05000271/LER-1980-004-03, /03L-0:on 800109,power Supply Overheated & Failed, Resulting in Loss of All Rod Position Indication,Rpis Alarm,All Rod Drift Alarms,Rwm Rod Block & Overtravel Alarm. Caused by Failure of Cooling Fan in Power Supply

/03L-0:on 800109,power Supply Overheated & Failed, Resulting in Loss of All Rod Position Indication,Rpis Alarm,All Rod Drift Alarms,Rwm Rod Block & Overtravel Alarm. Caused by Failure of Cooling Fan in Power Supply

ML19262C258
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	02/04/1980
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19262C252	List: 05000271/LER-1980-004, Forwards LER 80-004/03L-0 05000271/LER-1980-004-03, /03L-0:on 800109,power Supply Overheated & Failed, Resulting in Loss of All Rod Position Indication,Rpis Alarm,All Rod Drift Alarms,Rwm Rod Block & Overtravel Alarm. Caused by Failure of Cooling Fan in Power Supply
References
LER-80-004-03L, LER-80-4-3L, NUDOCS 8002080489
Download: ML19262C258 (2)

LER-1980-004, /03L-0:on 800109,power Supply Overheated & Failed, Resulting in Loss of All Rod Position Indication,Rpis Alarm,All Rod Drift Alarms,Rwm Rod Block & Overtravel Alarm. Caused by Failure of Cooling Fan in Power Supply

Event date:
Report date:
2711980004R03 - NRC Website

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s VTVYS1 05000271 LER 80-4/3L EVENT DESCRIPTION AND PROBABLE CONSEOUENCES During nor=al operation, all rod position indication was lost, ac-companied by RPIS Inop Alarm, all rod drift alarms, RWM rod block and overtravel alarm. Position indication returned five minutes later.

This sequence was repeated six more times at five to six minute intervals, with each occurrence lasting five to seven minutes.

It was then discov-ered that the cooling f an in the power supply had failed causing the power supply to overheat and fail. When the power supply cooled, it would reenergize. The Lanediate solution was to slide the power supply out of the panel and remove the top cover.

The at=osphere cooling was sufficient to prevent tripping. The fan was subsequently replaced and position indication returned to normal. Rod position indication is re-quired to be operable by Tech. Spec. Table 3.2.6 which allows operation for 30 days without this parameter.

Based on the above there were no adverse conditions affecting the public health and safety.

There have been no occurrences reported to the Commission.