[Federal Register Volume 63, Number 96 (Tuesday, May 19, 1998)]
[Notices]
[Pages 27606-27607]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-13188]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-317 and 50-318]
Baltimore Gas and Electric Company; Calvert Cliffs Nuclear Power
Plant, Unit Nos. 1 and 2 Environmental Assessment and Finding of No
Significant Impact
The U.S. Nuclear Regulatory Commission (the Commission) is
considering issuance of an amendment to Facility Operating Licenses
Nos. DPR-53 and DPR-69, issued to Baltimore Gas and Electric Company
(the licensee), for operation of the Calvert Cliffs Nuclear Power
Plant, Unit Nos. 1 and 2, located in Calvert County, Maryland.
Environmental Assessment
Identification of the Proposed Action
The proposed action would revise the Technical Specifications (TSs)
to reduce the minimum Reactor Coolant System (RCS) total flow rate from
370,000 gpm to 340,000 gpm; reduce the Reactor Protective
Instrumentation trip setpoint for Reactor Coolant Flow--Low from
greater than or equal to 95% to greater than or equal to 92% of design
reactor coolant flow; adjust the reactor core thermal margin safety
limit lines to reflect the reduced RCS flow rate; and reduce the lift
setting range for the eight Main Steam Safety Valves (MSSVs) with the
highest allowable lift setting from the current range of 935 to 1065
psig to a more restrictive range of 935 to 1050 psig. In addition to
the changes to the TSs necessary to support an increased number of
plugged steam generator tubes, reanalysis of the accident analyses
affected by this change identified an Unreviewed Safety Question (USQ)
associated with these changes. The USQ results from the determination
that the Seized Rotor Event analysis involves an increased percentage
of failed fuel cladding. Finally, four reanalyzed events Main Steamline
Break (MSLB), Steam Generator Tube Rupture (SGTR) Loss of Coolant Flow,
and Boron Dilution) require Nuclear Regulatory Commission approval due
to changes to the methodology or assumptions used to analyze these
events.
The proposed action is in accordance with the licensee's
application for amendment dated January 31, 1997, as supplemented by
letters dated February 13, February 28, March 25, April 16, August 16,
and September 29, 1997, and January 22, March 17, April 8, and April
21, 1998.
The Need for the Proposed Action
During the 1998 Unit 1 refueling outage, Baltimore Gas and Electric
Company (BGE) will perform extensive steam generator tube inspections.
Tubes that experience excessive degradation reduce the integrity of the
primary-to-secondary pressure boundary. Eddy current examination is
used to measure the extent of tube degradation. When the reduction in
the tube wall thickness reaches the plugging or repair limit, as
specified in the Technical Specifications, the tube is considered
defective and a corrective action is taken.
Currently, the Calvert Cliffs TSs allow defective tubes to be
plugged and removed from service, or to be repaired using welded
sleeving techniques developed by Westinghouse Electric Corporation or
Combustion Engineering, Inc. The most widely used tube maintenance
technique at many pressurized water reactors, including Calvert Cliffs,
is removal of the degraded tube from service by installing plugs at
both ends of the tube. The installation of steam generator tube plugs
removes the heat transfer surface of the plugged tube from service, and
the increased flow resistance leads to a reduction in the primary
coolant flow available for core cooling. The minimum primary coolant
flow requirements in the TSs are based upon operation with no more than
800 plugged tubes in each steam generator. There is a possibility that
the results of steam generator tube inspections in the upcoming
refueling outage will necessitate exceeding the 800 plugged tube
criteria in at least one of the Unit 1 steam generators. If this is the
case, BGE will require implementation of the proposed TSs changes and
approval of the USQ prior to Mode 2 entry following the 1998 Unit 1
refueling outage.
Environmental Impacts of the Proposed Action
The Commission has completed its evaluation of the proposed action
and concludes that the proposed action will not have a significant
effect on the quality of the human environment. To the extent there is
any environmental impact from increasing the number of plugged steam
generator tubes, such impact results from the increased RCS temperature
and the reduced RCS flow rate expected to result from this activity.
Reanalysis of the Seized Rotor Event analyses has indicated a greater
percentage of fuel pin failures would be expected during these
postulated accidents due to the revised coolant temperature and flow
rates; the increased number of plugged tubes results in an increase in
offsite releases, relative to past analyses.
