuclide
travel paths. We request comment upon this approach, including
consideration of the practical limitations on characterizing the flow
system over several or tens of square kilometers.
Our intention is to develop ground water protection standards that
are implementable by NRC. In this regard, NAS indicated that
quantitative estimates of ground water contamination should be possible
(NAS Report p. 90). We are proposing to require DOE to project the
level of radioactive contamination it expects to be in the
representative volume of ground water. The representative
[[Page 47002]]
volume could be calculated to be in any aquifer which contains less
than 10,000 mg/L of TDS and is downgradient from Yucca Mountain. By
proposing this method, we intend to avoid requiring DOE and NRC to
project the contamination in a small, possibly unrepresentative amount
of water since we believe that this is not practical (see the
discussion of ``representative volume of ground water'' immediately
below). For example, we do not intend that NRC must consider whether a
few gallons of water in a single fracture would exceed the standards.
Thus, we are proposing to allow use of a larger volume of water which
must, on average, meet the standards. This larger volume, the
``representative volume,'' is discussed below.
Since the intended purpose of the engineered and natural barriers
of the geologic repository is to contain radionuclides and minimize
their movement into the general environment, we anticipate that
radionuclide releases from the repository will not occur for long
periods of time. With this in mind, we believe that ground water
protection for the Yucca Mountain site should focus upon the protection
of the ground water as a resource for future human use. It is the
general premise of this proposal that the individual-protection
standard would adequately protect those few current residents closest
to the repository. The proposed ground water standards are directed to
protecting the aquifer as a resource for current users, and a potential
resource for larger numbers of future users either near the repository
or for communities farther away comprised of as many as several hundred
thousand people. To implement this conceptual approach and develop an
approach for compliance determinations, we believe that the ground
water standards currently used, the MCLs, should apply to public water
supplies downgradient from the repository in aquifers at risk of
contamination from repository releases. Applying the MCLs assures that
the level of protection currently required for public water supplies
elsewhere in the Nation is also maintained for future communities using
the water supply downgradient from the Yucca Mountain repository.
To implement the standards in Sec. 197.35, we are proposing that
DOE use the concept of a ``representative volume'' of ground water in
which DOE and NRC would project the concentration of radionuclides
released from the Yucca Mountain disposal system for comparison against
the MCLs. The representative volume will be the volume of water that
would supply the annual water demands of a defined hypothetical
community that could exist in the future at the point of compliance for
the ground water protection standards. We believe that community size
and water demand estimates should reflect the current, general
lifestyles and demographics of the area, but not be rigidly constrained
by current activities since any potential contamination would occur far
into the future. In the area south of Yucca Mountain, the ground water
is currently used for domestic purposes, commercial agriculture (for
example, dairy cattle, feed crops, other crops, and fish farming),
residential gardening, commercial, and municipal uses. The water
resources, as reflected by estimates of current usage and aquifer
yields, indicate that there is theoretically enough water to support
communities of hundreds to thousands of people at the four alternative
proposed locations for the point of compliance. This sets an upper
bound on the size of the hypothetical community and its water demand.
On the other hand, the SDWA defines the minimum size for a public water
system as a system with 15 service connections or, regularly supplying
at least 25 people.
For the four alternative proposed downgradient distances for the
point of compliance (approximately 5, 18, 20, and 30 km from the
repository), current populations vary from hundreds of persons around
30 km, to about 10 people residing at 18-20 km, to no residents at 5
km. Current projections of population growth in the area indicate
increases at both the 20- and 30-km locations. Based upon current water
usage, lifestyles, projections of population increases, and the
potential number of people that could be supported by available ground
water, there is a range of annual ground water volumes that could
correspond to possible future public water system uses. While we
believe that, ideally, the representative volume should be fully
consistent with the protection objectives of the ground water
protection strategy, we also recognize the unique features of this
proposal. The extraordinary 10,000-year compliance period introduces
unresolvable uncertainties that make this situation fundamentally
different from the situations of clean-up or foreseeable, near-term
potential contamination to which the strategy ordinarily applies. We
therefore request comment upon a proposed representative ground water
volume and upon possible alternatives for the size of the
representative volume of ground water. These alternatives are based
upon variations in possible lifestyles for residents downgradient from
the repository and upon current and near-term projections of population
growth and land use in the area.
The proposed representative volume is based upon a small farming
community of 25 people and 255 acres of alfalfa cultivation, the
current economic base in the Amargosa Valley. This approach assumes a
community whose water needs include an agricultural component
comparable to present water usage in the vicinity of the repository.
The size of the average area of alfalfa cultivation, 255 acres, is
based upon site-specific information for the nine alfalfa-growing
operations which range in size from about 65 acres to about 800 acres.
Using a water demand for alfalfa farming in Amargosa Valley of 5 acre-
feet per acre per year, we estimate the water demand for the average
operation to be 1275 acre-feet per year. As discussed below, it is
appropriate to add 10 acre-feet per year for domestic uses resulting in
1285 acre-feet per year.
We request comment upon whether this approach is the most
appropriate representative volume of ground water, or whether other
values within the ranges discussed below are more appropriate. We
believe that there may be significant technical, policy, or practical
obstacles with the use of either very small or very large water
volumes.
We considered using volumes of 10 and 120 acre-feet per year.
Although the character of ground water movement in the saturated zone
makes it progressively more difficult to model smaller volume flow, we
are interested in comment upon the use of and whether, or how, it would
be practical and feasible, using scientifically defensible methods, for
the Commission to determine compliance with an alternative which
specifies smaller representative volumes, such as 10 acre-feet and 120
acre-feet per year. A volume of 10 acre-feet would be representative of
the annual water use of a non-farming family of four with average
domestic water usage, including a garden. This is also the lower bound
for the amount of water that would be used through 15 connections
serving at least 25 persons in a public water supply, as defined in the
SDWA. As mentioned in earlier discussions regarding the nature of
ground water flow in fractured rocks, modeling the flow of ground water
and the movement of contaminants involves significant uncertainties in
the exact quantitative relationship between ground water
[[Page 47003]]
movement in fractures versus its movement in the rock pore spaces.
Modeling these processes, of necessity, requires simplifying
assumptions and approximations that lower the level of confidence that
can be attached to estimating contaminant concentrations in
progressively smaller volumes of ground water. From our understanding
of the complexity of the flow system at Yucca Mountain and the
surrounding area, and the uncertainties involved in modeling it, a
small representative volume such as 10 acre-feet would be difficult to
model with a sufficient degree of certainty for regulatory confidence.
The Agency, of course, wants the size of the representative volume used
in compliance calculations to be scientifically defensible in order to
provide the public a reasonable certainty of their accuracy.
An annual water demand of 120 acre-feet assumes a community of 150
persons and is based upon current water use data for the area. This
population estimate is based upon recent population increases in the
area and 20-year projections of land use at the 20-km location, as
described in county planning documents. In such a scenario, it would be
important for commenters to look at whether it is appropriate to assume
this community would have an agriculture component, or whether a
primarily residential community is more appropriate.
We also considered using a volume of 4,000 acre-feet which would be
representative of the estimated perennial yield of the Jackass Flats
hydrographic sub-basin in which the proposed Yucca Mountain repository
is located. This volume represents the annual sustainable quantity of
water which could be removed from this sub-basin without significantly
decreasing the subsequent water yield and quality in the future. This
volume is not directly linked to any specific use, but rather is
included as representative of the volume of the water resource for
potential future, large-scale, sustainable ground water use.
As already stated, we believe that there may be significant
technical, policy, or practical obstacles that preclude the use of such
a large volume. Releases from the repository will migrate downward and
into the saturated zone where the contaminated ground water will move
generally southward. The Jackass Flats sub-basin covers a large area,
most of which is east of the repository site and not in the path of
ground water flow from the repository. The Agency did not include this
alternative in the rule since the use of 4,000 acre-feet would result
in a contaminant estimate based upon dilution by a large volume of
unaffected water. We are requesting comment upon the use of 4,000 acre-
feet as the basis for the Commission to determine compliance with an
alternative which specifies this volume as representative of the ground
water resource.
To implement these options, the Department would project the
radionuclide concentration in the representative volume or the
resultant doses, for the option selected, and compare them against the
appropriate MCLs. For these calculations, the movement of radionuclides
released from the repository must be calculated as they move
downgradient toward the compliance point. For the purpose of
demonstrating compliance with the ground water protection standards, we
intend for DOE and NRC to use the performance assessments to determine
compliance with the individual-protection standard to calculate the
concentration of radionuclides in the ground water.
There are two basic approaches between which DOE must choose for
calculating the concentrations of radionuclides at the point of
compliance. The Department may perform this analysis by determining how
much contamination is in: (1) a ``well-capture zone''; or (2) a ``slice
of the plume.'' (These approaches are explained immediately below.) For
either approach, the volume of water used in the calculations is equal
to the representative volume, i.e., the annual water demand for the
proposed future group using the ground water.
The ``well-capture zone'' is the volume from which a water supply
well, pumping at a defined rate, is withdrawing water from an aquifer.
The dimensions of the well-capture zone are determined by the pumping
rate in combination with aquifer characteristics assumed for
calculations, such as hydraulic conductivity, gradient, and the
screened interval. If this approach is used, DOE must assume that the:
(1) Well has characteristics consistent with public water supply
wells in Amargosa Valley, for example, well bore size and length of the
screened interval;
(2) Screened interval is centered at the highest concentration in
the plume of contamination at the point of compliance; and
(3) Pumping rate is set to produce an annual withdrawal equal to
the representative volume.
To include an appropriate measure of conservatism in the compliance
calculations for the well withdrawal approach, we are proposing that,
for the purpose of the analysis, DOE should assume that the community
water demand would be supplied from one pumping well located in the
center of any projected plume of contamination originating in the
repository. Conservatism is achieved by requiring that the entire water
demand is withdrawn from one well intercepting the center of the plume
of contamination so that the highest radionuclide concentrations in the
plume are included in the volume used for the compliance calculations.
The ``slice of the plume'' is a cross-section of the plume of
contamination centered at the point of compliance with sufficient
thickness parallel to the prevalent flow of the plume such that it
contains the representative volume. If DOE uses this approach, it must:
(1) Propose to NRC, for its approval, where the edge of the plume
of contamination occurs, for example, where the concentration of
radionuclides reaches 0.1% of the level of the highest concentration at
the point of compliance;
(2) Assume that the slice of the plume is perpendicular to the
prevalent direction of flow of the aquifer; and
(3) Set the volume of ground water contained within the slice of
the plume equal to the representative volume.
