ML19210E812

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Reports Faulty Overcurrent Trip Devices in Westinghouse DB 50 Circuit Breakers.End Cap Replacement & Calibr Schedule for Next Outage of Sufficient Duration
ML19210E812
Person / Time
Site: Vermont Yankee Entergy icon.png
Issue date: 11/13/1979
From: Moody D
VERMONT YANKEE NUCLEAR POWER CORP.
To: Grier B
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
WVY-79-131, NUDOCS 7912130018
Download: ML19210E812 (1)


Text

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VERMONT Y AN KEE NUCLEAR POWER CORPORATION SEVENTY SEVEN GROVE STREET 3.4 g g WVY 79-131 RUTLAND. VERS 10NT 05701 REPLY TO:

ENGINEERING OFFICE November 13, 1979 TuRNeixE RO AD WESTDORO M ASS ACHUSETTS 01581 TELEPHONE 647 366 9019 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 Attention: Mr. Boyce H. Grier, Director

References:

1) License No. DPR-28 (Docket No. 50-271)
2) USNRC Letter to VYNPC, dated May 22, 1979; IE Bulletin 79-11
3) VYNPC Letter to USNRC, dated July 6, 1979
4) VYNPC Letter to USNRC, dated September 21, 1979 Gentlemen:

Subj ect: Faulty Overcurrent Trip Devices in Westinghouse DB-50 Circuit Breakers While testing our Westinghouse DB-50 circuit breakers, '.n accordance with Reference 4, we experienced difficulties with the apecial test equip-ment required to test and calibrate these breakers. The equipment failed af ter completing the main breakers for both batteries. Therefore, we could not change end caps, test or calibrate our battery tie breakers.

Visual inspection and testing of the main breakers and visual inspection of the tie breakers in the as-found condition, revealed no evidence of cracked end caps.

The tie breakers which did not have their end caps replaced are normally open. These breakers are closed only to tie the spare battery charger to the DC bus in the event that the normal charger fails. Due to the design of our DC busses, it would be extremely risky to remove the tie breakers from the switchgear for testing during plant operation. There-fore, end cap replacement and calibration of the tie breakers will be completed at the next outage of sufficient duration to complete the work provided the test equipment is repaired and available.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION Y

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