05000338/LER-1980-040-03, /03L-0:on 800423,during Refueling Shutdown,Casing Cooling Tank Level Indicator LI-RS103A Found Out of Calibr. Caused by Bad Zenier Diode in Loop Power Supply Card.Card Replaced & Recalibr

/03L-0:on 800423,during Refueling Shutdown,Casing Cooling Tank Level Indicator LI-RS103A Found Out of Calibr. Caused by Bad Zenier Diode in Loop Power Supply Card.Card Replaced & Recalibr

ML19323F147
Person / Time
Site:	North Anna
Issue date:	05/22/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19323F142	List: 05000338/LER-1980-040, Forwards LER 80-040/03L-0 05000338/LER-1980-040-03, /03L-0:on 800423,during Refueling Shutdown,Casing Cooling Tank Level Indicator LI-RS103A Found Out of Calibr. Caused by Bad Zenier Diode in Loop Power Supply Card.Card Replaced & Recalibr
References
LER-80-040-03L, LER-80-40-3L, NUDOCS 8005280590
Download: ML19323F147 (2)

LER-1980-040, /03L-0:on 800423,during Refueling Shutdown,Casing Cooling Tank Level Indicator LI-RS103A Found Out of Calibr. Caused by Bad Zenier Diode in Loop Power Supply Card.Card Replaced & Recalibr

Event date:
Report date:
3381980040R03 - NRC Website

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Virginia Electric and Power Company North Anna Power Station, Unit #1 Attachment: Page 1 of 1 Docket No. 50-338 Report No. LER 80-40/03L-0

Description of Event

On December 7, 1979, with the unit in a refueling shutdown condition, Casing Cooling Tank level indicator LI-RS103A was found to be out of calibration because of a power supply card failure. The card failed such that it would not go below 5.2 VDC which prevented the indicator from reading tank levels below 56%. The occurrence was originally determined to be non-reportable due to the then existing plant conditions; however, upon re-review on April 23, 1980, it was determined reportable pursuant to T.S. 6.9.1.9.a and b.

Probable Consequences of Occurrence The purpose of the Casing Cooling Tank level indicator is to provide indication of level in the control room as well as automatically isolate the Casing Cooling Tank on low level by closing discharge valve MOV-RS100A.

The health and safety of the general public were not affected by the inoperability of LI-RS103A because even if the transmitter failed to close MOV-RS100A during an accident condition, the tank would have been isolated by the pump low flow switch which closes upstream valve MOV-RS101A.

There are no generic implications associated with this event.

Cause of Event

The power supply (NLP) card for LI-RS103A failed due to a bad zenier diode in the card circuitry.

Iamediate Corrective Action The loop power supply card was removed and replaced with a new card. The new NLP card was then satisfactorily calibrated in accordance with applicable calibration procedures and verified operational.

Scheduled Corrective Action No scheduled corrective action is required.

Actions Taken to Prevent Recurrence Since this is a random occurrence, no further actions are necessary.

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