ML20214P919

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Responds to IE Bulletin 86-003, Potential Failure of Multiple ECCS Pumps Due to Single Failure of Air-Operated Valve in Min Flow Recirculation Line. Unit Not Vulnerable to Single Failure or Problems Discussed in Bulletin
ML20214P919
Person / Time
Site: Rancho Seco
Issue date: 11/07/1986
From: Julie Ward
SACRAMENTO MUNICIPAL UTILITY DISTRICT
To: Martin J
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
IEB-86-003, IEB-86-3, JEW-86-809, NUDOCS 8612040421
Download: ML20214P919 (2)


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. ,- a-esuu. SACRAMENTO MUNICIPAL UTILITY DISTRICT C P. O. Box 15830, Sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEAR 7 OF CALIFORNIA t ,'>

JEW 86-809 3 November 7, 1986 g

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J. B. Martin, Administrator n U. S. Nuclear Regulatory Commission "

Region V Office of Inspection and Enforcement 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596 00CKET 50-312, RANCHO SECO NUCLEAR GENERATING STATION, UNIT NO. 1 RESPONSE TO IE COMPLIANCE BULLETIN NO. 86-03: POTENTIAL FAILURE OF MULTIPLE ECCS PUMPS DUE TO SINGLE FAILURE OF AIR-OPERATED VALVE IN MINIMUM FLOW RECIRCULATION LINE

Dear Mr. Martin:

The subject bulletin requested licensees to review their facilities and determine whether or not they are vulnerable to a single failure in the minimum flow recirculation line of any Emergency Core Cooling System (ECCS) pump that could cause a failure of more than one ECCS train. The District has completed its review of Rancho Seco's Decay Heat system (DHS) and its Seal Injection and Makeup System (SIM) and has concluded that Rancho Seco is not vulnerable to a single failure or similar problems as discussed in this bulletin.

The discharge pressure of the High Pressure Injection (HPI) pumps is greater than the set point of the Reactor Coolant ',ystem (RCS) pressurizer code safety relief valves, thus precluding the dead-heading of the running pumps. The shutoff head of the HPI pumps is 2900 psig whereas the pressurizer code safety setpoint is 2500 psig. The HPI pumps therefore provide sufficient minimum flow by operating against the maximum credible back pressure of the RCS.

The HPI pump recirculation valves are motor operated, normally open and fail as is. The llPI recirculation is directed back to the Makeup Tank rather than Borated Water Storage Tank (BWST) or Reactor Building Sump as discussed in the Bulletin. The two HPI Pump recirculation valves close on the Safety Features Actuation System signal, which also opens four HPI injection valves on the common HPI Pump discharge headers. There is no single failure which can automatically prevent adequate pump miniflow.

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DISTRICT HEADQUARTERS O G201 S Street, Sacramento CA 95817 1899 L//

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J. B. Martin JEW 86-809 November 7, 1986 The DHS pumps are provided with a miniflow line from the discharge of the DHS cooler to the suction of the pump. The miniflow can only be stopped by closing the " locked-open" pump discharge isolation valve which is manually operated. Valve position is dual verified per operating procedure and system flow is also verified quarterly by surveillance procedure. The DHS pumps can operate for twenty minutes without Nuclear Service Cooling Water (NCSW) and a single failure of NCSW would not affect both DHS pumps. Therefore, the design of the DHS miniflow line is such that there is no single failure that can result in depleting RCS inventory or preventing adequate miniflow requirements for the pumps.

If you have any questions or require any additional information, please contact Ray Ashley of my staf f at (916) 732-6345.

Sincerely, N )

John E. Ward Deputy General Manager s

Nuclear 9 th Sworn to and subscribed before me this I day of November, 1986.

OLO G (LLb70 Notary Public s

cc: Sydney Miner, NRC, Bethesda Tony D'Angelo, NRC, Rancho Seco ya 3

y DAWN DARLING

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