ML20209B350

Submits Torus Shell & Coupon Corrosion Rate Determination for Nmpns,Unit 1.Torus Meets ASME Code Requirements,Iaw NRC 920825 & 940811 SERs

ML20209B350
Person / Time
Site:	Nine Mile Point
Issue date:	06/25/1999
From:	Abbott R NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NMP1L-1445, NUDOCS 9907060406
Download: ML20209B350 (2)

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Niagara $ Mohawk' Richard B. Abbott Phone: 315.349.1812 Vice President Fax: 315.349.4417 NuclearEngineering dune 25, 1999 NMPIL 1445 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE: Nine Mile Point Unit 1 Docket No. 50-220 DPR-63

Subject:

Tonts Shelland Coupon Convslon Rate Detennination Gentlemen:

In accordance with the Nuclear Regulatory Commission's (NRC's) Safety Evaluation Reports (SERs) of August 25,1992, and August 11,1994, Niagara Mohawk Power Corporation (NMPC) installed sample coupons of the same material as that of the torus shell during the 1993 refueling outage. These coupons were placed in the torus with approximately one-half of the coupon above the water line and one-half below the water line. The corrosion rates obtained from the coupons are compared once per refueling outage to the corrosion rates obtained from the Ultrasonic Testing (UT) measurements of the shell with the most conservative corrosion rate being used to make future cormsion rate determinations. The two d SERs require that the results of this comparison be submitted to the NRC within approximately 60 days of completing the coupon inspections.

pg Laboratory and engineering analysis of the coupons removed during the 1999 refueling outage indicates an average corrosion rate of 0.534 mils per year including one standard deviation.

The maximum average corrosion rate as determined from UT measurements of the torus shell and a linear regression analysis is 0.653 mils per year. This second value represents the most conservative corrosion rate, which does not exceed the assumed maximum conesion rate of 1.26 mils per year stated in the NRC SER dated August 11, 1994. Therefore, the torus meets ASME Code requirements.

NMPC will continue to perform torus thickness measurements and coupon corrosion analyses in accordance with the August 11,1994, SER to ensure that the torus continues to meet ASME Code requirements.

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Very truly yours, 020013 Med - 8 4/J/

9907060406 990625 0 Richard B. Abbott

! DR ADOCK 0500 Vice President Nuclear Engineering RBA/IAA/ kap Nine Mae Point Nudear Station RO. Box 63, Lycoming New Yo* 13093-0063

• www.nimo.com

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xc: Mr. H. J. Miller, NRC Regional Administrator Mr. S. S. Bajwa, Section Chief PD-I, Section 1, NRR Mr. G. K. Hunegs, NRC Senior Resident Inspector Mr. D. S. Hood, Senior Project Manager, NRR Records Management i

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