ML19209D171

LER 79-086/03L-1:on 790725,train 2 of Control Room Emergency Ventilation Sys Was Inoperable.Cause by One of Three Thermistors in Compressor Motor Winding Failing to Open Circuit.Compressor Repaired & New One Will Be Installed

ML19209D171
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
ML19209D152	List: ML19209D151 ML19209D156 ML19209D160 ML19209D164 ML19209D171
References
LER-79-086-03L, LER-79-86-3L, NUDOCS 7910190489
Download: ML19209D171 (2)

Text

U. S. NUCLEAR REGULATORY CoMMISSloN

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DATE 8 cJ 61 COCK ET NUYSER EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h it was j 10 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, to 3 l found that #2 concensing unit train (S33-2) of the Control Room Emergency Ventilatioq j

o 4 System (EVS) would not start. This placed the unit in the Action Statement of T.S.

l lo 5 1 3.7.6.1. There was no danger to the health and saf ety of the public or station per-l 0 6 l sonnel. Train 1 of the Control Room EVS was available for use if an event recuiring 0 7 l EVS operation had ocegered. Each EVS train is designed for full capacity. l I

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l This occurrence was caused by component failure; one of three thermistors in the com-l i O

]i li ) { pressor motor winding had failed opening the circuit thus preventing it f rom s tarting .I The f aulty thermistor was bypassed and the system was successfully tested and declareq i 7 l FCR 77-291 will be implemented 1 l3) [ operable removing the unit from the Action Statement.

l 1 i_ [ ]l to bypass the " overload trip" function. ,

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TOLEDO EDISON COMPANY DAVIS-BLSSE NUCLEAR POWER STATION UNIT ONE SUPPLF21 ENTAL INFOR'tATION FOR LER NP-33-70-99 c

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 (MUT) = 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 Unit 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 f ailure 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 within the following thirty hours.

.

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Designation of Apparent Cause of Occurrence: The cause of this occurrence is component ~

failure. One out of the three thernistors in the windings of the compressor was faulty.

This simulated a high temperature condition in the windings which opened the comp *essor motor control circuit and prevented it f rom 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 operation 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 f aulty thermistor terminal. The two remaining thermistors were rested 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 Maintenance 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.

Per Maintenance Work Order 79-2962, the resistor was removed on September 8, 1979, and the thermistor terminals were jumpered out as directed by Power Engineering. This 1 action taken is part of FCR 77-291, which will bypass the " overload trip" function.

1174 065 Failure Data: There have been no previously reported similar occurrences.

LER #79-086