[Federal Register Volume 62, Number 121 (Tuesday, June 24, 1997)]
[Notices]
[Pages 34091-34095]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-16484]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-255, 50-266, 50-301, 50-313, 50-368, 72-5, 72-7, 72-13,
and 72-1007]
Consumers Power Company (Palisades Nuclear Plant), Wisconsin
Electric Power Company (Point Beach Nuclear Plant, Units 1 and 2),
Entergy Operations, Inc. (Arkansas Nuclear One, Units 1, and 2);
Issuance of Director's Decision Under 10 CFR 2.206
Notice is hereby given that the Director, Office of Nuclear
Material Safety and Safeguards, has issued a Director's Decision
concerning a Petition dated October 18, 1996, filed by Don't Waste
Michigan and the Lake Michigan Federation (Petitioners) under Section
2.206 of Title 10 of the Code of Federal Regulations (10 CFR 2.206).
The Petition requested that the U.S. Nuclear Regulatory Commission
order all users of Ventilated Storage Casks (VSC-24) systems to refrain
from loading any casks until the certificate of compliance (COC),
safety analysis report (SAR), and safety evaluation report (SER) are
amended to include operating controls and limits to prevent hazardous
conditions. Such conditions include the generation of explosive gases,
caused by the interaction between the VSC materials and the
environments, encountered during loading, storage, and unloading.
Further, Petitioners claim the VSC-24 should not be used until: (i)
An independent third-party review team has examined the safety issues
they raise; (ii) the potential impacts of all material aspects of the
casks have been fully assessed; (iii) there is experimental
verification of temperature calculations and heat transfer assessments
and other design assumptions; (iv) the safety of the material coatings
on components and structures has been justified; and (v) the SAR, SER,
and COC are amended to include the necessary operating control and
limits to direct safe use of the VSC-24.
The Director of the Office of Nuclear Material Safety and
Safeguards has determined that the Petition should be denied for the
reasons stated in the ``Director's Decision Under 10 CFR 2.206'' (DD-
97-15), the complete text of which follows this notice. The decision
and documents cited in the decision are available for public inspection
and copying in the Commission's Public Document Room, the Gelman
Building, 2120 L Street, NW., Washington, DC.
A copy of this decision has been filed with the Secretary of the
Commission for the Commission's review in accordance with 10 CFR
2.206(c). As provided therein, this decision will become the final
action of the Commission 25 days after issuance unless the Commission,
on its own motion, institutes review of the decision within that time.
Dated at Rockville, Maryland, this 18th day of June, 1997.
For the Nuclear Regulatory Commission.
Malcolm R. Knapp,
Acting Director, Office of Nuclear Material Safety and Safeguards.
Director's Decision Under 10 CFR 2.206
[DD-97-15]
I. Introduction
On October 18, 1996, Don't Waste Michigan and the Lake Michigan
Federation (Petitioners) filed a Petition pursuant to Section 2.206 of
Title 10 of the Code of Federal Regulations (10 CFR 2.206) requesting
that the U.S. Nuclear Regulatory Commission take the following action:
Prohibit loading of Ventilated Storage Casks (VSC-24s) until the
certificate of compliance (COC), the Safety analysis report (SAR),
and the safety evaluation report (SER) are amended following an
independent, third-party review of the VSC-24 design, to address
concerns raised by the Petitioners' engineering consultant, Dr.
Rudolf Hausler.
The Petition has been referred to me pursuant to 10 CFR 2.206. By
letter dated December 10, 1996, to Dr. Mary Sinclair and Ms. Eleanor
Roemer, on behalf of the Petitioners, NRC acknowledged receipt of the
Petition and provided the NRC staff's determination that the Petition
did not require immediate action by the NRC. Notice of receipt was
published in the Federal Register on January 13, 1997 (62 FR 1783).
On the basis of the NRC staff's evaluation of the issues and for
the reasons given below, I have determined that the Petitioners'
request should be denied.
