RBG-34047, Special Rept:On 901021,invalid Failure of Div II Diesel Generator Occurred.Caused by Operator Error.Occurrence Discussed in Shift Briefings

Special Rept:On 901021,invalid Failure of Div II Diesel Generator Occurred.Caused by Operator Error.Occurrence Discussed in Shift Briefings

ML20062G327
Person / Time
Site:	River Bend
Issue date:	11/20/1990
From:	Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RBG-34047, NUDOCS 9011290121
Download: ML20062G327 (4)

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GULF STATES UTILITIES COMPANY mivlt M NDSfAfl0% POST D'TICI 90X 2M $f PRANCtSvtLLE. LOutsiAhA 70776 AAi A CObt SM 635 0064 $46 0661 Novatber 20, 1990 RBG- 34047 File Nos. G9.5, G9.25.1.4 l

U.S. Nuclear Regulatory Carmission Docunent Control Desk -

Washington, D.C. 20555 Gentiment River Bend Station - Unit i Docket No. 50-458 ,.

Enclosed is Gulf States Utilities Cmpany's Special Report concerning an invalid failure of the Division II diesel generator at River Bend Station. This report is being sulxnitted pursuant to River Bend Station Technical Specification. 4.8.1.1.3 and 6.9.2.

Sincerely, a

W. f. Odell \

l Manager-Oversight River Dend Nuclear Grtup l IAE/PDG/ ' /DC21/DCP/ch cc U.S. Nuclear Regulatory Cannission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Prancisville, IA 70775 INPO Records Center 1100 Circle 75 Parkway Atlanta, GA 30339-3064 Mr. C. R. Oberty Public Utility Ccmnission of Texas 7800 Shoal Creek Blvd., Suite 400 North Austin, TX 78757 9011290121 901120 FDR jU

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. . t REFOfGTD 030ITIN At 1404 on 10/21/90 with the plant in Operational Condition 5 (Refueling), during post mintenance period testing, a Nuclear Control Orcrator (NCO) synchronized the Division II diesel generator (DG) out of phase, h out of phase synchronization occurred because the operator did not follow site procedure to determine when to close the DG output breaker. This is considered an invalid failure in accordance with legulatory Guide 1.108 position C.2.e.2. This Special Report is sulmitted pursuant to the requirenonts of River Bend 7bchnical Specifications 4.8.1.1.3 and 6.9.2.

_INVPEf1GATI N The sequence of events was as follows. h operator used the synch lights alone to determine when to close the DG output breaker, closing the breaker when the synch lights were dim. Approxis tely 0.2 seconds after the DG output breaker closed, the normal supply breaker to the bus tripped open. The diesel generator supplied about 900 W of power to the electrical loads on the bus as the only source of AC power.

After about 18 minutes of operation, the diesel generator was pealleled to the grid through the alternate feed breaker. The diesel load as increased to about 1800 m for about 24 minutes before the diesel wac shutdown. No abnormal conditions were detected during this period of dnsel generator operation.

7he diesel epgine and generator were inspected after this event to determine if an/ damage had been done to the equiptent. The following inspections of the diesel engine were performods h gear truin was inspected for damaged ccraponents. None weru found.

h main governor drive coupling was inspected for damage. No degradation of the coupling was identified.

l The grout supporting the engine-generator skid was inspected for degradation. No degradation of the grout was identified.

The engine-generator foundation bolt tor p s e checked. No loose bolts were found.

The portion of the crankshaft where connecting rod number 8 is attached was inspected using fluorescent liquid penetrant. No unsatisfactory conditions were identified.

h portion of the crankshaft between cylinders 7 and 8 that is supported by the nnin bearing journal was inspected using fluorescent liquid penetrant. No unsatisfactory conditions were identified.

A limited scope calculation was performed to determine if the flywheel bolting needed inspection. The results of this evaluation indicated that the flywheel bolting was not overstressed during the event.

2 no results of the nochanical inspection show Omt the diosol engine was not danaged as a result of this event. The generator and excitation system ccupononts were also inspected for drage. The inspections perforned were as follows:

The rotor poles, stator windings and support structure, and the slip rings were visually inspected for damaged ccrtponents. None were found.

The rotor shaft, rotor pole support plates, and stator supports were vistally inspected for cracking. No cracks were found in these ccxqponents.

One of the dowels in the generator pedestal bearing was inspected to determine if the pedestal bearing had shifted. The dowel could be renoved easily, had no apparent damage, and was reinstalled.

The excitation panel was inspected for dauaged ccrqponents. No danage was found to the silicon control metifiers and diodes within the panel. A ckmaged surge arrester was found and replaced.

CAUSE (F FAUURE The root cause of the out of phase synchronization of the Division II i diesel generator is operator error. The operator did not use the synch scope to determine when to close the diesel generator output breaker. As a result, the diesel was synchronized to the grid out of phase. %e operator's action violated site procedures which require that the synch scope and lights be used together to determine the correct timing for breaker closure.

nis situation cccurred while the Division II diesel generator was undergoing post naintenance period test runs. At no time during the out of phase synchronization was the Division II DG required to_ be cperable per the River Dend Technical Specifications. The operable DG was the Division I DG, and the ability of the Division I DG to perform

! its safety function was not impaired. In addition, the Division III DG was conservatively maintained in an operable condition during the out of phase synchronization.

CDRRECTIVE ACTICN This occurrence has beer. discussed in shift briefings to nake all cperators aware of the seriot,9 nature of synchronizing any generator out of phase. In addition, this report will be required reading for all operators by Januaq 11, 1991.-

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,e issth of Tim Diesel Generator was Out-of-Service:

6 days 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> i

Current Surveillance Interval ~!

Division I Monthly j Division II Monthly  !

Division III Monthly j i

Test Intervals Confor1ns to Technical Specifications j Yes. l

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b Failures for Division I: .

l 1 Valid failure in the last.20 Valid.h sts' i 1 Valid-failure in the'last 100 Valid Tests .i 1

.i' Failures for Division 113 0 Valid failures in tho.last 20 Valid Tests- j 4 Valid failures in the last 100 Valid Tests .)

Failures for Division III: .

l 0 Valid. failures in the last-20 Valid hsts  :

2 Valid Failures in the last 100 Valid % sts-

• Cunmilative Failures for all River Bend Diesel Generators: q 3 Valid Failures in the last 100 Valid Tests f

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