05000334/LER-1981-002-01, /01T-0:on 810107,during Shutdown,Seal Flow Dropped Below Min on 1C Reactor Coolant Pump.Caused by Sensitive Valving.Pump Restarted within 20 Minutes

/01T-0:on 810107,during Shutdown,Seal Flow Dropped Below Min on 1C Reactor Coolant Pump.Caused by Sensitive Valving.Pump Restarted within 20 Minutes

ML19341A644
Person / Time
Site:	Beaver Valley
Issue date:	01/21/1981
From:	Lacey W DUQUESNE LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19341A642	List: 05000334/LER-1981-002, Forwards LER 81-002/01T-0 05000334/LER-1981-002-01, /01T-0:on 810107,during Shutdown,Seal Flow Dropped Below Min on 1C Reactor Coolant Pump.Caused by Sensitive Valving.Pump Restarted within 20 Minutes
References
LER-81-002-01T, LER-81-2-1T, NUDOCS 8101270593
Download: ML19341A644 (2)

LER-1981-002, /01T-0:on 810107,during Shutdown,Seal Flow Dropped Below Min on 1C Reactor Coolant Pump.Caused by Sensitive Valving.Pump Restarted within 20 Minutes

Event date:
Report date:
3341981002R01 - NRC Website

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Attachment To LER 81-002/0tT Beaver Valley Power Station Duquesne Light Company Docket No. 50-334 4

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Because of a change made to the Reactor Coolant System (RCS) pressure requirements due to the overpressurization protection system, seal leak-off f rom the Reactor Coolant Pumps (RCPs) must be discharged to the Primary Drains Tank to provide less back-pressure on the No..1 RCP seal than the Volume Control Tank (VCT). When it becomes necessary to return the seal leak-of f flow to the normal system arrangement, the flow is directed to the VCT. The valving involved in this transfer can cause the flow to become unstable. If the flow is less than.2 gpm during the transfer, the operator must trip the RCP to protect the pump seal. Once the RCS pressure is increased to normal system pressure, the seal leak-off flow is stable and no further problems are encountered.

Westinghouse has proposed a partial solution to this problem. They have suggested a finer flow measurement system which would help alleviate the control problem. This finer indication, along with throttle valves that are more suitable for very low flows, will elta'inate valving and control problems.

The Onsite Engineering Group is evaluating this problem.

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