In both alternatives, we are proposing that DOE must determine the
physical dimensions and orientation of the representative volume during
the licensing process, subject to approval by the Commission. Factors
that would go into determining the orientation of the representative
volume would include hydrologic characteristics of the aquifer and the
well.
Under our proposal, the Department must demonstrate compliance with
the proposed ground water protection standards (Sec. 197.35) assuming
undisturbed performance of the disposal system. The term ``undisturbed
performance'' means that human intrusion or the occurrence of unlikely,
disruptive, natural processes and events do not disturb the disposal
system. This approach recognizes that human behavior is difficult to
predict and, if human intrusion occurs, that individuals may be exposed
to radiation doses that would be more attributable to human actions
than to the quality of repository siting and design (NAS Report p. 11).
The requirement that DOE project performance for comparison with the
ground water protection standards based upon undisturbed-performance
scenarios is consistent with our generally applicable standards for
SNF, HLW, and transuranic waste in 40 CFR part 191 (58 FR 66402,
[[Page 47004]]
December 20, 1993; 50 FR 38073 and 38078, September 19, 1985).
We also are proposing to require that DOE combine certain estimated
releases from the Yucca Mountain disposal system with the pre-existing
naturally occurring or man-made radionuclides to determine the
concentration in the representative volume (see Table 1 in the What
Should the Level of Protection Be? section earlier in this notice for
particular cases). This means that the releases of radionuclides from
radioactive material in the Yucca Mountain disposal system must not be
allowed to cause the projected level of radioactivity at the point of
compliance to exceed the limits in Sec. 197.35 with reasonable
expectation.
We request public comment upon these approaches. Comments also are
requested upon whether it is desirable and appropriate for us to
provide more quantitative requirements for the proposed representative
volume in the final standards. If so, please provide specifics.
III.F.1. Is the Storage or Disposal of Radioactive Material in the
Yucca Mountain Repository Underground Injection?
We first addressed the issue of whether the disposal of radioactive
waste in geologic repositories might be considered a form of
underground injection in a rulemaking to amend 40 CFR part 191. In the
preamble to the final amendments (58 FR 66398), we stated that it was
unnecessary to address whether the disposal of radioactive waste in a
geologic repository covered under 40 CFR part 191 constitutes
underground injection under the SDWA since the ground water protection
requirements in 40 CFR part 191 conformed with the MCLs. We also noted
that in NRDC v. EPA, 824 F.2d at 1270-71, the First Circuit Court of
Appeals itself did not resolve the underground injection issue. The
Court stated only that disposal in geologic repositories would
``likely'' constitute underground injection. Also, in the preamble to
the 40 CFR part 191 amendments, we reviewed the SDWA, its legislative
history, and the regulations governing the UIC program. We concluded
that the underground disposal of containerized radioactive waste in
geologic repositories subject to 40 CFR part 191 does not constitute
underground injection within the meaning of the SDWA or our regulations
governing the UIC program (58 FR 66398, 66408-66411, December 20,
1993). Similarly, in the present rulemaking, we propose to find that
the storage or disposal of containerized radioactive waste in Yucca
Mountain does not constitute underground injection.
Section 1421 of the SDWA defines ``underground injection'' as ``the
subsurface emplacement of fluids by well injection.'' 42 U.S.C.
300h(d)(1). The statute defines neither ``fluids'' nor ``well
injection.'' Moreover, neither the statute nor the legislative history
directly addresses whether the underground storage or disposal of
containerized radioactive waste constitutes the ``subsurface
emplacement of fluids by well injection.'' Even though the legislative
history states, ``[t]he definition of `underground injection' is
intended to be broad enough to cover any contaminant which may be put
below ground level and which flows or moves, whether the contaminant is
in semi-solid, liquid, sludge, or any other form or state,'' (H.R. Rep.
No. 1185, 93d Cong., 2d Sess. 31 (1974)), it does not specifically
address whether the underground storage or disposal of containerized
radioactive waste in a geologic repository, such as Yucca Mountain,
constitutes the ``subsurface emplacement of fluids by well injection.''
In this rulemaking, we are proposing to conclude that the
underground storage or disposal of containerized radioactive waste in
the Yucca Mountain repository does not constitute underground injection
both because the materials to be emplaced are not ``fluids'' and
because the mode of emplacement of these materials is not ``well
injection.'' We do not consider the type of containerized radioactive
wastes covered under today's proposal to be ``fluids.'' Instead, DOE
plans for the wastes to consist entirely of solid materials and to be
enclosed in thick metal waste packages. We do not believe that the
SDWA's reference to ``subsurface emplacement of fluids'' was intended
to address the subsurface storage or disposal of solid, containerized
materials. As noted above, neither the statute nor the legislative
history specifically address the subsurface emplacement of
containerized materials or solids. On the other hand, the legislative
history does address the injection of liquid materials that flow or
move at the time they are emplaced into the ground. For example, in
floor debate, Sen. Domenici stated that ``the [UIC] regulations would
cover all types of injection wells from industrial and nuclear disposal
wells, oil and gas injection wells, solution mining wells or any hole
in the ground designed for the purpose of injecting water or other
fluids below the surface'' (see 126 Cong. Rec. 30189, November 19,
1980, remarks of Sen. Domenici). Indeed, in amending the SDWA in 1985,
Congress stated ``underground injection is the process of forcing
liquids underground through a well.'' H.R. Rep. No. 168, 99th Cong.,
1st Sess. 30 (1985). Moreover, it is clear from the legislative history
of the SDWA that Congress intended to ratify EPA's policy regarding
deep-well injection contained in Administrator's Decision Statement #5,
entitled ``Subsurface Emplacement of Fluids,'' (39 FR 12922, April 2,
1974, H.R. Rep. No. 1185, 93rd Cong., 2d Sess. 31-32 (1974)).
Administrator's Decision Statement #5 contains parameters for well
injection including, among other things, data requirements for volume,
rate, and injection pressure of the fluid; degree of fluid saturation;
and formation and fluid pressure (39 FR 12923, April 9, 1974). Like the
legislative history itself, the policy does not mention the subsurface
emplacement of containerized radioactive wastes, but it does address
the injection of noncontainerized liquids as an object of regulatory
concern.
The legislative history of the SDWA indicates that Congress was
concerned about contamination of ground water from a variety of sources
of noncontainerized liquids and sludges. Quoting from a U.S. Department
of Health, Education and Welfare report entitled ``Human Health and the
Environment--Some Research Needs,'' Representative Rogers noted in
floor debate that ground water pollution was rapidly increasing from
sources including ``. . . waste water sludges and effluents . . . mine
drainage, subsurface disposal of oil-field brines, seepage from septic
tanks and storage transmission facilities, and individual on-site
waste-water disposal systems.'' (123 Cong. Rec. 22460 (July 12, 1977)).
Later in 1985, Congress made clear its intent that there would be early
detection of fluid migration into or in the direction of a USDW (H.R.
Rep. No. 168, 99th Cong., 1st Sess. 30 (1985)). Again, there is no
mention that Congress intended that the SDWA cover the subsurface
emplacement of containerized radioactive wastes.
Reflecting this statutory approach, our UIC regulations similarly
do not treat containerized radioactive wastes as fluids or liquids for
the purpose of control under the UIC program. Our regulations at 40 CFR
146.3 define ``fluid'' as ``material or substance which flows or moves
whether in a semisolid, liquid, sludge, gas, or any other form or
state.'' In adopting this regulatory definition of fluid, we did not
consider the emplacement of containerized
[[Page 47005]]
radioactive wastes into geologic repositories to be fluids subject to
the UIC regulations. There is no mention of this activity in the
preambles to the proposed or final UIC regulations. On the contrary,
the fluids regulated by our UIC program include: (1) Brines from oil
and gas production; (2) hazardous and industrial waste waters; (3)
liquid hydrocarbons (gasoline, crude petroleum, and others); (4)
solution mining fluids from uranium, sulfur, and salt solution mining;
and (5) sewage and treated effluent (40 CFR 144.6). All of these
materials can flow or move at the time they are emplaced into the
ground. There is no indication of any intention to cover containerized
materials as fluids under the UIC regulations.
Finally, we have never interpreted our UIC regulations to include
the subsurface emplacement of containerized wastes or solid materials
that do not flow or move. As explained in greater detail below, we have
stated instead that placement of containerized hazardous waste in
geologic repositories such as underground salt formations, mines, or
caves, is regulated under Subtitle C of the RCRA hazardous waste
program. Subtitle D of RCRA regulates the disposal of containerized,
nonhazardous wastes pursuant to the regulatory provisions at 40 CFR
257.1. Today's proposed standards for Yucca Mountain regulate the
emplacement and disposal of containerized radioactive wastes including
SNF and HLW.
In NRDC v. EPA, 824 F.2d 1258, the First Circuit was concerned that
radiation itself might be considered a fluid within the meaning of the
SDWA and EPA's UIC regulations (40 CFR 146.3). We believe that
radiation itself does not meet the UIC regulatory or statutory
definition of ``fluid.'' Radioactivity is a specific characteristic of
the radionuclides in the waste but does not define the form of the
waste. Also, radioactivity results in the emission of ionizing
radiation in the form of electromagnetic energy or subatomic particles.
Electromagnetic radiation is a form of energy, not a ``material or
substance.'' Hence, it is not a ``fluid.'' Subatomic particles, such as
alpha and beta particles, will be absorbed in either the waste or the
container and, therefore, not travel beyond the container, or will
travel very short distances, perhaps a few inches. In any event, as set
forth above, we believe that since the activity at the Yucca Mountain
repository will consist of the emplacement of containers of radioactive
wastes underground, this activity is emplacement of solid materials,
not ``fluids.'' Even though these materials might eventually
disintegrate or dissolve and release some radiation, liquids, or gases,
the activity in question still consists of emplacement of containers
and solid materials that will not flow or move at the time of
emplacement underground.
Moreover, we do not consider the emplacement into the Yucca
Mountain repository of containerized and solid wastes that do not flow
or move to be subsurface emplacement ``by well injection.'' At the
Yucca Mountain repository as currently conceived, a rail car will be
used to carry the containerized waste into the repository. The waste
containers then will be emplaced in drifts mined into the geologic
formation. Once enough containers are accumulated, each drift will be
closed. Closure of the disposal system will occur when all of the
openings into the repository have been backfilled and all entrance
ramps sealed.
