ML20055H819
| ML20055H819 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 07/25/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20055H817 | List: |
| References | |
| NUDOCS 9007300134 | |
| Download: ML20055H819 (3) | |
Text
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[e..,h, UNITED STATES y,
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t SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REbOLATION RELATED TO AMEN 0 MENT N05.131 AND 115 TO FACILITY OPERATING LICENSE NOS NPF-4 AND NPF 7 l
VIRGINIA ELECTRIC AND POWER COMPANY
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OLD DOMINION ELECTRIC COOPERATIVE 1
NORTH ANNA POWER STATION UNITS NO 1 AND NO. 2 DOCKET NOS. 50-338 AND 50-339 INTRODUCTION i
By letter dated October 13, 1989, as supplemented November 21, 1989, the Virginia Electric and Power Company (the licensee) requested changes to the i
Technical Specifications (TS) for the North Anna Power Station. Units No. 1 andNo.2(NA-1A2).
Specifically, the changes would add a new requirement to close the lolation valve on a drain pipe which passes through a flood control dy ke. This dyke was recently added around the west end of the NA-2 turbine 4
and service buildings. The change would require the closing of the isolation valve within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the main reservoir reaching a level of 252 feet above mean sea level (MSL).
In addition, the alert level for escalating surveillance of the main reservoir water level would be reduced from 255 feet MSL to 251 feet MSL, and the surveillance interval would be decreased from once every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to once every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> when the re$ervoir is below 251 feet MSL.
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The November 21, 1989 letter provided additional-information concerning rain runoff in the dyke depression area. The additional information did not alter in any way the staff's initial determination of no significant hazards consideration or the action noticed in the Federal Register on November 15, 1989 (54 FR 47610).
DISCUSSION A reanalysis of potential flooding conditions of NA-1&2 necessitated the addition of a flood control dyke around the west end of the NA-2 turbine and service buildings. The flood control dyke will provide prctection to safety-related equipment and facilities based on worst-case flooding conditions.
In order to accomodate drainage of normal accumulation from within the dyke-enclosed area, a drain pipe is provided through the dyke.
During potential flooding conditions,.this drain pipe must be isolated to prohibit reverse flow of water into the enclosure and then into the turbine and service buildings. This drain pipe has a manual valve which is operated from within the enclosed area, and an in-series check valve,. The check valve provides redundant isolation.
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- After the valve has been closed, rain falling'directly into the enclosure area and runoff from the turbine and service building roofs will accumulate in the depression area. The runoff has been calculated to accumulate to a point where it would enter the turbine building baserent and fill to a maximum elevation of 256 feet MSL. However, safety-related equipment that could be affected by flooding from the turbine building is protected to an elevation of 257 feet MSL by flood barriers at the doorways.
Also, there are three non-safety b
grade pumps in each of the three turbine building Sumps (nine pumps total),
and each pump has a flow capacity of 1300 gallons per minute with a discharge head of 57 feet.
Based on an analysis of the worst-case flooding condition, the reservoir level would be rising at a rate of 0.8 foot per hour.
Flooding of the turbine and service buildings occurs at 257 feet above MSL and, at that rate, would occur 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after the water level had risen to 252 feet.
Therefore, the requirement to close the drain pipe valve within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after reaching the 252-foot level will ensur: that the required protective actions will be taken in a timely manner and that the facility flood control measures will provide protection to the safety-related equipment. To insure that the drain pipe isolation valves remain operational, a periodic test will be implemented to operate the valves through a full-stroke movement at least once every 3 months.
The reduction of the trigger level for escalating surveillance from 255 feet to 251 feet and the decrease in the surveillance intrrval from once every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to once every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, with the reservoir levet e
below 251 feet, will ensure that an increasing water level will be detected in sufficient time to perform the actions required to isolate the dyke drain pipe during the maximum postulated lake inflow.
Therefore, the NA-1&2 TS Action Statement 3.7.6 would be modified to require closing of the drain pipe isolation valve within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the main reservoir level reaching 252 feet MSL. TS Surveillance Requirement 4.7.6 would be changed to reduce the normal surveillance interval for measuring the reservoir level from 24 to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, in addition, the reservoir level at which the level surveillance frequency is escalated from once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, is reduced from 255 feet MSL to 251 feet MSL.
EVALUATION The proposed changes will proviva additional controls, not currently in place in the NA-182 TS to reduce the probability of flooding and provide more restrictive surve,illance requirements for identifying rotential flooding conditions.
In addition, the installation of the dyke and the proposed TS change and surveillance requirements for potential worst-case flooding conditions will enhance protection of safety-related equipment for currently analyzed accidents.
Based on the above, we find the proposed changas to be acceptable.
ENVIRONMENTAL CONSIDERATION These amendments involve a change to a requirement with respect to installe?!on or use of a facility component located within the restricted area as defi w in 10 CFR Part 20 and changes surveillance requirements. We have determined uat the amendments involve no significant increase in the amounts, and no significant
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change in the types, of any effluents that ma/ be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Comission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public coment on such finding. Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
I CONCLUSION J
We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations, and the issuance of the amendments will not be inimical to the comon defense and security or to the health and safety of the public.
Date:
July 25, 1990 Principal Contributor:
Leon Engle l
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