ML20084G102

Ao:On 730717,during Periodic Test PT5,one Side of Bistable LC-427 A/C Failed to de-energize on Inserted Signal Equal to 5% Pressurizer Water Level.Caused by Cold Solder Joint Failure.Module Replaced

ML20084G102
Person / Time
Site:	Ginna
Issue date:	07/27/1973
From:	Green G ROCHESTER GAS & ELECTRIC CORP.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084G104	List: ML20084G102 ML20084G107
References
NUDOCS 8304210476
Download: ML20084G102 (2)

Text

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ROCHESTER GAS AND E! ECTRIC CORPORATION e 39 EAST AVENUE, ROCHESTER. H.Y. k%14649 L ' c-

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Mr. John F. O' Leary, Director 3 't Directorate of Licensing U. S. Atomic Energy Commission -

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Subject:

Failure of Safety Injection System k ,[ k, % h bistable to de-energize on test . ][ *> ghSg R. E. Ginna Nuclear Power Plant, Unit No.1 Docket No. 50-244 (hv' l

Dear Mr. O' Leary:

In accordance with the Ginna Station Technical Soecifications Section 6.6.2, Paragraph 1.9d, this is to report the abn5rmal occurrence of July 17,1973 wherein a bistable in the Reactor Protection System failed to de-energize on signal during the monthly surveillance test.

l During the performance of Periodic Test PT5 one side of Bistable LC-427 A/C failed to de-energize on the inserted signal that is equal to five percent pressurizer water level. The procedure is to insert signals into the various components of the protection channel to verify the bistable alarm setpoints. Bistable LC-427 A/C has a single input (pressurizer level) and a dual output (low and high pressurizer levels).

The high pressurizer level component performed correctly on the insertion of the appropriate signal.

While holding the channol in the trip mode, the Plant Operations Review Committee met and prepared an emergency maintenance procedure l to remove the defective module and to install and test the replacement. The change was effected and the test was satisfactorily completed.

Examination of the bistable indicated that the reference voltage required to establish an operating point for the bistable was interrupted by a " cold solder joint" on the alarm solid state card associated with the pressurizer low level. This joint failure prevented the reference voltage from being applied to the comparing circuit of signal and reference voltage.

In normal operation, a reference voltage equal to five percent levelis set

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ROCHESTER C A$ AND CLCC CORP. ) SHEET NO. 2

, o4rc July 27,1973 ro .Mr. John F. O' Leary by the dial of the bistable. A signal voltage equal to or greater than five percent energizes this bistable. This is a normal operating condition.

The lack of a reference voltage, therefore, did not give the actual signal a reference point to de-energize the bistable.

The safety injection logic calls for a combination of low level and low pressure in the logic train of any of three separate channels. As the other two channels containing this logic operated correctly safety injection would have occurred if necessary.

This is the first failure of this type to have occurred in the Safety Injection Logic System. Due to the redundancy provided with three channels of protection no potential safety problem is known to have existed.

V y truly yours,

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Gra j e 2. . Green xc: Mr. James P. O'Reilly L