Our UIC regulations define ``well injection'' as ``subsurface
emplacement of fluids through a bored, drilled or driven well; or
through a dug well, where the depth of the dug well is greater than the
largest surface dimension'' (40 CFR 146.3). The regulations define a
``well'' as ``a bored, drilled or driven shaft, or a dug hole, whose
depth is greater than the largest surface dimension'' (Id.). Although
movement of the materials underground in the Yucca Mountain repository
will involve waste handling, it will be drifts, that is, tunnels,
through which containerized solid materials are transported and
emplaced, not ``wells'' into which fluids are being ``injected'' within
the meaning and intent of the SDWA or our UIC regulations. In addition,
the overall configuration of the repository is far different from that
of a ``drilled,'' ``driven,'' or ``dug'' injection well.
We noted in the preamble to the proposed UIC rules setting forth
the definitions of ``well'' and ``well injection'' that the definitions
cover not only ``conventional'' deep wells, but also drilled, bored,
and driven wells. Dug wells and non-residential septic tanks also fall
under the term. We further stated, however, that ``although the
definition is broad, it is not without limitation.'' (44 FR 23738,
23740, April 20, 1979) For example, we stated that the term does not
cover simple depressions in the land or single-family domestic
cesspools or septic systems, nor does it cover surface impoundments
(Id.). Although we had been concerned initially about whether the UIC
regulations should impose conditions upon surface impoundments,
generally referred to as ``pits, ponds, and lagoons,'' since they pose
a threat to ground water, we noted that standards to control such
contamination are under the RCRA hazardous-waste management program (44
FR 23740, April 20, 1979). Thus, we recognized that there are some
disposal practices that might contaminate ground water that would not
be covered under the UIC program.
Similarly, we do not believe that the UIC program should cover
emplacement of containerized waste by way of a drift. Such emplacement
is in no way similar to the pressurized or gravity-driven flow of
fluids, liquids, or sludges injected into a well that has been the
traditional focus of the UIC program (for example, 41 FR 36726, 36732,
August 31, 1976). Even Class-V wells, a general category of injection
wells, are not used for the disposal of containerized waste. Class V
covers the subsurface emplacement of fluids, usually by gravity-driven
flow, into the injection well. Although Class-V wells include some
types of wells that traditionally might not be thought of as injection
wells, for example, septic systems, all of the well types involve the
emplacement of noncontainerized fluids into drilled, bored, dug, or
driven wells, typically through gravity-driven flow rather than
pressurized flow.
We specifically addressed the status of containerized waste under
RCRA and SDWA in the preamble to the final rule promulgating standards
for miscellaneous units used for the disposal of hazardous wastes under
subpart X of the RCRA regulations (40 CFR part 264). In the preamble to
the final rule, we stated: ``Placement of containerized hazardous waste
or bulk non-liquid hazardous waste in geologic repositories such as
underground salt formations, mines, or caves, either for the purpose of
disposal or long-term retrievable storage, is included under subpart
X'' (52 FR 46946, 46952, December 10, 1987).
We promulgated the subpart X regulations to address hazardous-waste
management technologies not covered under 40 CFR part 264 (RCRA
regulations for the disposal of hazardous waste) or 40 CFR part 146
(UIC program technical criteria and standards). As we indicated in the
preamble to the subpart X regulations, the 40 CFR part 146 technical
standards do not address practices other than the injection of
noncontainerized liquids, slurries, and sludges, and do not fully
address some potential disposal or storage practices that may fall
under our regulatory definition of well injection (52 FR 46946, 46953,
December 10, 1987). In the subpart X rule, we provided that, to the
extent that miscellaneous disposal practices subject to subpart X might
be
[[Page 47006]]
underground injection, a subpart X permit would constitute a UIC permit
for well injection of hazardous waste for which current 40 CFR part 146
technical standards are not generally appropriate. We stated, however,
that we were not ``specifying that these miscellaneous management
practices constitute underground injection'' (Id.).
Thus, we have never expressed an intent that the disposal of
containerized waste, including containerized radioactive waste, in
geologic repositories is an activity covered by the UIC program.
Instead, injection wells have been described as ``facilities [within]
which wastes, in a fluid (usually liquid) state, are injected into the
land under a pressure head greater than the pressure head of the ground
water into or above which they are injected for the purpose of
disposal. Discharge to the ground water is either direct or by direct
seepage of leachate from the well outlet (46 FR 11126, 11137-38,
February 5, 1981).
Moreover, we have never intended for the regulatory criteria and
standards applicable to underground injection, contained in 40 CFR
parts 144 and 146, to apply to a geologic repository such as Yucca
Mountain. The concepts of area of review, pressure buildup and pressure
monitoring, restrictions upon injection pressure, other operating
requirements, and mechanical-integrity testing of injection wells, that
are included in the 40 CFR part 146 regulations, are meaningless as
applied to Yucca Mountain. Further, as noted above, the Yucca Mountain
disposal system will have mined containment areas in which humans
operate mechanical equipment to emplace waste packaged in containers
surrounded by both engineered and natural barriers designed to isolate
such waste from the environment. The UIC regulations are directed at
injection of fluids by pressure or gravity flow where they are then in
direct contact with the natural, underground media; this activity is
far different, from an engineering perspective, than the subsurface
emplacement of containerized wastes planned for Yucca Mountain.
Finally, as explained below, we are proposing specific ground water
protection standards, in addition to other public health and safety
standards, to protect ground water resources in the vicinity of Yucca
Mountain. We believe these standards are adequate to protect public
health and the environment from the radiation exposure resulting from
releases following the emplacement of these containerized radioactive
wastes into the Yucca Mountain disposal system. Thus, it is not
necessary to expand the scope of the UIC program to cover this
activity.
III.F.2. Does the Class-IV Well Ban Apply?
Today's action provides protection, with one possible exception,
substantively similar to the SDWA through the proposed adoption of the
MCLs to protect ground water resources in the vicinity of Yucca
Mountain (proposed Sec. 197.35). The possible exception relates to the
provision of 40 CFR 144.13 banning ``Class IV'' injection wells. As
defined in 40 CFR 144.6(d), such wells include those which dispose of
radioactive waste into or above a formation which contains a USDW
within one-quarter (\1/4\) mile of the well. In the preamble to the
amendments to 40 CFR part 191 (58 FR 66398, 66410, December 20, 1993),
we said we would further consider the Class-IV well-ban issue in the
context of the Yucca Mountain rulemaking. We have done so and are
proposing in this rulemaking not to apply the Class-IV injection-well
ban to the Yucca Mountain repository. Our position is that this is
appropriate in light of the statutory and regulatory provisions,
discussed above, relating to ``underground injection'' and the
differences in the purposes of the UIC program and the authority
delegated to us under the EnPA to establish public health and safety
standards for Yucca Mountain.
The UIC regulations mandate minimum requirements for State programs
to prevent underground injection which endangers USDWs, while the 40
CFR part 197 standards proposed for Yucca Mountain are directed toward
protecting ground water in the accessible environment in the vicinity
of the Yucca Mountain site and establish requirements for performance
of the Yucca Mountain disposal system. As discussed below, we believe
that the proposed standards for the Yucca Mountain disposal system
achieve public health and environmental protections comparable to those
of the UIC program. Moreover, as discussed above, we do not believe
that the emplacement of radioactive waste in the Yucca Mountain
disposal system is a form of underground injection. Therefore, we are
proposing to find that the Class-IV well ban does not apply to, and is
not needed, in the case of the Yucca Mountain disposal system.
It is important to emphasize that our proposed decision not to
apply the Class-IV well ban to Yucca Mountain does not affect other
disposal systems that dispose of hazardous or radioactive waste into or
above a formation which, within one-quarter (\1/4\) mile of the
disposal system, contains a USDW. We are basing today's proposal upon
site-and facility-specific characteristics of the Yucca Mountain
repository, and today's proposal is limited to the Yucca Mountain
repository.
The Class-IV well ban is part of the UIC program and is recognized
in section 3020 of RCRA. As explained previously, the UIC program
addresses ``well injection'' in the common-sense meaning of that term.
In contrast, the proposed 40 CFR part 197 regulations address
emplacement of radioactive wastes into a uniquely designed and utilized
facility. The Yucca Mountain disposal system is planned to be subjected
to extremely sophisticated site characterization, design, engineering,
containerization, and operational requirements. Given such intense
scrutiny, applying a blunt instrument akin to the Class-IV well ban as
a siting prohibition appears to be both unnecessarily restrictive and a
poor substitute for more sophisticated site characterization studies
that may preclude siting of a disposal facility for reasons other than
those embodied in the Class-IV restriction. Further, if Congress
intended that the Yucca Mountain disposal system be subject to and
summarily precluded by the Class-IV well ban, we seriously question
whether Congress would have specifically directed us, under the EnPA,
to establish public health and safety standards for Yucca Mountain.
Previously, we explained our proposed conclusion that emplacement
of radioactive material into the Yucca Mountain disposal system is not
underground injection. The materials to be disposed are solid,
containerized radioactive wastes emplaced in a mined containment system
in which humans operate heavy mechanical equipment. Such emplacement
and such materials do not fall under the intent or meaning of the UIC
concepts or programs, or more specifically, the Class-IV well ban at 40
CFR 144.13, but are judged more appropriately by the standards mandated
by Congress under the EnPA specifically for Yucca Mountain. Further,
the ground water protection alternatives presented in today's proposal
provide protections very comparable to those under the UIC program.
Taken together, we believe these distinctions are sufficient to
justify nonapplicability of the Class-IV well ban under the SDWA. We
request comment upon our position that application of the UIC Class-IV
well ban is neither legally required nor
[[Page 47007]]
appropriate for the Yucca Mountain disposal system. Further, we will
not address in this rulemaking the relevance of the Class-IV well ban
to underground repositories generally.
III.F.3. Which Ground Water Should Be Protected?
Although we propose to find that the Yucca Mountain disposal system
is not a form of underground injection in the context of the SDWA, we
nevertheless consider the ground water protection principles embodied
in the SDWA to be important. Therefore, while not applying all aspects
of the SDWA, we are proposing ground water protection standards
consistent with the levels of the radionuclide MCLs.
We request public comment upon the proposal and the other
approaches, described below, that are designed to protect ground water
resources in the vicinity of the repository. We are concerned that
ground water resources in the vicinity of Yucca Mountain receive
adequate protection from radioactive contamination. The primary purpose
of our proposed standards is to prevent contamination of drinking-water
resources. (Since the proposed compliance period is 10,000 years after
disposal, references to levels of contamination mean those levels
projected to exist at specific future times, unless otherwise noted.
However, these projections will be made at the time of licensing.) This
prevents placing the burden upon future generations to decontaminate
that water by implementing expensive clean-up or treatment procedures.
