ML18095A194

Discusses Redundancy in Components of RHR Sys,Based on 891201 Event.Recommends That NRC Review Issue & Evaluate Safety Significance in Light of Design Criteria of 10CFR50,App a

ML18095A194
Person / Time
Site:	Salem
Issue date:	05/07/1990
From:	Tosch K NEW JERSEY, STATE OF
To:	Stone J Office of Nuclear Reactor Regulation
References
NUDOCS 9005140236
Download: ML18095A194 (2)

Text

State of New Jersey

.. DEPARTMENT OF ENVIRONMENTAL PROTECTION DIVISION OF ENVIRONMENTAL QUALITY CN415 Trenton, N.J. 08625-0415 (609) 987-6402 Fax (609) 987-6390 Jill Lipoti, Ph.D., Assistant Director Radiation Protection Programs May 7, 1990 Mr. James c. Stone Project Manager Project Direct6rate I-2 Off ice of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D.C. 20555

SUBJECT:

REDUNDANCY IN COMPONENTS OF RESIDUAL HEAT REMOVAL (RHR) SYSTEM - SALEM NUCLEAR GENERATING STATION

Dear Mr. Stone:

The Bureau of Nuclear Engineering (BNE) under the Department of Environmental Protection * (DEP) *has reviewed events: at other nuclear plants of similar design to those in the State of New Jersey *. The emergency event at Braidwood-1 on December 1, 1989 which resulted in declaration as 'ALERT' was reviewed by our staff because of its similarity to Salem Nuclear Generating station.

As you are aware, Braidwood experienced a virtual dry-out of its pressurizer while operating in the residual heat removal (RHR) mode during startup due to a stuck-open relief valve. Although the incident is not viewed as particularly serious, a review of Salem's RHR system does bring up some concerns.

The RHR system incorporates only one relief valve in the suction line to both pumps. Should this valve be stuck-open during the RHR mode of operation, the pump may lose its suction head resulting in loss of RHR capability.

I We interpret the General Design Criteria of 10 CFR 50 Appendix A, to require suitable redundancy in components of RHR to accomplish its safety function assuming single failure. Hence, each RHR train should have a relief valve in the suction line to each pump. While the NRC is concerned about interfacial system Loss of Coolant Accident * (LOCA) due to leaking check valves, the relief valve in question would be the component to mitigate the event. A classic example of malfunction of this non-redundant relief valve in the RHR can be taken from the incident on October 27, 1989. Salem Unit #2 was in hot shutdown and the heat up was in New Jersey is an Equal Opportunity Employer

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progress. The suction piping to one of the RHR pumps was inadvertently pressurized to 150 psig above its design pressure of 450 psig due to an improperly seated check valve at the RHR cold leg injection point. The relief valve which was set at 375 psig did not lift to relieve the system pressure.

This incident further emphasizes the need to have redundant relief valves in the suction to both RHR pumps for safety of the system even though the common relief valve is routinely inservice tested for operational readiness in accordance with the Technical Specification.

We recommend that the Nuclear Regulatory Commission review this issue and evaluate its safety significance in light of the design criteria of 10 CFR 50 Appendix A. Should you have any questions or wish to discuss this issue, please contact Pat Patnaik of my staff at 609-987-2038.

Sincerely, J .J_ '\

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Kent Tosch, Chief Bureau of Nuclear Engineering

c. Mr. Bruce A. Preston, Manager Licensing and Regulation Nuclear Department Public Service Electric and Gas Co P.O. Box 236 Hancocks Bridge, NJ 08038 Mrs. Marie Miller United States Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 Gerald P. Nicholls, Ph.D., Deputy Director Division of Environmental Quality Jill Lipoti, Ph.D., Assistant Director Radiation Protection Programs