ML20210S315

Revised Final Deficiency Rept Re Unsuccessful Attempt to Synchronize Diesel Generator W/Sys.Initially Reported on 860730.Generator Endturns Cleaned & Greased Before Repairs Made.Permissive Sychronization Relay Scheme Installed

ML20210S315
Person / Time
Site:	Bellefonte
Issue date:	02/04/1987
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	Grace J NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
References
NUDOCS 8702170605
Download: ML20210S315 (4)

Text

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e TENNESSEE VALLEY AUTHORITY SN 157B Lookout Place BLRD-50-438/86-09 10 CFR 50.55(e)

FEB 041987 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Office of Nuclear Reactor Regulation Washington, D.C. 20555 Attention: Dr. J. Nelson Grace In the Matter of the Application of ) DOCKET NOS. 50-438 Tennessee Valley Authority ) 50-439 BELLEFONTE NUCLEAR PLANT UNIT 1 - DIESEL GENERATOR OUT-OF-PHASE SYNCHRONIZATION - BLRD-50-438/86 REVISED FINAL REPORT The subject deficiency was initially-_ reported to NRC-OIE Inspector Art Johnson on July 30,_198E in accordance with 10 CFR 50.55(e) as SCR BLN 4929Rl. Our final report was submitted on September 4, 1986. Enclosed is our revised final report.

If there are any questions, please get in touch with D. L. Terrill at (205) 574-8820 Very truly yours, TENNESSEE VALLEY AUTHORITY R. . Gridl , Director Nuclear Saf ty and Licensing Enclosure cc: See page 2 87021 h $hhhbPDR 38

! PDR l

An Equal Opportunity Employer I

r 1 o-U.S. Nuclear Regulatory Commission FEB 041987 cc (Enclosure):

Mr. G. G. Zech, Director TVA Projects U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Bellefonte Resident Inspector -

Bellefonte Nuclear Plant P.O. Box 2000 Hollywood, Alabama 35752 Mr.' James Taylor, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Records Center Institute of Nuclear Power Operaations 1100 circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 1

e ENCLOSURE BELLEFONTE NUCLEAR PLANT UNIT 1 DIESEL GENERATOR OUT-OF-PHASE SYNCHRONIZATION BLRD-50-438/86-09 SCR BLN 4929 R1 10 CFR 50.55(e)

REVISED FINAL REPORT Description of Deficiency On June 26, 1986 a routine quarterly run of diesel generator lA was being conducted. The run was aborted when an attempt to synchronize the diesel generator with the system was unsuccessful., A loud noise and minor damage occurred due to an excessive out-of-phase condition at the time of breaker closure. Reverse power relay operation automatically tripped the generator

. breaker, removed excitation, and shut down the diesel engine.

Following these automatic actions, the engine coastdown was normal. No unusual noises or vibrations occurred during coastdown; however, cracked welds were discovered on the north end of the generator base mounting. These welds are skip welds that function to hold the baseplate to the generator foot during assembly.

The investigation determined that operator e,rror was the cause of the incident.t The operator inadvertently pushed the main control room pushbutton to close the breaker too early. All other elements of the diesel generator operation including planning, scheduling, equipment operation, procedure adequacy, procedure adherence, training, personnel attentiveness, and communications were essentially flawless.

l Because this problem was induced from operator error, there is a potential that other TVA diesel generators could be damaged due to similar operator error. Other TVA plants have been notified of this condition.

Safety Implication l

Failure of the subject diesel generator would cause the loss of train A l

engineered safety features during a loss of offsite power event. This could affect the safe operation of the plant.

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Corrective Action Following the out-of-phase event an investigation by the Office of Nuclear l

Power and vendor representatives was performed to determine the extent of the damage. This investigation revealed there was no significant equipment damage. Items inspected were the generator air gap alignment, structural alignment of various generator bolts and dowels, looseness in the stator windings, generator to engine coupling, engine bearing and web deflection, and generator megger and bridge inspections.

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Following this inspection TVA determined that the following corrective action is appropriate. The generator endturns will be cleaned to remove dirt and grease before any repairs are made. The endturn areas of the generator stator winding will be tightened in the areas where coils or leads have experienced movement. All welds on the sole plate will be tested and the cracked welds removed and new welds applied using a TVA-approved welding specification.

The load actually exerted on the engine during this incident will be calculated and this value backed into the crankshaft mathematical model to determine the most highly stressed journals / bearings. Since the identified failure mechanism for the crankshaft is fatigue, inspection and/or examination of the most highly stressed journals / bearings of the crankshaf t will be made to detect any cracks caused by this event which could lead to fatigue

. failure. Flywheel, bolting of diesel. generator.1A will be inspected and verified acceptable. Torsiograph testing will be reperformed to verify crankshaft stresses are within those previously analyzed. This will also give an indication of any changes in the rotational characteristics of the generator. Normal maintenance runs of the diesel will not jeopardize its integrity during the period until the determination of the most highly stressed journals / bearings and the torslograph testing is completed.

To prevent short-term recurrence, TVA has taken disciplinary action against the involved, operator.and has provided additional training to all operators at Bellefonte who perform or supervise generator synchronization operations. The short-term action to prevent recurrence is complete and is considered sufficient to allow diesel generator periodic testing. To prevent long-term recurrence, TVA will install, by six months before fuel load, a permissive synchronization relay scheme for use when manually paralleling the diesel generators to the system.

All unit 1 actions will be completed by six months before unit 1 fuel load.

Unit 2 action required to prevent recurrence will be complete by six months before fuel load of unit 2.

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