05000339/LER-1981-050-03, /03L-0:on 810619 & 20,during RCS Cooldown to Cold Shutdown Conditions,Individual Rod Position Indication B Shutdown Bank Rod G-7 & J-9 Deviated from Group Demand Position.Caused by Instrument Drift

/03L-0:on 810619 & 20,during RCS Cooldown to Cold Shutdown Conditions,Individual Rod Position Indication B Shutdown Bank Rod G-7 & J-9 Deviated from Group Demand Position.Caused by Instrument Drift

ML20009E908
Person / Time
Site:	North Anna
Issue date:	07/15/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009E898	List: 05000339/LER-1981-050, Forwards LER 81-050/03L-0 05000339/LER-1981-050-03, /03L-0:on 810619 & 20,during RCS Cooldown to Cold Shutdown Conditions,Individual Rod Position Indication B Shutdown Bank Rod G-7 & J-9 Deviated from Group Demand Position.Caused by Instrument Drift
References
LER-81-050-03L, LER-81-50-3L, NUDOCS 8107280537
Download: ML20009E908 (2)

LER-1981-050, /03L-0:on 810619 & 20,during RCS Cooldown to Cold Shutdown Conditions,Individual Rod Position Indication B Shutdown Bank Rod G-7 & J-9 Deviated from Group Demand Position.Caused by Instrument Drift

Event date:
Report date:
3391981050R03 - NRC Website

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

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

'/0/1/

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

/0/0/-/0/0/0/0/0/-/0/0/ (3)

/4/1/1/1/1 (4)

/ / / (5)

LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

/0/1/

REP

/L/ (6)

/0/5/0/0/0/3/3/9/

(7)

/0/6/1/9/8/1/

(8)

S /7 A # # /1/ (9)

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

/0/2/

/ On June 19 and 20, 1981, during RCS cooldown to cold shutdown conditions, the

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/ individual rod position indication for "B" shutdown bank rod G-7 and J-9,

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/ respectively, deviated from the group demand position by greater than 12 steps.

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/ On each occasion, the reactor trip breakers were immediately opened in compliance /-

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/ with T.S. 3.1.3.3 and tne IRPI was recalibrated, consequently the health and

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/ safety of the general pubic were not affected. This event is reportable pursuant /

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/ to T.S. 6.9.1.9.b.

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SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

/0/9/

/I/E/ (11) /E/ (12)

/E/ (13) /I/N/S/T/R/U/ (14)

/I/ (15)

/Z/ (16)

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

CODE TYPE NO.

(17)

REPORT NUMBER

/8/1/

/-/ /0/5/0/

/\\/

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/L/

/-/

/0/

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

/E/ (18) /Z/ (19)

/2/ (20) /2/ (21) /0/0/0/0/ (22) /Y/ (23)

/N/ (24) /N/ (25) /W/1/2/0/ (26)-

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

/1/0/

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

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

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/ tion systems.

I.t both cases, the rod position channel was properly recalibrated /

/1/3/

/ and returned to service.

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/1/4/

/

/

FACILITY METHOD OF STATUS

% POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION (32)

/1/5/

/G/ (28)

/0/0/0/ (29)

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NA

/ (30)

/A/ (31) /

OPERATOR OBSERVATION

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ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35)

LOCATION OF RELEASE (36)

/1/6/

/Z/ (33)

/Z/ (34) /

NA

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NA

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PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

/1/7/ /0/0/0/ (37) /Z/ (38) /

NA

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PERSONNEL INJURIES NUMBER DESCRIPTION (41)

/1/8/ /0/0/0/ (40) /

NA

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LOSS OF OR DAMAGE TO FACILITY (43)

TYPE

DESCRIPTION

/1/9/

/Z/ (42) /

NA

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PUBLICITY ISSUED DESCRIPTION (45)

NRC USE ONLY

/2/0/

/N/ (44) /

NA

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 8107280537 810715 050003 gDRADOCK

Virginia Electric and Power Company North Anna Power Station, Unit 2

Attachment:

Page 1 of 1 Docket No. 50-339 Report No. LER 81-050/03L-0 i

Description of Event

on June 19, 1981, an RCS cooldown to cold shutdown conditions was in progress when the Control Room operator observed a greater than 12 step disagreement between he Individual Rod Position Indicator (IRPI) for rod G-7 in shutdown bank "B" and the group demand indication.

On June 20, a greater than 12 step disagreement was also observed on the IRPI for "B" shutdown bank rod J-9.

Probable Consequences of Occurrence Operability of the control rod position indication is required to determine rod position and thereby ensure compliance with the control rod misalignment and insertion limits.

Since neither control rod wa's misaligned and both position indications were 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 dis.3reement 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

On both occasions, the reactor was immediately tripped as per T.S.

3.1.3.3 and the rod position indicator channel was satisfactorily recal-ibrated and returned to service.

Scheduled Corrective Action s

1 A long term investigation into the problems associated with the IRPI system is in progress.

No further corrective action is scheduled until an adequate design modification is developed and proven effective.

Actions Taken to Prevent Reccurrence i

No further actions are required at this time.

l 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 Anna Units 1 and 2.

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