ML19319B769

RO NP-33-77-51:on 770806,ability to Increase Auxiliary Feed Pump Turbine 1-2 Speed from Control Room Lost.Caused by Relay Failure Due to Insufficient Breaking Capacity (Design Defficiency).Addl Relay Contacts Added in Series by 780810

ML19319B769
Person / Time
Site:	Davis Besse
Issue date:	08/31/1977
From:	Chesko R, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19319B672	List: ML19319B671 ML19319B769
References
NUDOCS 8001270238
Download: ML19319B769 (2)

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V; TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INF0FJ\ TION FOR LER NP-33-77-51 DATE OF EVENT: August 6, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of ability to increase Auxiliary Feed Pump Turbine (AFPT) 1-2 speed from t'. Control Room Conditions Prior to Occurrence: The plant was in Mode 3, with Power (M*iT) = 0 and Load (MWE) = 0.

Description of Occurrence: On August 6, l'77 at 1132 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.30726e-4 months <br /> while conducting Preoperational Test Procedure, TP 600.11, to check the Integrated Control System (ICS) control of Steam Generator level, AFPT l-2 would not respond to speed increase pulses from the ICS or in Manual. The Auxiliary Feed Pu=p Turbine had originally come up to speed and then backed down to the minimum speed stop when the increase would not respond. The turbine was shutdown locally and declared inoperable, placing the Station in the Action State =ent or Technical Specifica-s tion 3.7.1.2. Investigation disclosed that there was a defective " raise" tslay g  ; in the speed control circuit which was replaced. The circuit was tested and the Nd pu=p was declared operable on August 6, 1977 at 1615 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.145075e-4 months <br />, re=oving the Station from the Action Statement of Technical Specification 3.7.1.2.

Designation ot Anoarent Cause of eturrence: The fai, lure ot the relay was the cause of the loss of speec increase control. Insufficient current breaking capacity (design deficiency) was the cause ot the relay failure.

Analysis of Occurrence: There was no threat to the health and safety of the public or to station staff. The reactor had not reached initial criticality, and there was no decay heat in the reactor core.

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Corrective Action: Facilities Change Request (FCR) 77-l99 requested additional relay contacts to be added in series with the failing contacts to increase the current breaking capability. This change was completed on August 10, 1977 under Maintenance Work order MWO 77-1658; therefore, this problem is not expected to recur.

Failure Data: Three previous occurrences (NP-33-77-11, NP-33-77-39, and NP-33-77-53)

[,_sT were caused by defective speed switches. l

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