AEP-NRC-2025-35, Annual Report of Loss-of-Coolant Accident Evaluation Model Changes
| ML25231A240 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 08/19/2025 |
| From: | Scarpello M Indiana Michigan Power Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| AEP-NRC-2025-35 | |
| Download: ML25231A240 (1) | |
Text
An MP Company BOUNDLESS ENERGr August19,2025 Docket Nos.: 50-315 50-316 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Donald C. Cook Nuclear Plant Units 1 and 2 ANNUAL REPORT OF LOSS-OF-COOLANT ACCIDENT EVALUATION MODEL CHANGES Indiana Michigan Power Cook Nuclear Plant One Cook Place Bridgman, Ml 49106 indianamichiganpower.com AEP-NRC-2025-35 10 CFR 50.46 Pursuant to 10 CFR 50.46, Indiana Michigan Power Company (l&M), the licensee for Donald C. Cook Nuclear Plant (CNP), is transmitting an annual report of loss-of-coolant accident (LOCA) evaluation of model changes affecting the peak cladding temperature (PCT) for CNP Units 1 and 2. l&M is providing, as an enclosure to this letter, the Units 1 and 2 Large Break and Small Break LOCA Analyses-of-Record PCT values and error assessments for calendar year 2024.
There are no new or revised commitments in this letter. Should you have any questions, please contact me at (269) 466-2649.
Michael K. Scarpello Regulatory Affairs Director JMT/sjh
Enclosure:
Donald C. Cook Nuclear Plant Units 1 and 2 Large and Small Break Loss-of-Coolant Accident Peak Clad Temperature Summary c:
EGLE - RMD/RPS J. 8. Giessner - NRC Region Ill NRC Resident Inspector N. Quilico - MPSC R. M. Sistevaris - AEP Ft. Wayne S. P. Wall - NRC Washington, D.C.
A. J. Williamson - AEP Ft. Wayne
Enclosure to AEP-NRC-2025-35 Abbreviations:
10 CFR ADAMS CNP ECCS EM F~H Fa HHSI l&M LBLOCA LOCA NOP/NOT NRC PCT RHR SGTP SBLOCA TCD OF
+
Summary:
ENCLOSURE TO AEP-NRC-2025-35 DONALD C. COOK NUCLEAR PLANT UNITS 1 AND 2 LARGE AND SMALL BREAK LOSS-OF-COOLANT ACCIDENT PEAK CLAD TEMPERATURE
SUMMARY
Title 10 of the Code of Federal Regulations NRC Agencywide Documents Access and Management System Donald C. Cook Nuclear Plant emergency core cooling system evaluation methodology nuclear enthalpy rise hot channel factor heat flux hot channel factor high head safety injection (safety injection system at CNP)
Indiana Michigan Power Company large break loss of coolant accident loss of coolant accident normal operating pressure/normal operating temperature Nuclear Regulatory Commission peak cladding temperature residual heat removal steam generator tube plugging small break loss of coolant accident thermal conductivity degradation degree Fahrenheit percent plus Page 1 By letter dated March 19, 2012, (ADAMS Accession No. ML12088A104), and supplemented by letter dated June 11, 2012, (ADAMS Accession No. ML12173A025), l&M, the licensee for CNP Units 1 and 2, submitted a report describing the impact of fuel pellet TCD on the LBLOCA ECCS evaluation model, and an estimate of the effect on the predicted PCT for CNP Units 1 and 2. This report was submitted pursuant to 10 CFR Part 50, Section 50.46, Paragraph (a)(3), and referred to a letter from Westinghouse Electric Company dated March 7, 2012, (ADAMS Accession No. ML12072A035). The report was subsequently found to be acceptable by NRC letter dated March 7, 2013, (ADAMS Accession No. ML13077A137).
By Westinghouse letter L TR-LIS-13-360, "D. C. Cook Units 1 and 2 10 CFR 50.46 Report for Revised Heat Transfer Multiplier Distributions," dated July 31, 2013, Westinghouse Electric Company notified l&M of significant errors in the EM for the LBLOCA analysis of record for CNP Unit 1. In a subsequent letter, L TR-LIS-13-406, "Additional Information on the Evaluation of Revised Heat Transfer Multiplier Distributions," dated August 14, 2013, Westinghouse Electric Company provided l&M additional detail on the nature of the errors and the corrections made.
Pursuant to 10 CFR Part 50, Section 50.46, Paragraph (a)(3), by letter dated August 30, 2013, l&M submitted a report to the NRC describing the impact of Revised Heat Transfer Multiplier
Enclosure to AEP-NRC-2025-35 Page 2 Distributions on the predicted PCT for CNP Unit 1 (ADAMS Accession No. ML13247A174). As documented in the subsequent rack-up sheets, the error results in a benefit to the calculated PCT.
By Westinghouse letter LTR-LIS-14-44, "D. C. Cook Units 1 and 2 10 CFR 50.46 Report for the HOTSPOT Burst Strain Error Correction," dated January 29, 2014, Westinghouse Electric Company notified l&M of significant errors in the EM for the LBLOCA analysis of record for CNP Unit 1.
Pursuant to 10 CFR Part 50, Section 50.46, Paragraph (a)(3), by letter dated February 27, 2014, l&M submitted a report to the NRC describing the impact of an Error in Burst Strain Application on the predicted PCT for CNP Unit 1 (ADAMS Accession No. ML14063A043).
By letter dated May 20, 2016, (ADAMS Accession No. ML16145A291 ), l&M submitted a report of significant changes to the ECCS EM as a result of CNP Unit 1 returning to NOP/NOT. This report was submitted pursuant to 10 CFR Part 50, Section 50.46.