We believe it is prudent to protect drinking water from contamination
through prevention rather than to rely upon clean-up afterwards. The
cost to remediate the effects of radionuclides released from a geologic
disposal system, such as Yucca Mountain, could far exceed the costs
typically associated with near-surface Superfund sites. Moreover,
absent this protection through prevention, the disposal system itself
could become subject to clean-up by future generations. Thus, our
proposed ground water protection standards stress pollution prevention
and provide protection from contamination of sources of drinking water
containing up to 10,000 mg/L of TDS. We emphasize that all ground water
pathways, including drinking water, are also covered under the proposed
individual-protection standard (Sec. 197.20).
The definition of USDW received extensive discussion in the
legislative history of the SDWA as reflected in the report of the House
Committee on Interstate and Foreign Commerce. To guide the Agency, the
Committee Report suggested inclusion of aquifers with fewer than 10,000
mg/L of TDS (H.R. Rep. No. 1185, 93d Cong., 2d Sess. 32, 1974). We have
reviewed the current information on the use of aquifers for drinking
water which contain high levels of TDS. This review found that ground
water containing up to 3,000 mg/L of TDS that is treated is in
widespread use in the U.S. In the Yucca Mountain vicinity, with few
exceptions (one being the Franklin Playa area), ground water contains
less than 1,000 mg/L of TDS. Our review also found that ground water
elsewhere in the Nation, containing as much as 9,000 mg/L of TDS,
currently supplies public water systems. Based upon this review and the
legislative history of the SDWA, we are proposing that it is reasonable
to protect the aquifers potentially affected by releases from the Yucca
Mountain disposal system. Therefore, the provisions found in proposed
Sec. 197.35 would apply to all aquifers, or their portions, containing
less than 10,000 mg/L of TDS. The proposed definitions associated with
Sec. 197.35 are taken directly from our UIC regulations found in 40 CFR
parts 144-146.
III.F.4. How Far Into the Future Should Compliance Be Projected?
We are proposing a 10,000-year compliance period for ground water
protection. This is consistent with the 10,000-year compliance period
we are proposing for the individual-protection standard and, therefore,
provides internal consistency within the proposed standards. This time
period would also make the ground water protection compliance period
consistent with 40 CFR part 191. Consistency also is achieved with
regulations covering long-lived chemically hazardous wastes which
present potential health risks similar to those from radioactive waste.
In addition to trying to achieve consistency with our other
hazardous and radioactive-waste programs, we are concerned about the
uncertainty associated with projecting radiation doses over periods
longer than 10,000 years. The NAS indicated that beyond 10,000 years
uncertainty will likely continue to increase (NAS Report p. 72). As a
result, it will become increasingly difficult to discern a difference
between the radiation dose from drinking water containing radionuclides
(limited by the MCLs) and the total dose arriving through all pathways
(which is limited by the individual-protection standard).
In fact, we considered incorporating a compliance period of time-
to-peak concentration within the geologic stability of the site.
However, this approach may be unworkable and duplicative of the
requirements already promulgated in the MCLs. The current MCLs for
radionuclides are expressed both in terms of radiation dose and
concentration. For man-made beta and photon emitters, the MCL is a dose
limit of 4 mrem/yr, with specific instructions for determining
radionuclide-specific concentrations corresponding to that dose (40 CFR
part 141.16(b)). For radium-226 (226 Ra) and 228
Ra combined, the MCL is a concentration level of 5 pCi/L of water,
while for gross-alpha activity (including 226 Ra but
excluding radon and uranium), the MCL is a concentration level of 15
pCi/L (40 CFR 141.15(a) and 141.15(b), respectively).
The Yucca Mountain disposal system will contain all of these types
of radionuclides. To express a regulatory limit for ground water
protection in terms of a single limit on peak concentration may be
impractical because of the separate, multiple, and distinct MCLs
established by regulation. Although the gross-alpha limit is set at 15
pCi/L to limit lifetime cancer risk to about 1 x 10-4, the
concentrations of specific alpha-emitting radionuclides corresponding
to this risk level may vary widely. For various thorium isotopes,
concentrations of 50 to 125 pCi/L are equivalent to this risk, while
for either neptunium-237 or plutonium-238, a concentration of 7 pCi/L
corresponds to a lifetime cancer risk of 1 x 10-4 (56 FR
33050, 33121, July 18, 1991). To develop a limit on the peak
concentration for each radionuclide would be unwieldy, because of the
large number of radionuclides involved. To establish a single, overall,
limiting peak concentration applicable to all radionuclides would be,
at best, an approximation of the public-health protection already
embodied in the MCLs. For these reasons, we are concerned that
expressing ground water protection requirements in terms of a single,
peak concentration or numerous radionuclide-specific limits is not
appropriate.
We request comment upon our proposal to impose the ground water
protection standards during the first 10,000 years following disposal
and whether we should, instead, adopt a compliance period of time-to-
peak concentration (see the How Far Into the Future Should Compliance
Be Projected? section earlier in this notice for a discussion of time-
to-peak-dose compliance period which is the basis of this concept).
Commenters recommending the time-to-peak-concentration approach should
address our concerns, particularly those related to implementability,
as expressed above.
[[Page 47008]]
III.F.5. How Will the Point of Compliance Be Identified?
To provide a basis for determining projected compliance with
Sec. 197.35, it is necessary to establish a geographic location where
DOE must project the concentrations of radionuclides in the ground
water over the compliance period. We refer to this location as the
``point of compliance.''
In this section, we will discuss two alternative approaches for
determining the location of the point of compliance. In the final rule,
we will specify the location to be used by NRC and DOE as the point of
compliance. One approach (used in Alternatives 1 and 4) would establish
the maximum size for an area around the repository (that is, a
``controlled area'') which would be exempt from the ground water
protection standards. In demonstrating compliance, the Department would
choose the point on the area's boundary located above the primary
ground water flow pathway and where the highest concentrations of
radionuclides are expected to be found. Under the second approach (used
in Alternatives 2 and 3), we would specify a specific geographic
location where we believe the primary ground water flow pathway and the
highest concentrations of radionuclides will be. If the Department's
improved knowledge of ground water flow direction changes the expected
location of the highest concentrations of radionuclides, DOE must
propose that location to NRC as an alternative point of compliance.
This new point of compliance, however, must be at the same distance
from the repository as the originally promulgated point of compliance.
As discussed below, DOE must obtain the approval of the Commission
prior to using the alternative point for demonstrating compliance.
Under the ``controlled area'' approach of Alternatives 1 and 4, the
standards would designate an area within which DOE would not have to
demonstrate compliance with the ground water protection standards.
These standards would apply outside of that area. Under this approach,
we are proposing that the Department would have to determine the point
on the boundary of the controlled area where the highest projected
concentrations of radionuclides will occur. That location would become
the point of compliance. In effect, a certain volume of the geologic
medium would be dedicated to delaying or keeping releases from the
waste within the controlled area and away from the accessible
environment. We adopted a generic definition of controlled area in 40
CFR part 191. The definition of controlled area for this rulemaking
could take into account unique features in the vicinity of the Yucca
Mountain site or we could adopt the definition from part 191. An
alternative for each definition is presented and discussed below.
Not applying the ground water protection standards inside a
controlled area is consistent with the approach in 40 CFR Part 191 in
which the natural geologic barriers surrounding radioactive-waste
repositories are a part of the disposal system and may be dedicated for
this purpose (50 FR 38066, 38077, September 19, 1985). We implemented
this concept in 40 CFR part 191 by requiring compliance with ground
water standards outside of the controlled area. This concept was upheld
by the First Circuit in NRDC v. EPA, 824 F.2d at 1272-73 & 1277-79. The
court reasoned that allowing for contamination of some area surrounding
a geologic repository was consistent with the site-selection provisions
of the NWPA and that Congress expected DOE to rely upon geologic
barriers and, therefore, ``knew of the inevitability of some
contamination of ground water in the immediate area of the stored
waste.'' NRDC v. EPA, 824 F.2d at 1278.
For Yucca Mountain, the EnPA also generally follows the approach of
dedicating some portion of the surrounding geology for containment and
requiring compliance in the accessible environment outside of such an
area. For example, section 801(a)(1) of the EnPA specifically uses the
term ``accessible environment'' (that is, outside of the controlled
area) when calling for us to prescribe standards for ``releases to the
accessible environment from radioactive materials stored or disposed of
in the repository.'' The EnPA also specifically incorporates the
definition from 40 CFR part 191 in its direction to NAS to address
whether a health-based standard based upon doses to individual members
of the public ``from releases to the accessible environment (as that
term is defined in the regulations in subpart B of part 191 of title
40, Code of Federal Regulations, as in effect on November 18, 1985)''
will provide a reasonable standard for protection of the general
public.
The second approach (Alternatives 2 and 3) for establishing a point
of compliance is the identification of a specific location where DOE
must project the concentration of radionuclides. Rather than
designating a ``controlled area,'' under this approach we would specify
a specific point as the point of compliance. This approach relies upon
current knowledge of the ground water flow system in the region around
Yucca Mountain with a realization that more information may be
available to DOE and NRC at the time of licensing. Therefore, if this
approach is the one we adopt in the final standard, it is important to
explain our current understanding of ground water flow in the area and
to establish a mechanism which allows flexibility for selecting an
alternative point of compliance during licensing if the current
conceptual model proves no longer valid at the time of licensing.
Despite the fact that a particular point would be designated, please
note that this approach would allow radioactive contamination in the
path of the plume of contamination between the repository footprint and
the point of compliance. In fact, the intervening area could contain
ground water which is contaminated above the ground water protection
standards. However, with this approach, those standards could not be
exceeded at or beyond the point of compliance during the proposed
10,000-year compliance period.
Our understanding, based upon current knowledge, of the flow of
ground water passing under Yucca Mountain is as follows. The general
direction of ground water movement in the aquifers under Yucca Mountain
is south and southwest. The major aquifers along the flow path are in
tuff, alluvium, and, underlying both of these, much deeper carbonate
rocks. At the edge of the repository, even the tuff aquifer is
relatively (several hundred meters) deep. It gets closer to the surface
as it moves toward its natural discharge points. Potential releases of
radionuclides from the engineered barrier system into the surrounding
rocks would be highly directional and would reflect the orientation of
fractures, rock unit contacts, and ground water flow in the area
downgradient from Yucca Mountain. Directly under the repository, we
anticipate that any waterborne releases of radionuclides will move
through the unsaturated zone and downward into the tuff aquifer, in an
easterly direction, between layers of rocks which slant to the east,
and then horizontally. The layer of tuff gradually thins proceeding
south (downgradient) from Yucca Mountain. As the tuff thins, the
overlying alluvium becomes thicker until the tuff disappears and the
water in the aquifer moves into the alluvium to become the ``alluvial
aquifer.'' Along the flow path, there might be movement of water
between the carbonate aquifer and either the tuff or alluvial aquifers.
