ML19242C508

LER 79-074/03L-0 on 790707:auxiliary Feedwater Pump 1-2 suction-before-strainer Pressure Switch PSL-4929B Actuated at Pressure Input Outside Allowable Tolerance.Caused by Component Failure Due to Misapplication.Switch Replaced

ML19242C508
Person / Time
Site:	Davis Besse
Issue date:	08/02/1979
From:	Hitchens D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19242C506	List: ML19242C505 ML19242C508
References
LER-79-074-03L, LER-79-74-3L, NUDOCS 7908100501
Download: ML19242C508 (1)

Text

I3A U. S. NUCLE AR RL GUL ATORY COMt.11bSION

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EVENT DEsCHI ' TION A D FHOH A L 5 GL NCES o ,

l On Jul y 7, 1979 at 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />, durinn the collection of drif t rate data, it was dis- J o , j covered that PSL-4929B, Auxiliary Feedwat er (An1) Pump 1-2 Suction Before Strainer __j jol;j j Pressure Switch, actuated at a pressure input outside of its allowabic tolerance. Thij n ., [ made AD.' Train 1-2 Inoperable, and placed the unit .n the Action Statement of Techni- ]

o c. Ical Specification 3.7.1.2. There was no danger to the health and safety of the publicl o i or to station personnel. The unit vas suberitical and ARJ 'Irain 1-1 uns operable i o a I throughout this occurrence. (NP-33-79-82) 80 l

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i o l The probable cause was component failure of the pressure switch due to connonent mis-l

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, l placement was installed and satisf actorily tested on 7/7/79. removing the unit from li13l l the Ac t ion Statement. The einht ARJ pump pressure switches will be replaced with j i l switches having stainless steel diaphragns. _ _

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATIM UNIT ONE SUPPLEMENTAL INFOR'4ATION FOR LER NP-33-79-82

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DATE OF EVENT: July 7, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE : Auxiliary Feedwater (AFW) Suction Pressure Switch PSL-4929B out of calibration Conditions Prior to Occurrence: The unit was in Mode 3, with Power (> RTE) = 0, and Load (Gross K4E) = 0.

Description of Occurrence: On July 7, 1979, at 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br /> during surveillance testing under Maintenance Work order (YWO) IC-334-79, Instrument and Control peronnel discovered tha t PSL-49 29D, Auxiliary Teedwater Pump 1-2 Suction Before Strainer Pressure Switch, actuated at a pressure input outside of its desired tolerance. The desired setpoint is 3.3 psig + 0.5 psig decreasing. The switch actuated at 2.25 psig decreasing. This made AFW Train 1-2 incapable of shifting suction to service water if the condensate storage tanks were unavailable and placed the unit in the Action Statement of Technical Specification 3.7.1.2, which requires two independent steam generator auxiliary feed-water pumps and associated flowpaths to be operable in Modes 1, 2, and 3.

Designation of Apparent Cause of decurrence. Ou day 21, 1979, a similar event had occurred (reported in Licensee Event Report NP-33-79-64). After that occurrence, two pressure switches were returned to the manufacturer, Static-0-Ring Pressure Switch Company for analysis of th? failure. PSL 4929B was taken to the factory for testing with the previous two switches. The failure of all three switches was determined to be the permeating of the fluid (demineralized water with ammonia added for pH control) through the thin Buna N diaphragm onto the aluminum piston, causing the piston to cor-rode severely. A second contributing factor was a shift in the overtravel of the piston, which causes non-repeatibility. The cause of this shif t was not determined.

The instrument could have been dropped, or hit, etc.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The unit had been shutdown since March 31, 1979, and was shut-down at the time of this occurrence. AFW Train 1-1 was operable throughout the occurrence.

Corrective Action: MWO IC-335-79 was initiated to calibrate and install a replacement switch for USL-4929B. This replacement switch was satisfactorily tested at 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br /> on July 7, 1979 under ST 5071.04, the Auxiliary Feedwater System Channel Functional Test. This removed the station from the action statement of Technical Specification

3. 7.1. 2.

The root causes of this occurrence (and the Ray 21, 1979 occurrence) will be corrected LER #79-074 s i f ,* ', I( I

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TOLEDO EDISO:! COMPANY DAVIS-BESSE !!UCLEAR POWER STATION U'iIT ~ 0NE SUPPLE:!E:;TAL 1:;I'OP3fATION FOR LER :!P-33-79-82 PAGE 2 as follows. Facility Change Request 79-293 has been initiated and a purchase order written to replace the eight Auxiliary Feeduater Ptrap suction pressure switches with switches which have stainless steel diaphragns and pressure I>rts. This will pre-clude the permeation of the pressure sensing diaphragm and subsequent corrosion /

oxidation of the pistons. In addition, a Maintenance Instruc tion is being written for calibration of Static-0-Ring pressure switches. This Maintenance Instruction will delineate the method to be used to ensure that the microswitch over travel has not shifted both on new switches (bench calibration) and installed switches.

Failure Data: Previous inoperabilities of Auxiliary Feedwater Pump suction switches were reported in Licensee Event Report :!P-33-79-64.

LER #79-074

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