ML20029A832
| ML20029A832 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 02/27/1991 |
| From: | Wallace E TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9103040340 | |
| Download: ML20029A832 (2) | |
Text
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U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20535 Centlemen:
l 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) - 10 CFR 50.46 A%TAL REPORT
Reference:
1.
TVA's letter to NRC dated March 5, 1990, "Sequoyah Nuclear Plant (SQN) - Exemption to 10 CFR 50.46(a)(1) For Operating Cycle 4" 2.
TVA letter to NRC dnted January 12, 1990, "Sequoyah Nuclear Plant (SQN) - Technical Specification (TS)
Change 89-25" 10 CFR 50.46 requires reporting, on at least an annual basis, each change l
to or error discovered in an acceptable loss of coolant accident (LOCA) i evatuation model or in the application of such a model that affects the peak clad temperature (PCT) calculation.
The purpose of this letter is I
to provide that report.
As indicated in Reference 1, SQN's exemption to 10 CFR 50.46(a)(1) would expire when the evaluation presented by Reference 2 became effective after removal of the upper head injection (UHI) during each units' l
l Cycle 4 refueling outage.
Reference 2 provided the calculated PCT, with any associated error or changes to the LOCA model, up to the time of restart for either units' Cycle 4 refueling outage.
Since these l
restarts, the large break LOCA PCT has been increased by 12 degrees Fahrenheit (F) to 2,013 degrees F.
The small break LOCA PCT bns not been l
impacted and remains at 2,105 degrees F.
The 12 degrees F inccease in i
the large break is a result of the current SQN cores containing a mixture l
of Vantage 5 Hybrid and standard Westinghouse Electric Corporation fuel.
It should be noted that several potential issues (e.g., cold leg streaming and chopped cosine flux distribution) have been identified that could impact the calculated PCT for both large and small break LOCAs.
The potential issues have had PCT margir. allocated by Westinghouse f
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{DR ADOCK 05000327 iyo 1
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U.S. Nuclear Regulatory Commission February 27, 1991 to ensure the cumulative effects are tracked such that the 10 CFR 50.46 PCT limit of 2,200 degrees F is not exceeded.
At the present time, these issues have not been resolved and the permanent impact on the PCT bas not been quantified. These issues are being resolved through efforts with Westinghouse. Upon resolution of these issues, any impacts on the PCT will be reported in accordance with the reporting requirements of 10 CFR 50.46.
Please direct questions concerning this issue to J. D. Smith at (615) 843-6672.
Very truly yours, TENNESSEE VALLEY AUT110RITY
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G. Wallace, Manager Nuclear Licensing and Regulatory Affairs cc:
Ms. S. C. Black, Deputy Director Project Directorate II-4 U.S. Nuclear Regulatory Commission One White Flint, North 11535 Rockville Pike Rockville, Maryland 20852 Mr. J. N. Donohew, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Furry Road Soddy Daisy, Tennessee 37379 Mr. B. A. Wilson, Project Chief U.S. Nuclear Regulatory Ccmmission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
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