ML20064H861

/03L-0 on 781204:during Pwr Reduction,Axial Flux Difference Deviated Greater than 5%;during Return to Full Pwr Afd Deviated Greater than -5%.Caused by Load Reduction Caused by Unit Being on Load Following

ML20064H861
Person / Time
Site:	North Anna
Issue date:	12/18/1978
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20064H859	List: ML20064H857 ML20064H861
References
LER-78-127-03L, LER-78-127-3L, NUDOCS 7812270238
Download: ML20064H861 (2)

Text

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/ 8 60 68 DOCKET NUMBER 69 74 75 REPORT DATE ,80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES b10 10 l 21 l During a power reduction, the Axial FTux Difference (AFD) deviated greater than +5% l o 3 i from the target for a 2 minute duration. During the subsequent return to full power, I i o ,, , i the AFD deviated greater than -5% from the target for a 7 minute duration. In both l

,o,3, , cases, the AFD was returned to within the target band within the 15 minute allowance I i o ,, i i of the Action Statem^nt of T.S. 3.2.1. This event is reportable as per T.S. 6.9.1.9.bJ 10171 1 I 101811 1

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43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS 27 lilOi lThe cause of the first AFD deviation was a load reduction caused by unit beina on I i i l load following. Corrective action was a dilution by the coerator which ratiwd control I i 2 frods to drive in. The cause of the second AFD deviation was increase in load to full I h t

,l power. Corrective action was a boration by the operator which caused control rods to I g l drive out. No further corrective action was required. I F 8 9 80 ST S  % PUWER OTHER STATUS DIS RY DISCOVERY DESCRIPTION I i I s l l F l@ l 0l 7 l 5 l@l NA l lAl@l Operator Observation l ACTIVITY CO TENT EELE ASED OF RELE ASE AMOUNT OF ACTIVITY LOCATION OF RELEASE i o [Z_j @ [_Z_j@l NA l l NA l PeRSONNEt ExPOSuAe5 NuveER TYPE DESCRIPTION @

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L2_LO.] $StED81 NA l llllll!llllll; 2 a 9 to 68 69 80 5 NAME OF PREPARER W. R. Cartwright psone: 703-894-5151 2, .

,,- Virginia E1:ctric and Power Company North Anna Power Station, Unit #1

Attachment:

Page 1 of 1 Docket No. 50-338 Report No. LER 78-127/03L-0 Description of Event: ,

On 12-04-78 at 0306, during a power reduction, the Axial Flux Difference (AFD) deviated greater than +5% from the target for a 2 minute duration.

At 0746, during the subsequent return to full power, the AFD deviated -

greater than - 5% from the target for a 7 minute duration. These events are contrary to T.S. 3.2.1. .

In both cases, the AFD was returned to within the target band within the 15 minute allowance of the Action Statement.

These events are reportable as per T.S. 6.9.1.9.b.

Probable Consequences of Occurrences:

( 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 k 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 allotted, there was no effect upon the safe operation of the plant. As a result, the public health and safety was not endangered.

Cause of Occurrences:

The cause of the first AFD deviation was a load reduction caused by the station being on load follow.

The second AFD deviation was a result of the Unit returning to full power.

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Immediate Correction Action:

In the case of the first AFD deviation, the corrective action was a dilution by the operator. This drove the rods in, resulting in a downward shift of the flux toward the target.

During the return to full power, the operator borated which pulled the rods out. This resulted in the flux being shifted upward toward the target.

Scheduled Corrective Action:

No further corrective action was required.

Actions Taken to Prevent Recurrences:

No further action is required.