AECM-85-0101, Special Rept 85-003/0:on 850302,Phase C Linear Reactor of Div II Diesel Generator Failed During Maint Run.Caused by Breakdown of Reactor Insulation Due to Excessive Heat.All Linear Reactors in Div II Replaced

Special Rept 85-003/0:on 850302,Phase C Linear Reactor of Div II Diesel Generator Failed During Maint Run.Caused by Breakdown of Reactor Insulation Due to Excessive Heat.All Linear Reactors in Div II Replaced

ML20116F706
Person / Time
Site:	Grand Gulf
Issue date:	03/29/1985
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
85-003-0, 85-3, AECM-85-0101, AECM-85-101, TAC-52411, NUDOCS 8505010188
Download: ML20116F706 (2)

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MISSISSIPPI POWER & LIGHT COMPANY

] Helping Build Mississippi EuRAMildidd5 P. O. B O X 164 0. J A C K S O N, MIS SIS SIP PI 39215-1640

, s 29, 1985 d5 APR l Ah.: arch 13 NUCLE AR LICENSING & SAFETY DEPARTVENT U. S. Nuclear Regulatory Commission Region II 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323 Attention: Dr. J. Nelson Grace, Regional Administrator

SUBJECT:

Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 File: 0260/L-835.0 Special Report 85-003/0, Failure of a Division II Diesel Generator Linear Reactor AECM-85/0101 On March 2, 1985 at 1200 the C phase linear reactor of the Division II Diesel Generator failed during a maintenance run. The reactor, a power component in the Diesel Generator excitation system, had experienced a total service time of 1020 hours0.0118 days <br />0.283 hours <br />0.00169 weeks <br />3.8811e-4 months <br /> when the reactor windings overheated. The excessive heat caused a breakdown of the reactor insulation which subsequently burned.

The local operator noticed smoke coming from the cabinet and informed the control room operator who reduced the engine load and shutdown the diesel generator. All of the linear reactors in Division II were replaced and the Diesel Generator was returned to service approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> later.

A similar failure (Special Report 84-028) occurred on the Division I Diesel Generator and as a result, all of the linear reactors in the Division I Diesel Generator were replaced on June 28, 1984. In both cases excessive testing appeared to thermally age the reactor prematurely, therefore a design change is being initiated to provide additional cooling to the Division I and Division II Diesel Generator excitation panels. The design change is expected to be implemented prior to 900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br /> of operating time on the linear reactors (the anticipated end of life for the linear reactors).

A trip due to loss of generator excitation would have occurred if the reactor had shorted to ground.

8505010188 85v329 i PDR ADOCK 05000416 S PDR

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J0P13AECM85032501 - 1 Member Middle South Utilities System

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, AECM-85/0101 Page 2 This failure is considered invalid in accordance with Position C.2.e(3) of Regulatory Guide 1.108. The diesel generator had operated continuously at greater than 50%. load for 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The surveillance test interval remains at 7 days. This is a final report.

Yours truly.

.b L. F. Dale

, Director EBS/SHH:vog cc: Mr. J. B. Richard Mr. O. D. Kingsley, Jr.

Mr. R. B. McGehee Mr. N. S.~Reynolds Mr. G. B. Taylor Mr. James M. Taylor, Director Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 s

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