ML20206P219
| ML20206P219 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 12/30/1998 |
| From: | Krich R COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9901110021 | |
| Download: ML20206P219 (2) | |
Text
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Commonweahh Edison Company M
i 100 Opus Place l
Downers Grose. IL 6M15 5701 l
l December 30,1998 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington. D. C. 20555 - 0001 i
Subject:
Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455 l
Braidwood Station, Units 1 and 2 l
Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Steam Generator Laser Welded Sleeves l
References:
- 1) Letter from S. E. Thomas (South Texas Project Electric Generating i
Station) to U.S. NRC, " Notification of Revised Analysis Utilized in Evaluation of Steam Generator Tube Laser Welded Sleeving,"
dated September 24,1998.
- 2) Letter from R. A. Assa (U.S. NRC) to D. L. Farrar (Comed),"
l lsmance of Amendments," dated March 4,1994.
The purpose of this letter is to notify the Nuclear Regulatory Commission (NRC) that Byron and Braidwood Stations, Units 1 and 2, will be using the revised design basis l
information related to Westinghouse laser welded sleeves inside steam generator tubes at the tube support plate and tubesheet regions. This revised infuTnation is contained in WCAP - 13698/13699, Revision 2, Addendum 1, " Laser Welded Sleeves for % inch Diameter Tube eedring-Type and Westinghouse Preheater Steam c
Generators." These WCxPs have been previously provided to the NRC in the Reference i submittal for the South Texas Project Electric Generating Station, NRC
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Docket Nos. STN 50-498 and STN 50-499.
The sleeve qualification analysis for the South Texas Project is identical to that l
provided by Westinghouse to Commonwealth Edison (Comed) Company, therefore, l
WCAPs 13698 and 13699 will also apply to the laser-welded sleeves inside steam generator tubes at Byron Station and Braidwood Station. As discussed in a 4 g/;
teleconference, held between representatives of Comed and the NRC on October 22, 1998, Comed is referencing WCAPs - 13698 and 13699, Revision 2, Addendum 1, rather than providing an additional, separate submittal of these WCAPs.
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9901110021 981230 PDR ADOCK 05000454 P
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U.S. Nucigar Regulatory Commission Page 2 In the Reference 2 letter, the NRC issued amendments to the Facility Operating Licenses for Byron and Braidwood Station Units 1 and 2. The amendments allowed the installation of Westinghouse laser-welded sleeves inside steam generator tubes at the tube support plate and tubesheet regions. Recently, Comed was informed by Westinghouse Electric Company that analysis to evaluate the effect of revised operating conditions on steam generator tube laser welded sleeve inte0rity lead to the determination that the finite element model used to initially qualify the 0.015 inch weld width under-predicted the shear stress in these welds. The design of the laser welded sleeve is predicated on the design rules of Section 111 of the American Society of Mechanical Engineers (ASME) Code. Section Ill of the ASME Code provides two alternative approaches to qualify a component, by analysis or experiment. Utilizing conventional analysis techniques, it was determined the shear stress for the 0.015 inch min: mum weld width exceeded the ASME Code allowable limit. Consequently, a verification program using experimental analysis has been performed by Westinghouse Electric Company to show that the 0.015 inch weld remains in compliance with Section ill of the ASME Code.
The acceptability of the 0.015 inch laser weld was evaluated using pressure tests to establish the pressure retaining capability of the welds (i.e., primary stress), and a revised finite element analysis to evaluate fatigue usage in the welds. Overall, the verification effort shows that a minimum weld width of 0.015 inch for the tube / sleeve weld is acceptable and meets the requirements of the ASME Code.
The addendum to WCAP-13698, " Laser Welded Sleeves for % inch Diameter Tube Feedring-Type and Westinghouse Preheater Steam Generators," provides the revised design basis information for the 0.015 inch weld width. This report applies only to the qualification of the 0.015 inch laser weld width. The qualification of the sleeve and tube documented in earlier revisions of the generic topical and/or plant specific WCAP report still applies. All other aspects of the existing licensing documentation for laser welded sleeves are unaffected by the recent weld width verification effort and remain in effect.
Please address any comments or questions regarding this matter to Mr. Joseph A.
Bauer at (630) 6S3-7287.
Respectfully, R. M. Kric Vice President - Regulatory Services cc:
Regional Administrator-USNRC, Rlli NRC Senior Resident inspector-Braidwood NRC Senior Resident inspector-Byron
. G:\\NLA\\BYRBWD\\ laser welded sleeves. doc