ML19317F562

Ro:On 780221,control Rod Drive Sys Trip Circuit Breaker Cabinets Found to Have Inadequate Welds.Welds to Be Lengthened to Conform W/Shaker Table Test During Apr 1978 Outage

ML19317F562
Person / Time
Site:	Davis Besse
Issue date:	02/24/1978
From:	Roe L TOLEDO EDISON CO.
To:
References
REF-PT21-78-032-000 NUDOCS 8001150883
Download: ML19317F562 (2)

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ATTACHED IS PART 21 REPORT FROM IE MAIL UNIT - R0011317 E/W PART 21 IDENTIFICATION NO. COMPANY NAME #4EAC [fjJ#A/

7 ff - 0 3 2 - B S O DOCKET NO. So - S .76 DATE OF LETTER _2 - 2. y-7 P DATE DISTRISUTED 2,/22 /7f ORIGINAL REPORT SUPPLE!!ENTARY O DISTRIBUTION:

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REACfdR(R) FUEL CYCLE AND SAFEGUARDS (S)

MATERIALS (M)

NRR/ DOR (Stello) NMSS/FC&MS ,

NRR/ DOR (Stello)

NRR/DPM (Scy AD/FF&MSI

, NMSS/SG AD/ROI (Snipzey/Seyfrit) PDR

, AD/SG-IE AD/RCI -

MIPC AD/ROI MIPC REGIONS REGIONS REGIONS NSIC -

MIPC PDR TIC PDR LPDR IE FILES (2) LPDR NSIC CENTRAL FILES-SS 396 NSIC TIC CENTRAL FILES (CHRON) TIC IE FILES (2) _

, IE FILES (2)

CENTRAL FILES 016 CENTRAL' FILES 016

' CENTRAL FILES (CHRON) , CENTRAL FILES (CHRON.

CE,NTRAL FILES - SS E ACTION:

PRELI1INARY EVALUATION OF THE ATTACHED REPORT INDICATES LEAD RESPONSIBILITY FOR FOLLOW-UP AS SHOWN BELOW:

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NRR [ NMSS O OTHER [

FFMS 800115.0 8 83 3

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February 24, 1978 .

Serial No. 417 m aa y% EDISON Docket No. 50-346 E

License No. NPF-3 h,0(,

.e* ,. e... -m (4194 2S9 $242 Mr. James G. Keppler Regional Director, Region III _

Office of Inspection & Enforce =ent " 1'OOO ,

U. S. Nuclear Regulatory Con.Lission 799 Roosevelt Road Glen Ellyn, Illinois 601.37

Dear Mr. Keppler:

In accordance with 10CFR Part 21.21(b), this is a report of a defect in components ins.alled in the Davis-Besse Nuclear Power Station Unit No. 1. The components involved are the control rod drive system trip circuit breaker cabinets.

These circuit breaker cabinets were supplied by Babcock & Wilcox.

The defect involves the veld used in the mounting of these cabinets.

Recent inspectica shows that the welds (both inside and outside the cabinets) are of a shorter length than those used on the cabinet that was qualified by a shaker table test. Although the existing welds may, in fact, be adequate for this installa-tion (the shaker table test was more severe than required to qualify the cabinets for Davis-Besse Unit No. I service), we consider the existing installation to be an unanalyzed installation. The safety hazard which could be created by this defect is, if the cabinet installation failed during a seismic event, it could beccme impossible to trip the control rod drive trip breakers. This capability is required by General Design Criterion 19. There are four cabinets (C4603, C4606, C4612 and 04806) containing this defect at Davis-Besse Unic No. 1.

On February 21, 1978, the deviation was evaluated by Toledo Edison to he a defect.

This matter was reported to your Mr. T. Tambling on February 21, 1978.

The corrective action to be taken is to add additional weld length to conform with the design that was qualified by test. The corrective action will include deenergizi.

the breaker cabinets to perform velding inside the cabinets. Until this welding has been ccmpleted, the control roca operators will be provided with an emergency procedure to locally trip the feeder breakers on the BE and BF buses to provide a backup in the event more than two of the four control rod drive trip circuit breakers fail to open as designed. Wa expect to complete this additional velding during the i

April outage.

This information has not been given to other licensees or purchasers.

Yours very truly, M/

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