ML20210J895
ML20210J895 | |
Person / Time | |
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Site: | Byron, Braidwood ![]() |
Issue date: | 07/29/1999 |
From: | Krich R COMMONWEALTH EDISON CO. |
To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
References | |
GL-95-07, NUDOCS 9908050136 | |
Download: ML20210J895 (3) | |
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Commonwealth I'diwn Company 1400 Opus Place
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Downers Grove, IL N)515-5701
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July 29,1999 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Facility Operating Licer. e rsos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
Response to Request for Additional Information Generic Letter 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," dated August 17,1995
References:
(1)
NRC Generic Letter 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," dated August 17, 1995 (2)
Letter from P. L. Piet (Comed) to U.S. NRC, " Commonwealth Edison Company (Comed) 180 Day Response to NRC Generic Letter (GL) 95-07, ' Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves,'" dated February 13, 1996 (3)
Letter from R. M. Krich (Comed) to U.S. NRC, " Commonwealth Edison Company (Comed) Response to NRC Generic Letter (GL) 95-07, ' Pressure Locking and Thermal Binding of Safety-Related O
Power-Operated Gate Valves,'" dated May 29,1998 In Reference 1, the NRC requested licensees to report the status of actions taken to address the issues related to pressure locking and thermal binding of safety-related power-operated gate valves. In Reference 2, we submitted our 180 day response to the subject Generic Letter, in Reference 3, we submitted additional analyses and information supporting our 180 day response. Reference 3 specifically addressed o
crediting natural depressurization of the valve bonnet volume over an 8.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period after accident initiation, for those valves susceptible to pressure locking, which are opened during the hot leg recirculation phase of Emergency Core Cool;ng System operation.
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PDR A Unicom Company
m July 29,1909 U. S. Nuclear Regulatory Commission Page 2
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In subsequent telephone conference calls with representatives of the NRC and Commonwealth Edison (Comed) Company, the NRC indicated that crediting valve bonnet natural depressurization would not be acceptable until a period of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or more had elapsed after accident initiation. The specific valves of concem are:
1(2) Sl8802A/B, safety injection (SI) pump to reactor coolant system (RCS) hTt leg injection, and 1(2) Sl8840, residual heat removal (RHR) to RCS hot leg injection.
In light of the extended period for valve bonnet natural depressurization, other actions, as described below, will be taken for these valves to resolve potential pressure locking concems.
Valves 1(2) Sl8802A/B A modification will be performed on these valves to increase the motor gearing capability to ensure that the motor operator will be capable of opening the valves under maximum expected pressure locking conditions. The Comed pressure locking thrust prediction methodology will be used to determine the thrust and actuator capability requirements.
Schedule:
This modification will be performed during the fall 2000 refueling outage for Byron Station Unit 1; during the spring 2001 refueling outage for Byron Station Unit 2; during the fall 2001 refueling outage for Braidwood Station Unit 1; and during the fall 2000 refueling outage for Braidwood Station Unit 2.
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l Valves 1(2) Sl8840
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l An analysis will be performed and documented to show that opening these valves during accident conditions is not necessary in order to achieve acceptable post accident results. The Byron /Braidwood Updated Final Safety Analysis Report (UFSAR) will be updated to reflect this analysis. No other actions will be taken for valves 1(2)
Sl8840.
Schedule:
This analysis and UFSAR change will be completed by October 29,
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- 1999, i
i An additional scenario was also discussed with the NRC which affects valves 1(2) CV8804A, RHR pump discharge to charging pump suction, and 1(2)Sl88048, RHR discharge to safety injection pump suction. In this scenario, these valves could be susceptible to pressure and thermally induced pressure locking in Technical Specification (TS) Mode 4, while shutdown cooling is operating, and could potentially remain pressure locked following entry into TS Mode 3 when these valves are required to be operable. The action that will be taken for each of these valves is described
- below, j
July 29,1999 U. S. Nuclear Regulatory Commission Page 3 Valves 1(2)CV8804A In the above scenario, these valves are susceptible to pressure and thermally induced pressure locking. A modification to drill a hole in one side of the valve disk will be performed on these valves to ensure that pressure will not be allowed to build up in the valve bonnets.
Schedule:
This modification will be performed during the fall 2000 refueling outage for Byron Station Unit 1; during the spring 2001 refueling outsge for Byron Station Unit 2; during the fall 2001 refueling outage for Braidwood Station Unit 1; and during the fall 2000 refueling outage for Braidwood Station Unit 2.
Valves 1(2)S18804B in the above scenario, these valves are susceptible to pressure induced pressure locking. They are not subject to thermally induced pressure locking due to the distance between the valve and the heat source (i.e., approximately 70 pipe diameters). The Comed pressure locking thrust prediction methodology will be performed to show that these valves have adequate motor gearing capability to open under the maximum expected bonnet pressure.
I Schedule:
This calculation will be completed by September 1,1999.
Should you have any further questions concerning this matter, please contact Mr. J. A. Bauer at (630) 663-7287.
Respectfully,
?'
7 [o r-R. M. Krich i
Vice President-Regulatory Services l
cc:
Regional Administrator-NRC Region ill NRC Senior Resident inspector-Braidwood Station NRC Senior Resident inspector-Byron Station
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