05000324/LER-1980-102-03, /03L-1:on 801212,full-out Position Indication Could Not Be Achieved W/Rod 26-35 Fully Withdrawn.Caused by Defective Light Isolator,In Rod Group Auxiliary Buffer Board Circuitry,Preventing Switching Transistor from Conducting

/03L-1:on 801212,full-out Position Indication Could Not Be Achieved W/Rod 26-35 Fully Withdrawn.Caused by Defective Light Isolator,In Rod Group Auxiliary Buffer Board Circuitry,Preventing Switching Transistor from Conducting

ML20003G270
Person / Time
Site:	Brunswick
Issue date:	04/15/1981
From:	Pastva M CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20003G269	List: 05000324/LER-1980-102, Forwards LER 80-102/03L-1 05000324/LER-1980-102-03, /03L-1:on 801212,full-out Position Indication Could Not Be Achieved W/Rod 26-35 Fully Withdrawn.Caused by Defective Light Isolator,In Rod Group Auxiliary Buffer Board Circuitry,Preventing Switching Transistor from Conducting
References
LER-80-102-03L, LER-80-102-3L, NUDOCS 8104280645
Download: ML20003G270 (2)

LER-1980-102, /03L-1:on 801212,full-out Position Indication Could Not Be Achieved W/Rod 26-35 Fully Withdrawn.Caused by Defective Light Isolator,In Rod Group Auxiliary Buffer Board Circuitry,Preventing Switching Transistor from Conducting

Event date:
Report date:
3241980102R03 - NRC Website

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8 60 88 DOCKET NUMe E R 68 89 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROSABLE CONSEQUENCES h g l During a norinal reactor startup, when rod 26-35 was fully withdrawn " full-out" l

g l position indication could not be achieved. The rod was bypassed in the Rod Sequence l

l Control System (RSCS), in cccordance with technical specifications, in order to allow I l continuation of the startup. This event did not affect the health or safety of the l

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40 48 42 43 44 4F CAUSE DESCRIPTION AND CORRECTIVE ACTIONS lA defective light isolator, Model No. 798D2270003, located in the rod group auxiliary l

, o l buffer board circuitry, prevented the rod switching transistor', Q2, frota conductinst.

gThe light isolator was replaced and the Q2 circuit was verified for proper operation. I I

lThe rod reed switch " full-out" position was declared operable and the rod was returnedI

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Facility: BSEP Unit No. 2 Event Date 12-12-81 1

From a review of past similar events, it has been determined that of the approximate 7,000 control rod reed switches and associated circuitry utilized in each unit, less than five total events involving this circuitry are reporta-ble each year. Due to the low failure rate compared to the high number in use, the failure of the light isolator is considered an isolated event requiring no further corrective action.

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