ML19317F487

RO 270/76-07:on 760706,reactor Protective Sys Channel B Failed to Trip on High Pressure Setpoint During Startup. Caused by Isolated Pressure Transmitter.Procedures Being Revised

ML19317F487
Person / Time
Site:	Oconee
Issue date:	08/05/1976
From:	DUKE POWER CO.
To:
Shared Package
ML19317F479	List: ML19317F478 ML19317F487
References
RO-270-76-07, RO-270-76-7, NUDOCS 8001140717
Download: ML19317F487 (1)

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DUKE POWER COMPANY OCONEE UNIT 2 i

Report No.: R0-270/76-7 Report Date:_ August 5, 1976 Occurrence Date:_ July 6, 1976 Facility: Oconee Unit 2, Seneca, South Carolina Failure of Reactor Protective System Channel Identification of Occurrence:

"B" to trip on high pressure setpoint during startup Startup in progress Conditions Prior to Occurrence:

Description of Occurrence:

On July 6, 1976, during the startup of Oconce Unit 2, Reactor Protective System (RPS) Channel "B" failed to trip as required when the reactor coolant pressure reached 1720 psig.

This is the high pressure setpoint when the RPS is in the shutdown bypass mode during startup or shutdown.

The other three channels of the RPS did function properly.

Apparent Cause of Occurrence:

Investigation revealed that the instrument root valve for the RPS Channel This resulted "B" pressure transmitter had been inadvertently left closed.

in isolation of the pressure transmitter which prevented the channel from 3

tripping when the 1720 psig setpoint was reached. The valve had been left open as required following calibration of the pressure transmitter on May 2, 1976, but had been closed at some subsequent time before the unit startup was initiated.

Analysis of Occurrence:

Although RPS Channel "B" failed to trip as required in the shutdown bypass mode, the other three RPS channels tripped when the 1720 psig setpoint was reached.. The Reactor Protective System utilizes a two-out-of-four redundant logic, and would have been disabled only if two other channels were inoperable. . It is concluded that this occurrence did not impair the operability of the Reactor Protective System,and therefore, the health and safety of the public was not affected.

Corrective Action:

followir.-

Station procedures are currently being revised to assure that, refueling outages, instrumentation is checked for proper operation prior to unit heatup; and to assure that, following the performance of maintenance, These instrument valves are returned to their pre-maintenance position.

. revisions will be completed by August 15, 1976. It is felt that these measures will prevent further recurrences of this type.

8001140'7/7 ,