ML20084E447

Ao:On 700818,overpower Rod Stop & Reactor Trip Bistable TC 407A/B Found Faulty.Caused by Malfunctioning Zener Diode in Regulated Power Supply.Bistable Replaced

ML20084E447
Person / Time
Site:	Ginna
Issue date:	08/26/1970
From:	Drake F, Platt C ROCHESTER GAS & ELECTRIC CORP.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084E449	List: ML20084E447 ML20084E492
References
NUDOCS 8304150072
Download: ML20084E447 (2)

Text

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9 August 26, 1970 l h /1, .,.

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Dr. Peter A. Morris, Director QN5 Division of Reactor Licensing y U.S. Atomic Energy Commission /g Q1 h , [.

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Bethesda, Maryland 20014 Q 4)' -

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Dear Dr. Morris:

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Subj ect:

R. E. Ginna Nuclear Power Plant Unit No.1 Docket No. 50-244 Report of Abnormal Occurrence Observed on August 18,19 70 (Technical Specification 15. 6. 6) .

On Tuesday , Aucust 18, 1970 at approximately 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />, periodic testing involving reactor system channel III of the overpower Delta T trip protection began. Prior to testing, this channel was placed in the trip mode.

At approximately 1533 hours0.0177 days <br />0.426 hours <br />0.00253 weeks <br />5.833065e-4 months <br />, the overpower rod stop and reactor trip bistable TC 407A/B was found to be faulty. Immediate replacement of the bistable began, and the channel was returned to service at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />.

On August 19, 1970, further investigation revealed that the faulty bistable would result in a reactor trip set point, for stable conditions, in excess of that described in Section 2.3.1.2.e of the Technical Specifications, Limiting Safety System Settings, Protection Instrumentation. It was therefore concluded that for some length of time between July 30, 1970, the date of the last test, and August 18, 1970, the trip set point on this one channel was exceeded.

l In compliance, therefore, with our interpretation of Section 6.2 of the Technical Specifications and the definition of abnormal occurrence (Section 1.8), this item was reported as an abnormal occurrence.

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o o Dr. Pcter A. Morris Page 2 Itugu st 26, 1970 l

Mr. Norm Mosely of the AEC Compliance in Newark, New Jersey was notified immediately and a telegram sent to Mr. R. W. Kirkman, Director - Region I, Division of Compliance.

The Plant Operating Review Committee has also met and reviewed this occurrence.

/' Failure was caused by a malfunctioning zoner diode in the regulated power supply. Examination of our start-up and testing experience, and a review of the manufacturer's tests of bistable TC 407A/B show this to be the only incident of this type of failure. In addition, a review of our present testing frequency of electronic protection equipment confirms our testing program to be satisfactory for maintaining overall reliability.

Very truly yours,

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C. E. Platt, Superintendent Ginna Nuclear Station

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' Francis E . Drake, Jr. '/

Chairman of the Board

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