ML13330B400

Agrees W/Licensee That No Actions Required to Improve Reliability of Salt Water Cooling Sys Per SEP Topic IX-3, Item 4.32.7.If Complete Loss of Salt Water Cooling Occurs, Backup Pumps Can Provide Interim Cooling

ML13330B400
Person / Time
Site:	San Onofre
Issue date:	10/03/1988
From:	Trammell C Office of Nuclear Reactor Regulation
To:	Baskin K Southern California Edison Co
References
RTR-NUREG-0829, RTR-NUREG-829, TAC-65149, TASK-09-03, TASK-9-3, TASK-RR NUDOCS 8810110245
Download: ML13330B400 (4)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20555 October 3, 1988 Docket No.:

50-206 Mr. Kenneth P. Baskin Vice President Southern California Edison Company 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770

SUBJECT:

SALT WATER COOLING RELIABILITY (SEP TOPIC IX-3, ITEM 4.32.7)

(TAC NO. 65149)

Re:

San Onofre Nuclear Generating Station, Unit No. 1 By letter dated April 1, 1987, as supplemented July 22, 1988, Southern California Edison submitted a reliability study of the Salt Water Cooling System (SWCS) in response to a recommendation in NUREG-0829, "Integrated Plant Safety Assessment."

On the basis of our review of the licensee's submittals, we agree with the licensee that no actions are needed at this time to improve the reliability of the existing SWCS. Our reasonings are stated as follows:

(1) The SWCS study indicates that electrical failures leading to a station blackout scenario are a dominant conwributor to the SWCS unavailability, which is estimated to be about 3*10-.

The licensee estimates that these electrical failures contribute about 88% to the SWCS unavailability. The SWCS consists of two full-capacity safety-related SWC pumps and another full-capacity non-safety-related auxiliary SWC pump. Hence, because of this redundancy in the SWCS, the SWCS component failures do not appear in the dominant cut sets. The results of the licensee's analysis do not identify any modifications to the SWCS for reducing the SWCS unavailability significantly.

(2) During an event which also involves the 'loss of all SWCS pumps, the screen wash pumps or fire water pumps may be used as a backup to the SWCS pumps.

For example, on March 10, 1980, SONGS-1 experienced a complete loss of SWCS flow for about 10 minutes. However, the screen wash pumps were used to provide cooling for the component cooling water heat exchanger before the auxiliary SWCS pump was restored to service. If the screen wash pumps fail, the fire water pumps also may be used since the pump performance specifications of the fire water pumps are similar to that of the screen wash pumps. Therefore, we conclude that if a complete loss of SWC occurs, the backup pumps can provide interim cooling and give operators more time for mitigative actions.

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October 3, 1988 (3) Since the 1980 loss of SWCS event, SONGS-1 has taken corrective actions to improve the SWCS reliability. For example, to prevent the north SWC pump discharge valve from failing to open, the valve has been left in the normally open position. In addition, to prevent air from leaking into the Auxiliary SWC Pump Air Priming System, all places where air could leak into the system were resealed. We believe that the corrective actions taken are appropriate for improving the SWCS reliability.

Based on the above, we consider item 4.32.7, "Salt Water Cooling System Reliability" to be resolved. This action also completes SEP Topic IX-3, "Station Service and Cooling Water Systems," since item 4.32.7 was the only item not considered resolved when NUREG-0829 was issued in December 1986.

Sincerely, Charles M. Trammell, Senior Project Manager Project Directorate V Division of Reactor Projects -

III, IV, V and Special Projects cc:

See next page

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-October 3, 1988 (3) Since the 1980 loss of SWCS event, SONGS-1, has taken corrective actions to improve the SWCS reliability. For example, to prevent the north SWC pump discharge valve from failing to open, the valve has been left in the normally open position. In addition, to prevent air from leaking into the Auxiliary SWC Pump Air Priming System, all places where air could leak into the system were resealed. We believe that the corrective actions taken are appropriate for improving the SWCS reliability.

Based on the above, we consider item 4.32.7, "Salt Water Cooling System Reliability" to be resolved. This action also completes SEP Topic IX-3, "Station Service and Cooling Water Systems," since item 4.32.7 was the only item not considered resolved when NUREG-0829 was issued in December 1986.

Sincerely, original signed by Charles M. Trammell, Senior Project Manager Project Directorate V Division of Reactor Projects -

III, IV, V and Special Projects cc: See next page DISTRIBUTION Docket FiTe NRC & LPDRs CTrammell (2)

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Mr. Kenneth P. Baskin San Onofre Nuclear Generating Southern California Edison Company Station, Unit No. 1 cc Charles R. Kocher, Assistant Mr. Jack McGurk, Acting Chief General Counsel Radiological Health Branch James Beoletto, Esquire State Department of Health Southern California Edison Company Services Post Office Box 800 714 P Street, Office Bldg. 8 Rosemead, California 91770 Sacramento, California 95814 David R. Pigott Mr. Hans Kaspar, Executive Director Orrick, Herrington & Sutcliffe Marine Review Committee, Inc.

600 Montgomery Street 531 Encinitas Boulevard, Suite 105 San Francisco, California 94111 Encinitas, California 92024 Mr. Robert G. Lacy Manager, Nuclear San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector/San Onofre NPS U.S. NRC P. 0. Box 4329 San Clemente, California 92672 Mayor City of San Clemente San Clemente, California 92672 Chairman Board of Supervisors County of San Diego 1600 Pacific Highway Room 335 San Diego, Californid 92101 Director Energy Facilities Siting Division Energy Resources Conservation &

Development Commission 1516 - 9th Street Sacramento, California 95814 Regional Administrator, Region V U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, California 94596