ML20070M783
| ML20070M783 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/26/1994 |
| From: | Capra R Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20070M784 | List: |
| References | |
| NUDOCS 9405030210 | |
| Download: ML20070M783 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION BALTIM0RE GAS xND ELECTRIC COMPANY-DOCKET NO 50-318 ENVIRONMENTAL ASSESSMENT AND FINDING 0F NO SIGNIFICANT IMPACT The U.S. Nuclear Regulatory Commission (the Commission) is considering issuance of amendments to Facility Operating License Hos. 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. I 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 valve (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 9405030210 940426 PDR ADOCK 05000317 P
PDR-
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. high efficiency particulate 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. I 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 UFSAR 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."
Ngad for the Proposed Action:
Restoration of full-flow capability to the 4-inch vent / purge lines by removing t%e 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 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> versus 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />).
In addition, venting now occurs
y,
. 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 'falves 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 BGtE 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 Imoacts of the Prooosed 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 accident (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.
d.
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 i
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 i
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.
Il-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.
In1 addition, the removal of the orifice plates would reduce the required time to vent from 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 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 previcasly-considered in the April 1973 Final Environmental Statement for the Calvert Cliffs Nuclear Power Plant, Unit Nos. I and 2.
Acencies 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 proposef
" ion will not have a significant effect on the l
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. 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 IMdZ-. [
Robert A. Capra, Director Project Directorate I-l Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation i
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.4 Mr. Robert E. Denton April 26, 1994 This notice is being forwarded to the Office of the Federal Register for Publication.
Sincerely, Original signed by:
Daniel G. Mcdonald, Senior Project Manger Project Directorate I-1 j
Division of Reactor Projects - I/II i
Office of Nuclear Reactor Regulation
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Enclosure:
Environmental Assessment cc w/ enclosure:
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