ML20064E442

/03X-1 on 780915:during Periodic Test,A Bistable (FC-1485 in Protec Channel Iv)Associated W/Hi Steamline Flow S.I.Actuation Failed to Trip,Due to Defective Bistable Card

ML20064E442
Person / Time
Site:	North Anna
Issue date:	11/13/1978
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20064E436	List: ML20064E435 ML20064E438 ML20064E442
References
LER-78-089-03X, LER-78-89-3X, NUDOCS 7811170189
Download: ML20064E442 (2)

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LICENSEE EVENT REPORT l Update Report - Previous R: port Date 10-10-78 CONTROL BLOCK: l l l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) i e  ;

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• EVENT DESCRIPTION AND PROBADLE CONSEQUENCES h i

[O 121 l Durin9 the performance of a periodic test, it was observed that a bistable (FC-1485 g o ,3, ,

in protection Channel IV) . associated with "Hi Steamline Flow S. I. Actuation", failed I jog,,g ot trip as expected. This event is reportable as per Tech Spec 6.9.1.9.b. l I

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41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS g lThe bistable card proved to be defective and was replaced. The instrument 1000 was I

.b g grecalibrated and retested by the periodic test. Redundant circuitry was availahlo _]

if required by an accident situation and the health and safety of the general r"blic- l g,y g

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Virginia Electric and Power Company North Anna Power Station, Unit #1

Attachment:

Page 1 of 1 Docket No. 50-338 Report No. LER/R0 78-089/03X-1 Description Of Event .

On 9/15/78, a periodic test was performed to demonstrate the operability of the Engineered Safeguard System. Upon testing the feature for Safety Injection Actuation due to a "Hi Steamline Flow Condition with Low Steamline Pressure or Low Low Tavg", a flow bistable (FC-1485 in protection channel IV) failed to trip as expected.

Probable Consequence Of Occurrence This type of failure is considered by the design criteria of the Engineered Safeguard System as a single failure. The system provides for this type of failure by the ability of redundant logic to produce the same equipment response when required by an accident situation. This was evidenced when the redundant channel was tested and found to operate satisfactorily. The occurrence of these

(- types of failures is also provided for by the administrative requirement to perform periodic tests to determine operability of the Engineered Safeguard

• System as was demonstrated by the discovery of this equipment failure. As a result of the above mentioned provisions, the health and safety of the general public was not endangered.

Cause Of Occurrence -

The bistable proved to be defective and was replaced. .

Scheduled Corrective Action After replacing the bistable card, the instrument loop was recalibrated and retested as per the periodic test by which the problem was discovered.

Action Taken To Prevent Recurrence This is believed to be an isolated occurrence and cannot be traced to any known mode of failure. No further action is required.

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