NOC-AE-19003627, 10 CFR 50.46 Annual Report of ECCS Model Revisions

10 CFR 50.46 Annual Report of ECCS Model Revisions

ML19063D875
Person / Time
Site:	South Texas
Issue date:	03/04/2019
From:	Page M South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-19003627, STI 34806286
Download: ML19063D875 (10)

Text

Nuclear Operating Company SUV Hi ST' South Te.w Project Electric Cenerating Station nO.Bm 389 Wadmwrlh, Texas 77483 March 04, 2019 NOC-AE-19003627 10CFR 50.46 (a)(3)(i) 10CFR 50.46 (a)(3)(ii)

U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 South Texas Project Units 1 & 2 Docket Nos. STN 50-498 and STN 50-499 10 CFR 50.46 Annual Report of ECCS Model Revisions

References:

Letter from R. Dunn to NRC Document Control Desk, "Units 1 & 2 10 CFR 50.46 Thirty-Day Report of Significant ECCS Model Changes and Annual Report," dated May 7, 2018, NOC-AE-18003572 (ML18128A361)

In accordance with the requirements of 10 CFR 50.46 (a)(3)(i) and 10 CFR 50.46 (a)(3)(ii),

STP Nuclear Operating Company (STPNOC) is submitting the Annual Report for South Texas Units 1 and 2 and to address errors to the accepted Emergency Core Cooling System (ECCS) evaluation model. The following summarize these errors and impact on the calculated peak clad temperature (PCT) for the limiting ECCS analysis. The changes were not significant.

For Unit 2 Cycle 20, there is a large break loss-of-coolant accident (LBLOCA) PCT penalty of 2°F due to a violation of the gamma energy deposition model (GEDM) loss-of-coolant accident (LOCA) reload safety analysis checklist (RSAC) limit used in the analysis. The total PCT for Unit 2 LBLOCA is 2125°F. This change was submitted in the referenced letter.

A typographical error was discovered in the implementation of the U02 fuel pellet heat capacity. The erroneous formulation results in an overprediction of heat capacity that increases with fuel temperature. The small overprediction in U02 fuel pellet heat capacity has been evaluated to have a negligible effect on existing large and small break LOCA analysis results due to the small magnitude of the change, leading to an estimated PCT impact of 0°F.

STP Unit 1 and Unit 2 large break and small break LOCA PCTs have not changed since the submittal in the referenced letter. No schedule for reanalysis is proposed since the PCT for both Units 1 and 2 remain below the 10 CFR 50.46 (b)(1) limit of2200°F.

There are no commitments in this letter.

STI34806286

NOC-AE-19003627 Page 2 of 3 If there are any questions regarding this information please contact Safdar Hafeez at 361-972-8906.

l&llFcnSfiWpage7 General Manager, Engineering

Attachment:

Unit 1 & Unit 2 Annual Report (PCT Assessment)

STI34806286

NOC-AE-19003627 Page 3 of 3 ec:

(Paper Copy)

Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 1600 East Lamar Boulevard Arlington, TX 76011-4511 Lisa M. Regner Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (09E01) 11555RockvillePike Rockville, MD 20852 NRC Resident Inspector U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN116 Wadsworth, TX 77483 STI34806286

Attachment NOC-AE-19003627 Unit 1 & Unit 2 Annual Report (PCT Assessment) Page 1 of 6 EVALUATION OF THE SOUTH TEXAS PROJECT UNIT 2 CYCLE 20 LOCA RSAC GEDM VIOLATION

Background

The South Texas Project Unit 2 Cycle 20 reload core design resulted in a violation of the gamma energy deposition model (GEDM) loss-of-coolant accident (LOCA) reload safety analysis checklist (RSAC) limit used in the large-break LOCA analysis. This violation was evaluated for South Texas Project Unit 2 Cycle 20 and represents a change in a plant configuration or associated set point(s), distinguished from an evaluation model change in Section 4 of WCAP-13451.

Affected Evaluation Models(s) 1981 Westinghouse Large Break LOCA Evaluation Model with BASH Estimated Effect The impact of the Cycle 20 GEDM violation was estimated to result in a 2°F increase to the calculated large-break LOCA PCT for South Texas Project Unit 2.

