ML20217F581

Forwards Insp Data & Naesco Evaluation of a EDG Exhaust Insp Conducted on 990407.Insp Ensured That Unacceptable Wall Thinning Will Not Occur During 40-year Design Lifetime of Sys

ML20217F581
Person / Time
Site:	Seabrook
Issue date:	10/13/1999
From:	Feigenbaum T NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NYN-99089, NUDOCS 9910210005
Download: ML20217F581 (6)

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North Atlantic Energy Senice Corporation O ;NO ' o ""* 3ao k.

Seabrook, Nil 03874 l

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(co3>474932i The Northeast Utilities System I i

October 13,1999 l

Docket No. 50-443 NYN-99089 United States Nucleh Regulatory Commission .

Attention: Document Control Desk Washington, D.C. 20555 Seabrook Station Emergency Diesel Generator Exhaust Inspection

. Enclosed is the inspection data and the North Atlantic Energy Service Corporation (North

~ Atlantic) evaluation of the "A"' Emergency Diesel Generator (EDG) Exhaust Inspection conducted on April 7,1999. The purpose of the inspection is to ensure that unacceptable wall thinning will not occur during the 40-year design lifetime of the system. The results of this inspection are being forwarded to the Nuclear Regulatory Commission (NRC) for your review and eveluation as. committed in. section 9.5.8 of: NUREG-0896 " Safety Evaluation Report Rc!:ted to the Operation of Seabrook Station, Units 1 and 2," dated March 1983.

North Atlantic has concluded that the EDG exhaust elbow is acceptable for continued operation l .and the observed loss of wall thickness will not exceed the code minimum required wall thickness within the'40-year. design lifetime of the system. The results of the first inspection conducted on the "A" EDG during refueling outage 05 were forwarded to the NRC by letter (NYN-97068)' dated June 27,1997. This concludes North Atlantic's commitment to inspect the EDG exhaust piping.' As a result, no further inspections are planned.

Should 'you have any questions regarding this matter, please contact Mr. James M. Peschel, Regulatory Compliance Manager, at (603) 773-7194.

Very truly yours, NORTH ATLANTIC ENERGY SERVICE CORP.

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-g'ph9I led C. Feir;c um Executive Vice President o and Chief Nuclear Officer 9910210005 991013-PDR ADOCK 05000443 g PDd

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i ec: H. J. Miller, NRC Regional Administrt .r J. T. Harrison, NRC Project Manager 1

R. K. Lorson, NRC Senior Resident Inspector

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1 ENCLOSURE 9 NYN-99089 :

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ULTRASONIC THICKNESS EXAMINATIONy///1'l 9 REPO LOCATION _DG //355 F24/A/ SYSTEM DS-WORK REQUEST N003/0

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DESCRIPTION OF EXAMINATION AREA AND RESULTS

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Page 1 of 1 ES1807.0129 Rev.I

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I Ev,aluatio.n The A" train' EDG exhaust elbow is acceptable for continued operation. This conclusion is based on the following rational:

The minimum wall thickness measured during the refueling outage 6 inspection is 0.530 inches i as identified at grid location N-4. A review of the baseline data for grid location N-4 indicates an initial thickness of 0.640 inches. Therefore, the maximum wear is 0.110 over the first ten-year period of plant operation. IIence, the total loss for the next 30 years of operation will be 0.330 inches. The predicted wall thickness over a 40-year expected life is 0.200 iraches. i Plant Calculation C-S-1-45623 indicates that the required code minimum wall thickness is 0.061

. inches, which is much lower thaa the predicted wall thickness of 0.200 inches.

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