ML24066A200

10 CFR 50.46 Thirty-Day Report of Significant ECCS Model Changes

ML24066A200
Person / Time
Site:	South Texas
Issue date:	03/06/2024
From:	Georgeson C South Texas
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NOC-AE-24004018, STI: 35561165
Download: ML24066A200 (1)

Text

March 6, 2024 NOC-AE-24004018 10 CFR 50.46(a)(3)(i) 10 CFR 50.46(a)(3)(ii)

STI: 35561165 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

South Texas Project Unit 2 Docket No. STN 50-499 10 CFR 50.46 Thirty-Day Report of Significant ECCS Model Changes

In accordance with the requirements of 10 CFR 50.46(a)(3)(ii), STP Nuclear Operating Company (STPNOC) is submitting a 30-day report for a significant change in the South Texas Unit 2 Emergency Core Cooling System Model.

For Unit 2 Cycle 24, there is a large break loss-of-coolant-accident (LBLOCA) Peak Clad Temperature (PCT) penalty of 17F due to the gamma energy deposition model (GEDM). The total PCT for Unit 2 LBLOCA is 2140F. See the Enclosure for the detailed PCT Summary.

Since the absolute value of the PCT changes from the analysis of record for Unit 2 Cycle 24, exceeds 50°F, the change is considered significant in accordance with 10 CFR 50.46(a)(3)(i).

No schedule for reanalysis is proposed since the Unit 2 Cycle 24 PCT remains below the 10 CFR 50.46(b)(1) limit of 2200°F.

There are no commitments in this letter.

If there are any questions regarding this information, please contact Zachary Dibbern at 361-972-4336 or me at 361-972-7806.

Christopher Georgeson General Manager, Engineering

Enclosure:

Evaluation of the South Texas Project Unit 2 Cycle 24 LOCA RSAC GEDM Violation

cc:

Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 E. Lamar Boulevard Arlington, TX 76011-4511

Enclosure NOC-AE-24004018 Page 1 of 2

EVALUATION OF THE SOUTH TEXAS PROJECT UNIT 2 CYCLE 24 LOCA RSAC GEDM VIOLATION

Background

The South Texas Project Unit 2 Cycle 24 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 24 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 24 GEDM violation was estimated to result in a 17°F increase to the calculated large-break LOCA peak cladding temperature (PCT) for South Texas Project Unit 2.

Enclosure NOC-AE-24004018 Page 2 of 2

Westinghouse LOCA Peak Clad Temperature Summary

Plant Name: SOUTH TEXAS 2 Utility Name: STPNOC EM: BASH AOR

Description:

Appendix K Large Break Summary Sheet Status Cycle 24

PCT (°F)

ANALYSIS-OF-RECORD 2090

ASSESSMENTS Delta PCT

(°F)

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. Rebaseline of AOR 46

8. GEDM Violation Evaluation (Cycle 24) 17 AOR + ASSESSMENTS PCT = 2140 °F