ML19312C864

AO-270/75-20:on 751006,temp Detector in Reactor Protective Sys Channel a Failed.Caused by Faulty Resistance Temp Detector.Resistance Temp Detector to Be Replaced Next Shutdown.Channel a Returned to Svc 751201

ML19312C864
Person / Time
Site:	Oconee
Issue date:	10/20/1975
From:	DUKE POWER CO.
To:
Shared Package
ML19312C863	List: ML19312C862 ML19312C864
References
NUDOCS 8001130024
Download: ML19312C864 (1)

Text

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t DUKE POWER COMPANY OCONEE UNIT 2 fp[ "J W

Report No.. A0-270/75-20 Report Date: October 20, 1975 -

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Occurrence Date: October 6, 1975 i

Facility: Oconee Unit 2, Seneca, South Carolina Identification,of Occurrence: Failure of Temperature Detector in Reactor Protective System Channel A Conditions Prior to Occurrence: Unit at Full Power Description of Occurrence:

l On October 6, 1975, erratic temperature indications were observed on one leg of the Reactor Coolant System. Temperature indications varied between 5400F and 5920F vith 5920F being the approximate correct temperature.

Instrument technicians determined the RTD in the instrument string to be the cause of the erratic indication. Since this RTD provides an input to Reactor Protective System Channel A, this channel was placed in manual bypass.

1 Designation of Apparent Cause of Occurrence: 1 A f aulty RTD was determined to be tha apparent cause of this occurrence.

The exact cause of the RTD's failure can not 'e determined until the RTD is removed from the Reactor Coolant System.

Analysis of Occurrence:

This RTD provides the hot leg temperature input into the high temperature and variable low pressure trip functions of the Reactor Protective System Channel A. The failure of this RTD resulted in erroneous input to the Reactor Protective System; however, a trip of two of the three remaining independent channels would have caused a reactor trip, if necessary. It is concluded that the health and safety of the public was not affected.

Corrective Action:

The fLiled RTD will be replaced during the next unit shutdown which requires draining of the Reactor Coolant System loops. Reactor Protective System Channel A will be returned to service by December 1,1975 by changing the hot leg temperature input to a spare RTD.

Failure Data:

The failed RTD is a Rosemount Type 177 GY S/N 2314. No previous failures of this component have been experienced.

80011300 M

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