The licensee's results of the MSLB event reanalysis with reduced
RCS flow indicate a reduction in the 0-2 hour thyroid dose at the
Exclusion Area Boundary (EAB) from 81 rem to 5 rem, and a decrease in
the 0-2 hour whole body dose at the EAB from 0.3 rem to 0.2 rem. The
licensee's results of the Seized Rotor Event reanalysis indicate the
resultant 0-2 hour EAB thyroid dose increases from 3.6 rem to 12 rem,
whereas the whole body dose at the EAB is reduced from 0.4 rem to 0.2
rem. The licensee presented, for the first time, doses at the low
population zone (LPZ) for the MSLB and the Seized Rotor Events. These
doses were 1.2 rem thyroid and 0.04 rem whole body for the MSLB and 1.0
rem thyroid and 0.04 rem whole body for the Seized Rotor Event. The
guideline dose limits for accidents involving fuel failure are the 10
CFR Part 100 limits of 300 rem to the thyroid and 25 rem to the whole
body.
The licensee presented the results of an SGTR analysis. Two cases
were presented. The first case was based upon primary coolant being at
the 100 hour technical specification value for dose equivalent \131\ I
of 1 CI/g and iodine spiking factor of 500. The
[[Page 27607]]
licensee calculated the thyroid and whole body doses at the EAB as 13
rem and 0.55 rem, respectively.
The LPZ doses, which were reported for the first time by the
licensee, were calculated as 5 rem thyroid and 0.15 whole body. The
second case, which was evaluated, assumed primary coolant was at the
maximum instantaneous technical specification value of dose equivalent
\131\ I of 60Ci/g. The results of this case were presented for
the first time. The licensee calculated the doses at the EAB as 22 rem
thyroid and 0.66 rem whole body. The LPZ doses were calculated as 6 rem
thyroid and 0.18 rem whole body.
Even though there is some increase in dose for the Seized Rotor
Event, the actual total dose is a fraction of the limits of 10 CFR part
100, as noted above, and there is a low probability of these accidents.
This change does not significantly affect the risk of any dominant
accident scenario, and the effect on overall risk of an accident at
Calvert Cliffs Nuclear Power Plant is insignificant. The change will
not increase the probability or consequences of accidents, no changes
are being made in the types of any effluents that may be released
offsite, and there is no significant increase in the allowable
individual or cumulative occupational radiation exposure. Accordingly,
the Commission concludes that there are no significant radiological
environmental impacts associated with the proposed action.
The staff has performed confirmatory calculations of the
consequences of an MSLB, SGTR and Seized Rotor Events. The staff has
confirmed that the consequences of these accidents will result in
offsite doses which are a small fraction of the 10 CFR part 100 dose
guidelines. In addition, the staff has determined that the proposed
action will not result in an increase in normal radiological effluents
from the Calvert Cliffs Nuclear Power Plant such that 10 CFR part 20
and Appendix I to 10 CFR part 50 will continue to be met.
With regard to potential nonradiological impacts, the proposed
action does involve features located entirely within the restricted
area as defined in 10 CFR part 20. It does not affect nonradiological
plant effluents and has no other environmental impact. Accordingly, the
Commission concludes that there are no significant nonradiological
environmental impacts associated with the proposed action.
Alternatives to the Proposed Action
The principal alternative to approving the license amendment
request needed to allow plugging up to 2500 tubes per steam generator
would be to deny the request and retain the current coolant flow
limitations. However, this alternative could reduce operational
flexibility as it may prevent a Unit 1 start-up following the upcoming
refueling outage, if the steam generator tube inspections necessitate
plugging greater than 800 tubes in either of the unit's two steam
generators. Furthermore, denial of the amendment would not
significantly enhance the protection of the environment as the impacts
of this alternative and the proposed action are similar.
Alternative Use of Resources
This action does not involve the use of any resources not
previously considered in the Final Environmental Statement for the
Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2 dated April 1973.
Agencies and Persons Consulted
In accordance with its stated policy, on May 5, 1998, the staff
consulted with the Maryland State official, Richard I. McLean of the
Maryland Department of Natural Resources, regarding the environmental
impact of the proposed action. The State official had no comments.
Finding of No Significant Impact
Based upon the environmental assessment, the Commission concludes
that the proposed action will not have a significant effect on the
quality of the human environment. Accordingly, the Commission has
determined not to prepare an environmental impact statement for the
proposed action.
For further details with respect to the proposed action, see the
licensee's letter dated January 31, 1997, as supplemented by letters
dated February 13, February 28, March 25, April 16, August 16, and
September 29, 1997, and January 22, March 17, April 8, and April 21,
1998, which are available for public inspection at the Commission's
Public Document Room, The Gelman Building, 2120 L Street, NW.,
Washington, DC, and at the local public document room located at the
Calvert County Library, Prince Frederick, Maryland 20678.
Dated at Rockville, Maryland, this 12th day of May 1998.
For The Nuclear Regulatory Commission.
S. Singh Bajwa,
Director, Project Directorate I-1, Division of Reactor Projects--I/II,
Office of Nuclear Reactor Regulation.
[FR Doc. 98-13188 Filed 5-18-98; 8:45 am]
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