STI34806286

Attachment NOC-AE-19003627 Unit 1 & Unit 2 Annual Report (PCT Assessment) Page 2 of 6 U02 FUEL PELLET HEAT CAPACIPf

Background

A typographical error was discovered in the implementation of the U02 fuel pellet heat capacity as described by Equation C-4 ofWCAP-8301 [1] for fuel rod heat-up calculations within the Appendix K Large Break and Small Break LOCA evaluation models. The erroneous formulation results in an over- prediction of heat capacity that increases with fuel temperature. The corrected formulation results in a maximum decrease in heat capacity on the order of approximately 1.2% for existing analyses of record. This represents a Non-Discretionary Change in accordance with Section 4.1.2 ofWCAP-13451.

Affected Evaluation Model(s) 1981 Westinghouse Large Break LOCA Evaluation Model with BASH 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effect The small over-prediction in U02 fuel pellet heat capacity has been evaluated to have a negligible effect on existing large and small break LOCA analysis results due to the small magnitude of the change, leading to an estimated PCT impact of 0°F.

Reference

1) WCAP-8301, "LOCTA-IV Program: Loss-of-Coolant Transient Analysis," June 1974.

STI34806286

Attachment NOC-AE-19003627 Unit 1 & Unit 2 Annual Report (PCT Assessment) Page 3 of 6 Westinghouse LOCA Peak Clad Temperature Summary Plant Name: SOUTH TEXAS 1 Utility Name: STPNOC EM: BASH AOR

Description:

Appendix K Large Break PCT (°F)

ANALYSIS-OF-RECORD 2090 ASSESSMENTS Delta PCT

(°AF)

1. IMP Database Error Corrections 0

2. PAD Version 4.0 Implementation -30

3. LOCBART Pellet Volumetric Heat Generation Rate 6

4. PWROG TCD Evaluation - Rebaseline of AOR 5

5. PWROG TCD Evaluation - Effect of TCD and 0 Assembly Power/Peaking Factor Burndown

6. Effect of Containment Purge 6

7. RebaselineofAOR 46 AOR + ASSESSMENTS PCT = 2123 °F STI34806286

Attachment NOC-AE-19003627 Unit 1 & Unit 2 Annual Report (PCT Assessment) Page 4 of 6 Westinghouse LOCA Peak Clad Temperature Summary Plant Name: SOUTH TEXAS 1 Utility Name: STPNOC EM: NOTRUMP AOR

Description:

Appendix K Small Break PCT (°F)

ANALYSIS-OF-RECORD 1578 ASSESSMENTS Delta PCT

(°AF)

1. IMP Database Error Corrections 0

2. NOTRUMP Version 38.0 Namelist Error Correction 0

3. NOTRUMP Bubble Rise / Drift Flux Model Inconsistency 34 Corrections

4. Burst and Blockage/Time in Life 0 AOR + ASSESSMENTS PCT=1612°F STI34806286

Attachment NOC-AE-19003627 Unit 1 & Unit 2 Annual Report (PCT Assessment) Page 5 of 6 Westinghouse LOCA Peak Clad Temperature Summary Plant Name: SOUTH TEXAS 2 Utility Name: STPNOC EM: BASH AOR

Description:

Appendix K Large Break PCT (°F)

ANALYSIS-OF-RECORD 2090 ASSESSMENTS Delta PCT

(°AF)

1. IMP Database Error Corrections 0

2. PAD Version 4.0 Implementation -30

3. LOCBART Pellet Volumetric Heat Generation Rate 6

4. PWROG TCD Evaluation - Rebaseline of AOR 5

5. PWROG TCD Evaluation - Effect of TCD and 0 Assembly Power/Peaking Factor Burndown

6. Effect of Containment Purge 6

7. GEDM Violation Evaluation (Cycle 20) 2

8. RebaselineofAOR 46 AOR + ASSESSMENTS PCT = 2125 °F STI34806286

Attachment NOC-AE-19003627 Unit 1 & Unit 2 Annual Report (PCT Assessment) Page 6 of 6 Westinghouse LOCA Peak Clad Temperature Summary Plant Name: SOUTH TEXAS 2 Utility Name: STPNOC EM: NOTRUMP AOR

Description:

Appendix K Small Break PCT (°F)

ANALYSIS-OF-RECORD 1578 ASSESSMENTS Delta PCT

(°AF)

1. IMP Database Error Corrections 0

2. NOTRUMP Version 38.0 Namelist Error Correction 0

3. NOTRUMP Bubble Rise / Drift 34 Flux Model Inconsistency Corrections

4. Burst and Blockage/Time in Life 0 AOR + ASSESSMENTS PCT=1612°F STI34806286