ML20216E979
| ML20216E979 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/11/1998 |
| From: | Alexion T NRC (Affiliation Not Assigned) |
| To: | Cottle W HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 9803180215 | |
| Download: ML20216E979 (4) | |
Text
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March 11, 1998 Mr. William T. Cottle President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Sex 289 Wadsworth,TX 77483 SUEJECT:
FUEL ROD BOWING QUESTION ABOUT PHASE 1, ZlRLO-CLAD, FUEL !N SOUTH TEXAS PROJECT, UNITS 1 AND 2 (STP)
Dear Mr. Cottle:
By letter dated August 19,1997, the Nuclear Regulatory Commission (NRC) issued Amendment Nos. 8g and 76 for STP. The amendments revised Technical Specification (TS) 5.3.1, Fuel Assemblies, and TG 6.9.1.6, Core Operating Limits Report, to show use of an attemate (Phase 1) zirconium-based fuel cladding, ZlRLO, and limlied substitution of fuel rods by ZlRLO filler rods.
Following issuance of the amendments, questions have been raised from within the NRC staff regarding the possibility of a typical fuel rod bowing with the new fuel design. This question was initially discussed with your s3ff during a site visit by Dr. Dale A. Powers on October 27,1997.
Specifically, the new fuel design, in part, decreases the stress placed on the thimble tubes by allowing the fuel rods to be suspended much closer to the bottom nozzle such that with irradiation, the fuel rods will grow and touch the bottom nozzle early in the, first cycle of irradiation. The result is that the new fuel rods will basically be on the bottom nozzle throughout most of their residence in the core. This is expected to relieve stress on the thlmble tubes to help remedy the phenomenon of incomplete control rod insertion experienced with previous STP cores.
As a result of the specific design change discut ser. above, the staff now suspects that the possibility exists that fuel rod bowing behavior with the new fuel can be significantly different from other Westinghouse fuel designs. Previously, fuel elongation could be accommodated by fuel rod growth in either vertical direction (up or down). However, in the new fuel design, rod growth is very quickly limited to the upward direction only. In addition, having a 14 foot fuel rod length with the additional grid (compared to the 12-foot design) creates a potential for more resistance to growth and may result in bowing skewed toward the bottom of the core and potentially
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increased in magnitude.
The NRC staff, therefore, requests that data or analysis be provided that addresses fuel rod bowing for the new fuel design. If none is available, the staff requests that a plan for confirmatory post-irradiation examination be proposed. Such examination should be conducted 1
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William T. Cottle at the first refueling opportunity. The staff also requests that a response is provided within 90 days from the date of this letter. Should there be any questions on the above, I can be reached at (301) 415-1326.
Sincerely, g
Thomas W. Alexion, Project. anager Project Directorate IV-1 Division of Reactor Projects lil/IV Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499 cc: See next page l
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at the first refueling opportunity. The staff also requests that a response is provided within 90 days from the date of this letter. Should there be any questions on the above, I can be reached l
at (301) 415-1326.
Sincerely, ORIGINAL SIGNED BY:
Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects lil/IV Office of Nuclear Reactor Regulation Docket Nos. 50-498 ond 50-499 I
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Mr. William T. Cottle STP Nuclear Operating Company South Texas, Units 1 & 2 cc:
Mr. David P. Loveless Jack R. Newman, Esq.
t Senior Resident inspector Morgan, Lewis & Bocklus U.S. Nuclear Regulatory Commission 1800 M Street, N.W.
P. O. Box 910 Washington, DC 20036-5869 Bay City, TX 77414 Mr. Lawrence E. Martin A. Ramirez/C. M. Canady Vice President, Nuc. Assurance & Licensing City of Austin STP Nuclear Operating Company Electric Utility Department P. O. Box 289 721 Barion Springs Road Wadsworth,TX 77483 Austin, TX 78704 Office of the Govemor Mr. M. T. Hardt ATTN: John Howard, Director Mr. W. C. Gunst Environmental and Natural City Public Service Board Resources Policy P. O. Box 1771 P. O. Box 12428 San Antonio,TX 78296 Austin,TX 78711 Mr. G. E. Vaughn/C. A. Johnson Jon C. Wood Central Power and Light Company Matthews & Branscomb P. O. Box 289 One Alamo Center Mail Code: N5012 106 S. St. Mary's Street, Suite 700 Wadsworth, TX 74483 San Antonic, TX 78205-3692 INPO Arthur C. Tate, Director i
Records Center Division of Compliance & Inspection 700 Galleria Parkway Bureau of Radiation Control Atlanta, GA 30339-3064 Texas Department of Health 1100 West 49th Street Regional Administrator, Region IV Austin,TX 78756 U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suito 400 Jim Calloway Arlington,TX 76011 Public Utility Commission of Texas Electric industry Analysis D. G. Tees /R. L. Balcom P. O. Box 13326 Houston Lighting & Power Co.
Austin, TX 78711-3326 P. O. Box 1700 Houston,TX 77251 Judge, Matagorda County Matagorda County Courthouse 1700 Seventh Street Bay City, TX 77414 m