ML19343C355

AO 50-219/74/30:on 740514,pressure Switch PSH-C Failed to Trip at Nominal Trip Pressure of 180 Psig.Cause Under Investigation.Switch Recalibr & Tested Satisfactorily

ML19343C355
Person / Time
Site:	Oyster Creek
Issue date:	05/23/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
AO-50-219-74-30, NUDOCS 8103120372
Download: ML19343C355 (2)

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s OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. S0-219/74/30 Report Date May 23, 1974 Occurrence Date bhy 14, 1974 Identification of Occurrence Violation of the Technical Specifications, Table 3.1.1.A.12, which requires the generator load rejection scram to be operable at turbine steaming rates greater than 40% of rated while in the RUN mode. This-event is considered-to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15B.

Conditions Prior to Occurrence

'Ihe plant was shut down for refueling.

Description of Occurrence While performing routine surveillance testing on the generator load rejection anticipatory scram, it was observed that pressure switch PSH-C failed to trip at the nominal trip pressure of 180 psig. The switch senses third stage extraction pressure from the H.P. turbine and forms a bypass around the PSL-C pressure switch contacts, which senses acceleration relay oil pressure, and f the turbine stop valve position switch contacts. These act to initiate a reactor scram through the condenser low vacuum contacts in the scram circuitry (1K11,1K12, 2K11, and 2K12) . As part of the surveillance test, PSH-C was pressurized to 180 psig without the corresponding trip. The pressure was increased to ascertain the trip point and it was found to operate at 19' psig.

A third stage extraction pressure of 180 psig corresponds to turbine a*.e im flow of 40% and 197 psig corresponds to a flow of approximately 45% Therefore, the bypass around the PSL-C and S.V. position switch contacts w .io have been in leffect at 45's turbine flow during power operation instead of 40's. It should be noted that its associated redundant switch PSH-A performed satisfactorily.

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Abnormal Occurrence No. 50-219/74/30 Page 2 I

Apparent Cause of Occurrence Possible mishandling of the switches during the maintenance outage and poor instrument repeatability are considered causes for this occurrence.

l Analysis of Occurrence The safety significance of this occurrence is minimal since the redundant switch (PSH-A) performed :;atis factorily. In addition, the purpose of the switch is to bypass the reactor scram due to turbine trip at a point when the bypass valves are able to accept the reactor steam production. The anticipatory scram acts to minimize fuel thermal transients in the event -

of a turbine trip with failure' to bypass at power levels in excess of 40%

of rated turbine steam flow. Since the plant is designed to withstand this transient, the switch operation at 45'. of rated steam flow would, in the event the redundant switch failed to operate, be of no concern.

Corrective Action The switch was recalibrated ar ' tested satisfactorily. A lower setpoint i:s being considered to allow fe. instrument repeatability error.

Failure Data Manufacturer: Barksdale 8B2T-A12SS Range: Adjustable from 50-1200 psig Proof Pressure: 1800 psig i

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