ML20205H735
| ML20205H735 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/13/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20205H739 | List: |
| References | |
| NUDOCS 8608200140 | |
| Download: ML20205H735 (2) | |
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U TENNESSEE VALLEY AUTHORITY SN 157B Lookout Place AU613 806 Director of Nuclear Reactor Regulation Attention: Mr. B. Youngblood, Project Director PWR Project Directorate No. 4 Division of Pressurized Water Reactors (PWR)
Licensing A U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Dear Mr. Youngblood:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 Discussions in 1984 between NRC and Westinghouse Electric Corporation, regarding methodology used for analyzing main steamline break mass and energy releases, disclosed potential liapact upon calculated primary containment temperatures and pressures for a number of utilities. Following notification of this issue. TVA identified the main steam valve vaults as also being affected and met with NRC in July 1984 for further discussion. Specifically, during certain main steamline break accidents inside containment or main steam valve vaults outside containment, portions of steam generator tubes will be uncovered which would result in the release of superheated steam. The resolution of this issue for inside containment is summarized in Volume II of the TVA Nuclear Performance Plan (NPP).
For the valve vaults, the effect of superheated steam was originally estimated to increase temperatures by 1500F to 2000F, potentially invalidating the environmental qualification of electrical equipment located in those areas.
i In order to address this concern, TVA has undertaken three parallel programs which are also discussed in Volume II of the NPP. The option which TVA believes will resolve the issue satisfactorily is the subject of this letter.
TVA is submitting the enclosed report entitled " Main Steamline Break Environmental Qualification Study for Tennessee Valley Authority Sequoyah Units 1 and 2 Main Steam Valve Vaults," dated July 1986 for formal review by NRC. This study reflects comments received from NRC as a result of discussions and meetings held during the preparation of the report and NRC's review of the draft, following informal submittal by TVA on July 9, 1986. The final report incorporates NRC comments from that review, as well as changes made by TVA. The only variations between the draft and final versions are as follows:
1.
Section 3.3 includes additional discussion of the blowoff roofs.
2.
Figure 4.3-1 was added to illustrate a simplified flow diagram of main steam.
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Editorial changes were made to Sections 2.0, 3.5, 6.1, 6.2, 6.3, 6.4, and 8.0.
4.
Mass and energy release tables (3) requested from WCAP-10961 are provided to NRC by copy of Westinghouse letter NS-NRC-86-3148 from E. P. Rahe, Jr.,
to H. L. Thompson, Jr., dated July 10, 1986.
In summary, the enclosed report shows that the safety-related electrical equipment located in the valve vaults will perform its intended function at the temperatures that occur during main steamline breaks.
If you have any questions concerning this matter, please get in touch with B. L. Hall at 615/870-7459.
Very truly yours, TENNESSEE VA EY AUTHORITY
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R. Gridley, D ector Nuclear Safet and Licensing Enclosure cc (Enclosure):
U.S. Nuclear Regulatory Commission Region II Attn:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. Carl Stahle Sequoyah Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814
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