II. Background
On May 28, 1996, a hydrogen gas ignition occurred during the
welding of the shield lid after spent fuel had been loaded into a VSC-
24 at the Point Beach Nuclear Plant. The hydrogen was formed by a
chemical reaction between a zinc-based coating (Carbo Zinc 11) and the
borated water in the spent fuel pool. On June 3, 1996, the NRC issued
confirmatory action letters (CALs) to those licensees using or planning
to use VSC-24s for dry storage of spent nuclear fuel, i.e., licensees
for Point Beach Nuclear Plant, Palisades Nuclear Generating Plant, and
Arkansas Nuclear One (ANO). The CAL issued to the licensee for ANO was
supplemented on June 21, 1996, and the CALs issued to the licensees for
Point Beach and Palisades were supplemented on June 27, 1996. The CALs,
as supplemented, documented the licensees' commitments not to load or
unload a VSC-24 without resolution of material compatibility issues
identified in a forthcoming general communication and subsequent NRC
confirmation of corrective actions taken by the licensees. The generic
communication was issued on July 5, 1996, in the form of NRC Bulletin
96-04, ``Chemical, Galvanic, or Other Reactions in Spent Fuel Storage
and Transportation Casks.'' NRC Bulletin 96-04 notified addressees
about the potential for adverse chemical, galvanic, or other reactions
among the materials of a spent fuel storage or transportation cask, its
contents, and the environments the cask may encounter during use. The
actions requested in Bulletin 96-04 included reviewing the cask
materials for potential adverse reactions, evaluating the short-term
and long-term effects of any identified reactions, and
[[Page 34092]]
determining the adequacy of cask operating procedures to minimize the
consequences of any identified reactions. The NRC staff has
acknowledged that the event demonstrated that the cask vendor's (Sierra
Nuclear Corporation) SAR for the VSC-24 and related NRC review, as
documented in the NRC staff's SER, did not adequately address the use
of a zinc-based coating and its reaction with the acidic water in spent
fuel pools.
In response to Bulletin 96-04 and to subsequent NRC staff
inquiries, the licensees for ANO, Point Beach, and Palisades submitted
to the NRC evaluations of possible material interactions and the
effects of such interactions on cask performance and operation. The
licensees also submitted information on the operating controls and
limits that were implemented to prevent hazardous conditions which may
result from adverse material interactions. The operating controls and
limits included controls for the environments that the casks encounter
during use, requirements for inspections and environmental sampling,
and additional precautions for various cask operations.
The NRC staff evaluated the responses submitted by the licensee for
ANO. As documented in the staff's safety evaluation dated December 3,
1996, the staff determined that the licensee's submittals provided the
necessary level of confidence that the VSC-24 can be used to safely
store spent fuel over the 20-year period of the certificate. The staff
also determined that the operating controls and limits proposed by the
licensee are acceptable and satisfy regulatory requirements. By a
separate letter, also dated December 3, 1996, the staff informed the
licensee for ANC that its corrective actions had been verified by
inspections performed by the NRC staff. Shortly thereafter, the
licensee initiated cask loading activities.
The NRC staff also evaluated the responses submitted by the
licensees for Point Beach and Palisades. As documented in the staff's
safety evaluations dated respectively April 8, 1997, and June 12, 1997,
the staff determined that the licensees evaluations and proposed
operating controls and limits are acceptable and satisfy regulatory
requirements. However, the CALs placed on Point Beach and Palisades
still remain in place until an NRC inspection is performed to verify
that the licensees' corrective actions are properly implemented.
III. Discussion
The Petition requests an NRC order to users of VSC-24s not to load
additional casks until: (1) The COC, SAR, and SER are amended to
contain operating controls and limits to prevent hazardous conditions;
(2) an independent third-party review team has examined the safety
issues raised by the Petitioners; (3) the potential impacts of all
material aspects of the casks have been fully assessed; (4) there is
experimental verification of temperature calculations and heat transfer
assessments and other design assumptions; and (5) the safety of the
material coatings on components and structures has been justified.
