ML24303A278
| ML24303A278 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 10/29/2024 |
| From: | Para W Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML24303A278 (1) | |
Text
200 Energy Way Kennett Square, PA 19348 www.constellation.com 10 CFR 50.46
October 29, 2024=
U.S. Nuclear Regulatory Commission=
Attn: Document Control Desk=
Washington, DC 20555-0001=
Limerick Generating Station, Units 1 and 2=
Renewed Facility Operating License Nos. NPF-39 and NPF-85=
NRC Docket Nos. 50-352 and 50-353=
Subject:
10 CFR 50.46 Annual Report
Reference:
Letter from David P. Helker (Constellation Energy Generation, LLC) to U.S. Nuclear Regulatory Commission, 10 CFR 50.46 Annual Report, dated October 30, 2023=
The purpose of this letter is to submit the 10 CFR 50.46 reporting information for Limerick Generating Station (LGS), Units 1 and 2. The most recent annual 10 CFR 50.46 Report for LGS, Units 1 and 2, (Reference) provided the cumulative Peak Cladding Temperature (PCT) errors for the most recent fuel design through October 30, 2023. =
Five attachments are included with this letter that provide the current LGS, Units 1 and 2, 10 CFR 50.46 status. There are two fuel types, GNF2 and GNF3, in operation at LGS, Units 1 and 2. Attachment 1 provides the GNF2 Peak Cladding Temperature Rack-Up Sheet for Limerick Generating Station, Unit 1. Attachment 2 has been designated as GNF3 Peak Cladding Temperature Rack-Up Sheet for Limerick Generating Station, Unit 1. provides the GNF2 Peak Cladding Temperature Rack-Up Sheet for Limerick Generating Station, Unit 2, and Attachment 4 provides the GNF3 Peak Cladding Temperature Rack-Up Sheet for Limerick Generating Station, Unit 2. Attachment 5, Assessment Notes, contains a detailed description of each change/error reported.=
Since the previous 10 CFR 50.46 report there have been no changes to the net PCT, Licensing Basis PCT, or PCT adder for GNF2 and GNF3 fuel.=
There are no regulatory commitments in this letter.=
If you have any questions, please contact Steve Flickinger at 267-533-5302.=
Respectfully, =
Wendi Para=
Sr. Manager - Licensing =
Constellation Energy Generation, LLC=
Limerick Generating Station, Units 1 and 2 10 CFR 50.46 Annual Report October 29, 2024 Page 2
Attachments:
- 1) GNF2 Peak Cladding Temperature Rack-Up Sheet (Limerick Generating Station, Unit 1)
- 2) GNF3 Peak Cladding Temperature Rack-Up Sheet (Limerick Generating Station, Unit 1)
- 3) GNF2 Peak Cladding Temperature Rack-Up Sheet (Limerick Generating Station, Unit 2)
- 4) GNF3 Peak Cladding Temperature Rack-Up Sheet (Limerick Generating Station, Unit 2)
- 5) Assessment Notes (Limerick Generating Station, Units 1 and 2)
cc: USNRC Region I, Regional Administrator USNRC Senior Resident Inspector, LGS USNRC Project Manager, LGS Director, Bureau of Radiation Protection - Pennsylvania Department of Environmental Protection
Limerick Generating Station, Units 1 and 2 10 CFR 50.46 Annual Report October 29, 2024 Page 3
bcc: Sr. Vice President, MidAtlantic Operations Vice President, Nuclear Security and Licensing Site Vice President - LGS Plant Manager - LGS Director, Operations - LGS Director, Engineering Director, Site Engineering - LGS Director, Licensing - KSA Sr. Manager, Licensing - KSA Manager, Regulatory Assurance - LGS M. Tudisco - KSA G. Budock - LGS S. Flickinger - KSA PA DEP BRP Inspector - LGS Commitment Coordinator - KSA Licensing Records - KSA
ATTACHMENT 1
10 CFR 50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors
Assessments as of October 29, 2024
GNF2 Peak Cladding Temperature Rack-Up Sheet
Limerick Generating Station, Unit 1
Report of the Emergency Core Cooling System Attachment 1 Evaluation Model Changes and Errors Page 1 of 1 Assessments as of October 29, 2024=
Peak Cladding Temperature Rack-Up Sheet, LGS Unit 1=
PLANT NAME:= Limerick Unit 1=
