05000339/LER-1980-045-03, /03L-0:on 800803,during RCS Cooldown,Control Room Operator Observed Greater than 12 Step Deviation Between Rod Indicator & Demand Indicator.Caused by Instrument Drift. Rod Position Indicator Recalibr

/03L-0:on 800803,during RCS Cooldown,Control Room Operator Observed Greater than 12 Step Deviation Between Rod Indicator & Demand Indicator.Caused by Instrument Drift. Rod Position Indicator Recalibr

ML19331D826
Person / Time
Site:	North Anna
Issue date:	08/27/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19331D824	List: 05000339/LER-1980-045, Forwards LER 80-045/03L-0 05000339/LER-1980-045-03, /03L-0:on 800803,during RCS Cooldown,Control Room Operator Observed Greater than 12 Step Deviation Between Rod Indicator & Demand Indicator.Caused by Instrument Drift. Rod Position Indicator Recalibr
References
LER-80-045-03L-02, LER-80-45-3L-2, NUDOCS 8009030619
Download: ML19331D826 (2)

LER-1980-045, /03L-0:on 800803,during RCS Cooldown,Control Room Operator Observed Greater than 12 Step Deviation Between Rod Indicator & Demand Indicator.Caused by Instrument Drift. Rod Position Indicator Recalibr

Event date:
Report date:
3391980045R03 - NRC Website

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

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/_ On August 3,1980, during an RCS cooldown to 450*F, the Control Room Operator /

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observed that the individual rod position indication for rod N-9 in shutdown

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bank "A" deviated from the group demand position by greater than 12 steps. The/

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reactor trip breakers were imnediately opened in compliance with T.S. 3.1.3.3 /

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and the IRPI was recalibrated, consequently the health and safety of the

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general public were not affected. This event is reportable pursuant to T.S.

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6.9.1.9.b.

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SYSTEM

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SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT 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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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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The cause of this indicator disagreement was attributed to instrument drift.

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This is a recurring problem and is generic to Westinghouse analog rod position /

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indication systems. The rod position indicator channel for N-9 was properly

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recalibrated and returned to service.

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FACILITY METHOD OF

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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 l

3009030 619

1 Virginia Electric and Power Company North Anna Power Station, Unit #2 Attachment: Page 1 of 1 Docket No. 50-339 Attachment to LER 80-045/03L-0

Description of Event

On August 3,1990, an RCS cooldown in Mode 3 was in progress when the Contro' Room Operator observed a greater than 12 step disagreement between the Individual Rod Position Indicator (IRPI) for rod N-9 in shutdown bank "A" and the group demand indication.

Probable Consequences of Event Operability of the control rod pcsition indication is required to determine rod position and thereby ensure compliance with the control rod alignment and insertion limits. Since the control rod was not misaligned and the position indication was properly restored, there was no effect on the safe operation of the plant. As a result, the health and safety of the general public were not affected.

Cause of Event

The cause of the disagreement in rod position indication was instru-ment drift. This drift can be caused by changes in the temperature of the rod drive line, changes in the frequency of the excitation source, and by changes in secondary loadings.

Immediate Corrective Action

The reactor was immediately tripped as per T.S. 3.1.3.3 and the rod position indicator channel for rod N-9 was satisfactorily recalibrated and returned to service.

Scheduled Corrective Actie A long term investir,ation into the problems associated with the IRPI system is in progrr.ss. No further corrective action is scheduled until an adequate design modification is developed and proven effective.

Actions Taken to Prevent Recurrence No further actions are required at this time.

Generic Implications Rod position indicator drift is a generic problem with the Westing-house analog rod position indication system. This system is used in North Anni Units 1 and 2.

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