ML20039D183

LER 81-028/03L-0:on 811125,steam Generator low-low Level Trip & Alarm Bistables BS-494-A1 & BS-494-A2 Found to Be Inoperable During Periodic Test PT-5.5 W/Unit at Cold Shutdown.Caused by Failure of Instrument Channel LI-494

ML20039D183
Person / Time
Site:	Robinson
Issue date:	12/23/1981
From:	CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20039D180	List: ML20039D179 ML20039D183
References
LER-81-028-03L, NUDOCS 8112310400
Download: ML20039D183 (3)

Text

NRC FORM J66 U.S. NUCLEAR REGULATORY COMMISSION (7 77) d LICENSEE EVENT REPORT CONTROL BLOCX: l l l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 1 6 l0 l 18 l9 l S l LICENSEE 7

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7 8 61 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h l o 121 lOn November 25, 1981, at approximately 1710 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.50655e-4 months <br /> with the unit at colc! shutdown. the I g o ,3 ; [ steam genaator low-low level trip and alarm bistables BS-494-Al and BS-494-A2 were l lo l4 j lfound to be inoperable during the performance of Periodic Test PT-5.5. This event I 10 I s l Iresulted in less than the minimum degree of redundancy required by Technical i lo le i ISPecification table 3.5-2 and is reportable pursuant to 6.9.2.b.2. Since the other 1 jog 7; l channels were operable, there was no threat to the public health and safety. I l

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47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l i l 0 l lI nstrument Channel LI-494 wa s declared inoperable and the bistables were tripped l i i panually at 1740 hours0.0201 days <br />0.483 hours <br />0.00288 weeks <br />6.6207e-4 months <br />. The failed component, LC-494A was replaced with a new unit. I I

, , palibrated, tested, and the instrument channel was declared operable at 2010 hours0.0233 days <br />0.558 hours <br />0.00332 weeks <br />7.64805e-4 months <br /> on I g l November 25, 1981. This event is the result of component failure due to normal wear. I

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SUPPLEMENTAL INFORMATION FOR LICENSEE EVENT REPORT 81-28

1. Cause Description and Analysis:

On November 25, 1981, at approxima tely 1710 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.50655e-4 months <br /> with the unit at cold shutdown conditions, reactor protection bistables BS-494-Al and BS-494-A2 ("C" steam generator low-low level trip and and lo-lo level alarm respectively) were found inoperable during the performance of Periodic Test PT-5.5. BS-494-Al would not trip in response to test signals and BS-494-A2 was out of acceptable tole ra nce . Sub sequent investiga tion revealed tha t the failure was due to a bad filter capacitor in the power supply section of dual compara tor LC-494A.

Although the unit was in cold shutdown conditions, this event would have resulted in less than the minimum degree of redundancy required by Technical Specification table 3.5-2 during operation and is reportable pursuant to 6.9.2.b.2. Since the other two channels were operable, there was no threat to the public health and safety.

2. Corrective Action:

Instrument channel LI-494 was declared inoperable and the bistables were tripped manually at 1740 hours0.0201 days <br />0.483 hours <br />0.00288 weeks <br />6.6207e-4 months <br />. This res tored the minimum degree of redundancy required by Technical Specification table 3.5-2.

The failed component, LC-494A, was replaced with a new unit, calibrated, tested, and the instrument channel was declared operable a t 2010 hours0.0233 days <br />0.558 hours <br />0.00332 weeks <br />7.64805e-4 months <br /> on November 25, 1981.

3. Corrective Action to Prevent Recurrence:

This event is the result of component failure due to normal wear.

No further action is considered necessary.

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