[Federal Register Volume 59, Number 86 (Thursday, May 5, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-10827]
[[Page Unknown]]
[Federal Register: May 5, 1994]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-317 and 50-318]
Baltimore Gas and Electric Company; Environmental Assessment and
Finding of No Significant Impact
The U.S. Nuclear Regulatory Commission (the Commission) is
considering issuance of amendments to Facility Operating License Nos.
DPR-53 and DPR-69 issued to Baltimore Gas and Electric Company (the
licensee, BG&E) for operation of the Calvert Cliffs Nuclear Power
Plant, Unit Nos. 1 and 2, located in Calvert County, Maryland.
Environmental Assessment
Identification of Proposed Action
By letter dated November 4, 1993, BG&E requested Technical
Specifications (TSs) amendments which would allow the removal of an
orifice in the 4-inch containment vent/purge line resulting in greater
flow. The Unit 1 containment and the Unit 2 containment each have a
separate but identical system. Penetration room exhaust fans in the
auxiliary building draw air through an in-containment moisture
separator and an in-containment motor-operated value (MOV). The air is
passed through the auxiliary building via the vent lines which have an
outside containment MOV, flow reducing orifice, a flow monitoring
system, a motor-operated butterfly valve, and a set of two high
efficiency particular air and two charcoal filters in parallel (the
penetration room ventilation system filter bank). The air is then
discharged by the fans through the main plant vent. Vented air is
replaced through a separate penetration. The use of this system as a
containment vent was approved by TS Amendment Nos. 115 and 98 for Unit
Nos. 1 and 2, respectively, dated February 20, 1986. The maximum
hypothetical accident doses in the Updated Final Safety Analysis Report
(UFSAR), Chapter 14.42, were revised to include venting of the
containment at the initiation of an accident. The NRC staff's Safety
Evaluation (SE) which supported TS Amendment Nos. 115 and 98 also
approved the higher calculated offsite dose than was currently
described in the USFAR at that time. Subsequently, BG&E identified
calculational errors in the offsite dose, which when corrected,
indicate an offsite dose higher than that approved in the NRC staff's
SE. An orifice plate with a 1-inch opening was installed in each of the
vent lines in order to maintain the approved offsite dose levels.
Reanalysis have been performed to support the removal of the
orifice plates which indicate that the offsite dose would be increased.
Although the consequences of the maximum hypothetical accident would
result in an increase in the fission product release, the total dose is
well within the limits of 10 CFR part 100, ``Factors to be considered
when evaluating sites.''
Need for the Proposed Action
Restoration of full-flow capability to the 4-inch vent/purge lines
by removing the orifice plates will significantly reduce the time
required to vent or purge. It now takes 7 times longer to vent a
containment than it did with a 4-inch line (28 hours versus 4 hours).
In addition, venting now occurs over three operating shifts instead of
being completely contained within one shift. Venting is a manually
controlled operation, in that it requires operator attention (the
operator opens and closes the valves from the control room). Stretching
the venting over three shifts introduces the possibility of additional
human error into the venting process. Another consideration is that the
probability of an accident occurring during venting decreases with
decreased vent time. Reducing the venting time will not increase the
number of times BG&E needs to vent, because the starting and ending
conditions for venting remain the same. Therefore, the total amount of
time the containment vents would be open will be decreased.
Environmental Impacts of the Proposed Action
The environmental impact of allowing increased flow results from
consideration of the maximum hypothetical accident (large break loss-
of-coolant accident) occurring when a vent is open. Fission products
would be released until the in-containment and outside containment
isolation valves receive a safety injection actuation signal (SIAS) or
a containment radiation signal (CRS) which would close the valves
isolating the vent line.
BG&E's reanalysis of the hypothetical loss-of-coolant (LOCA)
indicate a dose of 118 rem to the thyroid and 10.6 rem to the whole
body at the exclusion area boundary (EAB) and 39.3 rem to the thyroid
and 2.7 rem to the whole body at the low-population zone (LPZ)
boundary. The previously approved doses in the UFSAR, Chapter 14, are a
dose of 124 rem to the thyroid and 3.0 rem to the whole body at the EAB
and 33 rem to the thyroid and 0.8 rem to the whole body at the LPZ.
The reanalyses results show a slight dose decrease to the thyroid
at the EAB and a slight dose increase to the thyroid at the LPZ. The
whole-body doses are increased by approximately 3.5 times at the EAB
and LPZ. The 10 CFR part 100 limits are 300 rem to the thyroid and 25
rem to the whole body at both the EAB and LPZ. The increase doses to
the whole body are approximately 40% at the EAB and 10% at the LPZ of
the 25 rem limit provided in 10 CFR part 100.
The results of the reanalysis are similar to the licensing basis
evaluation contained in the Commission's Safety Evaluation Report (SER)
dated August 28, 1972. The SER results are 110 rem to the thyroid and 4
rem to the whole body at the EAB and 80 rem to the thyroid and 3.0 rem
to the whole body, at the LPZ with no containment venting or purging
assumed. It should be noted that the dose estimates in the reanalysis
represent an extreme upper bound because the release from the
containment was assumed to contain fission products derived from a
uniform mixing in the containment atmosphere of the iodines and noble
gases specified in TID-14844. Even though the percentage increase in
offsite doses is not small, the actual total doses are a fraction of
the limits of 10 CFR part 100, as noted above. In evaluating the impact
of the increased doses, it is important to view these results in light
of the low probability of the accident. This change does not
significantly affect the risk of any dominant accident scenario and the
effect on overall risk of accident at this facility is insignificant.
With regard to normal environmental releases when venting during
power operation with the orifice plates removed, the release limits are
controlled by the previously approved TS for each of the Calvert Cliffs
units. Therefore, the removal of the orifice plates and reestablishing
full flow through the vent lines will result in no additional
environmental impact for non-accident releases.
Alternatives to the Proposed Action
The principal alternative to approving the removal of the orifice
plates allowing full flow for venting or purging would be to deny the
request and retain the limited flow capability. However, this
alternative would not significantly enhance the protection of the
environment. As noted above, the total doses based on the reanalysis
are similar to those in the initial licensing basis SE dated August 28,
1972. The doses represent an extreme upper bound, and the doses are a
fraction of the 10 CFR part 100 limits. In addition, the removal of the
orifice plates would reduce the required time to vent from 28 hours to
4 hours and the probability of an accident occurring during venting
decreases with a decreased vent time.
Alternate Use of Resources
This action does not involve the use of any resources not
previously considered in the April 1973 Final Environmental Statement
for the Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2.
Agencies and Persons Consulted
The NRC staff contacted the State of Maryland, Department of
Natural Resources, regarding the environmental impact of this proposed
action.
Finding of No Significant Impact
Based upon the foregoing environmental assessment, the NRC staff
concludes that the proposed action will not have a significant effect
on the quality of the human environment and has determined, therefore,
not to prepare an environmental impact statement for the proposed
action.
For further details with respect to this action, see the
application dated November 4, 1993, which is available for public
inspection at the Commission's Public Document Room, The Gelman
Building, 2120 L Street, NW., Washington, DC 20555, and at the local
public document room located at Calvert County Library, Prince
Frederick, Maryland 20678.
Dated at Rockville, Maryland, this 26th day of April 1994.
For the Nuclear Regulatory Commission.
Robert A. Capra,
Director, Project Directorate I-1, Division of Reactor Projects--I/II,
Office of Nuclear Reactor Regulation.
[FR Doc. 94-10827 Filed 5-4-94; 8:45 am]
BILLING CODE 7590-01-M
