ML19309H149

LER 80-038/03L-0:on 800409,during Power Escalation,Axial Flux Difference Deviated Greater than Limit for three-minute Duration.Caused by Overinsertion of Control Rods Resulting from Continued Dilution During Hold in Power Escalation

ML19309H149
Person / Time
Site:	North Anna
Issue date:	05/01/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19309H146	List: ML19309H145 ML19309H149
References
LER-80-038-03L, LER-80-38-3L, NUDOCS 8005080516
Download: ML19309H149 (2)

Text

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l so si coCxsra. ween es se avs=T oars amicar sars EVENT DESCRIPTICN AND PRCBASLA CCNSICUENCES to;2i l Durinc a power escalation on Apri , 1980, the Axial Flux Difference deviated g (TIT] l greater than -5% from the target for a 3 minute duration. Since there was less g t o t a l I than ore hour penalty accumulation, power operation was allowed to continue as l ITITI l -n.- ACTION statement a.2 of T.S. 3.2.1. The health and safety of the general  ;

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1. i,al l The cause of the AFD de*. ' ition was an overinsertion of the control rods which  ;

y Iwas the result of a continued dilution during a hol'd in power escalation. g l Corrective action was for the operator to restore the AFD to within the target ,

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Attachment:

Page 1 of 1 Docket No. 50-338 Report No. LER 80-038/03L-0 Description of Event On April 9, 1980, during a power escalation from 74% power, the Avial Flux Difference (AFD) deviated greater than -5% from target for a 3 minute duration. This event is contrary to T.S. 3.2.1.

Since there was less than one hour penalty accumulation, operation was allowed to continue as per ACTION statement a.2 of T.S. 3.2.1.

This event is reportable as per T.S. 6.9.1.9.b.

Probable Consequences of Occurrence Surveillance of the Axial Flux Difference assures that the limits of the heat flux hot channel factor are not exceeded during normal operation or in the event of Xenon redistribution following power changes.

This provides protection against exceeding the DNBR and peak fuel clad temperatures.

Since the AFD was returned to its correct limit within the time allotted, there was no effect upon the safe operation of the plant. As a result, the public health and safety were not affected. There are no generic implications associated with this occurrence.

Cause of Event During a power escalation, a dilution was in progress. Because of a chemistry hold, the power increase and dilution were stopped. Following the securing of dilution, a further small dilution occurred due to mixing. This caused the control rods to step in, resulting in the AFD deviation.

Immediate Corrective Action Boration of the RCS was initiated and control rods were withdrawn by the operator which restored the AFD to within the target band.

Scheduled Corrective Action I

Surveillance of the AFD continued during the power escalation to l prevent any further AFD deviations.

Actions Taken to Prevent Recurrence No further actions are required.