05000338/LER-1980-074-03, /03L-0:on 800810,w/unit in Mode 1,axial Flux Difference Deviated Greater than 5% from Target & Quadrant Power Tilt Ratio Exceeded 1.02.Caused by Xenon Transient During & After Load Reduction

/03L-0:on 800810,w/unit in Mode 1,axial Flux Difference Deviated Greater than 5% from Target & Quadrant Power Tilt Ratio Exceeded 1.02.Caused by Xenon Transient During & After Load Reduction

ML19337A311
Person / Time
Site:	North Anna
Issue date:	09/03/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19337A304	List: 05000338/LER-1980-074, Forwards LER 80-074/03L-0 05000338/LER-1980-074-03, /03L-0:on 800810,w/unit in Mode 1,axial Flux Difference Deviated Greater than 5% from Target & Quadrant Power Tilt Ratio Exceeded 1.02.Caused by Xenon Transient During & After Load Reduction
References
LER-80-074-03L, LER-80-74-3L, NUDOCS 8009090512
Download: ML19337A311 (2)

LER-1980-074, /03L-0:on 800810,w/unit in Mode 1,axial Flux Difference Deviated Greater than 5% from Target & Quadrant Power Tilt Ratio Exceeded 1.02.Caused by Xenon Transient During & After Load Reduction

Event date:
Report date:
3381980074R03 - NRC Website

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i U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

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DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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On August 10, 1980, with the unit in mode 1, the Axial Flux Difference deviated /

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greater than 5% from the target for a four minute duration during a unit ramp- /

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down. One hour later and on the following day, the Quadrant Power Tilt Ratio /

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exceeded 1.02.

This is contrary to T.S. 3.2.1 and T.S. 3.2.4 and reportable

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pursuant to T.S. 6.9.1.9.b.

Since AFD and the Quadrant Power Tilt Ratio were /

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restored within the required operating bands in the time specified by the Ac- /

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tion Statement, the health and safety of the general public w'ere not affected. /

SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE.

COMPONENT CODE SUBCODE SUBCODE

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SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0- EVENT YEAR REPORT NO.

CODE TYPE NO.

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP.

COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER

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The cause of AFD and Quadrant Power Tilt exceeding T.S. limits was due to a

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xenon transient during and after load reduction. The condition was corrected /

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by borating the control rods out to a higher position in the core.

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FACILITY METHOD OF STATUS

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PERSONNEL EXPOSURES NUMBER TYPE

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 j

8808080Y12.-

'e Virginia Electric.and Power Company North Anna Power Station, Unit #1 Attachment: Page 1 of I Docket No. 50-338 Report No. LER 80-074/03L 4

Description of Event

On August 10, 1980, after power was reduced from 100 percent to approximately 61 percent to accomodate system load requirements, the axial flux difference deviated greater than 5% from the -target for a four minute duration. One hour later, the quadrant power tilt ratio exceeded 1.02 but was less_than 1.09.

On the following day the quadrant power tilt ratio again' exceeded 1.02 but not 1.09 after the power level was increased to 100 percent. The condition was corrected by lowering reactor power approximately 1 percent and withdrawing control rods two -

steps. Deviating the axial flux difference greater than 5 percent from the target is contrary to T.S. 3.2.1 and exceeding 1.02 of the power tilt ratio is contrary to T.S. 3.2.4 and reportable pursuant to T.S.

6.9.1.9.b.

Probable Consequences of Occurrence Surveillance of the axial flux difference and quadrant power tilt ratio assures that the limits of the heat flux hot channel factor are not exceeded during normal operation or in the event of xenon redistri-bution following power changes. This provides protection against exceeding the DNER and peak fuel clad temperature. Since the AFD and the quadrant power tilt ratio were returned to the required values within the allotted time, the health and safety of the general public were not affected.

Cause of Occurrence

- The AFD and power tilt deviations were due to xenon oscillations in the core subsequent to changes in power level.

Immediate Corrective Action

To correct the AFD and power tilt upon reduction of power, the control rods were borated out until the condition was corrected. To correct the power tilt after returning to 100 percent power, the power was reduced approximately one percent and control rods were withdrawn two steps and the power tilt surveillance test was performed to assure

~that the power tilt ratio was below 1.02.

Scheduled Corrective Action No scheduled corrective action was performed.

Action Taken to Prevent Recurrence No further actions are required.

Generic Implications

'There are no generic implications.

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