ML20003J097
| ML20003J097 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/04/1981 |
| From: | Clark R Office of Nuclear Reactor Regulation |
| To: | Mayer L NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 8105080445 | |
| Download: ML20003J097 (2) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION I *y,% l j
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W ASHINGTON, D. C. 20555
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MAY 041981 Docket Nos. 50-282 and 50-306
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q Mr. L. O. Mayer, Manager gf M/if 0 7 IS8AT Nuclear Support Services
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Northern States Power Company 414 Nicollet Mall, 8th Floor Q
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Minneapolis, Minnesota 55401 1
Dear Mr. Mayer:
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In our July 21, 1980 letter, we concluded that the control rod guide thimble wear issue is resolved for the 14 x 14 fuel assemblies designed by Westinghouse for the Prairie Island units. We, also, stated that our review of this subject for facilities using fuel assemblies designed by Exxon was continuing.
We believe that the propensity for guide thimble tube wear in Exxon reload fuel should be, to a first approximatior., equivalent to that in Westinghouse fuel in the same plant. Examinations of Exxon fuel that was discharged from H. B. Robinson, Unit 2, as reported by Exxon letter dated February 25, 1980, revealed no through-wall wear nor major differ-ences in the wear from that wear which was measured on Westinghouse fuel that was discharged from Pt. Beach, Units No.1 and 2.
The Exxon examinations were performed on 5 fuel assemblies that had been under control rod banks for one cycle of reactor operation. One assembly was from Cycle 4 and four assemblies were from Cycle 5 operation. Of the 100 guide thimble tubes examined by an eddy current testing (ECT) method, only 11 had detectable wear (i.e., wear greater than about 3 mils local wall thinning). The ECT measurements did not reveal the azimuthal distribution of the wear, but if the worst wear that was detected had been concentrated on one side of the guide thimble tube wall, it would have indicated that a minimum of 23% of the wall thickness remained.
We conclude that (a) the degree of wear measured by Exxon is acceptable, (b) the degree of wear in the Exxon fuel is similar to that in Westinghouse fuel, which we have found acceptable, and (c) the issue of guide thimble wear in Exxon-fuelcd/ Westinghouse-NSSS plants has been adequately resolved.
Sincerely,
.m Cw l-Rob t'A. C1'a'rk, Chief N
Operating Reactors Branch #3 Division of Licensing cc: See next page
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f.orthern States Power Ccreany cc:
Gerald Charnoffn Esquire Bernard M. Cranu:
Shaw, Pitte.an, Pctts and Trowbridge Bureau of Indian Affairs, COI 1E00 M Street, N.W.
831 Second Avenue South Washingen, D. C.
20035 Minneapolis, Minnesota 55432 Ms. Terry Hoffman Directer, Criteria and Standards Divisic.
Executive Director Office cf Radiaticn Progra=s (A'iR 450)
Minnescia Pollutien Centrol Agency U.S. Envirenrental Protecticn Agency 1935 W. County Road B2 Washingen, D. C.
20450 Reseville, Minnescia 55113 U. S. Envirenrental Prctection Agency The Environ.. ental Conservation Library Federal Activities Branch Minneapolis Public Library Regicn V Office 300 Nicollet Mall ATIN: EIS COORDINATOR Minneapolis, Minnesota 55401 230 South Dearcorn Street Chicago, Illinois 60504 Mr. F. P. Tierney, Plant Manager Prairie Island Nuclear Generating Plant Northern States Power Ccepany Reute 2 Welch, Minnesota 55039 Chairran, Public Service Ccrnission Jeclyn F. Olsen, Esquire of Wisconsin Special Assistant Atterrey General Hill Far=s State Office Building Minnescta Pollution Centrol Agency Madisen'dic cnsin 53702 1935 W. County Road B2 Reseville, Minntosta 55113 Robert L. Nybo, Jr., Chairran Minnesota-Wisconsin Boundary Area Ccenission 519 Second Street Hudson, Wisconsin 54016 U.S. Nuclear Regulatory Cornission Resident Inspectors Office Reute #2, Box 500A Welch, Minnesota 55089 Mr. Jchn C. Davidsen, Chairran Goedhue County Board of Cornissioners 321 West Third Street Red Wing,-Minrrncta 55066
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