05000265/LER-1979-003-03, /03L-0 on 790214:during High Temp Isolation Calibr Procedure,Temp Switch TS 2-2373A Was Found to Trip in Excess of Tech Spec Limit.Caused by Setpoint Drift.Switch Recalibrated & Retested

/03L-0 on 790214:during High Temp Isolation Calibr Procedure,Temp Switch TS 2-2373A Was Found to Trip in Excess of Tech Spec Limit.Caused by Setpoint Drift.Switch Recalibrated & Retested

ML19282B819
Person / Time
Site:	Quad Cities
Issue date:	02/28/1979
From:	Kopacz J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19282B816	List: 05000265/LER-1979-003, Forwards LER 79-003/03L-0 05000265/LER-1979-003-03, /03L-0 on 790214:during High Temp Isolation Calibr Procedure,Temp Switch TS 2-2373A Was Found to Trip in Excess of Tech Spec Limit.Caused by Setpoint Drift.Switch Recalibrated & Retested
References
LER-79-003-03L-10, LER-79-3-3L-10, NUDOCS 7903160221
Download: ML19282B819 (2)

LER-1979-003, /03L-0 on 790214:during High Temp Isolation Calibr Procedure,Temp Switch TS 2-2373A Was Found to Trip in Excess of Tech Spec Limit.Caused by Setpoint Drift.Switch Recalibrated & Retested

Event date:
Report date:
2651979003R03 - NRC Website

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While performing the HPCI Turbine Area High Temperature Isolation Calibration, procedure QlS 27-1, temperature switch TS 2-2373A was found to trip at 207 F l

exceeding Technical Specification Table 3.2-1 limit of 200 F.

The sixteen HPCI l

g turbine area high temperature switches are arranged in groups of four, with each y

- -,.aL group connected in a one-out-of-two-twice logic scheme.

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33 34 sS 3G 31 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h jijoll The cause of this occurrence was due to setpoint dri f t.

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to recalibrate the switch and secure the adjustment screw.

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LER NUMBER:

LER/R0 79-03/03L-0 ll.

LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill.

FACILITY NAME: Unit Two IV.

DOCKET NUMBER: 050-265 V.

EVENT DESCRIPTION

On February 10, 1979, wi th Uni t Two shutdown for minor repai rs, the HPCI Tuurbine Area High Temperature Isolation Calibration surveillance, Procedure QlS 27-1, was performed. While checking setpoints, temperature switch TS 2-2373A tripped at 207 F exceeding Technical Specification, Table 3.2-1, limiting condition for operation limit of less than or equal to 200 F.

All other HPCI temperature switches were found to trip at less than or equal to 200 F.

VI.

PROBABLE CONSEQUENCES OF THE OCCURRENCE:

The sixteen HPCI turbine area high temperature switches are arranged in groups of four, with each group connected in a one-out-of-two-twice logic scheme.

Therefore, a failure or setpoint drift of one switch does not render the system inoperable.

Had adverse conditions arisen, the other switches would have initiated the Group IV isolation at or below the 200 F LC0 as designed.

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CAUSE

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

The setpoint adjusting screw on temperature switch TS 2-2373A was found to be loose.

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CORRECTIVE ACTION

The immediate corrective action was to recalibrate the tempera-ture switch.

The set screw on the temperature switch was also secured.

Switch TS 2-2373A was successfully retested, tripping at 185 F.

The HPCI turbine area high temperature switches are manufactured by United Electric and are model F-7