Item 1: Prohibit Loading of VSC-24s Pending Amendment of Documents
As noted in the NRC letter to the Petitioners on December 10, 1996,
the Petitioners' request to amend the COC, SAR, and SER is similar to a
request made by the Citizen's Utility Board (CUB) in a Petition dated
September 30, 1996. The NRC staff denied the CUB petition on April 17,
1997, for the reasons that are identical to the reasons stated here in
denying the first part of the Petitioners' request.
The circumstances set forth above made clear that, following the
event at Point Beach, the NRC staff recognized that additional
evaluation of potential material interactions was warranted for all
spent fuel transportation and storage casks. In regard to the VSC-24,
the event and subsequent NRC inspections made it apparent that actual
changes in the operating procedures or the design of the cask would be
necessary. CALs were issued to confirm licensees' commitments to
refrain from loading VSC-24s pending completion of the NRC staff's
review of the responses to Bulletin 96-04 and verification of the
associated corrective actions. As discussed, the CALs established a
process by which the NRC staff could obtain confidence that operating
controls and limits to address potential hazardous conditions are
developed and implemented by each licensee using VSC-24s.
In particular, the CAL process ensures that licensees will
incorporate the necessary operating controls and limits into revised
plant procedures. Moreover, under existing NRC requirements, the
licensee must adequately implement those revised procedures. For this
reason, no changes to the COC or SAR are needed to ensure that
enforceable operating controls and limits are in place to address
potential hazardous conditions during the loading or unloading of a
cask. Further, as previously indicated, the NRC staff has documented
the process, information, and results of its review of the licensees'
responses to Bulletin 96-04 for use of the VSC-24 at ANO, Point Beach,
and Palisades in safety evaluations available for public review.
Although the actions taken as part of the CAL process provide
adequate assurance that technical and regulatory compliance issues
raised by the event at Point Beach will be resolved before a licensee
loads or unloads a VSC-24, the NRC staff agrees with the Petitioners
that it would be beneficial if the SAR and other licensing basis
documents accurately describe the identified chemical reaction and the
associated operating controls and limits. The NRC staff is currently
reviewing a proposed amendment to the SAR and COC for the VSC-24 design
and will ensure that the information related to the identified chemical
reaction and associated operating controls is adequately addressed in
the appropriate licensing-basis documents. In addition, the NRC staff
is processing a petition for rulemaking, PRM-72-3, that may lead to
additional updating of independent spent fuel storage installation SARs
and the inclusion of information on operating controls and limits
implemented as a result of the event at Point Beach. However, the
previously discussed controls to be implemented by the licensees and
verified by the staff as part of the CAL process, and the
enforceability of those controls under existing NRC requirements, make
it unnecessary to require revision of the specific licensing documents
cited by the Petitioners as a precondition for resuming cask operations
at the facilities using VSC-24s. Therefore, there would be no
regulatory basis for granting the first part of the Petition to require
amendment of the COC, SAR, or SER before further loading of VSC-24s.
Item 2: Prohibit Loading of VSC-24s Pending Independent, Third-Party
Review
Petitioners request the NRC to prohibit loading of VSC-24s until
the COC, SAR and SER are amended following an independent, third-party
review to address concerns raised by the Petitioners. The NRC staff
performed a review of the VSC-24 design prior to certification in 1993.
As a result of the review, the staff determined that the design and
operation of the cask system is in compliance with 10 CFR Part 72. The
staff also concluded, with a high degree of assurance, that the VSC-24
will safely store spent fuel over the 20-year period of the
certificate. Notwithstanding the staff's review and
[[Page 34093]]
determination in 1993, the Petitioners are claiming that a new,
independent review is needed before further VSC-24s are loaded.
While the event at Point Beach revealed the need for additional
evaluation by licensees and NRC of potential material interactions in
the VSC-24 (and other transportation and storage casks), the actions
already taken, in the staff's judgment, provide an adequate response.
