05000312/LER-1981-027, Forwards LER 81-027/03L-0.Detailed Event Analysis Also Submitted

Forwards LER 81-027/03L-0.Detailed Event Analysis Also Submitted

ML20004D587
Person / Time
Site:	Rancho Seco
Issue date:	06/02/1981
From:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20004D588	List: 05000312/LER-1981-027, Forwards LER 81-027/03L-0.Detailed Event Analysis Also Submitted 05000312/LER-1981-027-03, /03L-0:on 810502,RBS Pump Breaker 3A09 Tripped When Attempting Start from Control Room.Cause Unknown.Trip Reset
References
NUDOCS 8106090555
Download: ML20004D587 (2)

LER-1981-027, Forwards LER 81-027/03L-0.Detailed Event Analysis Also Submitted

Event date:
Report date:
3121981027R00 - NRC Website

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ISMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT O.6201 S Street, Box 15830 Sacramento, California 95813; (916) 452 3211 June 2, 1981 y (f)N,9 -

R. H. ENGELKEN, DIRECTOR N

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b OPERATING LICENSE DPR-54 N'N 49 [gqTh DOCKET NO. 50-312 REPORTABLE OCCURRENCE 81-27 in accordance with Technical Specifications for Rancho Seco Nuclear Generating Station, Section 6.9.4.2b and Regulatory riuide 1.16, Revision 4, Section C.2b(2), the Sacramento Municipal Utility District is hereby submitting a thirty-day report of Reportable Occurrence 81-27 On May 2, 1981, while performing SP 204.03A, Quarterly RBS System A Locp Surveillance and Inservice Test, breaker 3A00, P.BS pump P-291A power supply, tripped during a stut atterrpt from the control room.

Individuals sent to the breaker r..ed an 86 lockout and bell alarm.

The alarm was cleared and the 86 iockout reset.

A second attempt at starting the pump was successful and the Quarterly Surveillance test was completed without any additional discrepancies.

A review of the breaker schematics indicated that the 86 lockout relay and/or the bell alarm are received if an overcurrent condition exists.

However i f an overcurrent condition did exist, it could not be repeated during subsequent starts.

To determine whether or not the in rush current could have peaked within the tolerance values of the instanta-neous overcurrent relay, in rush current measurements were taken.

Thece measurements were well below the instantaneous overcurrent relay setpoints.

As a result, the cause of the occurrence on May 2 cannot be determined.

Further investigation or troubleshooting the breaker is considered inconsequential since the trip condition cannot be repeated.

Additionally, the surveillance test frequency is considered adequate to provide early 1

detection of a similar problem.

I f any recurrence of this unidentified problem is observed, detailed investigations and corrective actions will be Instituted.

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- R.-H.-Engelken

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'The breaker-Is a Model'No. K-600 480 Volt Switchgear manufactured by ITE C87; cit.. Breaker.

.There were no plant, transients nor power reductions associated with' this occurrence.

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J j'Jo'hnU.Mattimoe Assistant General Manager an'd. Chief Engineer-F cc:

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