If there is significant upward flow from the carbonate aquifer,
contamination in
[[Page 47009]]
overlying aquifers could be diluted. It is generally believed, however,
that any such flow would not significantly affect the concentration of
radionuclides in the overlying aquifers. Conversely, downward movement
of ground water from the tuff aquifer could contaminate the carbonate
aquifer. Today, most of the water for human use is withdrawn between 20
and 30 km away from the repository footprint (that is, at Lathrop Wells
and farther south through the Town of Amargosa Valley) where it is more
easily and economically accessed for agricultural use and human
consumption. It is likely that water within the alluvial aquifer is the
source of this water.
Another basis of our understanding is the historical record of
water use in the region. That record indicates that significant, long-
term human habitation has not occurred in the southwestern area of the
NTS, or for that matter anywhere in the vicinity of Yucca Mountain,
except where ground water is very easily accessible, for example, in
Ash Meadows. This observation coincides with current practice whereby
the number of wells generally decreases relative to the greater depth
to ground water. The difficulty in accessing ground water in the tuff
aquifer in the near vicinity of Yucca Mountain is made more difficult
by the rough terrain, the relative hardness of the tuff formations
containing the aquifer, and the great depth to ground water there. As
described earlier, the ground water flow from under Yucca Mountain is
thought to be generally south and southwest. In those directions, the
ground water gets progressively closer to the Earth's surface the
farther away it gets from Yucca Mountain until it is thought to
discharge to surface areas 30-40 km away (the southern boundary of NTS
is about 18 km from Yucca Mountain). This means that access into the
upper aquifer is easier at increasing distance from Yucca Mountain. It
should also be pointed out, the Yucca Mountain site is on several
Federally controlled areas of land, i.e., the Nellis Test Range, NTS,
and Bureau of Land Management land. In these areas, the U.S. government
is the senior appropriator and holds water rights, i.e., water is
appropriated for beneficial use by and for the U.S. government.
Because of DOE's ongoing site characterization studies, it is
possible that, at the time of licensing, data not now available will
reveal important inaccuracies in the preceding conception of ground
water flow. In proposing Alternatives 2 and 3 (see discussion below),
we intend that the location of the point of compliance will be where
the highest concentrations of radionuclides within the plume are
projected by DOE and NRC to be. We believe, based upon current
information, that the locations specified for the proposed alternative
points of compliance in Alternatives 2 and 3 are likely to include such
concentrations.
However, if DOE and NRC determine that the direction of ground
water flow or location of the highest concentration is different than
now believed because new knowledge is available at the time of
licensing, we propose to require the Department to propose to the
Commission the location where the highest concentration is projected to
be. Any such new point of compliance would replace the one we specify
in the final rule only if it is at the same distance from the
repository as the original point of compliance and is approved by the
Commission. It may be moved only to account for new information
regarding flow-direction or the location of the highest concentration.
We believe such flexibility will enhance the quality of NRC's licensing
decision and will provide greater protection of public health and the
environment by taking into account the latest available information. We
request comment upon this approach.
III.F.6. Where Will the Point of Compliance Be Located?
Introduction to the alternatives. We are presenting four
alternatives for comment prior to determining the location of the point
of compliance. They are presented in the proposed regulatory text (see
proposed Sec. 197.37) and are discussed here in no particular order of
preference. For convenience, we refer to them as Alternatives 1, 2, 3,
and 4, respectively.
We note that Alternatives 2 and 3 rely upon our current knowledge
of ground water flow and use in the region. As discussed above, we are
also proposing a method for proceeding under Alternatives 2 and 3, if
further knowledge changes the understanding of the flow of the region's
ground water or the location of the highest concentrations of
radionuclides.
Alternatives in proposed Sec. 197.37. Alternative 1 would establish
a ``controlled area.'' In this case, we would define the extent of the
controlled area (in proposed Sec. 197.12) as it is in 40 CFR part 191
(with the substitution of the term ``repository footprint'' for the
original wording, ``outer boundary of the original location of the
radioactive wastes in a disposal system''):
(1) A surface area, identified by passive institutional
controls, that encompasses no more than 100 square kilometers and
extends horizontally no more than five kilometers in any direction
from the repository footprint; and (2) the subsurface underlying the
surface area.
The Department would determine where on the controlled area's boundary
to place the point of compliance based upon the projected direction of
ground water flow and the expected locations of the highest
concentrations of radionuclides.
As mentioned earlier, this approach would be consistent with 40 CFR
part 191 and would, therefore, maintain consistency with the generic
standards which apply to WIPP, GCD, and any future disposal system for
SNF, HLW, and transuranic radioactive waste which is subject to 40 CFR
part 191. (As described earlier, the GCD facility is a complex of 120-
foot deep boreholes, located within NTS, which contains disposed
transuranic radioactive waste and WIPP is a geologic disposal system,
in New Mexico, for defense-related transuranic radioactive waste.)
While this alternative would not provide explicitly for consideration
of site-specific factors in determining the size of the controlled
area, it would ensure that the boundary of the controlled area would
not extend substantially beyond Yucca Mountain itself. This alternative
would have the effect of providing natural topographic constraints on
access to ground water within the controlled area. Therefore, it would
provide a safeguard against use of ground water within the controlled
area during the compliance period.
In Alternative 2, we would specify the location of the point of
compliance. In this case, the point of compliance would be located near
the intersection of U.S. Route 95 and Nevada State Route 373, commonly
referred to as Lathrop Wells (Lathrop Wells is actually an area within
the Town of Amargosa Valley and is the location closest to Yucca
Mountain where the general population currently consumes water). We
have found that the depth to the water currently withdrawn for domestic
use within the Town of Amargosa Valley ranges from a few meters in the
southern parts of the town to 110 meters near Lathrop Wells (see the
BID). This alternative would put the point of compliance near the
currently assumed location of the RMEI.
In Alternative 3, we would establish an area located about 30 km
south of Yucca Mountain within which DOE and NRC would identify a
specific point as the point of compliance. The area would be bounded by
Frontier Street on the
[[Page 47010]]
north, Nevada State Route 373 on the east, the Nevada-California border
on the south/southwest, and Casada Way on the west. About 75% of the
current population and about 60% of the current water-supply wells in
what we understand to be the downgradient direction from Yucca Mountain
are within this area. This is an area where it is relatively easy to
access ground water (see the BID). This option would, therefore,
provide direct protection for most of the population currently using
drinking water from the alluvial aquifer.
In Alternative 4, the Department, with the consent of NRC, would
establish a controlled area outside of which the ground water standards
would apply. Its size would be determined by DOE (without exceeding the
limits set by us). This controlled area would be a combination of
Alternative 1 and site-specific considerations for Yucca Mountain. The
site-specific consideration is the proximity of the repository
footprint and NTS. The boundary of the controlled area could be no more
than five kilometers from the footprint (the same limit applied in
Alternative 1), except in those cases where the five kilometers is
located within the NTS. In that case, DOE may extend the controlled
area to include all or part of the NTS.
We base this alternative, in part, upon the fact that NTS has
existed under the control of DOE for about 50 years. Another basis is
that we believe that future generations will be aware of the extensive,
well-publicized nuclear activities that occurred there. This will
likely increase the effectiveness of the passive institutional
controls, as discussed below. The NTS is well-known around the world
for many reasons but most notably for the approximately 900 tests of
nuclear weapons conducted there. This makes NTS unique in the Western
Hemisphere because of the resultant presence of hundreds of millions of
curies of radionuclides (see the BID). This will presumably lead the
Federal government to document the extent of radionuclide contamination
and the activities which occurred there, including the Yucca Mountain
disposal system, more thoroughly and retain records for longer periods
than might occur elsewhere.
To repeat for clarification, the conceptual difference between
Alternatives 1 and 4 and Alternatives 2 and 3 is that in Alternatives 1
and 4, we will define an area surrounding the repository outside of
which the ground water standards would apply, whereas for Alternatives
2 and 3, we will specify limited areas downgradient from the repository
within which DOE and NRC must place the point of compliance.
We request comment upon all of the alternatives discussed above.
Commenters should address the effectiveness of these or other
alternatives for protecting ground water, including consideration of
site-specific characteristics and reasonable methods of implementing
the alternatives.
IV. Specific Questions for Comment
In addition to requesting comment upon all aspects of this
rulemaking, many of which we have highlighted in the preceding sections
of this notice, we also request comment based upon the following
specific questions. To be most useful to us, please provide your
reasoning in your answers.
1. The NAS recommended that we base the individual-protection
standard upon risk. Consistent with this recommendation and the
statutory language of the EnPA, we are proposing a standard in terms of
annual CEDE incurred by individuals. Is our rationale for this aspect
of our proposal reasonable?
2. We are proposing an annual limit of 150 Sv (15 mrem)
CEDE to protect the RMEI and the general public from releases from
waste disposed of in the Yucca Mountain disposal system. Is our
proposed standard reasonable to protect both individuals and the
general public?
3. To define who should be protected by the proposed individual-
protection standard, we are proposing to use an RMEI as the
representative of the rural-residential CG. Is our approach reasonable?
Would it be more useful to have DOE calculate the average dose
occurring within the rural-residential CG rather than the RMEI dose?
4. Is it reasonable to use RME parameter values based upon
characteristics of the population currently located in proximity to
Yucca Mountain? Should we promulgate specific parameter values in
addition to specifying the exposure scenarios?
5. Is it reasonable to consider, select, and hold constant today's
known and assumed attributes of the biosphere for use in projecting
radiation-related effects upon the public of releases from the Yucca
Mountain disposal system?
6. In determining the location of the RMEI, we considered three
geographic subareas and their associated characteristics. Are there
other reasonable methods or factors which we could use to change the
conclusion we reached regarding the location of the RMEI? For example,
should we require an assumption that for thousands of years into the
future people will live only in the same locations that people do
today? Please include your rationale for your suggestions.
7. The NAS suggested using an NIR level to dismiss from
consideration extremely low, incremental levels of dose to individuals
when considering protection of the general public. For somewhat
different reasons, we are proposing to rely upon the individual-
protection standard to address protection of the general population. Is
this approach reasonable in the case of Yucca Mountain? If not, what is
an alternative, implementable method to address collective dose and the
protection of the general population?
8. Is our rationale for the period of compliance reasonable in
light of the NAS recommendations?
9. Does our requirement that DOE and NRC determine compliance with
Sec. 197.20 based upon the mean of the distribution of the highest
doses resulting from the performance assessment adequately address
uncertainties associated with performance assessments?
