ML20215M535

Final Deficiency Rept (55(e)-86-08) Re Failure of Elgar Class 1E Inverters Fuse Block Connection.Initially Reported on 860508.Vendor-recommended Mods Which Provide Proper Block to Bar Connection Will Be Completed by 860701

ML20215M535
Person / Time
Site:	Nine Mile Point
Issue date:	06/10/1986
From:	Mangan C NIAGARA MOHAWK POWER CORP.
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
(55(E)-86-08), (55(E)-86-8), (NMP2L-0742), (NMP2L-742), NUDOCS 8611030008
Download: ML20215M535 (2)

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'. O O M Y NIAGARA R UMOHAWK NIAGARA MOHAWK FOWER CORPORATION /300 ERIE BOULEVARD WEST, SYPACUSE, N.Y.13202/ TELEPHONE (315) t?4-1511 June 10, 1986 (NMP2L 0742)

Mr. R. W. Starostecki, Director U.S. Nuclear Regulatory Commission Region I Division of Project and Resident Programs 631 Park Avenue King of Prussia, PA 19406 Re: Nine Mile Point Unit 2 Docket No. 50-410

Dear Mr. Starostecki:

Enclosed is a final report in accordance with 10CFR50.55(e) for the problem concerning Elgar Class lE inverters - fuse block problems. This problem was reported via telecon to G. Meyer, of your staff, on May 8,1986.

Very truly yours, C. V. Man n Senior Vice President GAG:ja i 1713G l Enclosure xc: Director of Inspection and Enforcement U.S. Nuclear Regulatory Comission Washington, DC 20555 R. A. Gram, Resident Inspector Project File (2) ,

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,? w O O NIAGARA M0 HAWK POWER CORPORATION NINE MILE POINT UNIT 2 DOCKET NO. 50-410 Final Report for a Problem Concerning Elgar Class 1E Inverters - Fuse Block Problems (55(e)-86-08)

Description of the Problem The problem involves the failure of the fuse block connection. The assembly of the fuse block was improper and resulted in the fuse block stud pulling loose from the block when the attachment nuts were tightened. The deficient fuse block assembly could result in loss'of de input to the inverter.

The above problem pertains-to both Division I and II Uninterrupted Power Supply units which are identical.

Analysis of Safety Implications Loss of de input to the inverter of both the Uninterrupted Power Supplies, concurrent with the Unit 2 design basis event, could result in loss of uninterruptible 120V ac power to Class 1E instrument and control loads. When considered simultaneously with a loss of cooling accident, the unavailability of-120V power output could result in inability of loss of cooling accident auxiliary relays and contacts to initiate operation of the Emergency Core Cooling System.

Based on the described condition above, if this problem had remained uncorrected, it could have adversely affected the safety of operations of the plant during accident conditions.

Corrective Action Vendor-recommended modifications which provide a proper block-to-bar connection will be completed in accordance with Engineering and Design Coordination Report No. 292,304 by July 1,1986.

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