05000338/LER-1981-021-03, /03L-0:on 810408,during Testing,Rod Position Indicators Showed Two Control Rods in B Bank Greater than 12 Steps from Demand Position.Cause Unknown.Reactor Was Shut Down.Reactor Trip Breakers Opened

/03L-0:on 810408,during Testing,Rod Position Indicators Showed Two Control Rods in B Bank Greater than 12 Steps from Demand Position.Cause Unknown.Reactor Was Shut Down.Reactor Trip Breakers Opened

ML20004C585
Person / Time
Site:	North Anna
Issue date:	05/07/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20004C584	List: 05000338/LER-1981-021, Forwards LER 81-021/03L-0 05000338/LER-1981-021-03, /03L-0:on 810408,during Testing,Rod Position Indicators Showed Two Control Rods in B Bank Greater than 12 Steps from Demand Position.Cause Unknown.Reactor Was Shut Down.Reactor Trip Breakers Opened
References
LER-81-021-03L, LER-81-21-3L, NUDOCS 8106040299
Download: ML20004C585 (2)

LER-1981-021, /03L-0:on 810408,during Testing,Rod Position Indicators Showed Two Control Rods in B Bank Greater than 12 Steps from Demand Position.Cause Unknown.Reactor Was Shut Down.Reactor Trip Breakers Opened

Event date:
Report date:
3381981021R03 - NRC Website

text

LICENSEE EVENT REPORT

. _ CONTROL BLOCK / / /-/ / / / (1) (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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/V/A/N/A/S/1/ (2)

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LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT 10/1/)

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/0/4/0/8/8/1/ (8) /0/5/0/7/8/1/ (9) s DOCKET NLHBER

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EVENT DATE REPORT CATE l}

EVENT DESCRIPTION AND PROBABLE CONSEQUENCES'(10)

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On April 8, 1981, while performina a reactor startup physics testing, the rod /'

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position indicators showed that two control rods in D Bank were areater than 12/

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steps from demand position. After verifying that both control rods position

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indicators showed more than 12 steps from demand position as per T.S. 3.1.3.2, /

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the unit was shutdown to hot standby within 1 bour. Therefore, the health and /

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safety of the puolic were not affected. This item is reportable pursuant to

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T.S. 6.9.1.9.b.

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'1 SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE' SUBCODE SUBCODE

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/I/F/ (11) g/ N0) LX/ (13) /I/N/S/T/R/U/ (14) g/ (15).

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SEQUENTIAL OCCURRENCE REPORT REVISION l-LER/R0 EVEN "sIAR REPORT NO.

CODE TYPE NO.

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I ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER' MANUFACTURER i.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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The cause of the error in the position of 2 control rods in one bank cannot-be / -

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identified. The calibration of the rod position' indicators was checked with no/

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affect on displayed position. Therefore, the reactor was 'immediately shut down/

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and the reactor trip breakers opened.

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FACILITY METHOD OF

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STATUS

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LC/ (23)

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OPERATOR OBSERV3 TION

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d ACTIVITY CON 1 3T RELEASED OF RELEAd2 AMOUNT OF ACTIVITY (35)

LOCATION OF RELEASE (36) i

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PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

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LOSS OF OR DAMAGE TO FACILITY (43)

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PUBLICITY ISSUED DESCRIPTION (45)

NRC USE ONLY

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 18106040ff/,

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Virginia Electric and Power Company North Anna Power Station, Unit

<>l Attachment: Page 1 of 1 Docket No. 50-338 Report No. LER 81-021/03L-0

Description of Event

On April 8,1981, while performing reactor physics testing, control rods PS in D Bank (group 1) and F6 in D Bank (group 2) indicated greater than 12 steps from the group demand position. When this error was noticed, an immediate calibration check of the rod position indication channels was performed. This action was taken since previous experience with indicated rod misalignment had shown the problem was actually due to instrument error. However, the calibration check did not provide confidence that the rods were in the position indicated. This indicated position was greater than 12 steps from the group demand position for 2 control rods.

Probable Consequences of Occurrence Operability of the position indication system is required to determine control rod position and thereby ensure compliance with the coctrol rod alignment and insertion limits. When actual rod position could not be verified, the reactor was immediately shut down and the reactor trip breakers opened.

Therefore, the health and safety of.the public were not affected.

Cause of Event

The exact cause of the error in rod position indication cannot be determined. This misalignment did not reappear during the subsequent reactor start-up.

Immediate Corrective Action

The reactor was shut down immediately and the trip breakers were opened to ensute that there was no actual misalignment of control rods.

The rod position indicators were recalibrated and the reactor subsequently started. up.

All indicators and critical boron calculations verified the effectiveness of this carrective action.

Scheduled Corrective Action No further corrective action is scheduled.

Actions Taken to Prevent Recurrence No further actions are necessary.

Generic Implications There are no generic implications for this event.

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