In particular, Bulletin 96-04 was issued to request additional
information from licensees using the VSC-24 on material interactions
and compatibility in the VSC-24 and on the corrective actions
implemented. The NRC staff then received and reviewed the responses
submitted by the licensees for ANO, Point Beach, and Palisades. The
staff's reviews (as well as the licensees') have been exhaustive and
were performed by an inter-disciplinary team of engineers knowledgeable
in materials, corrosion, metallurgy, chemistry, structural engineering,
heat transfer, nuclear engineering, and other technical fields needed
to perform the review. The results of the staff's reviews, including
the necessary corrective actions, are documented and justified in the
staff's December 3, 1996, April 8, 1997, and June 12, 1997, safety
evaluations. These corrective actions include: cleanliness checks
before placing the cask in the spent fuel pool, venting and monitoring
of the air space beneath the VSC-24 shield lid during welding or
cutting activities, discontinuing welding or cutting should the
hydrogen concentration exceed 0.4% by volume (10% of the minimum amount
necessary for a combustible concentration), and sampling the boron
concentration in the spent fuel pool and multi-assembly sealed basket
(MSB) water. While the staff agreed that the corrective actions were
necessary to prevent hazardous conditions during the loading and
unloading of VSC-24s, the information submitted by the Petitioners does
not raise any new issues or provide any reason for the staff to
question its conclusion that the VSC-24 will safely store spent fuel
over the 20-year period of the certificate.
In reaching this conclusion, the NRC staff evaluated the specific
concerns raised by the Petitioners related to the design of the VSC-24.
The staff believes that these concerns have already been addressed by
the recent evaluations submitted in response to Bulletin 96-04, by
information submitted to NRC to support the certification of the VSC-24
design in 1993, or by other information submitted in support of NRC
review and inspection activities. Each of the Petitioners's specific
concerns is addressed below.
(i) The Petitioners claim that the cask design allows for fuel
elements to be in contact with the zinc primer creating a galvanic
couple which will accelerate the corrosion of the zinc. The NRC staff
considered galvanic effects between the Zircaloy fuel rods and the
Carbo Zinc 11 coating. The staff agrees that a galvanic effect would
increase the corrosion rate of the zinc, with a corresponding increase
in the hydrogen gas generation rate, as the zinc in the Carbo Zinc 11
coating is polarized to a more active potential. However, in the VSC-24
design, several factors reduce the amount of zinc polarization such
that there would not be a significant increase in hydrogen generation.
One factor is the contact resistances between the stainless steel fuel
assembly end-fittings and the Zircaloy fuel rods and between the end-
fittings and the Carbo Zinc 11 paint. Another factor is the geometry of
the VSC-24 and the fuel assemblies. The fuel assemblies are placed in
fuel storage sleeves with a clearance of approximately 0.1 inch to 0.5
inch between the sides of the fuel assembly and the sleeves. This
clearance and the physical design of the fuel assemblies create
shielding between the fuel rod surfaces and the Carbo Zinc 11 coating.
This shielding effectively reduces the galvanic action between the
Zircaloy fuel rods and the Carbo Zinc 11 coating. The Zircaloy fuel
rods could contact the Carbo Zinc coated sleeves if the fuel assembly
is not centered in the storage sleeves or if the fuel rods are bowed.
However, the shielding effect and small Carbo Zinc/Zircaloy contact
area would still prevent significant galvanic action. Hydrogen
concentration measurements made at Point Beach and the hydrogen
monitoring performed at ANO during loading of a VSC-24 in December 1996
(NRC Inspection Report Nos. 50-313/96-25 and 72-13/96-02) support the
conclusion that significant galvanic action between the Zircaloy and
zinc coating, and hence, increased hydrogen generation, is not
occurring in the VSC-24. In addition, even if there was an increase in
hydrogen generation because of the galvanic action, the staff has
determined that the controls implemented by the licensees for ANO and
Point Beach would prevent accumulation of a combustible concentration
of hydrogen and its ignition. The staff will also review and verify the
adequacy of the controls implemented by the licensee for Palisades.
(ii) The Petitioners claim that there were numerous discrepancies
in the responses to Bulletin 96-04. As noted, the NRC staff completed
its review of responses for ANO, Point Beach, and Palisades. The staff
found these responses to be acceptable and found no discrepancies of
concern. There were minor differences in the operating controls
implemented at the three facilities. However, the staff reviewed these
controls and concluded that all three sets of controls are adequate to
preclude hazardous conditions during cask operation.
