ML19319B760

RO NP-33-77-39:on 770802,deliberate Dc Power Lost to Speed Switches 55815 & 55816.Auxiliary Feedwater Valve Operation Observed After Faulty Speed Switches Were Replaced

ML19319B760
Person / Time
Site:	Davis Besse
Issue date:	08/26/1977
From:	George T, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19319B651	List: ML19319B650 ML19319B760
References
NUDOCS 8001270223
Download: ML19319B760 (2)

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TOLEDO EDISON COMPANY D DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-39 DATE OF EVENT: August 2, 1977 FACILITY: Davis-Besse' Unit 1 IDENTIFICATION OF OCCURRENCE: Deliberate loss of DC power to speed switches SS 815 and SS 816.

Conditions Prior to Occurrence: The plant was in Mode 3, with Power (MWT) = 0, and Load (MWE) = 0.

Description of Occurrence: At 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br /> on August 2, 1977, DC power was de-ener-gized to Auxiliary Feedwater Pumps Speed Switches SS 815 and SS 816 one at a time to observe the proper operation of Auxiliary Feedwater Valves AF 360 and AF 388.

This action placed the station in the Action Statement of Technical Specification 3.7.1.2, since each Auxiliary Feed Pump was inoperable one at a time.

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Designation of Accarent Cause of Occurrence: On February 11, 1977, a Non-Confor-mance Report (51-77) was issued to repair and replace speed switches SS 815 and SS 816. These speed switches were faulty and would cause the Auxiliary Feedwater Valves to cycle continuously until the motor burned out if power was lost to the speed switches. The speed switches were repaired and replaced on April 21, 1977.

To test these switches, DC power was removed from them one at a time.

Analysis of Occurrence: Since one of the Auxiliary Feed Pumps was operable at all times to supply the required feedwater flow, there was no threat to the health and safety of the public or to Station personnel.

l Corrective Action: After the speed switches (SS 815 and SS 816) were tested and verified operable, DC power was restored and the Auxiliary Feedwater System was declared operable. This removed the station from the Action Statement of Techni-cal Specification 3.7.1.2.

Failure Data: The Auxiliary Feedwater Pumps were out of service on two prior occasions, (NF-32-77-ll and NP-33-77-42) but for different causes.

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