05000293/LER-1981-050-01, /01T-0:on 810812,during Normal Operation,Ground Fault Indication on 125-volt Dc Sys Was Received.Caused by Short Circuit in Topaz Dc to Ac Inverter.Inverter Repaired & Procedures Rewritten

/01T-0:on 810812,during Normal Operation,Ground Fault Indication on 125-volt Dc Sys Was Received.Caused by Short Circuit in Topaz Dc to Ac Inverter.Inverter Repaired & Procedures Rewritten

ML20011A434
Person / Time
Site:	Pilgrim
Issue date:	09/29/1981
From:	Whitney G BOSTON EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20011A430	List: 05000293/LER-1981-050, Forwards LER 81-050/01T-0 05000293/LER-1981-050-01, /01T-0:on 810812,during Normal Operation,Ground Fault Indication on 125-volt Dc Sys Was Received.Caused by Short Circuit in Topaz Dc to Ac Inverter.Inverter Repaired & Procedures Rewritten
References
LER-81-050-01T, LER-81-50-1T, NUDOCS 8110130344
Download: ML20011A434 (2)

LER-1981-050, /01T-0:on 810812,during Normal Operation,Ground Fault Indication on 125-volt Dc Sys Was Received.Caused by Short Circuit in Topaz Dc to Ac Inverter.Inverter Repaired & Procedures Rewritten

Event date:
Report date:
2931981050R01 - NRC Website

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BOS'TCN EDISON COMPANY PILGRIM NUCLEAR POWER STATION DOCKTT J0 50-29.1 Attachment to LER 81-050/017-0

Event Description

During normal operations en September 12, 1981, 9 ground fault indication on the 125 VDC System was received. An investigation was immedir.tely initiated.

Following procedure, a number of breaker isolations determined the fault to be in the systems served by breaker D4-3.

Individual fuses were then pulled and returned until the fault was isolated in the circuit serving the Topaz DC to AC inverter. No replacement inverter was available, therefore, permission to remove the inverter for repair was requested from the Watch Engineer. He indi-cated the RCIC System would be made inoperative when the breaker was opened.

This condition lasted until September 16, 1981.

Primary containment was maintained throughout this period but some of the logic contributing to the automatic isolatien of RCIC valves MO 1101-16 & 17 did not have the minimum number of operable instrument channels available.

Cause and Corrective Actions

The root cause of the ground fault has been determined to be a failed capacitor in the inverter which was repaired. In addition, conclusions to be dravn from the investigation were that station personnel were not aware that they had antered a limiting ccndition of operation of the PCIS, and did not perform the required action. The cause was an improper isolation due to implications of associated logic circuitry. The long term corrective action is to implement a policy whereby isolations of the D4, DS, D6 and Yl, Y2, Y3 and Y4 breaker panels will be allowed on a single component only basis unless e detailed study is performed and ap-proved by the ORC. The policy hae been incorporated by special order on 9/24/81.

In addition, it I o-been recognized that routine trouble shooting procedures do not fully document the controls presently imposed. Revision to the existing

" Inspection / Trouble Shooting-Electrical Circuits" Procedure, 3.M.3-8 will be initiated to provide that guidance and record thereof. This action will be completed by October 1, 1981.

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