(iii) The Petitioners claim that the epoxy-coating applied to the
exterior of the Multi-Assembly Sealed Basket (MSB) could not withstand
the temperatures developed during long-term storage. Technical data on
the type of epoxy coating used on the MSB were provided by the
licensees in their responses to Bulletin 96-04. The data show that the
epoxy is temperature-resistant up to 350 deg.F. The SAR for the VSC-24
(which the staff reviewed and accepted prior to certification in 1993)
shows that under normal or off-normal storage conditions, the
temperature of the MSB exterior will not exceed 300 deg.F. for the
maximum allowable heat load of 24 kW and, therefore, will not degrade
the epoxy.
(iv) The Petitioners claim that the low-temperature specification
in the COC for moving the VSC-24 MSB was not properly translated to the
MSB shell material compositions. Low-temperature embrittlement of the
MSB shell material was evaluated by the NRC staff during its safety
review before certification of the VSC-24. The composition of the MSB
shell material (SA516, Grade 70 carbon steel) is specified in the
American Society for Mechanical Engineers, Boiler & Pressure Vessel
Code, Section II, SA-516, ``Specification for Pressure Vessel Plates,
Carbon Steel, for Moderate- and Lower-Temperature Service.'' The impact
testing requirements for the MSB material are found in American Society
for Testing and Materials Specification A370 (ASTM A370). ``Methods and
Definitions for Mechanical Testing of Steel Products.'' As specified in
the COC, SER, and SAR, each MSB shell material must be shown, during
fabrication, by Charpy test per ASTM A370, to have 15 ft-lbs of
absorbed energy at -50 deg.F. Further, movement of the MSB must occur
only at ambient temperatures of 0 deg.F or above to avoid potential
brittle fracture of the MSB material.\1\ The NRC staff considers the
[[Page 34094]]
50 deg.F temperature difference to provide sufficient margin because
it places the MSB material at a temperature that is significantly above
the temperature where brittle fracture could occur. It should also be
noted that the temperature of the MSB shell itself would actually be
substantially higher than the ambient temperature (e.g., 20 deg.F for
25-year-old fuel), thus providing an even higher margin. In addition,
it is highly unlikely that any MSB movement activity would take place
at temperature below 0 deg.F.
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\1\ At Palisades, the licensee has administratively set a
minimum ambient temperature of 10 deg.F for moving the first four
MSBs (CMSB-01 through -04) to be loaded because the shell material
for these MSBs does not have 15 ft-lbs of absorbed energy at -50
deg.F. Rather, these MSBs have 15 ft-lbs of absorbed energy at -40
deg.F. Thus, to retain the 50 deg.F temperature margin, the
licensee has restricted movement of these four MSBs to an ambient
temperature of 10 deg.F or above. The NRC staff has reviewed and
approved the licensee's administrative limit, as documented in NRC
safety evaluation dated September 26, 1995.
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(v) The Petitioners claim that zinc-steel interaction at 800 deg.F
to 1000 deg.F and possible steel embrittlement over a 20-year period
were not considered. Zinc-steel interaction at the 800 deg.F to 1000
deg.F temperature range was not considered and is not a concern
because, as documented in the VSC-24 SAR, temperatures in the MSB will
not reach 800 deg.F during storage. Maximum temperatures would be 688
deg.F under normal conditions and 708 deg.F under off-normal
conditions, for the maximum allowable heat load of 24 kW. Furthermore,
over the storage period, the temperatures within the MSB will continue
to decrease as the heat load decreases due to the decay of the spent
fuel.
(vi) The Petitioners claim that the effect of molten zinc on
Zircaloy has not been verified experimentally. The NRC staff evaluated
the durability and behavior of the zinc coating under the range of
storage temperatures. The presence of molten zinc is not expected under
the storage temperatures and conditions, thus the effect of molten zinc
on Zircaloy is not a concern. However, as documented in the staff's
safety evaluations for ANO (dated December 3, 1996), Point Beach (dated
April 8, 1997), and Palisades (dated June 12, 1997), the staff did
evaluate the potential interaction between zinc vapor and Zircaloy and
the effect of this interaction. Based on the information provided in
the responses to Bulletin 96-04, the staff concluded that the potential
interaction between zinc vapor and Zircaloy presented no immediate or
long-term safety concern for the spent fuel stored in the VSC-24.
