ML19274D939

LER NP-33-77-64 on 770827:reactor Coolant Pump 1-1-2 Tripped,Removing One of Two Reactor Coolant Pumps from Operation.Caused by Damage to Surge Capacitors Due to Insufficient Mounting Base

ML19274D939
Person / Time
Site:	Davis Besse
Issue date:	09/22/1977
From:	Beeler T, Lingenfelter J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19274D938	List: ML19274D937 ML19274D939 ML19289D517
References
NUDOCS 7902270260
Download: ML19274D939 (2)

Text

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DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-64 DATE OF EVENT: August 27, 1977 FACILITY: Davis-Besse Unit 1 Reactor Coolant Pump Motor 1-1-2 was declared IDENTIFICATION OF OCCURRENCE:

inoperable on August 27, 1977.

The plant was in Mode 2, with Power (MWT) = 125 Conditions Prior to Occurrence:

and Load (MWE) = 0.

Reactor Coolant Pump Motor 1-1-2 tripped at 1740 hours0.0201 days <br />0.483 hours <br />0.00288 weeks <br />6.6207e-4 months <br /> Description of Occurrence _:

on August 27, 1977, with instantaneous ground (50GS) and differential current relay (87m/A-B-C) targets indicating the fault. This placed the Station into the Action Statement of Technical Specification 3.4.1 since one of the two Reactor Coolant Pumps in the loop were not in operation.

Designation of Apparent Cause of Occurrence: Upon inspection of the Reactor Coolant Pump 1-1-2 motor terminal box, Station maintenance personnel discovered It has been determined by Westing-B&C phase surge capacitors to be damaged.

house the design of the capacitor base was insufficient for the application.

There was no danger to the health and safety of the Analysis of Occurrence:

public or Station personnel. The thermal power was at a low value and the remaining three Reactor Coolant Pumps were supplying the required coolant flow.

Corrective Action: The high flux and the flux-delta-flux setpoints were reset for three pump operation as required by the Action Statement of Technical Specification Station maintenance personnel replaced C-phase surge capacitors and re-3.4.1.

installed B-phase surge capacitors after caulking the crack in the porcelain and opening in the seam with RTV silicone sealant.

At 0058 hours6.712963e-4 days <br />0.0161 hours <br />9.589947e-5 weeks <br />2.2069e-5 months <br /> on August 31, 1977, Reactor Coolant Pump 1-1-2 was declared operable.

This removed the station from Action Statement of Technical Specification 3.4.1.a.

29, 1977, an inspection was made on the remaining reactor coolant pump On AugustA defective capacitor was found in A phase for Reactor Coolant Pump 1-2-2.

motors.

As Station maintenance personnel replaced A phase surge capacitor with a new one.78-470, the capacitors on all four Reactor Coolant per Facility Change Request 2

Pump motors have been replaced with new units which incorporate a new design mount-ing base as of January 20, 1979.

Failure Data: No previous similar events have occurred.