10. Is the single-borehole scenario a reasonable approach to judge
the resilience of the Yucca Mountain disposal system following human
intrusion? Are there other reasonable scenarios which we should
consider, for example, using the probability of drilling through a
waste package based upon the area of the package versus the area of the
repository footprint or drilling through an emplacement drift but not
through a waste package? Why would your suggested scenario(s) be a
better measure of the resilience of the Yucca Mountain disposal system
than the proposed scenario?
11. Is it reasonable to expect that the risks to future generations
be no greater than the risks judged acceptable today?
12. What approach is appropriate for modeling the ground water flow
system downgradient from Yucca Mountain at the scale (many kilometers
to tens of kilometers) necessary for dose assessments given the
inherent limitations of characterizing the area? Is it reasonable to
assume that there will be some degree of mixing with uncontaminated
ground water along the radionuclide travel paths from the repository?
13. Which approach for protecting ground water in the vicinity of
Yucca Mountain is the most reasonable? Is there another approach which
would be preferable and reasonably implementable? If so, please explain
the approach, why it is preferable, and how it could be implemented.
14. Is the 10,000-year compliance period for protecting the RMEI
and ground water reasonable or should we
[[Page 47011]]
extend the period to the time of peak dose? If we extend it, how could
NRC reasonably implement the standards while recognizing the nature of
the uncertainties involved in projecting the performance of the
disposal system over potentially extremely long periods?
15. As noted by NAS, some countries have individual-protection
limits higher than we have proposed. In addition, other Federal
authorities have suggested higher individual-dose limits with no
separate protection of ground water. Therefore, we request comment upon
the use of an annual CEDE of 250 Sv (25 mrem) with no separate
ground water protection, including the consistency of such a limit with
our ground water protection policy.
16. We are proposing to require, in the individual-protection
standard, that DOE must project the disposal system's performance after
10,000 years. Are the specified uses of the projections appropriate and
adequate?
V. Regulatory Analyses
V.A. Executive Order 12866
Section 3(f) of Executive Order 12866 (E.O. 12866) defines
``significant regulatory action'' for purposes of centralized
regulatory review by the Office of Management and Budget (OMB) to mean
any regulatory action that is likely to result in a rule that may:
(1) Have an annual effect upon the economy of $100 million or more
or adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or tribal governments or
communities;
(2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
(3) Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs or the rights and obligations of recipients
thereof; or
(4) Raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
We are classifying this proposed action as significant under the
fourth clause. These standards have been mandated by the EnPA which
gave us, for the first time, the authority to set site-specific
environmental radiation protection standards. Also, the subject of this
rulemaking, Yucca Mountain, Nevada, is a unique facility since it is
the first and only one of its kind in the United States being studied
for the potential disposal of SNF and HLW.
The OMB has reviewed the text of the draft of this rulemaking and
associated materials. In accordance with Sec. 6(a)(3)(E) of E.O. 12866,
we have placed interagency review materials into the docket and other
locations listed at the beginning of this notice. The interagency
materials include: (1) the draft document(s) provided to OMB; and (2)
document(s) identifying the substantive changes made between the draft
submitted to OMB and the proposed rulemaking, and identifying those
changes that we made at the suggestion or recommendation of OMB.
V.B. Executive Orders on Federalism
Under Executive Order 12875 (E.O. 12875), ``Enhancing
Intergovernmental Partnerships,'' we may not issue a regulation that is
not required by statute and that creates a mandate upon a State, local,
or tribal government, unless the Federal government provides the funds
necessary to pay the direct compliance costs incurred by those
governments, or unless we consult with those governments. If we comply
by consulting, E.O. 12875 requires us to provide to OMB a description
of the extent of our prior consultation with representatives of
affected State, local, and tribal governments; the nature of their
concerns; any written communications from the governments; and a
statement supporting the need to issue the regulation. In addition,
E.O. 12875 requires us to develop an effective process permitting
elected officials and other representatives of State, local, and tribal
governments ``to provide meaningful and timely input in the development
of regulatory proposals containing significant unfunded mandates.''
Today's rule does not create a mandate upon State, local, or tribal
governments. The rule does not impose any enforceable duties upon those
entities. Accordingly, the requirements of section 1(a) of E.O. 12875
do not apply to this rule. Despite this fact, we nonetheless held
public meetings in Nevada and Washington, D.C. in September 1995 (see
the How Has the Public Participated in Our Review of the NAS Report?
section earlier in this notice) during which we received comments from
and had discussions with representatives of the State of Nevada and
county officials. There were also informal meetings with State and
local officials in which those personnel were apprised of the status of
the rulemaking.
Finally, while there is a new executive order on federalism, it
will not go into effect for 90 days. In the interim, under the current
Executive Order 12612 on Federalism, this rule does not have a
substantial direct effect upon States, upon the relationship between
the national government and the States, or upon the distribution of
power and responsibilities among the various levels of government,
because the rule only prescribes standards appropriate for one facility
in one State.
V. C. Executive Order 12898
Executive Order 12898, ``Federal Actions to Address Environmental
Justice in Minority Populations And Low-income Populations
(Environmental Justice),'' directs us to incorporate environmental
justice as part of our overall mission by identifying and addressing
disproportionately high and adverse human health and environmental
effects of programs, policies, and activities upon minority populations
and low-income populations.
We find no disproportionate impact in the outcome of this
rulemaking. No plan has thus been devised to address a disproportionate
impact.
V. D. Executive Order 13045
Executive Order 13045 (E.O. 13045), ``Protection of Children from
Environmental Health Risks and Safety Risks,'' (62 FR 19885, April 23,
1997) applies to any rule that (1) is determined to be ``economically
significant'' as defined under E.O. 12866, and (2) concerns an
environmental health or safety risk that we have reason to believe may
have a disproportionate effect upon children. If the regulatory action
meets both criteria, we must evaluate the environmental health or
safety effects of the planned rule upon children, and explain why the
planned regulation is preferable to other potentially effective and
reasonably feasible alternatives that we considered.
This proposed rule is not subject to E.O. 13045 because we do not
have reason to believe the environmental health risks or safety risks
addressed by this action present a disproportionate risk to children.
The public is invited to submit or identify peer-reviewed studies and
data, of which we may not be aware, that assessed results of early life
exposure to radiation.
V. E. Executive Order 13084
Under Executive Order 13084 (E.O. 13084), ``Consultation and
Coordination with Indian Tribal Governments,'' we may not issue a
regulation that is not required by statute, that significantly or
uniquely affects the communities of Indian tribal governments, and that
imposes substantial direct compliance costs upon those communities,
unless the Federal government provides the funds necessary to pay the
direct
[[Page 47012]]
compliance costs incurred by the tribal governments, or we consult with
those governments. If we comply by consulting, Executive Order 13084
requires us to provide to OMB, in a separately identified section of
the preamble to the rule, a description of the extent of our prior
consultation with representatives of affected tribal governments, a
summary of the nature of their concerns, and a statement supporting the
need to issue the regulation. In addition, E.O. 13084 requires us to
develop an effective process permitting elected officials and other
representatives of Indian tribal governments ``to provide meaningful
and timely input in the development of regulatory policies on matters
that significantly or uniquely affect their communities.''
Today's rule implements requirements specifically set forth by the
Congress in the EnPA without the exercise of any discretion by us.
Accordingly, the requirements of section 3(b) of E.O. 13084 do not
apply to this rule.
V. F. National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
Act of 1995 (NTTAA), Pub. L. No. 104-113, section 12(d) (15 U.S.C. 272
note) directs us to use voluntary consensus standards in our regulatory
activities unless to do so would be inconsistent with applicable law or
otherwise impractical. Voluntary consensus standards are technical
standards (e.g., materials specifications, test methods, sampling
procedures, and business practices) that are developed or adopted by
voluntary consensus standards bodies. The NTTAA directs us to provide
Congress, through OMB, explanations when we decide not to use available
and applicable voluntary consensus standards. This proposed rulemaking
does not involve technical standards. Therefore, we are not considering
the use of any voluntary consensus standards.
We request public comment upon this aspect of the proposed
rulemaking and, specifically, ask you to identify potentially
applicable voluntary consensus standards and to explain why such
standards could be used in this regulation.
V. G. Paperwork Reduction Act
We have determined that this proposed rule contains no information
requirements within the scope of the Paperwork Reduction Act, 42 U.S.C.
3501-20.
V. H. Regulatory Flexibility Act/Small Business Regulatory Enforcement
Fairness Act of 1996
Under the Regulatory Flexibility Act, 5 U.S.C. 601 et seq.,
agencies must prepare and make available for public comment an initial
regulatory flexibility analysis assessing the impact of a proposed rule
upon ``small entities'' (5 U.S.C. 603). ``Small entities'' include
small businesses, small not-for-profit enterprises, and government
entities with jurisdiction over populations of less than 50,000 (5
U.S.C. 601). However, the requirement to prepare a regulatory
flexibility analysis does not apply if the Administrator certifies that
the rule will not, if promulgated, have a significant economic impact
upon a substantial number of small entities (5 U.S.C. 605(b)). The rule
proposed today would establish requirements that apply only to DOE.
Therefore, it does not apply to small entities. Accordingly, I hereby
certify that the rule, when promulgated, will not have a significant
economic impact upon a substantial number of small entities.
V.I. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA, Pub. L.
104-4) establishes requirements for Federal agencies to assess the
effects of their regulatory actions upon State, local, and tribal
governments and the private sector. Under section 202 of UMRA, we
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures by State, local, and tribal governments, in
the aggregate, or to the private sector, of $100 million or more in any
one year. Before we promulgate a rule for which a written statement is
needed, section 205 of UMRA generally requires us to identify and
consider a reasonable number of regulatory alternatives and adopt the
least costly, most cost-effective, or least burdensome alternative that
achieves the objectives of the rule. The provisions of section 205 do
not apply when they are inconsistent with applicable law. Moreover,
section 205 allows us to adopt an alternative other than the least
costly, most cost-effective, or least burdensome if the Administrator
publishes with the final rule an explanation as to why that alternative
was not adopted. Before we establish any regulatory requirements that
significantly or uniquely affect small governments, including tribal
governments, we must develop, under section 203 of UMRA, a small-
government-agency plan. The plan must provide for notifying potentially
affected small governments, enabling officials of affected small
governments to have meaningful and timely input into the development of
regulatory proposals with significant Federal intergovernmental
mandates, and informing, educating, and advising small governments on
compliance with the regulatory requirements.