(vii) The Petitioners claim that the vacuum-drying process does not
seem to have been experimentally verified. Vacuum drying is a well-
established, widely used method for removing moisture from spent fuel
storage and transportation casks. The process used for the VSC-24 is a
common process, which the NRC staff evaluated and determined to be
acceptable during the safety review before certification in 1993. In
the staff's judgment, experimental testing to verify a well-established
process is unnecessary.
(viii) The Petitioners claim that the thermal analyses for the VSC-
24 have not been experimentally verified. The thermal analyses for the
VSC-24 contained conservative key assumptions, including a total heat
generation of 1 kW per assembly (a total of 24 kW per cask). This
assumption is conservative because it is highly unlikely that each
assembly loaded in the cask will generate 1 kW of heat. In addition,
the assembly and total cask heat loads will continually decrease over
time as the spent fuel decays. In light of the conservatisms in the
thermal analyses, the staff does not see the need for requiring
experimental verification of the VSC-24 thermal analyses. Nevertheless,
the COC requires that a thermal test be performed on the first VSC-24
to be loaded. The purpose of the test is to measure the heat removal
performance of the VSC-24 system. The licensee for Palisades performed
such a test and summarized its results in a letter to NRC dated June
10, 1993. The temperatures measured during the test were lower than the
predicted temperatures. The results thus indicate that the VSC-24
performs its intended heat removal function. The thermal test at
Palisades was performed with a 12 kW heat load. To date, no VSC-24s
have been loaded with greater than 12 kW heat load. As required by the
COC, the thermal test must be performed for the first cask to use any
higher heat loads, up to 24kW.
The NRC staff believes, based on the foregoing, that an
independent, third-party review is not warranted by the Petitioners'
specific concerns. However, NRC review activities relating to the VSC-
24 will nonetheless continue. In particular, NRC inspection activities
at the facilities operated by the licensees, the VSC-24 vendor, and the
VSC-24 fabricators may lead to additional reviews of the VSC-24. In
addition, the staff is currently reviewing a proposed amendment,
submitted by the VSC-24 vendor, to the SAR and COC for the VSC-24
design. This review will be performed in accordance with the staff's
``Standard Review Plan for Dry Cask Storage Systems'' (NUREG-1536) to
ensure the thoroughness, quality, and consistency of the review. Where
relevant, recent operational, technical, and safety issues related to
the VSC-24 design will be considered by the staff in this review.\2\
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\2\ Recent concerns relating to the MSB closure welds, as
documented in NRC Inspection Report No. 72-1007/97-204, dated April
15, 1997, may result in further evaluations of the VSC-24 design
and, if necessary, appropriate regulatory action to ensure continued
safe use of the VSC-24.
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In addition, it is my judgment that the NRC staff is fully capable
of fulfilling the responsibility for reviewing, approving, and
certifying dry cask storage systems to be used under 10 CFR Part 72
which, by law, belongs to the NRC. In conducting its review, the NRC
staff must have reasonable assurance that the cask system will safely
store spent fuel over the period of the certificate. Further, the staff
will assign the necessary resources and expertise to perform such
reviews. When the NRC staff lacks either the resources or expertise to
perform all or portions of the review in-house, the NRC may, and does,
supplement its own ranks by using outside specialists.
