ML19317F083

AO-287/75-08:on 750619,reactor Bldg Engineered Safeguards Pressure Transmitter Was Discovered Out of Calibr.Caused by Drift of Pressure Transmitter.Channel C of Pressure Transmitter Recalibr.Surveillance Will Continue

ML19317F083
Person / Time
Site:	Oconee
Issue date:	07/03/1975
From:	DUKE POWER CO.
To:
Shared Package
ML19317F033	List: ML19317F031 ML19317F083
References
NUDOCS 8001080773
Download: ML19317F083 (2)

Text

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DUKE POWER COMPANY OCONEE UNIT 3 Report No.: AO-287/75-8 Report Date: July 3, 1975 Occurrence Date: June 19, 1975 Facility: Oconee, Unit 3, Seneca, South Carolina Identification of Occurrence: Reactor Building Engineered Safeguards pressure transmitter out of calibration Conditions Prior to Occurrence: Unir in cold shutdown Description of Occurrence:

On June 19, 1975, a Reactor Building Engineered Safeguards pressure trans-mitter calibration was performed for Oconee Unit 3. This calibrr..on was performed because the Periodic Instrument Surveillance Test of Reactor Building Engineered Safeguards pressure transmitters indicated that agree-ment among the three transmitters was not within the required 0.6 psi. The calibration indicated that the "C" channel transmitter would not have tripped until an PLcual Reactor Building pressure of 4.615 psig was achieved.

Technical Specification 3.5.3 requires that the Engineered Safeguards high Reactor Building pressure actuation occur at less than or equal to 4 psig.

Designation of Apparent Cause of Occurrence:

The apparent cause of this incident was drift of the Reactor Building Engineered Safeguards pressure transmitter. This drift was detected by periodic instrument surveillance testing.

Analysis of Occurrence:

The ES system actuates at a Reactor Building pressur. of 4 psig to start the Reactor Building cooling system and to provide antainment integrity.

In addition, these pressure transmitters serve as backup to the reactor coolant system pressure transmitters to initiate actuation of the high pressure injection and low pressure injection systems. The design of the Engineered Safeguards system requires a two-out-of-three coincidence logic to ;.oduce an ES actuation. In this incident, two channels of the ES RB pressure were properly calibrated and would have tripped at the proper Reactor Building pressure. In addition, the fact that the "C" channel would have tripped at a Reactor Building pressure of 4.615 psig vice 4.0 psig would not have significantly affected the operation of the ES system. l It is concluded that the health and safety of the public was not affected.

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• . , , ,g Corrective Action:

The Channel'C Reactor Building Engineered Safeguards pressure transmitter has been recalibrated. It is considered that periodic surveillance will continue to provide early indication of instrument drift.

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