AEP-NRC-2021-50, Annual Report of Loss-of-Coolant Accident Evaluation Model Changes

Annual Report of Loss-of-Coolant Accident Evaluation Model Changes

ML21237A447
Person / Time
Site:	Cook
Issue date:	08/25/2021
From:	Scarpello M American Electric Power, Indiana Michigan Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
AEP-NRC-2021-50
Download: ML21237A447 (10)

Text

t:m INDIANA Indiana Michigan Power MICHIGAN Cook Nuclear Plant POWER* One Cook Place Bridgman, Ml 49106 A unit ofAmerican Electric Power lndianaMichiganPower.com August 25, 2021 AEP-NRC-2021-50 10 CFR 50.46 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 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 model changes affecting the peak cladding temperature (PCT) for CNP Units 1 and 2. l&M is providing, as 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 2020.

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/mll

Enclosure:

Donald C. Cook Nuclear Plant Units 1 and 2, Large and Small Break Loss-of-Coolant Accident Peak Clad Temperature Summary

U.S. Nuclear Regulatory Commission AEP-NRC-2021-50 Page 2 c: R. J. Ancona - MPSC EGLE - RMD/RPS J.B. Giessner- NRC Region Ill NRC Resident Inspector R. M. Sistevaris - AEP Ft. Wayne J.E. Walcutt-AEP Ft. Wayne S. P. Wall - NRC Washington, D.C.

A. J. Williamson-AEP Ft. Wayne, w/o enclosures

ENCLOSURE TO AEP-NRC-2021-50 DONALD C. COOK NUCLEAR PLANT UNITS 1 AND 2 LARGE AND SMALL BREAK LOSS-OF-COOLANT ACCIDENT PEAK CLAD TEMPERATURE

SUMMARY

Abbreviations:

10CFR Title 10 of the Code of Federal Regulations ADAMS Agencywide Documents Access and Management System CNP Donald C. Cook Nuclear Plant OF degrees Fahrenheit ECCS emergency core cooling system EM evaluation methodology FdH nuclear enthalpy rise hot channel factor Fa heat flux hot channel factor HHSI high head safety injection (Safety Injection System at CNP) l&M Indiana Michigan Power Company LB large break LOCA loss of coolant accident NOP/NOT normal operating pressure/normal operating temperature NRC Nuclear Regulatory Commission PBOT/PMID power integrals in the bottom-third/middle-third PCT peak cladding temperature RHR residual heat removal SGTP steam generator tube plugging SB small break TCD thermal conductivity degradation Summary:

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 LB LOCA 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 LTR-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 LB LOCA analysis of record for CNP Unit 1. In a subsequent letter, LTR-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

Enclosure to AEP-NRC-2021-50 Page2 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 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 LB LOCA 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 SB LOCA analysis as a result of the reactor vessel upflow conversion modification. This report was submitted pursuant to 10 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 SB LOCA analysis as a result of the reactor vessel upflow conversion modification. This report was submitted pursuant to 10 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, changes to grid blockage ratio and porosity (Unit 2 only), and plant modification evaluations on the CNP Units 1 and 2 LB LOCA analyses of record. Pages are included that also summarize the SB LOCA PCT analyses of record for CNP Units 1 and 2. In addition, the impact on the SB and LB LOCA PCT analyses of record from the upflow conversion in Units 1 and 2 is addressed.

Enclosure to AEP-NRC-2021-50 Page 3 CNP UNIT 1 LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Applicable to U1C29 Evaluation Model: ASTRUM (2004)

Fa=2.15 FdH = 1.55 SGTP = 10% Break Size: Split Analysis Date: November 2008 Notes: Post-Analysis evaluation for Fa of 2.09 and FdH of 1.53 LICENSING BASIS Analysis-of-Record PCT= 2128°F MARGIN ALLOCATIONS (Delta PCT)

A. PREVIOUS 10 CFR 50.46 ASSESSMENTS

1. Return to NOP/NOT Including Pellet Thermal 404°F(a)

Conductivity Degradation and Peaking Factor Burndown

2. Revised Heat Transfer Multiplier Distributions for -91°F NOP/NOT Conditions

3. Error in Burst Strain Application 85°F

4. Decay Group Uncertainty Factors Errors -29°F B. PLANNED PLANT MODIFICATION EVALUATIONS

1. Design Input Changes with Respect to Plant Operation -489°F(a) for Return to NOP/NOT Evaluation

2. Upflow Conversion 14°F C. NEW 10 CFR 50.46 ASSESSMENTS D. OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS PCT= 2022°F Notes:

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-2021-50 Page 4 CNP UNIT 1 LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Applicable to U1C30 Evaluation Model: ASTRUM (2004)

Fa=2.15 FdH = 1.55 SGTP = 10% Break Size: Split Analysis Date: November 2008 Notes: Post-Analysis evaluation for Fa of 2.09 and FdH of 1.53 LICENSING BASIS Analysis-of-Record PCT= 2128°F MARGIN ALLOCATIONS (Delta PCT)

A. PREVIOUS 10 CFR 50.46 ASSESSMENTS

1. Return to NOP/NOT Including Pellet Thermal 404°F{a)

Conductivity Degradation and Peaking Factor Burndown

2. Revised Heat Transfer Multiplier Distributions for -91°F NOP/NOT Conditions

3. Error in Burst Strain Application 85°F

4. Decay Group Uncertainty Factors Errors -29°F B. PLANNED PLANT MODIFICATION EVALUATIONS

1. Design Input Changes with Respect to Plant Operation -489°F{a) for Return to NOP/NOT Evaluation

2. Upflow Conversion 14°F

3. PBOT/PMID Evaluation for Cycle 30 0°F(b)

C. NEW 10 CFR 50.46 ASSESSMENTS D. OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS PCT= 2022°F

Enclosure to AEP-NRC-2021-50 Page 5 Notes:

a. These assessments are coupled via an evaluation of burnup effects which include thermal conductivity degradation, peaking factor burndown and design input changes.

b. Normalized PBOT/PMID of the core were slightly exceeding limits used in the best estimate LB LOCA analysis of record. It was determined that expanding the PBOT/PMID box to include the Cycle 30 values is acceptable and the violations have a 0°F peak cladding temperature impact on the best estimate LB LOCA analysis of record.

Enclosure to AEP-NRC-2021-50 Page6 CNP UNIT 1 LOCA Peak Clad Temperature Summary for Appendix K Small Break Applicable to U1C29 and U1C30 Evaluation Model: NOTRUMP Fa=2.32 FdH=1.55 SGTP=10% 3.25 inch cold leg break Analysis Date: January 26, 2012 LICENSING BASIS Analysis-of-Record PCT= 1725°F MARGIN ALLOCATIONS (Delta PCT)

A. PREVIOUS 10 CFR 50.46 ASSESSMENTS B. PLANNED PLANT MODIFICATION EVALUATIONS 0°F

1. Upflow Conversion 107°F (a)

C. NEW 10 CFR 50.46 ASSESSMENTS D. OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS PCT= 1832°F Notes:

a. The evaluation resulted in a minor shift in limiting break size from 3.25 inches to 3.00 inches.

Enclosure to AEP-NRC-2021-50 Page 7 CNP UNIT 2 LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Evaluation Model: ASTRUM (2004)

Fa= 2.335 FdH = 1.644 SGTP = 10% Break Size: Split Analysis Date: February 11, 2009 Notes: Post-Analysis evaluation of 1.5% SGTP and FdH of 1.61 LICENSING BASIS Analysis-of-Record PCT= 2107°F MARGIN ALLOCATIONS (Delta PCT)

A. PREVIOUS 10 CFR 50.46 ASSESSMENTS

1. Evaluation of TCD and Peaking Factor Burndown 73°F(a)

2. Changes to Grid Blockage Ratio and Porosity 16°F

3. Revised Heat Transfer Multiplier Distributions -3°F

4. Error in Burst Strain Application 13°F B. PLANNED PLANT MODIFICATION EVALUATIONS

1. Plant Evaluations associated with TCD -239°F(a)

2. Upflow Conversion 37°F

c. NEW 10 CFR 50.46 ASSESSMENTS 0°F D. OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS PCT= 2004°F Notes:

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-2021-50 Page 8 CNP UNIT 2 LOCA Peak Clad Temperature Summary for Appendix K Small Break Evaluation Model: NOTRUMP Fa= 2.32 FdH = 1.62 SGTP = 10% 4 inch cold leg break Analysis Date: June 28, 2011 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

1. Upflow Conversion 75°F C. NEW 10 CFR 50.46 ASSESSMENTS 0°F D. OTHER LICENSING BASIS PCT+ MARGIN ALLOCATIONS PCT= 1349°F Notes:

a. Analysis models RHR injection flow diversion to RHR spray and HHSI cross-tie valves open during cold leg recirculation.