PNO-II-85-100, on 851024,480-volt Circuit Breaker or Associated Components for One Battery Room Exhaust Ventilation Fan Failed,Causing Trip of Another Breaker. Plant Gradually Shut Down

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PNO-II-85-100:on 851024,480-volt Circuit Breaker or Associated Components for One Battery Room Exhaust Ventilation Fan Failed,Causing Trip of Another Breaker. Plant Gradually Shut Down
ML20134A298
Person / Time
Site: North Anna Dominion icon.png
Issue date: 10/24/1985
From: Brownlee V, Elrod S
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-85-100, NUDOCS 8511040329
Download: ML20134A298 (2)


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- October 24, 1985 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-85-100 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public _ interest significance. The information is as initially received without verifi-cation or evaluation, and is basically all that is known by the Region II staff on this date.

FACILITY: Virginia Electric & Power Company Licensee Emergency Classification:

North Anna Unit 1 X Notification of Unusual Event Docket No. 50-338 Alert Mineral, Virginia Site Area Emergency General Emergency Not Applicable

SUBJECT:

LOSS OF COOLING WATER TO REACTOR COOLANT PUMP MOTOR At 3:30'a.m. '(EDT) today, the 480-volt circuit breaker--or associated components--for one r of the unit's _ battery room exhaust ventilation fans failed, damaging other components in i

the breaker cubicle as well as the bus bar to which the breaker was connected. This failure caused the trip of another breaker, one in the circuit feeding power to the entire motor control center where the damaged cubicle was located. Among components which were de-energized were the battery chargers for two of four instrument busses and the solenoid valves in the cooling water system for all three reactor coolant pump motors.

Operators at 3:45 a.m. began a gradual shutdown of the plant--which was operating at 100 percent power--and declared an unusual event. They manually tripped the reactor and turbine at 3:50 a.m. and stopped the reactor coolant pumps at 3:52 a.m., maintaining the I

unit in hot standby'by natural circulation. Subsequently, cooling water was restored to one reactor coolant pump motor, making it possible to restart the pump at 6:45 a.m. By 7:54 a.m.. .the damaged bus bar components had been replaced, and power had been restored to the motor control center. The unusual event was ended at 9:02 a.m.

Region II is monitoring Virginia Power's follow-up analysis of this incident and is keeping the Offices of Inspection and Enforcement and Nuclear Reactor Regulation advised.

Region II also has informed the Commonwealth of Virginia.

North Anna Unit 2 is operating at 100 percent power.

Virginia Power is prepared to respond to media inquiries.

The licensee informed the NRC headquarters incident response center of this occurrence by telephone at 4:08 a.m. today. .

This infonnation is current as of 1 p.m.

Contact:

S. A. El rod, 242-5536 V. Brownlee, 242-5583 8511040329 851024 M-Ikk5-100 PDR O \

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DISTRIBliTION:

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Applicable Resident Site 7: 02-k 4

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