05000338/LER-1981-003-03, /03L-0:on 810104,loop 3 Reactor Coolant Flow Protection Channel II,F-1435,found Out of Tolerance High. Caused by Voltage Drift in Flow Transmitter Serving Loop. Channel Recalibr

/03L-0:on 810104,loop 3 Reactor Coolant Flow Protection Channel II,F-1435,found Out of Tolerance High. Caused by Voltage Drift in Flow Transmitter Serving Loop. Channel Recalibr

ML20003A292
Person / Time
Site:	North Anna
Issue date:	01/29/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20003A290	List: 05000338/LER-1981-003, Forwards LER 81-003/03L-0 05000338/LER-1981-003-03, /03L-0:on 810104,loop 3 Reactor Coolant Flow Protection Channel II,F-1435,found Out of Tolerance High. Caused by Voltage Drift in Flow Transmitter Serving Loop. Channel Recalibr
References
LER-81-003-03L, LER-81-3-3L, NUDOCS 8102030428
Download: ML20003A292 (2)

LER-1981-003, /03L-0:on 810104,loop 3 Reactor Coolant Flow Protection Channel II,F-1435,found Out of Tolerance High. Caused by Voltage Drift in Flow Transmitter Serving Loop. Channel Recalibr

Event date:
Report date:
3381981003R03 - NRC Website

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REGULATORY COMMISSyoy LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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

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/ On January 4,1981, with the unit in Mode 5, loop 3 reactor coolant flow

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/ protection channel II (F-1435) was found out of tolerance high during the 18

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/ month periodic channel calibration check. The worst case would have caused both /

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/ indicator and computer point to read 3.99% higher than actual resulting in a

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/ delayed reactor trip signal on low flow for that channel. Because redundant loop /

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/ flow instrumentation was operational, the health and safety of the general public/

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/ were not affected. Reportable pursuant to T.S. 6.9.1.9.a.

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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 LEf((18) [Z/ (19) /Z/ (20) /Z/ (21) /0/0/0/0/ (22) g/ (23) [Nf_ (24) /N/ (25) /F/1/8/0/ (26)

E CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27) i

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/ The cause of the error in indication was a voltage drift in the flow transmitter /

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/ serving the instrument loop. Corrective action was to properly recalibrate the /

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FACILITY METHOD OF STATUS

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Surveillance Test

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NRC USE ONLY

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 b]G:.C30 &

Virginia Electric and Power Company North Anna Power Station, Unit 1 Attachment: Page 1 of 1 Docket No. 50-338 Report No. LER 81-003/03L-0

Description of Event

On January 4,1981, with the unit in a cold shutdown condition, loop 3 reactor coolant flow protection channel II (F-1435) was found out of tolerance high during the 18 month periodic channel calibration check. The worst case would have caused both the associated indicator and computer point to read 3.99% higher than actual resulting in a delayed reactor trip signal on low flow for the particular channel.

This event is contrary to T.S. 3.3.1.1 and reportable pursuant to T.S.

6.9.1.9.a.

Probable Consequences of Occurrence Protection channel II (F-1435) monitors reactor coolant loop 3 flow and provides signals for indication, alarm and reactor trip. Flow is monitored by three differential pressure measurements (F-1434, F-1435, F-1435) at a piping elbow in loop 3.

These measurements on a two out of three coincidence signal provide a low flow signal to actuate a reactor trip. Because loop 3 reactor coolant flow protection channels I and III remained operable to initiate a low flow reactor trip if required, the health and safety of the general public were not affected.

Cause of Event

The cause of the channel being out of calibration was a voltage drift in flow transmitter FT-1435.

Immediate Corrective Action

The affected channel was placed in the tripped condition and satis-factorily recalibrated in accordance with approved procedures. The channel is then returned to service.

~

Scheduled Corrective Action No scheduled corrective action is required.

Actions Taken to Prevent Reccurrence No further actions are required.

Generic Implications No generic implications exist for this event.