ML19345H327
| ML19345H327 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 05/07/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W CONNECTICUT YANKEE ATOMIC POWER CO. |
| References | |
| LSO5-81-05-008, LSO5-81-5-8, NUDOCS 8105200117 | |
| Download: ML19345H327 (3) | |
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NRC PDR L PCR VAy 7 1981 ORB #5 reading Docket No. 50-213 DCrutchfield LS05 05-008 WHazel ton WRoss RCaruso
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/O Mr. William G. Counsil, Vice president
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TERA g;n 15 Connecticut Yankee Atomic Power Company Post Office Box 270 NSIC 6,
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you provided revife'dh g #
By letters dated February 25, and April 15, 1981, data generated by Westinghouse regarding the integrity of the low pres turbine discs at the Haddam Neck Plant along with supplemental information regarding your evaluation of the revised data. We had requested this information so that the staff could deternine whether the Haddam Neck turbine could continue to operate until the scheduled refueling outage in October 1981.
In your letter you stated that the input data you used in your technical evaluation is the most recent as supplied by Westinghouse and transmitted to us in your February 25, letter.
The operating time basis is a total of 10,585 hours0.00677 days <br />0.163 hours <br />9.672619e-4 weeks <br />2.225925e-4 months <br /> from the May 1980 inspection to the October,1981 refueling outage. The disc which is limiting is the number two-generator end of low pressure turbine number tu with a flaw depth of 0.438 inches (the maximum NDE flaw reported by Westinghouse is 0.378 inches, plus 0.06 inches measurement uncertainty) and a crack growth rate of 2.94 x 10-5 inches / hour. Westinghouse reports a fracture toughness of 198 ksi'/Iiiand a critical crack size of 1.71 inches.
Given the initial conditions identified above, and utilizing the Westing-house analytica.1 methodology you predicted the crack depth at the October refueling outage to be 0.75 inches. A comparison of your predicted crack to the critical crsck size of 1.71 inches shows that the predicted flaw will not exceed 44% of the critical flaw size with continued operation until Octcber 1981. Yer conclude that this margin is ample to technically substantiate continued safe operation.
Your further assessment of the Westinghousa methodology has IV. you to conclude that these crack growth predictions are conservative, based on
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(1) tse of plant specific data yields a crack growth rate prediction which is approximately 18% lower than that utilized in the above evalua tion.
(2) The critical crack size was detennined fmm the Westinghouse K-solution. Comparison of this approach to Paris and Tada's or Raju and Newman's X-solutions for surface cracks indicates that the Westinghouse solution for stress intensity factors is conservative by approximately 15%.
(3) The bore stress utilized in this evaluation is the maximum tensile stress associated wii.h plant startup, which is the condition at which the potential for brittle fracture is considered to be the greatest. Power operation, which is the mode you anticipate maintaining until the October outage, results in a tensile bore stress lower than that asstmed in the evaluation.
On the basis of our independent calculations, we have determined that the predicted crack depth at the October refueling cutage will indeed be less than one-half of the critical crack size, and we have, therefore, concluded that this margin is adequate to justify continued, safe, full-power operation until the outage. This letter documents our previous telephone conversations and confinns our understanding of your plan to re-inspect the low pressure tuttine discs during the 1981 refueling outage.
The staff is continuing its analysis of fabrication and operation data for Westinghouse turbines. We plan to raview our interim position when this information and the results of re-inspections of several turtines have been evaluated. We shall notify you if our reassessment affects Haddam Neck.
We appreciate your continued cooperation in this matter.
Sincerely, Dennis M. CnJtchfield, Chief Operating Reaccors Branch f5 Division of Licensing cc: See next page V
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OFFICIAL RECORD COPY
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- r. !;. 3. Ccunsii Cc Day, Serry & Howard U. S. Envirenrantal Prceectica Ccunselors at Law Agency Cne Ccnstitution Plaza Regicn ! Office Har:ferd, Ccndecticu 06103 ATTN: EIS COORDINATOR JFK Federal Suilding Superintendent Besten, Massachusetts 02203 Haddar Neck Plant RFD #1 Residen Ins;:ecter Pes: Office Sex 127E Hadcam Neck Nuclear Pcwer Station East Hampton, Ccnnecticut C6n4 c/o U. S. NRC East Haddam Pcs-Office Mr. J ares R. Himmelwri ght Eas: Haddam, Ccnnecticut 06423 Northeast Utilities Service Ccmpany P. O. Box 270 Har ferd, Ccnnecticut 06101 xussell Library 119 Brcad Street Middle:cwn, Cennecticut 06457 Scard of Selectmen Tcwn Hall Haddam, Ccnnecticut 06101 Connecticut Energy Agency ATTN: Assistant Directer Research and Policy Develc; ment Oe;:antent of Planning and Energy Policy 20 Grand Street Hartford, Connecticut 06106 Cirecter, Criteria and Standards Divisien Office of Radiatien Programs (ANR 460)
U. S. Ervirencental Prctection Agency Washingten, D. C.
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