ML19305A096

LER 78-031/03L-0 on 791122:pressure Switch 1-5600-PS-3 to Failed During electo-hydraulic Control Pressure Sensor Functional Surveillance Due to Setpoint Drift.Switch Was Recalibr

ML19305A096
Person / Time
Site:	Quad Cities
Issue date:	12/14/1978
From:	Swales J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19305A095	List: ML19305A094 ML19305A096
References
LER-78-031-03L, LER-78-31-3L, NUDOCS 7901040124
Download: ML19305A096 (2)

Text

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. LICENSEE EVENT REPORT

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MEASE PRWT on TYPE ALL REQUIRED INFORMATION)

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EVENT OCSCRIPTION AND PROB ABLE CONSEQUENCES h '

f o l2] l While performing EHC Pressure Sensor functional surveillance. Qls._39. pressure I

[o l3[ l switch 1-5600-PS-3 failed to operate at greater than 900 psig as required by i I o 14 l l Technical Specification Table 3 1-3 Pressure swi tch I-5600-PS-3 did operate I io;3; l at 880 psig. The other three EHC pressure switches operated at or above 900 g

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1 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS I

The cause of this occurrence is attributed to instrument setpoint drift.

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! Corrective actions taken were to recalibrate and functionally test pressure l <

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7, g ,; g switch I-5600-PS-3 All other EHC pressure switches on both units were also l l  ;;3, j functionally tested successfully on November 22, 1978. [

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1. LER NUMBER: LER/R0 78-31/03L-0

11. LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill. FACILITY NAME: Unit One IV. DOCKET NUMBER: 050-254 V. EVENT DESCRIPTION:

On November 22, 1978 while performing routine Electro-Hydraulic Control (EHC) Pressure Sensor functional surveillance, QlS-39, pressure switch 1-5600-PS-3 failed to operate at greater than 900 psig as required by Technical Specification Table 3.1-3 Pressure Switch 1-5600-PS-3 did operate at 880 psig and the other three EHC pressure switches operated at or above 900 psig as required. Pressure switch 1-5600-PS-3 was immediately recalibrated to actuate at 930 psig and was successfully function-ally tested. The only occurrence of this type since 1975 is reported in Reportable Occurrence Report RO 50-265/77-23 VI. PROBABLE CONSEQUENCES OF OCCURRENCE:

These four EHC pressure switches initiate a Reactor Protection System (RPS) scram in anticipation of a neutron flux spike due to turbine control valve fast closure. Since the switches are arranged in a one out of two twice logic system, a trip of the three other switches at the correct pressure would have provided the proper signal to the RPS. Therefore the safety of the plant was unaffected by this occurrence.

Vll. CAUSE:

i l The cause of this occurrence was attributed to instrument set-point drift. The switch is a Barksdale piston type model #C-9612-2 pressure switch.

Vill. CORRECTIVE ACil0N:

The immediate corrective action taken was to recalibrate and functionally test pressure switch 1-5600-PS-3 All other EHC pressure switches on both units were also functionally tested on November 22, 1978.

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