05000346/LER-1979-086-03, /03L-0 on 790725:while Performing Routine Preventative Maint,Condensing Unit Train 2 of Control Room Emergency Ventilation Sys Would Not Start.Caused by Failure of Thermistor in Compressor Motor Winding

/03L-0 on 790725:while Performing Routine Preventative Maint,Condensing Unit Train 2 of Control Room Emergency Ventilation Sys Would Not Start.Caused by Failure of Thermistor in Compressor Motor Winding

ML19276G933
Person / Time
Site:	Davis Besse
Issue date:	08/21/1979
From:	Rudolph J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19276G932	List: 05000346/LER-1979-086, Forwards LER 79-086/03L-0 05000346/LER-1979-086-03, /03L-0 on 790725:while Performing Routine Preventative Maint,Condensing Unit Train 2 of Control Room Emergency Ventilation Sys Would Not Start.Caused by Failure of Thermistor in Compressor Motor Winding
References
LER-79-086-03L, LER-79-86-3L, NUDOCS 7908280721
Download: ML19276G933 (2)

LER-1979-086, /03L-0 on 790725:while Performing Routine Preventative Maint,Condensing Unit Train 2 of Control Room Emergency Ventilation Sys Would Not Start.Caused by Failure of Thermistor in Compressor Motor Winding

Event date:
Report date:
3461979086R03 - NRC Website

text

NRC FORM 366 U. S. NUCLEAR REGULATORY COMMISSION (7 77)

LICENSEE EVENT REPORT CONTROL BLOCK: l l

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60 61 DOCKET NUYBER 68 69 EVENT DATE 74 75 REPORT D ATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 l At 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on 7/25/79 while performing routine preventative maintenance, it was I

o a j found that #2 condensing unit train (S33-2) of the Control Room Emergency Ventilatiot) o 4

l System (EVS) would not start. This placed the unit in the Action Statement of T.S.

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3.7.6.1.

There was no danger to the health and safety of the public or station per-l o 6 i sonnel. Train 1 of the Control Room EVS was available for use if a.. event requiring l

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Each EVS train is designed for full capacity.

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33 35 36 31 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h oj l This occurrence was caused by component failure; one of three thermistors in the com-l i

li li j l pressor motor winding had failed opening the circuit thus preventing it from startine.l The f aulty thermistor was bypassed and the system was successfully tested and declareq

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g[g l operable removing the unit from the Action Statement. A new compressor unit will be j li l 41 l installed during the next maintenance outage.

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NAME OF PREPARER

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEP POWER STATION UNIT ONE SUPPLEMENTAL INFORM iION FOR LER NP-33-79-99 DATE OF EVENT: July 25, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE:

Train 2 of the Control Room Emergency Ventilation System inoperable Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 2772, and Load (Gross MWE) = 910 Description of Occurrence: At 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on July 25, 1979, a maintenance repairman found that the No. 2 Condensing Unic Train (S33-2) of the Control Room Emergency Ventilation System (EVS) would not start.

This was detected while performing Pre-ventative Maintenance Work Order 79-1911 on the Control Room EVS.

Technical Specification 3.7.6.1 requires both EVS trains to be operable in Modes 1-4.

This failure put the station in the Action Statement of Technical Specification 3.7.6.1 which requires the system be restored to operable status within seven days or the unit be in at least hot standby within the next six hours and cold shutdown wit' 'n the following thirty hours.

Designation of Apparent Cause of Occurrence:

The cause of this occurrence is component failure. One out of the three thermistors in the windings of the compressor was faulty.

This simulated a high temperature condition in the windings whi h opened the compressor motor control circuit and prevented it from starting.

Analysis of Occurrence:

There was no danger to the health and safety of the public or to station personnel. Train 1 of the Control Room EVS was available for use if EVS opera tion had been required.

Each EVS train is designed for full capacity.

Corrective Action

The compressor was repaired per Maintenance Work Order 79-2571 by jumpering with a resistor across the faulty thermistor terminal. The two remaining thermistors were tested and proven operable. A new compressor will be installed during the next maintenance outage.

The system was successfully tested and declared operable per ST 5076.01, " Control Room EVS Monthly" and >bintenance Work Order 79-1911, " Control Room EVS Quarterly Preventa-tive Maintenance" on July 30, 1979. This removed the unit from the Action Statement of Technical Specification 3.7.6.1.

Further investigation into the cause of the thermistor failure will be done when the compressor is replaced.

Failure Data:

There have been no previsouly reported similar occurrences.

LER #79-086 20k