By letter dated May 4, 2018, (ADAMS Accession No. ML18130A580), l&M submitted a report of a significant change in calculated PCT for the CNP Unit 2 SBLOCA analysis as a result of the reactor vessel upflow conversion modification. This report was submitted pursuant to 1 O CFR Part 50, Section 50.46 within 30-days of reactor start-up.
By letter dated May 9, 2019, (ADAMS Accession No. ML19133A060), l&M submitted a report of a significant change in calculated PCT for the CNP Unit 1 SBLOCA analysis as a result of the reactor vessel upflow conversion modification. This report was submitted pursuant to 1 O CFR Part 50, Section 50.46 within 30-days of reactor start-up.
The following pages summarize the impact of TCD, peaking factor burndown, heat transfer multiplier distribution revisions, error in burst strain application, decay group uncertainty factors errors (Unit 1 only), changes to grid blockage ratio and porosity (Unit 2 only), and plant modification evaluations on the CNP Units 1 and 2 LBLOCA analyses of record. Pages are included that also summarize the SBLOCA PCT analyses of record for CNP Units 1 and 2. In addition, the impact on the SBLOCA and LBLOCA PCT analyses of record from the upflow conversion in Units 1 and 2 is addressed.
Enclosure to AEP-NRC-2025-35 CNP UNIT 1 LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Evaluation Model: ASTRUM (2004)
Fa=2.15 FllH = 1.55 SGTP = 10%
Break Size: Split Analysis Date: November 2008 Notes: Post-Analysis evaluation for Fa of 2.09 and FllH of 1.53 LICENSING BASIS Analysis-of-Record MARGIN ALLOCATIONS (Delta PCT)
A.
B.
C.
D.
PREVIOUS 10 CFR 50.46 ASSESSMENTS
- 1. Return to NOP/NOT Including Pellet Thermal Conductivity Degradation and Peaking Factor Burndown
- 2. Revised Heat Transfer Multiplier Distributions for NOP/NOT Conditions
- 3. Error in Burst Strain Application
- 4. Decay Group Uncertainty Factors Errors PLANNED PLANT MODIFICATION EVALUATIONS
- 1. Design Input Changes with Respect to Plant Operation for Return to NOP/NOT Evaluation
- 2. Upflow Conversion NEW 10 CFR 50.46 ASSESSMENTS OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS Notes:
PCT= 2128°F 404°F (a)
-91 °F 85°F
-29°F
-489°F(a) 14°F 0°F 0°F PCT= 2022°F Page 3
- a. These assessments are coupled via an evaluation of burnup effects which include thermal conductivity degradation, peaking factor burndown and design input changes.
Enclosure to AEP-NRC-2025-35 Page4 CNP UNIT 1 LOCA Peak Clad Temperature Summary for Appendix K Small Break Evaluation Model:
NOTRUMP Fa=2.32 Ft1H=1.55 SGTP=10%
3.25 inch cold leg break Analysis Date: July 2012 LICENSING BASIS Analysis-of-Record MARGIN ALLOCATIONS (Delta PCT)
A.
B.
C.
D.
PREVIOUS 10 CFR 50.46 ASSESSMENTS PLANNED PLANT MODIFICATION EVALUATIONS
- 1. Upflow Conversion NEW 10 CFR 50.46 ASSESSMENTS OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS Notes:
PCT= 1725°F 0°F 0°F 107°F (a) 0°F 0°F PCT= 1832°F
- a. The evaluation resulted in a minor shift in limiting break size from 3.25 inches to 3.00 inches.
Enclosure to AEP-NRC-2025-35 Pages CNP UNIT 2 LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Evaluation Model: ASTRUM (2004)
Fa= 2.335 F~H = 1.644 SGTP = 10%
Analysis Date: February 2009 Break Size: Split Notes: Post-Analysis evaluation of 1.5% SGTP and Ff1H of 1.61 LICENSING BASIS Analysis-of-Record MARGIN ALLOCATIONS (Delta PCT)
A.
PREVIOUS 10 CFR 50.46 ASSESSMENTS
- 1. Evaluation of TCD and Peaking Factor Burndown
- 2. Changes to Grid Blockage Ratio and Porosity
- 3. Revised Heat Transfer Multiplier Distributions
- 4. Error in Burst Strain Application B.
PLANNED PLANT MODIFICATION EVALUATIONS C.
D.
- 1. Plant Evaluations associated with TCD
- 2. Upflow Conversion NEW 10 CFR 50.46 ASSESSMENTS OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS Notes:
PCT= 2107°F 73°F(a) 16°F
-3°F 13°F
-239°F(a) 37°F 0°F 0°F PCT= 2004°F
- a. These assessments are coupled via an evaluation of burnup effects which include thermal conductivity degradation, peaking factor burndown and design input changes.
Enclosure to AEP-NRC-2025-35 CNP UNIT 2 LOCA Peak Clad Temperature Summary for Appendix K Small Break Fa= 2.32 Evaluation Model: NOTRUMP SGTP = 10% 4 inch cold leg break Analysis Date: June 2011 Page 6 LICENSING BASIS Analysis-of-Record PCT= 1274°F (a)
MARGIN ALLOCATIONS (Delta PCT)
A.
PREVIOUS 10 CFR 50.46 ASSESSMENTS B.
PLANNED PLANT MODIFICATION EVALUATIONS C.
D.
- 1. Upflow Conversion NEW 10 CFR 50.46 ASSESSMENTS OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS Notes:
0°F 75°F 0°F 0°F PCT= 1349°F