05000338/LER-1981-022-03, /03L-0:on 810406,TH Indication for Channel III Differential Temp/Tavg Protection Found Reading Higher than Actual Output.Caused by Extra Resistance Across Terminals Due to Loose Terminal Board Connections

/03L-0:on 810406,TH Indication for Channel III Differential Temp/Tavg Protection Found Reading Higher than Actual Output.Caused by Extra Resistance Across Terminals Due to Loose Terminal Board Connections

ML20003H722
Person / Time
Site:	North Anna
Issue date:	04/30/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20003H717	List: 05000338/LER-1981-022, Forwards LER 81-022/03L-0 05000338/LER-1981-022-03, /03L-0:on 810406,TH Indication for Channel III Differential Temp/Tavg Protection Found Reading Higher than Actual Output.Caused by Extra Resistance Across Terminals Due to Loose Terminal Board Connections
References
LER-81-022-03L, LER-81-22-3L, NUDOCS 8105070325
Download: ML20003H722 (3)

LER-1981-022, /03L-0:on 810406,TH Indication for Channel III Differential Temp/Tavg Protection Found Reading Higher than Actual Output.Caused by Extra Resistance Across Terminals Due to Loose Terminal Board Connections

Event date:
Report date:
3381981022R03 - NRC Website

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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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/0/4/0/6/8/1/ (8) /n/4 h /n/n h / (9) 0, DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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On April 6, 1981, during Mode 3 operation above P-12, TH indication for Channel /

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III AT/TAVG Protection was found reading 16*F above actual temperature causing /

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TAVG to be higher by approximately 8*F.

This error would have resulted in de- /

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layed feedwater isolation and SI actuation signals for that channel on Low and /

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Low-Low TAVG respectively. Because redundant temperature protection channels /

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were operational, 'he public health and safety were not affected. Reportable /'^

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pursuant to T.S. 6.9.1.9.b.

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SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

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/I/B/ (11) [A/ (12) /C/ (13) /I/N/S/T/R/U/ (14) /E/ (15)

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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 [X/ (18) [H/ (19) [Z/ (20) /Z/ (21) /0/0/0/0/ (22) /Y/ (23) [N/ (24) [N/ (25) /R/3/6/9/ (26)

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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Loose terminal board connections for the hot leg RTD, due to failure of test

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personnel to tighten the lugs following RTD cross calibration, resulted in ex- /

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tra resistance across the terminals causing higher than actual output. The

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connections were tightened and the channel was satisfactorily calibrated. All /

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other RTD connections were checked to ensure the leads were properly landed.

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FACILITY METHOD OF DISCOVERY DESCRIPTION (32)

STATUS

% POWER OTHER STATUS

/ HOT STANDBY / ( 0) DISCOVERY

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/0/0/0/ (29)

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OPERATOR OBSERVATION

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ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35)

LOCATION OF RELEASE (36)

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PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

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NA

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PERSONNEL INJURIES NUMBER DESCRIPTION (41)

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LOSS OF OR DAMAGE TO FACILITY f 3)

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DESCRIPTION

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PUBLICITY ISSUED DESCRIPTION (45)

NRC USE ONLY

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8105 0 70ME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151

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Virginia Electric and Power Company North Anna Power Station, Unit #1 Attachment: Page 1 of 2 Docket No. 50-338 Report No. LER 81-022/03L-0

Description of Event

- On April 6,1981, during Mode 3 operation above the P-12 setpoint (543*F), hot leg temperature (T ) for Channel III 6T/T Protection g

AVG was found reading 16'F higher than the actual temperature causing calculated T to be higher by approximately 8 F.

This is contrary tot.S.3.3.$YSandreportablepursuanttoT.S.6.9.1.9.b.

Probable Consequences of Occurrence With T f r Protection Channel III reading 8*F higher than actual, boththeLowk feedwater isolation and Low-Low T safety injection AV actuationpermissivesignalsfromLoop3wouldhavebeendelayedby gyg AG not being generated until an actual temperature of 8*F below the Tech Spec trip setpoints had been reached. The overpower and overtemperature aT reactor trip functions were not adversely affected by this occurrence because they would have occurred earlier than before and thus be core conservative. Because the channel was placed in the tripped condition within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and redundant temperature protection channels for Loops 1 and 2 were operable to initiate the engineered safety systems at the correct setpoint if required, the health and safety of the general public were not affected.

Cause of Event

Loose connections on the terminal board for the Loop 3 hot leg RTD caused an extra resistance across the terminals resulting in a l

higher than actual output for the detector. The loose tecninal beard l

connections were the result of test personnel failing to tighten lugs j

after test equipment for RTD cross calibration was removed the previous day.

Immediate Corrective Action

Af ter the channel was placed in the tripped condition, the terminal board connections for the affected RTD were tightened and the temperature channel was satisfactorily calibrated. All terminal board connections for each of the other RTD's were then checked to ensure that all leads were properly terminated.

Scheduled Corrective Action No scheduled corrective action is required.

Actions Taken to Prevent Recurrence l

Personnel involved were reinstructed on the importance of l

returning systems to normal conditions following removal of test equipment.

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Attachment: Page 2 of 2 Generic Implications This is an isolated event and therefore no generic implications exist.

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