Today's proposed rule is not subject to the requirements of
sections 202 and 205 of UMRA because it implements requirements
specifically set forth by the Congress in section 801 of the EnPA. We
are proposing rules which, when final, would establish requirements
that DOE and NRC must follow in connection with licensing the Yucca
Mountain disposal system. The EnPA directs the Administrator of EPA to
promulgate standards for the protection of the public from releases
from radioactive materials stored or disposed of in the repository at
Yucca Mountain, Nevada.
Also, today's proposed rule does not impose new, enforceable duties
upon State, local, or tribal governments, or the private sector. Thus,
we have determined that this rule contains no regulatory requirements
that might significantly or uniquely affect small governments as
contemplated in section 203 of UMRA.
List of Subjects in 40 CFR Part 197
Environmental protection, Nuclear energy, Radiation protection,
Radionuclides, Uranium, Waste treatment and disposal, Spent nuclear
fuel, High-level radioactive waste.
Dated: August 18, 1999.
Carol M. Browner,
Administrator.
The Environmental Protection Agency is proposing to add a new part
197 to Subchapter F of Chapter I, title 40 of the Code of Federal
Regulations, as follows:
SUBCHAPTER F--RADIATION PROTECTION PROGRAMS
PART 197--ENVIRONMENTAL RADIATION PROTECTION STANDARDS FOR YUCCA
MOUNTAIN, NEVADA
Subpart A--Environmental Standards for Storage
Sec.
197.1 What does subpart A cover?
197.2 What definitions apply in subpart A?
197.3 How is subpart A implemented?
197.4 What is DOE required to do relative to stored radioactive
material?
197.5 When will this part take effect?
[[Page 47013]]
Subpart B--Environmental Standards for Disposal
Introduction
197.11 What does subpart B cover?
197.12 What definitions apply in subpart B?
197.13 How is subpart B implemented?
197.14 What is reasonable expectation?
197.15 How must DOE take into account the changes that will occur
during the next 10,000 years?
Individual-Protection Standard
197.20 What standard must DOE meet?
197.21 Who is the reasonably maximally exposed individual (RMEI)?
Human-Intrusion Standard
197.25 What standard must DOE meet?
197.26 What are the circumstances of the human intrusion?
Other Considerations
197.30 What other projections must be made by DOE?
Ground Water Protection Standards
197.35 What standards must DOE meet?
197.36 What is a representative volume?
197.37 Where is the point of compliance?
Additional Provisions
197.40 Are there limits on what must be considered in the
performance assessments?
197.41 Can the EPA amend this rule?
Authority: Sec. 801, Pub. L. 102-486, 106 Stat. 2921, 42 U.S.C.
10141 n.
Subpart A--Environmental Standards for Storage
Sec. 197.1 What does subpart A cover?
This subpart covers the storage of radioactive materials by DOE in
the Yucca Mountain repository and on the Yucca Mountain site.
Sec. 197.2 What definitions apply in subpart A?
Annual committed effective dose equivalent means the committed
effective dose equivalent plus the effective dose equivalent received
by an individual in one year from radiation sources external to the
individual.
Committed effective dose equivalent means the total effective dose
equivalent received by an individual from radionuclides internal to the
individual following a one-year intake of those radionuclides.
DOE means the Department of Energy.
Effective dose equivalent means the sum over specified tissues of
the products of the dose equivalent received following an exposure of,
or an intake of radionuclides into, specified tissues of the body,
multiplied by appropriate weighting factors.
EPA means the Environmental Protection Agency.
General environment means everywhere outside the Yucca Mountain
site, the Nellis Air Force Range, and the Nevada Test Site.
High-level radioactive waste means high-level radioactive waste as
defined in the Nuclear Waste Policy Act of 1982 (Public Law 97-425).
Member of the public means anyone who is not a radiation worker for
purposes of worker protection.
NRC means the Nuclear Regulatory Commission.
Radioactive material means matter composed of or containing
radionuclides subject to the Atomic Energy Act of 1954, as amended.
Radioactive material includes, but is not limited to, high-level
radioactive waste and spent nuclear fuel.
Spent nuclear fuel means spent nuclear fuel as defined in the
Nuclear Waste Policy Act of 1982 (Public Law 97-425).
Storage means retention (and any associated activity, operation, or
process necessary to carry out successful retention) of radioactive
material with the intent or capability to readily access or retrieve
such material.
Yucca Mountain repository means the mined portion of the facility
constructed underground within the Yucca Mountain site.
Yucca Mountain site means the site recommended by the Secretary of
DOE to the President under section 112(b)(1)(B) of the Nuclear Waste
Policy Act of 1982 (42 U.S.C. 10132(b)(1)(B)) on May 27, 1986.
Sec. 197.3 How is subpart A implemented?
The NRC implements this subpart A. The DOE must demonstrate to NRC
that operations on the Yucca Mountain site will occur in compliance
with this subpart before NRC may grant to DOE a license to receive and
possess radioactive material on the Yucca Mountain site.
Sec. 197.4 What is DOE required to do relative to stored radioactive
material?
(a) The DOE must ensure that no member of the public in the general
environment receives more than an annual committed effective dose
equivalent of 150 microsieverts (15 millirems) from the combination of:
(1) Management and storage (as defined in 40 CFR 191.02) of
radioactive material which:
(i) Is subject to 40 CFR 191.03(a); and
(ii) Occurs outside of the Yucca Mountain repository but within the
Yucca Mountain site; and
(2) Storage (as defined in Sec. 197.02) of radioactive material
inside the Yucca Mountain repository.
Sec. 197.5 When will this part take effect?
The standards in this part take effect on [sixty days after
publication of the final standards in the Federal Register].
Subpart B--Environmental Standards for Disposal
Introduction
Sec. 197.11 What does subpart B cover?
This subpart covers the disposal of waste in Yucca Mountain by DOE.
Sec. 197.12 What definitions apply in subpart B?
All definitions in subpart A of this part and the following:
Active institutional control means controlling access and/or
performing work on the Yucca Mountain site by any means other than
passive institutional controls.
Aquifer means an underground geological formation, group of
formations, or part of a formation that can yield a significant amount
of water to a well or spring.
Barrier means any material, structure, or feature that, for a
period to be determined by NRC, prevents or substantially reduces the
rate of movement of water or radionuclides from the Yucca Mountain
repository, or prevents the release or substantially reduces the
release rate of radionuclides from the waste. For example, a barrier
may be a geologic feature, an engineered structure, a canister, a waste
form with physical and chemical characteristics that significantly
decrease the mobility of radionuclides, or a material placed over and
around the waste, provided that the material substantially delays
movement of water or radionuclides.
Alternative 1 for Sec. 197.12, Definition of Controlled Area:
Controlled area means:
(1) A surface area, identified by passive institutional controls,
that encompasses no more than 100 square kilometers and extends
horizontally no more than five kilometers in any direction from the
repository footprint; and
(2) The subsurface underlying the surface area. [This definition
would be included only if Alternative 1 for Sec. 197.37 were chosen.]
Alternative 2 for Sec. 197.12, Definition of Controlled Area:
Controlled area means:
(1) A surface area, identified by passive institutional controls,
that extends horizontally no more than five kilometers in any direction
from the repository footprint except that DOE may include in the
controlled area any
[[Page 47014]]
contiguous area within the boundary of the Nevada Test Site (as
established as of the date of promulgation of this part); and
(2) The subsurface underlying the surface area. [This definition
would be included only if Alternative 4 for Sec. 197.37 were chosen.]
Disposal means emplacement of radioactive material into the Yucca
Mountain disposal system with the intent of isolating it for as long as
reasonably possible and with no intent of recovery, whether or not the
design of the disposal system permits the ready recovery of the
material. Disposal of radioactive material in the Yucca Mountain
disposal system begins when all of the ramps and other openings into
the Yucca Mountain repository are backfilled and sealed.
Ground water means water below the land surface and in a saturated
zone.
Human intrusion means breaching of any portion of the Yucca
Mountain disposal system by human activity.
Passive institutional controls means:
(1) Markers, as permanent as practicable, placed on the Earth's
surface;
(2) Public records and archives;
(3) Government ownership and regulations regarding land or resource
use; and
(4) Other reasonable methods of preserving knowledge about the
location, design, and contents of the Yucca Mountain disposal system.
Peak dose means the highest annual committed effective dose
equivalent projected to be received by the reasonably maximally exposed
individual.
Performance assessment means an analysis that:
(1) Identifies the processes, events, and sequences of processes
and events (except human intrusion), and their probabilities of
occurring over 10,000 years after disposal, that might affect the Yucca
Mountain disposal system;
(2) Examines the effects of those processes, events, and sequences
of processes and events upon the performance of the disposal system;
and
(3) Estimates the annual committed effective dose equivalent
received by the reasonably maximally exposed individual, including the
associated uncertainties, as a result of releases caused by all
significant processes, events, and sequences of processes and events.
Period of geologic stability means the time during which the
variability of geologic characteristics and their future behavior in
and around the Yucca Mountain site can be bounded, that is, they can be
projected within a reasonable range of possibilities.
Plume of contamination means that volume of ground water that
contains radioactive contamination from releases from the Yucca
Mountain disposal system. It does not include releases from any other
potential sources on or near the Nevada Test Site.
Point of compliance is the place where DOE must project the amount
of radionuclides in the ground water for purposes of Sec. 197.35. The
point of compliance is located above the highest concentration in the
plume of contamination as specified in Sec. 197.37.
Repository footprint means the outline of the outermost locations
of where the waste is emplaced in the Yucca Mountain repository.
Slice of the plume means a cross-section of the plume of
contamination with sufficient thickness parallel to the prevalent flow
of the plume that it contains the representative volume.
Total dissolved solids means the total dissolved (filterable)
solids in water as determined by use of the method specified in 40 CFR
part 136.
Undisturbed performance means that human intrusion or the
occurrence of unlikely, disruptive, natural processes and events do not
disturb the disposal system.
Waste means any radioactive material emplaced for disposal into the
Yucca Mountain disposal system.
Well-capture zone means the volume from which a well pumping at a
defined rate is withdrawing water from an aquifer. The dimensions of
the well-capture zone are determined by the pumping rate in combination
with aquifer characteristics assumed for calculations, such as
hydraulic conductivity, gradient, and the screened interval.
Yucca Mountain disposal system means the combination of underground
engineered and natural barriers at the Yucca Mountain site which
prevents or substantially reduces releases from the disposed
radioactive material.
Sec. 197.13 How is subpart B implemented?
