05000339/LER-1980-083-03, /03L-0:on 801027,F(Q) Limit Exceeded Twice.Caused by Rod Movement at Beginning of Core Life When F(Q) Limit Margins in Core Ctr Are at Min.Power Reduced

/03L-0:on 801027,F(Q) Limit Exceeded Twice.Caused by Rod Movement at Beginning of Core Life When F(Q) Limit Margins in Core Ctr Are at Min.Power Reduced

ML19345B465
Person / Time
Site:	North Anna
Issue date:	11/19/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19345B457	List: 05000339/LER-1980-083, Forwards LER 80-083/03L-0 05000339/LER-1980-083-03, /03L-0:on 801027,F(Q) Limit Exceeded Twice.Caused by Rod Movement at Beginning of Core Life When F(Q) Limit Margins in Core Ctr Are at Min.Power Reduced
References
LER-80-083-03L-01, LER-80-83-3L-1, NUDOCS 8012010362
Download: ML19345B465 (2)

LER-1980-083, /03L-0:on 801027,F(Q) Limit Exceeded Twice.Caused by Rod Movement at Beginning of Core Life When F(Q) Limit Margins in Core Ctr Are at Min.Power Reduced

Event date:
Report date:
3391980083R03 - NRC Website

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4 LEAR REGULATORY COMMISSION.

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LICENSEE EVENT REPORT

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DOCKET NUMBER EVENT DATE REPORT DATE EVENT r"'SCRIPTTON AND PROBABLE CONSEQUENCES (10)

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0.i cctober 27, 1980, the F(Q) limit was exceeded two times.

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reac',r power was reduced to restore F(Q) to within the T.S. ' 3.2.2 limit.

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SYSTEM

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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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These events were caused by rod movement at the beginning of core life when

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F(Q) limit margins in the center of the core are at their minimum.

Power was /

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reduced to restore margin to F(Q).

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_NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 8 012 0103M-

e Virginia Electric and Power Company North Anna Power Station, Unit 2 Attachment: Page 1 of 1 Docket No. 50-339 Report No. LER 80-083/03L-0

Description of Event

On October 27, 1980, the F(Q) limit near the center of the core was exceeded at 1617 and again at 1708.

In both vents, the reactor power was reduced to restore F(Q) to within the lime.

Probable Consequences of Occurrence The limit placed on the heat flux hot channel factor F(Q) provides the assurance that the fuel integrity is maintanined throughout normal and accident conditions and to ensure the ECCS acceptance criteria is not exceeded. By reducing the reactor power 1% for every 1% the limit is exceeded, the F(Q) value returned to below the T.S. 3.2.2 limit.

Cause of' Event These. events were caused by rod motion in a new core. The margin of F(Q) to the limit is at a minimum at the center of the core at the beginning of life..The North Anna Unit 2 core had, at this time, less than 20 effective full power lays of burnup.

Immediate Corrective Action

- In each event, the power level was reduced 1% for every 1% the F(Q) limit was exceeded. To prevent similar occurrences, rod motion was minimized by borating rods to the fully withdrata position. This caused the~ power (flux) in the middle region of the core to decrease. The core flux was thereby flattened axially.

Scheduled Corrective Action No further action required at this time. The F(Q) margin will increase as the core burnup progresses.

Actions Taken to Prevent Recurrence The recurrence of this problem has been prevented by operating with the control rods near. the fully withdrawn position.

Generic Implications There are no generic implications associated with this event.

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