ML20030D649

Forwards Safety Evaluation Re Criteria for low-pressure Nuclear Turbine Disc Insp.Response Should Be Submitted within 30 Days

ML20030D649
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	08/28/1981
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Counsil W CONNECTICUT YANKEE ATOMIC POWER CO.
Shared Package
ML20030D650	List: ML20030D649 ML20030D652
References
LSO5-81-08-078, LSO5-81-8-78, NUDOCS 8109140130
Download: ML20030D649 (3)

Text

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August 28, 1981 Docket No. 50-213 LS05-81-08-078

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-3 Mr. W. G. Counsil, Vice President T

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SUBJECT:

TURBINE DISC CRACKING (HADDAM NEtx

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By letter dated February 25, 1980 we informed all licensee / users of Westinghouse low-pressure turbines that stress corrosion cracks were being found in the keyway and bore areas of low-pressure discs. Because l

these cracks were considered to increase the probability of disc failure we requested that you perform ultrasonic inspections on your low-pressure i

discs and justify that your plant could continue to operate safely.

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 icw-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-1-P, June 1981 (Pro-prietary) for review by the NRC staff.

Our appraisal of the Westinghouse approach is presented in the enclosed Safety Evaluation. We conclude that inspection schedules based on the recomendations in the Westinghouse Memorandum will provide an acceptably high degree of-assurance tnat 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 future disc 8109140130 810828 PDR ADOCK 05000213 0

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4.1 Mr. W. G. Counsit August 28, 1981 l

inspections. We believe that such a comitment will reduce the probability l

for a safety problem to such a degree that the NRC staff would no longer need to monitor your turbine inspections except through the rormal activi-ties of our Office of Inspection and Enforcement. Your commitment would also eliminate the need for you to report these inspection results to the staff or to transmit the computerized disc dats sheets that are prapared by Westinghouse.

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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 11, 1981 Westing-house transmitted two prcprietary reports related to turbine missiles for NRC staff review and evaluation. We have been advised by Westinghouse that the methodology described in these reports was used to provide its l

customers with estimates of the probability of disc rupture from stress corrosion cracking and with analyses of potential missile energies. Se shall provide Westinghouse with our evaluation of this methodology a>;

soon as our resources permit.

Sincerely.

Original signed by l

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Dennis H. Crutchlield, Chief l

Operating Reactors Branch 45 l

Division of Licensing i

Enclosure:

Safety Evaluation DISTRIBUTION Docket cc w/ enclosure NRC PDR Local PDR l

See next page ORB Reading NSIC TERA l

DCrutchfield HSmith WPaulson ACRS (10)

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Mr. W. G. Counsil August 28, 1981 cc Day, Berry & Howard

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Counselors at Law One Constitution Plaza Hartford, Connecticut 06103 Superintendent Haddam Neck Plant RFD #1 Post Office Box 127E East Hampton, Connecticut 06424 Mr. Richard R. L.,Jdenat Manager, Generation Facilities Licensing

• Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101 Russell Library 119 Broad Street Middletown, Connecticut 06457 Board of Selectmen Town Hall Haddam, Connecticut 06103 Connecticut Energy Agency ATTN: Assistant Director Research and Policy Development Departnent of Planning and Energy Policy 20 Grand Street Hartford, Connecticut 06'06 U. S. Envii.. mental Protection Agency Region I Office ATTN:

Regional Radiation Representative JFK Federal Building Boston, Massachusetts 02203 Resident Inspector Haddam Neck Nuclear Power Station c/o U. S. NRC East Haddam Post Office East Haddam, Connecticut 064iJ E

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