ML20127P476
| ML20127P476 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/28/1993 |
| From: | Fenech R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9302010299 | |
| Download: ML20127P476 (4) | |
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Tenressee Va! icy Authornty Post Office Box 2001 SoddcDisy, Ter.nmoe 373797x)0 l
Robert A. Fenech Vcc Preradent, Sequoyah Nucioar Plant anuary 28, 1993 i
U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk l
Washington, D.C. 20555 Gentlemen:
In the Matter of
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' Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - NRC INSPECTION REPORT NOS. 50-327/90-18 AND 50-328/90-18'- UNRESOLVED ISSUE (URI) 88-12 COMPONENT' DAMPING VALUES
Reference:
WA letter to NRC dated July 27, 1990, "Sequoyah Nuclear Plant (SQN) - NRC' Inspection Report Nos. 50-327/90-18 and 50-328/90-18" The purpose of this letter is to provide a_ revised response to Inspection Report.90-18 with respect to URI 88-12-08.
Thetlast response to.
URI-88-1_2-08 was contained in the above reference. This reference-indicated that the scope of the NRC concern reintes to the SQN.
seismic-margins review for mechan _ical components. This reference also indicated that the licensing basis for SQN, with respect to component damping values,_is three percent damping for the SQN safe shutdown earthquake (SSE). Based on conversations with NRC' staff, TVA's_ position on component c amping values is not-' acceptable to the staf f.
In an effort to move forward with resolution of this'. issue. TVA has performed preliminary _ scoping studies with a' component damping value.of two percent for the SQN SSE.
Based on these scoping studies, WA is revising its response provided in the above. reference with respect to URI 88-12-08, and will revise the SQN design basis te limit SSE damping
-to two percent for welded construction mechanical components of concern for SQN's' seismic margin program.
As a result of this change to the component damping value,'a reevaluation will be required. The components requiring reevaluation must satisfy all of the following bounding parameters.
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U.S. Nuclear Regulatory Commission Page 2 January 28, 1993 1.
Floor-or wall-mounted welded construction mechanical components required for safe shutdown. Specifically, the components aret a.
Floor-or wall-mounted tanks, heat exchangers, pressure vessels, and strainers and/or filters of welded construction.
b.
Required for safe shutdown as defined by SQN Design Basis Verification Program Calculation SQN-0SG7-048.
2.
Components that are located in rock supported structures.
Specifically, the components are located in structures listed in the Updated Final Safety Analysis Report Table 3.7.1-1, less the soil supported structures listed in Table 3.7.1-4.
3.
Components that are nonrigid (fundamental frequency less than 25 hertz).
4.
Components that
-ve been seismically analyzed after March 1982 using SSE damping val -
greater than two percent of critical.
It should be noted that the above reevaluation primarily will involve mechanical components previously evaluated for the restart of SQN.
IVA will complete the above reevaluation and implement any required modifications before restart from the Cycle 7 refueling outages.
The Units 1 and 2 Cycle 7 refueling outages are currently scheduled to start October 7, 1994, and April 7, 1995, respectively.
Based on a telephone conference with NRC staff on December 3, 1992, we anticipate the above revised position will allow for closure of URI 88-12-08.
If this effort is believed to not be acceptable for resolution, please inform TVA within 60 days.
Commitments contained in this letter are provided in the enclosure.
Please direct questions concerning this inaue to J. D. Smith at (615) 843-6672.
Sincerely,
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Robert A. Fenech Enclosure cc:
See page 3
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U.S. Nuclear Reguintory Commission-Page 3 January 28, 1993 Enclorure ec (Enclosure):
Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Mr. B. A. Wilson, Project Chief U.S. Nuclear Regulatory Commission Reg!on II' 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323-0199 m
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ENCLOSURE I
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1.
TVA will revise the appropriate design basis documentation to limit-safe shutdown earthquake damping to two percetit for welded construction mechanical components of concern for the SQN seismic margin program by May 3.-1993.
2.
TVA will complete a reevaluation of the affected mechanical.
components of concern for the SQN seismic margin program and implement any required modifications before restart from the Cycle 7 refueling outages.
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