ML20084S619

AO 50-265/75-41:on 751018,while Performing Monthly Diesel Generator Surveillance Test,Diesel Generator Reactive Power Meter in Control Room Pegged Full Scale.Megawatt Output Load Erratic.Operator Tripped Diesel.Caused by Equipment Failure

ML20084S619
Person / Time
Site:	Quad Cities
Issue date:	10/27/1975
From:	Hooverson O, Kalivianakis N COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084S621	List: ML20084S619 ML20084S629
References
A-50-265-75-41, A0-50-265-75-41, NUDOCS 8306170136
Download: ML20084S619 (4)

Text

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Li w; REPORT NUr3ER: A0 50-265/75-41 REPORT DATE: October 27, 1975 OCCURRENCE DATE: October 17, 1975 FACILITY: Quad-Ci ties Nuclear Power Station Cordova, Illinois 61242 IDENTI FICATION OF OCCURRENCE:

Unit 2 Diesel Generator failure due to field diode transient voltage sup-pressor failures.

CONDITIONS PRIOR TO OCCURRENCE:

Unit 2 was in the Cold Shutdown Condition for a core maintenance outage'.

DESCRIPTION OF OCCURRENCE:

At 3: 15 p.m. on October 17, 1975 while Uni t 2 Diesel Generator was running during a monthly operability surveillance test, the diesel generator reactive power meter in the control room was noticed to have ' pegged at full scale. The megawatt output load from the diesel generator was then observed to be very erratic. The Unit 2 control room operator tripped the diesel, and an equipment operator was sent to the diesel generator room to investigate the problem.

The operator found that two of the six selenium rectifier transient voltage surge suppressors associated with the generator field had. been damaged.

The diesel was taken out of service, and a work reques t written to initiate repa i rs .

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

Equi pmen t Fai lu re The apparent cause of this abnormal occurrence is equipment fa i l u re. The two surge suppressors had apparently shorted out, thereby providing a di rect short circuit around the field rectifiers thus collapsing the fleid. This in turn caused erratic megawatt output and reactive power readings. The exact cause of the surge suppressor failure is undetermined at this time.

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A0 50-265/75-41 October 27, 1975 ANALYSIS OF CCCURRENCE:

The safety implications related to this occurrence are minimized by the fact that Uni t 2 was in tha Cold Shutdown condition. The 1/2 Diesel Gen-erator was available to supply emergency power and normal of f-site power was available at all tines f rom the uni t reserve auxil iary trans forme r.

All 345 i(V lincs were operable and the switchyard was intact.

The re fo re , the safe operation of the facility was not compromised as a result of this occurrcnce.

CORRECTIVE ACTION:

The immediate corrective action consisted of shutting down the diesel generator. Work Peques t 4091-75 was initiated for the purpose of replacing all six surge suppressors. Later on October 17, at 7:25 p.m., the Unit 2 Diesel Generator was returned to service. The diesel was. started and operated normally at 9:45 p.m.

Investigations have been in progress by the Edison Station Electrical Engineering Department to conduct an extensive study as to the mode of failure of these surge suppressors, and to devise a replacement scheme for them, Modi fi ca t ions M-4-l (2)-75-25 and M-4-1/2-75-4 have been initiated to accomplish this replacement.

FAILURE DATA:

There have been 3 previous failures of the selenium surge suppressors for the Diesel Generators at quad-Cities Station. The investigations in progress at the present time and continued scheduled surveillance testing of the diesel generators should aid in minimizing the effects of these failures.

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- C:mmOcalth Edis: f'i Ouad-CA-dhchtr Poa ct Stat on d 1 Pmt Off'ce Bo< 216 Cordova. I:hno.s 61242 Teicphone 300/G54-2241 N

NJK-75-532 ,,.

, o ni,. c October 27, 1975 -

a" w-Director of Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Vashington D. C. 20555

Reference:

Quad-Cities Nuclear Power Station ,

Docket No. 50-265, DPR-30, Unit 2 Appendix A, Sections 1.0. A.2, 3 9. A.1, 6.6.B. I .a Enclosed please find Abnormal Occurrence Report No. A0 50-265/75-41 for Quad-Ci ties Nuclear Power Station. This occurrence was previously reported to Region lil, Of fice of Inspection and Enforcernent by telephone on Octo-ber 18, 1975 and to you and Region Ill, Office of inspection and Enforce-ment by telecopy on October 18, 1975 This report is submitted to you in accordance with the requi rements of Technical Speci fication 6.6.B. I .a.

Very truly yours, COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION

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N. J. Kalivianakis Station Superintendent NJK/0MH/lk -

cc: Region ill, Office of Inspection and Enforcement G. A. Abrell e

l 12479. I OOPY st;Nr REGION 2 l

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