NOC-AE-12002912, Submittal of 10 CFR 50.46 ECCS Evaluation Model Significant Change/Error Report

Submittal of 10 CFR 50.46 ECCS Evaluation Model Significant Change/Error Report

ML12310A383
Person / Time
Site:	South Texas
Issue date:	10/17/2012
From:	Dunn R South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-12002912
Download: ML12310A383 (5)

Text

Nuclear Operating Company South Texas Pm/cc Electric Generating Station PO. &x 289 Wadsmwrth. Texas 77483 -------

October 17, 2012 NOC-AE-12002912 10 CFR 50.46 STI: 33610705 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 10 CFR 50.46 ECCS Evaluation Model Significant Change/Error Report

References:

1. WCAP-10266-P-A, Revision 2, Addendum 3-A, Revision 1, "Incorporation of the LOCBART Transient Extension Method into the 1981 Westinghouse Large Break LOCA Evaluation Model with BASH (BASH-EM)," October 2007.

In accordance with the requirements of 10 CFR 50.46(a)(3)(ii), the STP Nuclear Operating Company (STPNOC) is submitting the enclosed South Texas Project Electric Generating Station Units 1 & 2 (STPEGS) Emergency Core Cooling System (ECCS) evaluation model significant change/error report. The attachment documents the 10 CFR 50.46 reporting text for the evaluation to estimate the effect of fuel pellet thermal conductivity degradation (TCD) and assembly power/peaking factor burn down in the South Texas Units 1 and 2 Appendix K Large-Break Loss-of-Coolant Accident (LBLOCA) analysis. The estimated effects for South Texas Units 1 and 2 were determined based on plant-specific calculations. The evaluation incorporated the approved LOCBART Transient Extension Method (TEM) (Reference 1) and met the Limitations and Conditions in Reference 1.

The revised LBLOCA Peak Cladding Temperature (PCT) rackup sheet is included in the attachment. The first line item in the 2012 ECCS Model Assessment section reflects the effects of updates to the codes and methods and is denoted as a "rebaseline" of the analysis of record (AOR). The second line item in this section reflects the combined effects of pellet TCD and assembly power/peaking factor burndown. While the combined effect of pellet TCD and assembly power/peaking factor burndown was estimated as 00 F, the change is characterized as significant per 10 CFR 50.46.

NOC-AE-12002912 Page 2 of 3 Schedule for Re-Analysis The resulting PCT continues to meet the criterion of 10 CFR 50.46(b)(1) (i.e., -< 2200 OF) with sufficient margin such that no reanalysis is required.

There are no commitments in this submittal.

If there are any questions, please contact Mr. Charles Albury at (361) 972-8901 or me at (361) 972-7743.

R.F. Dunn Manager Nuclear Fuel and Analysis cra

Attachment:

BASH-EM EVALUATION OF FUEL PELLET THERMAL CONDUCTIVITY DEGRADATION

NOC-AE-12002912 Page 3 of 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 1600 East Lamar Boulevard Arlington, TX 76011-4511 Balwant K. Singal U. S. Nuclear Regulatory Commission Balwant K. Singal John Ragan Senior Project Manager Chris O'Hara U.S. Nuclear Regulatory Commission Jim von Suskil One White Flint North (MS 8 B13) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 Kevin Polio NRC Resident Inspector Richard Pena U. S. Nuclear Regulatory Commission City Public Service P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 C. M. Canady Peter Nemeth City of Austin Crain Caton & James, P.C.

Electric Utility Department 721 Barton Springs Road C. Mele Austin, TX 78704 City of Austin Richard A. Ratliff Texas Department of State Health Services Alice Rogers Texas Department of State Health Services

NOC-AE-12002912 Attachment Page 1 of 2 BASH-EM EVALUATION OF FUEL PELLET THERMAL CONDUCTIVITY DEGRADATION

Background

Evaluations have been completed to estimate the effect of fuel pellet Thermal Conductivity Degradation (TCD) on Peak Cladding Temperature (PCT) for analyses using the 1981 Westinghouse Large-Break Loss of- Coolant Accident Evaluation Model with BASH (BASH-EM) with the LOCBART Transient Extension Method.

These evaluations utilized fuel rod performance input from a version of the PAD code that accounts for pellet TCD and considered the beneficial effects of assembly power and peaking factor burndown resulting from the depletion of fissionable isotopes. This change represents a Non- Discretionary Change in accordance with Section 4.1.2 of WCAP-13451.

Affected Evaluation Model(s) 1981 Westinghouse Large-Break LOCA Evaluation Model with BASH Estimated Effect The estimated effect was determined on a plant-specific basis. The peaking factor burndown used in the evaluation is provided in Table 1. The peaking factor burndown is conservative for the current cycles and will be validated as part of the reload design process. STP Nuclear Operating Company and its vendor, Westinghouse Electric Company LLC, utilize processes which ensure that the corresponding LOCA analysis input parameters conservatively bound the as-operated plant values.

Table l 1:

1ofPeaking Factors TCD Assumed in the Evaluation Rod Burnup FAH(1,2) FQ(1)

(GWD/MTU) 0 1.62 2.55 30 1.62 2.55 60 1.40 2.04 62 1.40 2.04

1. Includes uncertainties.

2. Hot assembly average power (PHA) follows the same burndown since it is a function of FAH.

NOC-AE-12002912 Attachment Page 2 of 2 Westinghouse LOCA Peak Clad Temperature Summary for Appendix K Large Break Plant Name: South Texas Units 1 & 2 Utility Name: STPNOC Revision Date: 9/20/2012 Analysis Information Analysis Date: 7/1/1998 Evaluation Model: BASH Limiting Break Size: Cd=0.8 FQ: 2.55 FAH: 1.62 Fuel: RFA / Vantage 5H Steam Generator Tube Plugging (%): 10 Notes: 1. RFA Re-analysis -FAH = 1.55 for Once Burned Standard Fuel

2. Limiting Break run was performed with Minimum SI, High Tave, and IFBA Licensing Basis Clad Temp (2 1F)

Analysis of Record 2090 PCT Assessments (Delta PCT)

A. Prior ECCS Assessments

1. Imp Database Error Correction 0

2. PAD Version 4.0 Implementation -30

3. LOCBART Pellet Volumetric Heat Generation Rate 6

4. Rebaseline of AOR 46 B. Planned Plant Modification Evaluations

1. None 0 C. 2012 ECCS Model Assessments

1. PWROG TCD Evaluation - Rebaseline of AOR 5

2. PWROG TCD Evaluation - Effect of TCD and Assembly 0 Power Peaking Factor Bumdown Licensing Basis PCT + PCT Assessments 2117