ML19254D724

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Responds to IE Bulletin 79-11.Discusses Alteration of Testing Scheme for Faulty Overcurrent Trip Devices in Westinghouse DB-50 Circuit Breakers
ML19254D724
Person / Time
Site: Vermont Yankee Entergy icon.png
Issue date: 09/21/1979
From: Moody D
VERMONT YANKEE NUCLEAR POWER CORP.
To: Grier B
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
WVY-79-108, NUDOCS 7910290420
Download: ML19254D724 (2)


Text

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  • fg VERMONT Y AN KEE NUCLEAR POWER CORPORATION V SEVENTY SEVEN GROVE STREET 3.N.2.1 RuTLAso, VERMONT 05701 WY 79-108 REPLY TO:

ENGINEERING OFFICE TURNPIKE ROAD WESTBORO, M ASS ACHUSETTS 01581 TELEPHONE 697 366-9013 September 21, 1979 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Drassia, 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, da'ed July 6, 1979 Gentlemen:

Subject:

Faulty Overcurrent Trip Devices in Westinghouse DB-50 Circuit Breakers In response to Reference (2) we stated in reference (3) Item 4, that we would change end caps, test and calibrate all four of our Westinghouse DB-50 circuit breakers at the forthcoming refueling outage. We also committed to test two of four breakers every subsequent refueling.

We have reviewed our plans for the testing and calibration of the C8-50 breakers and have decided to alter our previous testing scheme. Item 4 of Reference (3) will now read as follows:

4. The integrated ECCS Test will continue to be performed at each refueling outage. In addition, we will test all subject circuit breakers (with new end caps installed) at the forthcoming refueling outage. During the 1980 refueling, we will test again all four DB-50 breakers. If the time current characteristics are acceptable at that time, we will begin a surveillance test interval of once every three years.

If the time current characteristics are unacceptable, we will recalibrate the breakers and plan to test all four at the next subsequent refueling outage.

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e United States Nuclear Regulatory Commission September 21, 1979 Attention: Mr. Boyce H. Grier, Director Page 2 We believe it is prudent to retest all four breakers to determine the effectiveness of the new end caps. The three year interval is based on an assessment of the effort required to perform the test, the probability that a problem with a breaker will go undetected during the annual ECCS Test, and the good performance history of the breakers over many years of service.

We trust that you will find this information satisfactory; however, if you should require additional information, please contact us.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION D. E. Mo dy Manager of Operations dep "8 357