ML20091B066
| ML20091B066 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 05/16/1984 |
| From: | Mangan C NIAGARA MOHAWK POWER CORP. |
| To: | Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| NMP2L-0056, NMP2L-56, NUDOCS 8405300172 | |
| Download: ML20091B066 (3) | |
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M V NIAGARA R UMOHAWK NIAGARA MOHAWM POWER CORPORATION /300 ERIE BOULEVARD WEST, SYRACUSE N Y.13202/ TELEPHONE (315) 4741511 May 16, 1984 (NMP2L0056)
Mr. R. W. Starostecki, Director U.S. Nuclear Regulatory Commission Region I Division of Project and Resident Programs 631 Park Avenue King of Prussia, PA 19406 Re: Nine Mile Point Unit 2 Docket No. 50-410
Dear Mr. Starostecki:
Enclosed is a final report in accordance with 10CFR50.55(e) for the problem concerning backpressure on valves furnished by Clow Corporation
( 55 (e)-84-10).
This problem was reported in a telephone conversation between Mr. T. Loomis (Nine Mile Point Unit 2 Licensing) and Mr. S. Collins of your staff on February 16, 1984. An interim report was submitted via our letter dated March 21, 1984.
Very truly yours, C. V. Mangan Vice President Nuclear Engineering & Licensing CVM/TL:ja Enclosure xc : Director of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 R. A. Gramm, Resident inspector 8
5300172 840516 ADOCK 05000
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f NIAGARA M0 HAWK POWER CORPORATION NINE MILE POINT'- UNIT 2 DOCKET NO. 50-410 Final Report for a Proolem Concerning Backpressure on Valves Furnisned by Clow Corporation
- Description of the' Problem
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The problem pertains to the tricentric valves furnished by.Clow corporation.
These valves were designed based on the maximum' differential pressures applied in the normal flow (to-seat) direction.
A review of design criteria indicates that some of these valves could be subject to backpressure under certain plant
. conditions. Backpressure was not a design criterion in the design of tnese valves.
Analysis of Safety Implications LThe Niagara Mohawk arenitect/ engineer (Stone & Webster Engineering Corporation) performed a review of'all systems containing Clow valves to determine which valves were susceptible to backpressure.
This information was
. forwarded to Clow wnere a computer analysis was. performed for every valve.
-The analysis indicated that stress levels could exceed ASME Code allowables for certain' valves when exposed to.prescrioed backpressures.
It also was concluded that althougn ASME stress levels would be exceeded, no permanent.
deformation of valve materials or valve damage would occur.
It was concluded that the only noticeable effect resulting from backpressurization would be increased leakage in the reverse direction. Witn tne exception of two valves, 2RHSH0VI A and 18, it was determined tnat tne leakage would be contained witnin the system and would not affect operability of any system.
Valves 2RHSH0VI A and 18 are RHR suppression pool suction valves, and leakage from these valves is directly.to the suppression pool.
In the worst case, the leakage would result in a low water level (Iow water level 3) signal tnat-would automatically initiate the closing of isolation valves 2RHSH0V112 and 2RHS H0V113.
The reactor water level would be restored by feedwater, nign pressure core spray, low pressure core spray, etc... depending upon tne
- reactor / plant conditions.
Consequently, tnis deficiency would not nave adversely affected the safe operation of the plant'and would not be reportable under10CFR50.58i(e).
Corrective Actions The following corrective actions have been taken to accommodate backpressure in the subject safety-related valves without exceeding ASME stress allowables:
1.
Valves, Mark Nos. 2SWPH0V3A and 38 and 2SWPHOV50A and 50B, nave been reworked with new shafts and keys.
2.
Valves, Mark Nos. 2RHSH0VI A and 18, 2HRSH0V9A and 98, 2RHSH0V12A
.and 128, and 2HRSH0V30A and 308 will be replaced with new valves.
E:
3.
Clow valves, listed below, in the low pressure core spray, residual heat removal, and service water systems will be reoriented and/or given special operating instructions:
2CSL*V121 2SWP*M0V93A&B 2RHS*MOVIC 2CSL*MOVil2 2SWP*MOV74A,B,C,0,E&F 2CSL*HCVil8 25WP*MOV92A&B This action will be completed by October 31, 1984.
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