The NRC implements subpart B. In the case of the specific numerical
requirements in this subpart, NRC will determine compliance based upon
the mean or median (whichever is higher) of the highest results of
DOE's performance assessments projecting the performance of the Yucca
Mountain repository for 10,000 years after disposal. The DOE must
demonstrate to NRC that there is a reasonable expectation of compliance
with this subpart before NRC can issue a license.
Sec. 197.14 What is reasonable expectation?
Reasonable expectation means that the Commission is satisfied that
compliance will be achieved based upon the full record before it.
Reasonable expectation:
(a) Requires less than absolute proof because absolute proof is
impossible to attain for disposal due to the uncertainty of projecting
long-term performance;
(b) Is less stringent than the reasonable assurance concept that
NRC uses to license nuclear power plants;
(c) Takes into account the inherently greater uncertainties in
making long-term projections of the performance of the Yucca Mountain
disposal system;
(d) Does not exclude important parameters from assessments and
analyses simply because they are difficult to precisely quantify to a
high degree of confidence; and
(e) Focuses performance assessments and analyses upon the full
range of defensible and reasonable parameter distributions rather than
only upon extreme physical situations and parameter values.
Sec. 197.15 How must DOE take into account the changes that will occur
during the next 10,000 years?
The DOE should not attempt to project changes to society, human
biology, or increases or decreases to human knowledge. In all analyses
done to demonstrate compliance with this part, DOE must assume that all
of those factors remain constant as they are at the time of license
submission to NRC. However, DOE must vary factors related to the
geology, hydrology and climate based on environmentally protective but
reasonable scientific predictions of the changes that could affect the
Yucca Mountain disposal system over the next 10,000 years.
Individual-Protection Standard
Sec. 197.20 What standard must DOE meet?
The DOE must demonstrate, using performance assessment, that there
is a reasonable expectation that for 10,000 years following disposal
the reasonably maximally exposed individual receives no more than an
annual committed effective dose equivalent of 150 microsieverts (15
mrem) from releases from the undisturbed Yucca Mountain disposal
system. The DOE's analysis must include all potential pathways of
radionuclide transport and exposure.
Sec. 197.21 Who is the reasonably maximally exposed individual (RMEI)?
The RMEI is a hypothetical person who could meet the following
criteria:
[[Page 47015]]
(a) Based upon current understanding, lives within one-half
kilometer of the junction of U.S. Route 95 and Nevada State Route 373,
unless NRC determines that the RMEI would receive a higher dose living
in another location at the same distance from the Yucca Mountain
repository;
(b) Has a diet and living style representative of the people who
are now residing in the Town of Amargosa Valley, Nevada. The DOE must
use the most accurate projections which might be based upon surveys of
the people residing in the Town of Amargosa Valley, Nevada, to
determine their current diets and living styles and use the mean values
in the assessments conducted for Secs. 197.20 and 197.25; and
(c) Drinks 2 liters of water per day from wells drilled into the
ground water at the location where the RMEI lives.
Human-Intrusion Standard
Sec. 197.25 What standard must DOE meet?
Alternative 1 for Sec. 197.25:
The DOE must demonstrate that there is a reasonable expectation
that for 10,000 years following disposal the reasonably maximally
exposed individual receives no more than an annual committed effective
dose equivalent of 150 microsieverts (15 mrem) as a result of a human
intrusion. The DOE's analysis of human intrusion must include all
potential environmental pathways of radionuclide transport and
exposure.
Alternative 2 for Sec. 197.25:
The DOE must determine the earliest time after disposal that the
waste package would degrade sufficiently that a human intrusion (see
Sec. 197.26) could occur without recognition by the drillers. The DOE
must:
(a) Demonstrate that there is a reasonable expectation that the
reasonably maximally exposed individual receives no more than an annual
committed effective dose equivalent of 150 microsieverts (15 mrem) as a
result of a human intrusion, if complete waste package penetration can
occur at or before 10,000 years after disposal. The analysis must
include all potential environmental pathways of radionuclide transport
and exposure; and
(b) Include the results of the analysis and its bases in the
environmental impact statement for Yucca Mountain as an indicator of
long-term disposal system performance, if the intrusion cannot occur
before 10,000 years after disposal.
Sec. 197.26 What are the circumstances of the human intrusion?
For the purposes of the analysis of human intrusion, DOE must make
the following assumptions:
(a) There is a single human intrusion as a result of exploratory
drilling for ground water;
(b) The intruders drill a borehole directly through a degraded
waste container into the uppermost aquifer underlying the Yucca
Mountain repository;
(c) The drillers use the common techniques and practices that are
currently employed in the region surrounding Yucca Mountain;
(d) Careful sealing of the borehole does not occur, instead natural
degradation processes gradually modify the borehole;
(e) Only releases of radionuclides that occur as a result of the
intrusion and that are transported through the resulting borehole to
the saturated zone are projected;
(f) No releases are included which are caused by unlikely natural
processes and events; and
(g) The intrusion occurs at a time or within a range of time
determined by NRC. The NRC must make that determination based upon the
following factors
[Paragraph (g) would be included only if Alternative 1 for
Sec. 197.25 is chosen]:
(1) The earliest time that current drilling techniques could lead
to waste package penetration without recognition by the drillers;
(2) The time it would take for a small percentage of waste packages
to fail but before significant migration of radionuclides has occurred;
and
(3) Intrusion would not occur during the period of active
institutional control.
Other Considerations
Sec. 197.30 What other projections must be made by DOE?
To complement the results of Sec. 197.20, DOE must calculate the
peak dose of the reasonably maximally exposed individual that would
occur after 10,000 years following disposal but within the period of
geologic stability. While no regulatory standard applies to the results
of this analysis, DOE must include the results and their bases in the
environmental impact statement for Yucca Mountain as an indicator of
long-term disposal system performance.
Ground Water Protection Standards
Sec. 197.35 What standards must DOE meet?
In its license application to NRC, DOE must provide a reasonable
expectation that, for 10,000 years of undisturbed performance after
disposal, releases of radionuclides from radioactive material in the
Yucca Mountain disposal system will not cause the level of
radioactivity in the representative volume of ground water at the point
of compliance to exceed the limits in Table 1 as follows:
Table 1.--Limits on Radionuclides in the Representative Volume.
------------------------------------------------------------------------
Is natural
Radionuclide or type of Limit background
radiation emitted included?
------------------------------------------------------------------------
Combined radium-226 and radium- 5 picocuries per Yes
228. liter.
Gross alpha activity 15 picocuries per Yes
(including radium-226 but liter.
excluding radon and uranium).
Combined beta and photon 40 microsieverts (4 No
emitting radionuclides. millirem) per year
to the whole body or
any organ.
------------------------------------------------------------------------
Sec. 197.36 What is a representative volume?
(a) It is the volume of ground water that would be withdrawn
annually from an aquifer containing less than 10,000 milligrams of
total dissolved solids per liter of water to supply a given water
demand. The DOE must project the concentration of radionuclides from
the Yucca Mountain repository that will be in the representative
volume. The DOE must then use the projected concentrations to
demonstrate to NRC compliance with Sec. 197.35. The DOE must make the
following assumptions concerning the representative volume:
(1) It is centered on the highest concentration level in the plume
of contamination at the point of compliance;
[[Page 47016]]
(2) Its position and dimensions in the aquifer are determined using
average hydrologic characteristics for the aquifers along the
radionuclide migration path from the Yucca Mountain repository to the
compliance point as determined by site characterization; and
(3) It contains 1285 acre-feet of water (about 1,591,023,000 liters
or 418,690,000 gallons).
(b) The DOE must use one of two alternative methods for determining
the dimensions of the representative volume. The DOE must propose the
method, and any underlying assumptions, to NRC for approval.
(1) The dimensions may be calculated as a well-capture zone. If
this approach is used, DOE must assume that the:
(i) Water supply well has characteristics consistent with public
water supply wells in Amargosa Valley, Nevada, for example, well bore
size and length of the screened intervals;
(ii) Screened interval is centered in the highest concentration in
the plume of contamination at the point of compliance; and
(iii) Pumping rate is set to produce an annual withdrawal equal to
the representative volume.
(2) The dimensions may be calculated as a slice of the plume. If
this approach is used, DOE must:
(i) Propose to NRC, for its approval, where the location of the
edge of the plume of contamination occurs. For example, the place where
the concentration of radionuclides reaches 0.1% of the level of the
highest concentration at the point of compliance;
(ii) Assume that the slice of the plume is perpendicular to the
prevalent direction of flow of the aquifer; and
(iii) Assume that the volume of ground water contained within the
slice of the plume is equal to the representative volume.
Sec. 197.37 Where is the point of compliance?
Alternative 1 for Sec. 197.37:
The point of compliance is any point on the boundary of the
controlled area.
Alternative 2 for Sec. 197.37:
The point of compliance is any point within a one-half kilometer
radius of the intersection of U.S. Route 95 and Nevada State Route 373.
However, if NRC determines that there is another location, at the same
distance (approximately 20 kilometers) from the center of the
repository footprint, where the representative volume would have a
higher concentration of radionuclides which were released from the
Yucca Mountain disposal system, NRC must specify that location the
point of compliance.
Alternative 3 for Sec. 197.37:
The point of compliance is any point within the Town of Amargosa
Valley, Nevada, and within the area bounded by Frontier Street on the
north, Nevada State Route 373 on the east, the Nevada-California border
on the south/southwest, and Casada Way on the west (as they are located
at the time of promulgation of this part). However, if NRC determines
that there is another location, at approximately 30 kilometers, from
the center of the repository footprint where the representative volume
would have a higher concentration of radionuclides which were released
from the Yucca Mountain disposal system, NRC must specify that location
as the point of compliance.
Alternative 4 for Sec. 197.37:
The point of compliance is any point on the boundary of the
controlled area.
Additional Provisions
Sec. 197.40 Are there limits on what must be considered in the
performance assessments?
Yes. The DOE's performance assessments should not include
consideration of processes or events that are estimated to have less
than one chance in 10,000 of occurring within 10,000 years of disposal.
The NRC may change this limit to exclude slightly higher probability
events. In addition, with the NRC's approval, DOE's performance
assessments need not evaluate, in detail, the impacts resulting from
any processes and events or sequences of processes and events with a
higher chance of occurrence if the results of the performance
assessments would not be changed significantly.
Sec. 197.41 Can EPA amend this rule?
Yes. We can amend this rule by another notice-and-comment
rulemaking. However, if we amend this rule, there must be a public
comment period of at least 90 days and we must, at a minimum, hold
hearings in Washington, D.C. and the Nevada Counties of Nye and Clark.
[FR Doc. 99-21913 Filed 8-26-99; 8:45 am]
BILLING CODE 6560-50-P
