ML19269D666

LER 79-069/03L-0 on 790508:during Load Transient,Axial Flux Difference Deviated Greater than 5% from Target for Four Minutes.Caused by Rapid Load Reduction of 100 MW Due to Loss of Drain Pump A.Control Rods Withdrawn

ML19269D666
Person / Time
Site:	North Anna
Issue date:	06/06/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19269D662	List: ML19269D661 ML19269D663 ML19269D666 ML19269D668
References
LER-79-069-03L, LER-79-69-3L, NUDOCS 7906110202
Download: ML19269D666 (2)

Text

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7 8 60 61 DOCKET NUYBER 68 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h O 2 I Durine a load transient. the axial fi nv d if f eronen _ (AFn) dovinrod cro,cor thnn SY from!

l0lilltarRet for 4 minutes. This is contrary to T.S. 3.2.1. Action Statement a.1 of T.S. I This event is I o 4 1 3.2.1 was entered and the AFD was restored to its tarcet band.

I O l s l l reportable as per T.S. 6.9.1.9.b. This event did not affect the health or safety of l IoisIlthe neneral public. I I

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M IThe cause of the axial fluv deviatinn unn n rnnid innd 3educti ~ of lon W d"o Po Pho 11ItI lloss of H. P. Drain Pumn "A". I i 2 l Itunediate corrective action was to withdraw control rods which restored the AFD to l I

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Virginia Electric and Power Company

Attachment:

Page 1 of 1

' North Anna Power Station, Unit #1 Docket No. 50-338 Report No. LER 79-069/03L-0 Description of Event On 5-8-79, during a load transient, the axial flux difference (AFD) deviated greater than - 5% from target _for a 4 minute time period. This is contrary to T.S. 3.2.1.

Action statement a.1 of T.S. 3.2.1 was entered and the AFD was returned to within its target band within the 15 minute time allowance.

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 limit within the time allowed, there was no effect upon the safe operation of the plant. As a result, the public health and safety was not affected.

Cause of Occurrence The cause of the AFD deviation was a rapid load reduction of 100 MWe necessitated by the loss of H. P. Drain Pump "A".

Immediate Corrective Action Corrective action was a rod withdrawal by the operator which returned the AFD to within the target band.

Scheduled Corrective Action No further action required.

Actions Taken To Prevent Recurrence No further action required.