ML20086K412

AO 74-37:on 740703,static Inverter Tripped on Restart of Recirculation Pump a Motor Generator Set.Cause Unknown. Occurrence Under Investigation

ML20086K412
Person / Time
Site:	Peach Bottom
Issue date:	07/13/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086K415	List: ML20086K412 ML20086K421 ML20086K437
References
AO-74-37, NUDOCS 8401270077
Download: ML20086K412 (2)

Text

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July 13, 1974 Mr. A. Giambuss Deputy Director of Reactor Projects 50-277 United States Atomic Energy Commission Di rectorate of Licensing Washington, D.C. 20545

Subject:

Abnormal Occurrence

Dear Mr. Giambusso:

The following occurrence was reported to Mr. Donald Caphton, A.E.C. Region I Regulatory Operations Office on July 3,1974. Wri tten notification was made to Mr. James P. O'Reilly, Region I Regulatory Operations Office on July 5,1974. In accordance with Section 6.7.2.A of i.iie Tetin.iwai Sucui ricat;ei.a. Aguc.. dix A of DPf:A': fcc Unit 2 Peach Bottom Atomic Power Station, the following report is being sub-mitted to the Directorate of Licensing as an Abnormal Occurrence.

Reference:

License Number DPR-44, Amendment Number 1 Technical Speci fication . Table 3.5.D ,

Report No.: 50-277-74-37 Report Date: July 13, 1974 Occurrence Date: July 3, 1974 Facili ty: Peach Bottom Atomic Power Station R. D. 1, Delta, Pennsylvania 17314 Identi fication of Occurrence:

The static inverter which supplies a.c. power for the reactor

' core isolation cooling system flow controller and system indication,

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tripped on the restart of the "A" reci rculation pump M.G. set.

Condi tions Prior to Occurrence:

Reactor had scrammed from approximately 68% power. I .

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Mr. A. Giambusso m July 13, 1974 Page 2 Description of Occurrence:

Following a low vacuum scram, turbine trip, and fast bus transfer (which trips the recirculation pump M.G. sets) as the "A" M.G. set was being restarted, the RCIC inverter tripped. The trip-pod inverter was imediately identi ficd via annunciation and suc-cessfully reset.

Designation of Apparent Cause of Occurrence:

No cause of the tripping of the static inverter has been found. Two input conditions which will trip the inverter are un-dervoltage (100 V.D.C.) and overvoltage (147 V.D.C.) at the inverter inputs. At the time of the trip the "A" M.G. set was being started.

It is believed-that starting large motors may change input D.C. voltage from the battery chargers enough to cause an inverter trip.

Analysis of Occurrence:

Loss of the static inverter defeats the automatic mode of operation of the reactor core isolation ccoling system. The flow controller will not demand rated flow. Turbine speed indication is still availabic and the operator can use the test circuit to bring the turbine up to rated flew speed and inject water to the reactor.

Cesouau U.o L.- w . 9 c,f the i r.vertcr ..':: :nnunci ted 2nd :;uickly reset, this occurrence is of minor safety significance.

Corrective Action:

This occurrence is still under investigation.

Failure Data:

Two other trippings of the RCIC inverter had been reported as A0-50-277. 74.14 and A0. 50-277-74-20.

Very truly yours, ffjN/ncy M./J. Cooney<

As's' t Gen' 1 Superintendent Generation Division cc: Mr. J. P. O'Reilly Di rector, Region 1 Uni ted S tates Atomic Energy Commission 631 Park Avenue King of Prussia, PA 19406

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