ML19345A889

LER 80-029/03L-0:on 801027,during Surveillance Procedure, Pressure Suppression Chamber & Reactor Bldg Vacuum Breaker Actuation Calibr & Functional Test Found to Actuate at 0.52 Psid.Caused by Instrument Setpoint Drift.Switch Recalibr

ML19345A889
Person / Time
Site:	Quad Cities
Issue date:	11/17/1980
From:	Wykoff D COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19345A887	List: ML19345A886 ML19345A889
References
LER-80-029-03L-02, LER-80-29-3L-2, NUDOCS 8011250371
Download: ML19345A889 (2)

Text

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DATE 1 8 60 61 DOCK ET NUM8En 6d 69 EVENT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h gl While performing surveillance procedure QlS 48-1. Pressure Suooression Chamber and I lo la f l Reactor Building Vacuum Breaker Actuation Calibration and Functional Test, PS-2-1622A l

[o11l l was found to actuate at 0.52 psid. Technical Specifications reauire a setpoint l Io ls t I of less than or equal to 0.5 psid. The probable consequences were minimal since l l o 16 l l redundant 100 percent capacity system was found to actuate satisfactorily. l I

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26 31 40 41 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h liloll The cause of this occurrence is instrument setpoint dri f t of PS-2-1622A. The I tiliil pressure switch was immediatelv recalibrated and tested satisfactorily. I I

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1. LER HUMBER: R0 80-29/03L-0 II. LICENSEE NAME: Commonwealth Edison Company Quad-Cl*.!ss Nuclear Power Station Ill. FACILITY NAME: Unit Two IV. DOCKET NUMBER: 50-265 V. EVENT DESCRIPTION:

On October 27,1980, at 8 p.m. while performing routine surveillance Procedure QlS 48-1, Pressure Suppression Chamber and Reactor Building Vacuum Breaker Actuation Calibration and Functional Test, PS-2-1622A was found to actuate at 0.52 psid. Unit Two was in the RUN mode, operating at 815 MWe. Technical Specification 3.7.A.3.a. specifies that the pressure suppression chamber to reactor building vacuum breakers shall actuate at less than 0.5 psid vacuum. There was no evidence of physical damage, so the error in setpoint was attributed to instrument setpoint dri f t. The pressure switch was last calibrated on July 24, 1980.

VI. PROBABLE CONSEQUENCES LI THE OCCURRENCE:

The safety implications of this occurrence were minimal, since the other pressure switch for the redundant vacuum breaker was found to actuate satisfactorily.

The reactor bu'lding to Suppression Chamber Vacuum Breaker System con-sists of two, 100 percent flow capacity systems. Pressure switch 2-1622B would have actuated at the required setpoint and opened vacuum breaker A0-2-1601-20B relieving any negative pressure in the suppression chamber, had the need arisen. In. addition, the external design pressure of the suppression chamber is 2 psid. Both vacuum breakers would have opened before this c'esign limit would have been reached. Also check valves 2-1601-31 A and 2-1601-31B in-line with the air operated valves were unaffected by this occurrence.

Vll. CAUSE:

The cause of this occurrence was setpoint drift of-pressure switch 2-1622A. There was no evidence of damage to the switch. These switches were newly installed on January 21, 1978. The switches are manufactured by the Static-0-Ring Company, and are of a diaphragm type, model number 12B B- KK- 215V.

Vllt. CORRECTIVE ACTION:

The corrective action taken was to immediately recalibrate and test the pressure switch.

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