ML17258A143

Requests That Licensee Continue to Inspect Low Pressure Turbine Discs on Schedule Designed to Minimize Probability That Crack Would Cause Disc to Rupture.Appraisal of Westinghouse Approach Presented in Encl Safety Evaluation

ML17258A143
Person / Time
Site:	Ginna
Issue date:	08/28/1981
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Maier J ROCHESTER GAS & ELECTRIC CORP.
References
LSO5-81-08-080, LSO5-81-8-80, NUDOCS 8109110039
Download: ML17258A143 (5)

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.'>,dPIKjg UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 August 28, 1981 Docket No. 50-244" LS05-81-08-080'" "

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~ t ter. John tlaier Vice President Electric and Steam Production Rochester Gas 8 Electric Corporation 89 Ea'st Avenue Rochester, New York: 14649

SUBJECT:

TURBINE DISC 'CRACKING (GINNA)

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II>S,,WC'aamee COMMI$5ON By letter d'ated February 25, 1980 we informed all 'licensee/users of Westinghouse low-pressure turbines that stress corrosion'cracks were being found i'n the 'keyway and bore areas of low-pressure'iscs.,'.

Becau'se'hese cracks were considered to increase the probability of di'sc failure we requested that you,perform ultrasonic inspections on your low-pressure dis'cs and justify that your plant could continue to operate s'afely.

All Westinghouse

'low-'pressure turbines at operating nuclear power plants have now been inspected, at-least once, for keyway and bore cracks.

Indica-tion of, one or both types of these cracks has been found at 20 plants.

Al-though all factors related to cracking have not been positively established, operating, experience indicates that crack initiation and growth are related to disc temperature and material characteristics.

Westinghouse is continuing to evaluate the effect of other manufacturing and operational variables.

Until a, satisfactory solution can be found we believe that it would, be pru-dent for you to continue inspecting your low-pressure turbine discs on a

schedule designed to minimize the probability that a crack will form and grow to. a depth that would cause a disc to rupture.

Westinghouse has deve-loped a =method to determine safe inspection and re-inspection frequencies and. has submitted this -information in Memorandum MSTG-l-P, June 1981 (Pro-prietary) for review by the NRC staff.

I II Our appraisal of the Westinghouse approach is presented in the enclosed Safety Evaluation.

Me conclude that inspection schedules based on the recomIendations in the Westinghouse Memorandum will provide an acceptably high degree of assurance that discs will be inspected before cracks can grow to a size that could cause disc failure at speeds up to design speed.

In our Safety Evaluation we list four criteria for an acceptable inspection schedule.

I request that you comit to use these criteria for'uture disc

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. Hr. John Haier August 28,'981 inspections.

He believe that such a comitment will reduce the probability for a safety problem to such a degree that the NRC staff would no longer need to monitor your turbine inspections except through the normal activi-ties of our Office of Inspection and Enforcement.

Your comitment would also eliminate the need for you to report these inspection results to the staff or to transmit the computerized disc data sheets that are prepared by Westinghouse.

Your response to this request should be submitted within 30 days of re-ceipt of this letter.

I also take this opportunity to advise you that on June ll, 1981 Hestingoo house transmitted two proprietary reports related to turbine missiles for NRC staff review and evaluation.

He have been advised by Westinghouse that the methodology described in these reports was used to provide its customers with estimates of the probability of disc rupture from stress corrosion cracking and with analyses of potential missile energies.

He shall provide Westinghouse with our evaluation of this methodology as soon as our resources permit.

Sincerely, Original signed by Dennis H. Crutchfield, Chief Operating Reactors Branch 85 Division of Licensing

Enclosure:

Safety Evaluation cc w/enclosure See next page DISTRIBUTION Docket NRC PDR Local PDR NSIC TERA ORB REading DCrutchfield HSmith RSnaider ACRS (10)

OELD OI&E (3)

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Nr. John E. Maier August 28, 1981 CC Harry H. Yoigt, Esquire

LeBoeuf, Lamb, Leiby'nd HacRae 1333 New Hampshire

Avenue, N. M.

Suite 1100 Mashington, D. C.

20036 Nr. Michael Slade 12 Trailwood Circle Rochester, New York 14618 Ezra Bialik Assistant Attorney General Environmental Protection Bureau New York State Department of Law 2 Morld Trade Center New York, New. York 10047.

Jeffrey Cohen New York State Energy Office Swan Street Building Core 1, Second Floor Empire State Plaza

Albany, New York 12223

Director, Bureau of Nuclear Operations.

State of New York Energy Office Agency Building 2 Empire State Plaza

Albany, New York 12223 Rochester Public Library 115 South Avenue Rochester, New York 14604 Nr. Thomas B. Cochran Natural Resources Defense Council, Inc.

1725 I Street, N. M.

Suite 600 Washington, D; C.

20006" U. S. Environmental Protection Agency Region II Office ATTN:

Regional Radiation Representative 26 Federal Plaza New York, New York 10007 Herbert Grossman, Esq.,

Chairman Atomic Safety and Licensing Board U. S. Nuclear Regulatory Coomission Washington, D. C.

20555 Dr. Richard F.. Cole Atomic Safety and Licensing Board U. S. Nuclear Regulatory Commission Mashington, D. C.

20555 Dr. Emmeth A. Luebke

, Atomic Safety and Licensing Board U. S. Nuclear Regulatory Comnission Mashington, D. C.

20555 Supervisor of the Town of Ontario 107 Ridge Road West

Ontario, New York 14519 Resident Inspector R. E. Ginna Plant

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c/o U. S.

NRC 1503 Lake Road

Ontario, New York 14519 I