05000339/LER-1981-017-03, /03L-0:on 810206,reaction Chamber Gas Temp Indicating controller,TIC-5,failed High Offscale Resulting in Automatic Shutdown of Recombiner unit,2-HC-HC-1,on High Temp Interlock.Caused by Loose Plug Connection

/03L-0:on 810206,reaction Chamber Gas Temp Indicating controller,TIC-5,failed High Offscale Resulting in Automatic Shutdown of Recombiner unit,2-HC-HC-1,on High Temp Interlock.Caused by Loose Plug Connection

ML20008E959
Person / Time
Site:	North Anna
Issue date:	03/05/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20008E958	List: 05000339/LER-1981-017, Forwards LER 81-017/03L-0 05000339/LER-1981-017-03, /03L-0:on 810206,reaction Chamber Gas Temp Indicating controller,TIC-5,failed High Offscale Resulting in Automatic Shutdown of Recombiner unit,2-HC-HC-1,on High Temp Interlock.Caused by Loose Plug Connection
References
LER-81-017-03L-01, LER-81-17-3L-1, NUDOCS 8103100632
Download: ML20008E959 (2)

LER-1981-017, /03L-0:on 810206,reaction Chamber Gas Temp Indicating controller,TIC-5,failed High Offscale Resulting in Automatic Shutdown of Recombiner unit,2-HC-HC-1,on High Temp Interlock.Caused by Loose Plug Connection

Event date:
Report date:
3391981017R03 - NRC Website

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f U.S. NUCLEAR REGULATORY COMMISSION g

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

(PLEASE PRLNT OR TYPE ALL REQUIRED INFORMATION)

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LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

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

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On February 6, 1981, during surveillance testing of post accident hydrogen

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recombiner 2-HC-HC-1, the reaction chamber gas temperature indicating

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controller (TIC-5) failed high off scale causing automatic shutdown of the

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recombiner unit on a high temperature interlock. Because the recombiner was

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restored to operable status within 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> and redundant hydrogen recombiner /

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1-HC-HC-1 was available for use if required, the public health and safety were /

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not affected. This event is reportable pursuant to T.S. 6.9.1.9.b.

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SYSTEM

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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 g/ (18) g/ (19) LZ/ (20) g/ (21) /0/0/0/0/ (22) /Y/ (23) /N/ (24) M/ (25) /A/5/3/3/ (26)

CAUSE LESCRIPTION AND CORRECTIVE ACTIONS (27)

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The temperature indicating controller failed high due to a loose plug

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connection at the local recombiner control panel for the cable providing

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thermocouple input to TIC-5.

The tightening mechanism for the thermocouple

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cable plug was screwed down to ensure a proper connection with the receptacle /

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and the recombiner was retested satisfactorily.

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FACILITY METHOD OF i

STATUS

% POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION (32) l

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Periodic Testing

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ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35)

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NRC USE ONLY

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 8103100 63&r

a Virginia Electric and Power Company Attachment: Page 1 of 1 North Anna Power Station, Unit #2 Docket No. 50-339 Report No. LER 80-017/03L-0

Description of Event

On February 6,1981, post accident hydrogen recombiner 2-HC-HC-1 was started to verify operability. During this test the temperature indicating controller for reaction chamber gas temperature (TIC-5) failed high causing the recombiner to shutdown on a high temperature interlock. This rendered the equipment inoperable which is contrary to T.S. 3.6.4.2 and reportable pursuant to T.S. 6.9.1.9.b.

Probable Consequences of Occurrence Two skid mounted hydrogen recombiners, common to both reactcr units, are major components of the Containment Atmosphere Cleanup System which is designed to maintain the hydrogen concentration of the containment atmos-phere below the 4 percent lower flammability limit following a LOCA. Control of hydrogen below this limit following a LOCA can be accomplished with one of the recombiners. The other recombiner serves as a backup. Because recombiner 2-HC-HC-1 was restored to operable status within 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> and the redundant hydrogen recombiner was available for use if required, the health and safety of the general public were not affected.

Cause of Event

TIC-5 failed high off scale due to a loose plug connection in the cable supplying the thermocouple input to the controller.

It appeared that plug was not properly installed originally.

Immediate Corrective Action

The loose connection between the thermocouple cable plug and its receptacle was corrected by screwing down on the tightening mechanism for the connector. The recombiner was then retested satisfactorily returning it to operable status.

Scheduled Corrective Action No scheduled corrective action is required Action Taken to Prevent Recurrence r

No further actions are required.

Generic Implications

.There are no generic implications associated with this event.

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