Item 3: Prohibit Loading of VSC-24s Pending Assessment of Cask
Materials
Petitioners request the NRC to prohibit loading of VSC-24s until
the potential impacts of all material aspects of the casks have been
fully assessed. As previously stated, Bulletin 96-04 was issued to
request information on material interactions and compatibility in spent
fuel storage and transportation casks. In response to this request, the
licensees for ANO, Point Beach, and Palisades submitted evaluations on
possible material interactions in the VSC-24 and the effects of such
interactions on cask performance and operation. The only significant
material interaction identified was between the zinc-based coating and
the borated spent fuel pool water. As previously discussed, the
operating controls and limits put in place by the licensees provide an
adequate level of confidence to prevent the adverse effects of this
interaction (generation and possible ignition of hydrogen gas and
possible depletion of boron in the water). The staff reviewed these
evaluations and, based on the information provided, concluded that none
of the identified material interactions would adversely affect the VSC-
24's ability to safely store spent fuel over the 20-year period of the
certificate. The results of the staff's reviews are documented in the
staff's December 3, 1996, April 8, 1997, and June 12, 1997, safety
evaluations for ANO, Point Beach, and Palisades, respectively.
[[Page 34095]]
Item 4: Prohibit Loading of VSC-24s Pending Experimental Verification
of Thermal and Other Design Assumptions
Petitioners request the NRC to prohibit loading of VSC-24s until
there is experimental verification of temperature calculations and heat
transfer assessments and other design assumptions. The thermal and
other engineering and design analyses for the VSC-24 contained
conservative key assumptions which are discussed in the SAR and SER. In
addition, the acceptance criteria for these analyses have margins of
safety that the staff considers to be sufficient. In light of the
conservatisms and safety margins in the thermal and other analyses, the
staff does not see the need for requiring experimental verification of
the thermal and other design assumptions used in evaluating the VSC-24.
Item 5: Prohibit Loading of VSC-24s Pending Assessment of Material
Coatings
Petitioners request the NRC to prohibit loading of VSC-24s until
the safety of the material coatings on components and structures has
been justified. As discussed above, material interactions within the
VSC-24 and their effect on cask operations and performance were
evaluated by the licensees in response to Bulletin 96-04 and reviewed
by the staff. Specifically, the licensees evaluated, and the staff
reviewed, the use of the zinc-based coating, its reaction with borated
water and other cask environments, and the effect of the reaction or
reaction products on cask operations and on the performance of the
various cask components and structures. The staff concluded that use of
existing VSC-24s with the zinc-based coating is acceptable in light of
the operating controls and limits for preventing hazardous conditions
that must be properly implemented by licensees during cask loading and
unloading. Based on the information provided, the staff also concluded
that neither the coating itself, nor its reaction with borated water or
other cask environments, would have an adverse effect on the
performance of the cask components or structures during the period of
spent fuel storage.
IV. Conclusion
The Petitioners requested that the NRC prohibit loading of VSC-24s
until the COC, SAR, and SER are amended to contain operating controls
and limits to prevent hazardous conditions. After reviewing each of the
Petitioners' claims, I conclude that, for the reasons discussed above,
no adequate basis exists for granting the Petitioners' request to
prohibit licensees' use of the VSC-24 for dry cask storage of spent
nuclear fuel at Palisades, Point Beach, or ANO pending: (1) Revision of
the SAR, SER, and COC for the VSC-24 to contain operating controls and
limits to prevent hazardous conditions: (2) an independent third-party
review to examine the safety issues raised by the Petitioners; and (3)
experimental verification of temperature calculations and heat transfer
assessments and other design assumptions. Furthermore, I conclude that
the Petitioners' other two requests, an assessment of potential impacts
of VSC-24 material aspects and a safety justification of material
coatings on components and structures, have already been fulfilled
through the staff's review of the licensees' responses to Bulletin 96-
04.
A copy of this decision will be filed with the Secretary of the
Commission for the Commission to review in accordance with 10 CFR
2.206(c).
As provided by this regulation, this decision will constitute the
final action of the Commission 25 days after issuance, unless the
Commission, on its own motion, institutes a review of the decision
within that time.
Dated at Rockville, Maryland, this 18th day of June, 1997.
For the Nuclear Regulatory Commission.
Malcolm R. Knapp,
Acting Director, Office of Nuclear Material Safety and Safeguards.
[FR Doc. 97-16484 Filed 6-23-97; 8:45 am]
BILLING CODE 7590-01-M
