ML19246A777

LER 79-030/03X-1 on 790308:nonconservative Gain Setting on delta-flux Signal Feeding Overpower Delta T Protection Circuitry Observed.Caused by Improper Setting of delta-flux Gain.Signal Recalibr

ML19246A777
Person / Time
Site:	North Anna
Issue date:	07/02/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19246A775	List: ML19246A774 ML19246A776 ML19246A777 ML19246A778
References
LER-79-030-03X, LER-79-30-3X, NUDOCS 7907060333
Download: ML19246A777 (2)

Text

NRC FORM 366 . S. NUCLEAH HF.GULATOM Y COMM6SSION (7 77)

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LICENSEE EVENT REPORT UPDATE REPORT - PREVIOUS REPORT DATE 04-03-79 (PLE ASE PRINT OR TYPE All. REQUIREO INFORMATIOfJ)

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60 61 DOCS E T N U V.45 u EVENT DESCRIP ilO,'s ANO PHO3 ABLE CONSEQUENCES o 2 l 0n 3/8/79 during normal steady state operatien, a periodic calibration procedure wac l o 3 performed on the Overtemperature Delta T protection circuitry. This procedure revealed l o 4 j a nonconservative gain setting on the Delta-Flux signal feeding the Overpower Delta T l protection circuitry. Redundant circuitry was availa'g , therefore, the health and ots I o c ) I safety of the general public was not affected. This event is reportable as per l 0 , jT.S. 6.9.1.9.a. _

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33 35 3> 3/ 40 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i O lThe cause of the problem was ar imorope swinq of the delta flux cain. The i W iato I i i ., corrective action was to recalibrate the 41ta flux sianal which feeris tha over- I

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Update Report - Previous Report Date 04-03-79 Virginia Electric and Power Company North Anna Power Station, Unit #1

Attachment:

Page 1 of 1 Docket No. 50-338 Report No. LER 79-030/03X-1 Description of Event On 3/8/79 at approxima tely 0300 an instrument calibration " check" procedure was performed on the Channel III circuitry of Overtemperature AT protection. The result of this procedure was the discovery of a non-conservative gain setting on the lower power range detector flux signal which feeds this circuitry.

Probable Consequences of Occurrence Tha overtemperature AT channel is part of the reactor trip system instrumentation which ensures the reliability, redundance and diversity in the facility design for the protection and mitigation of accident and transient conditions. Since the redundant channels were still operable and capable of performing the required functions, there was no effect on the scfety and health of the general public.

Cause of Occurrence The cause of improper signal from the lower power range detector to the overtemperature AT circuitry was an improrer gain setting.

Immediate Corrective Action The immediate corrective action was to recaliarate the lower power range detector input signal.

ScheJuled Corrective Action No further action is required.

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Actions Taken to Prevent Recurrence No actions other than normal calibration surveillance is considered necessary.

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