ML18079A187

LER 79-036/01T-0 on 790410:util Notified of Design Deficiency Re Differential Relays Not Meeting Seismic Design Qualifications.Problem Exists in Both Units.Relays Will Be Disconnected Until Design Change Implemented

ML18079A187
Person / Time
Site:	Salem
Issue date:	04/24/1979
From:	Kapple A Public Service Enterprise Group
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML18079A186	List: ML18079A185 ML18079A187
References
LER-79-036-01T, LER-79-36-1T, NUDOCS 7905010555
Download: ML18079A187 (3)

Text

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I Report Number: 79-36/0lT Report Date: 4/24/79 Occurrence Date: 4/10/79 Facility: Salem Generating Station Public Service Electric & Gas Company Hancock's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

4 kV Vital Bus Differential Relays Seismic Deficiency CONDITIONS PRIOR TO OCCURRENCE:

Operational Mode 5 DESCRIPrION OF OCCURRENCE:

On 4/10/79, Public Service Engineering and Construction Department notified the station that an apparent design deficiency exists in that the General Electric 12PVD11CllA bus differential relays which provide current differential protection for the 4 kV vital busses may not meet design seismic qualifications. Due to the operating design of the relay armature and contacts, under certain conditions of the design basis earthquake, the relay contacts may mechanically operate, thereby isolating one or more of the vital busses from offsite power and the safeguards diesel generators.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

The apparent design deficiency was found during a NRC inspection of Salem Unit 2. Public Service Engineering and Construction Department was requested to investigate the probability that the same deficiency exists at the Salem Unit 1.

ANALYSIS OF OCCURRENCE:

With the differential relays disconnected, adequate protection will be afforded by the existing vital bus overcurrent relays. Public Service Engineering and Construction Department has been requested to submit an analysis of the conditions and safety implications which will be included in a supplemental report.

CORRECTIVE ACTION:

Design Change ED-523 was completed on 4/20/79 which will provide the immediate solution of disconnecting the trip contacts of the bus differential relays from their respective multitrips. The Engineer-ing and Construction Department is currently evaluating a permanent solution.which will be accomplished via a Design Change Request.

790501 o<;5S-

LER 79-36/0lT FAILURE DATA:

Not Applicable Prepared by A. W. Kapple .1/'i~

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Manager _/Salm GenratiilgStation SORC Meeting No. 29-79

NRC FORM 366 (7-771 9s. NUCLEAR REGULATURY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK: I

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~ I With the unit in Mode 5 for refueling, the station was notified by Enaineerina

~ and Construction Department that an apparent design deficiency exists in that the

~ differential relays for the 4 kV vital busses may not meet design seismic oualifi-

[IJJJ I cations under certain conditions of a design basis earthquake, the relay contacts

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~ I emergency diesel generator. This is the second occurrence of this type.

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2. Public Service Engineering and Construction Department investiaated and follnd the same problem in Salem Unit 1. The differential relays will be disconnected and

[JJJJ J bus protection will be afforded by the existing vital bus overcurrent relays until

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