ML20084J126

Ao:On 730506,during Planned outage,1/2 Diesel Generator Would Not Start Following Inadvertent Trip of Power Supply to Buses 13 & 13-1.Caused by Welding Together of Str/Hga Relay Contacts & Air Start Solenoid Valve

ML20084J126
Person / Time
Site:	Quad Cities
Issue date:	05/15/1973
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084J128	List: ML20084J126 ML20084J134
References
BBS-73-93, NUDOCS 8305120168
Download: ML20084J126 (2)

Text

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• I,@7 O '\'Ouad-Cit;es Nu': lear Power Station I ~ ,j Post Off.ce Box 216

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e Cordova, liiinois 61242 Telephone 309/654-2241 BE-73-93 foN

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- May 15, 1973 0

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• Mr. Angelo Giambusso Deputy Director for Reactor Projects y, ft Cp ;7,g'-

Directorate of Licensing U.S. Atomic Energy Commission Washington, D. C. 20545

Reference:

Quad-Cities Nuclear Power Station Docket Number 50-265, DPR-30, Appendix A, Section 1.0.A.2 and 3.9.E.1

Dear Mr. Giarbusso:

The purpose of this letter is to report the unavailability of the shared diesel generator with the Unit 2 reactor operating at 905 power. This abnormal occurrence was previously reported by telegram on May 7, 1973 DESCRIPTIC:1 OF EVENT At 8: 00 a.m. on May 6, 1973, during a planned outage on

. Unit one the power supply to buses 13 and 13-1 was in-advertent]y tripped while performing routine preventive maintenance checks on bus 13 switchgear. The No. 1/2 diesel generator auto started and restored power to bus 13-1. After normal auxiliary power was restored the diesel generator was shutdown. At 9:00 a.m. when the monthly surveillance test was attempted on the 1/2 diesel generator, it would not start. The diesel generator was declared inoperable when the starting air accumulators were found to be depressurized.

INVESTIGATIO:i Investigation revealed that the cause of the occurrence '

was due to the welding together of the STR/IIGA relav contacts to the governor oil booster pump D.C. motor and the air start solenoid valve when the relay was de-energized. The resultant continuous open signal to the solenoid valve caused the air start accumulators to depressurize thus disabling the diesel. The relay was

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8305120168 730515

{DRADOCK 05000265 PDR. o i

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COPY SENT REGION 3274

Mr. 'Angelo Giambusso May 15, 1973 l

- repaired and the air start accumulators charged.

Subsequent to a successful operability check, the l

shared diesel generator was declared operable and l

returned to service at 5: 15 p.m. on May 6, 1973 f

. CONCLUSIONS AND COPPECTIVE ACTION The shared diesel-Eenerator was inoperable for a period of about 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. Only Unit 2 was affected by the incident since Unit 1 was in the cold shutdown condition.

During this period the low pressure core cooling systems and containment cooling systems required to be operable by Technical Specifications 3.o.E.1 for this condition were satisfactorily tested. In addition, all off-site 345 KV lines and the reserve auxiliary transformer were available. The demonstrated availability of power and emergency systems thus greatly reduces any safety signi-ficance of this incident.

The STR relay contacts in the air start solenoid valve circuits of the Nos. 1 and 2 diesel-Benerators were also inspected and showed signs that arcing had occurred in the past. It is apparent, therefore, that this occurrence was caused by the circuit design rather than an individual component failure. To correct this condition a modification

- to all three diesels is currently being reviewed. This modification will replace the existing HGA type relay with an RFA type of the same rating. The HFA relay, however, has the necessary number of "a" contacts to per-

< mit wiring two contacts in series in the solenoid circuit which will reduce the arcing and minimize the probability of a recurrence.

Very truly yours, COMMONWEALTH EDISON COMPANY Quad-Cit uc ar Power Station j&Whenson

. B. St t Plant S perintendnet BBS/zm i

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