NOC-AE-02001233, CFR50.46 Annual Report of ECCS Model Revisions

CFR50.46 Annual Report of ECCS Model Revisions

ML020440436
Person / Time
Site:	South Texas
Issue date:	01/09/2002
From:	Leazar D South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-02001233
Download: ML020440436 (5)

Text

Nuclear Operating Company south Tews PrFetElectric Generaing Station PO. Box2&9 Wadsworth, Texas 77483 .

January 9, 2002 NOC-AE-02001233 File No.: G25 10CFR50.46 STI:31390130 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 10CFR50.46 Annual Report of ECCS Model Revisions

References:

1) Letter from D. A. Leazar to NRC Document Control Desk, "10CFR50.46 Annual Report of ECCS Model Revisions and 30 Day Report of Significant ECCS Model Changes," dated December 13, 2000 (NOC-AE-000980).

Pursuant to 10CFR50.46(a)(3)(ii), the South Texas Project (STP) submits this annual report concerning revisions to the accepted Emergency Core Cooling System (ECCS) evaluation model at STP Units 1 and 2. During 2001, a single Peak Cladding Temperature (PCT) assessment was applied to address errors in the shared Unit 1 / Unit 2 Large Break LOCA evaluation model. A Unit 2 Cycle 9 specific PCT assessment was applied to address a reload safety analysis limit violation. The sum of the absolute values of the Large Break LOCA evaluation model PCT assessments is less than 50'F. The Large Break LOCA evaluation model assessments, therefore, do not constitute a significant change as defined in 10CFR 50.46.

No PCT assessments were applied to the unit-specific Small Break LOCA evaluation models.

During 2001, the Large Break LOCA PCT increased from 2169°F (Ref. 1) to 2175°F.

The 6°F increase is the result of a PCT penalty, developed by Westinghouse, to address errors in the expressions used to evaluate radiation heat exchange between the rod, grid, and fluid during the reflood phase of the transient. The LBLOCA PCT penalty was developed through representative plant calculations. A schedule for reanalysis is not provided for the Large Break LOCA analysis since the revised PCT remains below the regulatory limit and the value of the PCT change is less than 50'F. f N

NOC-AE-02001233 Page 2 A second, 3 'F, Large Break LOCA PCT assessment was applied for Unit 2 Cycle 9 to address a cycle-specific violation of limits associated with the PCT benefit developed in 2000 for reduced Gamma Energy Deposition Model (GEDM) factors. A cycle-specific calculation was performed by Westinghouse to determine the PCT impact of the necessary GEDM factor increases. As a result of the PCT assessment, the Unit 2 Cycle 9 Large Break LOCA PCT increased from 2175°F to 2178 0 F.

The acceptance criteria for all models continue to be satisfied. Attachment 1 provides the current ECCS evaluation model PCT rack-ups. Attachment 2 provides a detailed description of the ECCS evaluation model changes that impacted the calculated PCT in 2001.

If you should have any questions concerning this matter, please contact Mr. Charles R.

Albury at (361) 972-8901 or me at (361) 972-7795.

D. A. La Director Nuclear Fuel and Analysis jmw/kaw Attachments cc: Licensing Library RMS

NOC-AE-02001233 File No.:G25 STI No.: 31390130 Page 3 cc:

Ellis W. Merschoff Jon C. Wood Regional Administrator, Region IV Matthews & Branscomb U.S. Nuclear Regulatory Commission 112 East Pecan, Suite 1100 611 Ryan Plaza Drive, Suite 400 San Antonio, Texas 78205-3692 Arlington, Texas 76011-8064 Institute of Nuclear Power Mohan C. Thadani Operations - Records Center Project Manager 700 Galleria Parkway U. S. Nuclear Regulatory Commission Atlanta, GA 30339-5957 1 White Flint North, Mail Stop: O-7D1 11555 Rockville Place Richard A. Ratliff Rockville, MD 20852-2738 Bureau of Radiation Control Texas Department of Health Cornelius F. O'Keefe 1100 West 49th Street U. S. Nuclear Regulatory Commission Austin, TX 78756-3189 P. 0. Box 289, Mail Code MN1 16 Wadsworth, TX 77483 R. L. Balcom/D. G. Tees Reliant Energy, Inc.

A. H. Gutterman, Esquire P. 0. Box 1700 Morgan, Lewis & Bockius Houston, TX 77251 1800 M. Street, N.W.

Washington, DC 20036-5869 C. A. Johnson/A. C. Bakken, III AEP - Central Power and Light Company M. T. Hardt/W. C. Gunst P. 0. Box 289, Mail Code: N5022 City Public Service Wadsworth, TX 77483 P. 0. Box 1771 San Antonio, TX 78296 U. S. Nuclear Regulatory Commission Attention: Document Control Desk A. Ramirez/C. M. Canady Washington, D.C. 20555-0001 City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704

NOC-AE-02001233 Attachment 1 Page 1 of 1 ATTACHMENT 1 2001 YEAR END PCT RACK-UPS Unit 1 and Unit 2 Large Break LOCA:

2000 Year End Large Break LOCA PCT (Reference 1) 2169 OF

+ 6°F LOCBART Cladding Emissivity Errors (Unit 1 and Unit 2)

+ 3°F Reduction in the PCT Benefit Associated with Reduced Gamma Energy Deposition Model (GEDM) Factors for Unit 2 Cycle 9 Revised Year End Large Break LOCA PCT (Unit 1 / Unit 2) 2175 OF / 2178 OF Unit 1 Small Break LOCA:

1578 OF Unit 1 Small Break LOCA PCT (Reference 1)

Unit 2 Small Break LOCA:

Unit 2 Small Break LOCA PCT (Reference 1) 195 1F

NOC-AE-02001233 Attachment 2 Page 1 of 1 ATTACHMENT 2 2001 PCT ASSESSMENTS LOCBART Cladding Emissivity Errors The cladding surface emissivity values used in the equations which model radiation heat exchange between the rod, grid, and the fluid during the reflood phase of the transient were determined to be lower than that which would be expected during the reflood phase of a LBLOCA. Representative plant calculations were used to evaluate the impact of the errors on the calculated LBLOCA PCT. For the South Texas Project, a 6°F penalty has been applied to conservatively bound the effect of the errors.

Reduction in the PCT Benefit Associated with Reduced Gamma Energy Deposition Model (GEDM) Factors for Unit 2 Cycle 9 During 2000, Westinghouse reduced the GEDM factors assumed in the Large Break LOCA analysis. The use of reduced GEDM factors resulted in a 20'F Large Break LOCA PCT benefit (Reference 1). As documented in Reference 1, the reduced GEDM factors are verified for each cycle through the reload safety analysis process. For Unit 2 Cycle 9, the reload core design could not support the reduced GEDM factors. Westinghouse performed a cycle-specific evaluation to account for the required GEDM factor increase. The increase resulted in a reduction of the previously reported benefit from 20 'F to 17'F for Unit 2 Cycle 9.