ECCS EVALUATION MODEL:= SAFER/GESTR-LOCA Supplemented with PRIME=
REPORT REVISION DATE:= 10/29/2024=
CURRENT OPERATING CYCLE:= 21
ANALYSIS OF RECORD CALCULATIONS
Limerick Generating Station Units 1 and 2 GNF2 ECCS-LOCA Evaluation, 0000-0111-9078-R0, February 2011.=
Fuels Analyzed in Calculations and in Operation: GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure (GNF2): Battery Failure Limiting Break Location: Recirculation Suction Line Limiting Break Size: Double-Ended Guillotine Break
Reference Peak Cladding Temperature (PCT): 1880°F
MARGIN ALLOCATION
A. PRIOR LOCA MODEL ASSESSMENTS
10 CFR 50.46 Report dated November 23, 2011 (See Note 1.1)= GNF2 PCT = +50°F 10 CFR 50.46 Report dated November 09, 2012 (See Note 1.2)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated December 12, 2012 (See Note 1.3)= GNF2 PCT = +45°F=
10 CFR 50.46 Report dated November 08, 2013 (See Note 1.4)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated November 07, 2014 (See Note 1.5)= GNF2 PCT = +10°F=
10 CFR 50.46 Report dated November 06, 2015 (See Note 1.6)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated November 04, 2016 (See Note 1.7)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated November 06, 2017 (See Note 1.8)= GNF2 PCT = +30°F=
10 CFR 50.46 Report dated November 06, 2018 (See Note 1.9)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2019 (See Note 1.10) GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2020 (See Note 1.11)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2021 (See Note 1.12)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2022 (See Note 1.13)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 30, 2023 (See Note 1.14)= GNF2 PCT = 0°F=
Net PCT (GNF2) 2015 °F
B. CURRENT LOCA MODEL ASSESSMENTS
Total PCT Change from Current Assessments (See Note 2)= GNF2 PCT = 0°F=
Cumulative PCT Change from Current Assessments= GNF2 lPCTl = 0°F=
Net PCT (GNF2) 2015 °F ATTACHMENT 2
10 CFR 50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors
Assessments as of October 29, 2024
GNF3 Peak Cladding Temperature Rack-Up Sheet
Limerick Generating Station, Unit 1 Report of the Emergency Core Cooling System Attachment 2 Evaluation Model Changes and Errors Page 1 of 1 Assessments as of October 29, 2024=
GNF3 Peak Cladding Temperature Rack-Up Sheet, LGS Unit 1=
PLANT NAME:= Limerick Unit 1=
ECCS EVALUATION MODEL:= SAFER/PRIME-LOCA=
REPORT REVISION DATE:= 10/29/2024=
CURRENT OPERATING CYCLE:= 21
ANALYSIS OF RECORD CALCULATIONS
Limerick Generating Station Units 1 and 2 GNF3 ECCS-LOCA Evaluation, 005N3990 Rev 0, December 2020.=
Fuels Analyzed in Calculations and in Operation: GNF3 Limiting Fuel Type: GNF3 Limiting Single Failure (GNF3): Battery Failure Limiting Break Location: Recirculation Suction Line Limiting Break Size: Double-Ended Guillotine Break =
Reference Peak Cladding Temperature (PCT): 1940°F MARGIN ALLOCATION
A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 Report dated October 29, 2022 (See Note 1.13)=GNF3 PCT = 0°F=
10 CFR 50.46 Report dated October 30, 2023 (See Note 1.14)=GNF3 PCT = 0°F=
B. CURRENT LOCA MODEL ASSESSMENTS Total PCT Change from Current Assessments (See Note 2)= GNF3 PCT = 0°F=
Cumulative PCT Change from Current Assessments= GNF3 lPCTl = 0°F=
Net PCT (GNF3) 1940 °F ATTACHMENT 3
10 CFR 50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors
Assessments as of October 29, 2024
GNF2 Peak Cladding Temperature Rack-Up Sheet
Limerick Generating Station, Unit 2 Report of the Emergency Core Cooling System Attachment 3 Evaluation Model Changes and Errors Page 1 of 1 Assessments as of October 29, 2024=
GNF2 Peak Cladding Temperature Rack-Up Sheet, LGS Unit 2=
PLANT NAME:= Limerick Unit 2=
ECCS EVALUATION MODEL:= SAFER/GESTR-LOCA Supplemented with PRIME=
REPORT REVISION DATE:= 10/29/2024=
CURRENT OPERATING CYCLE:= 18
ANALYSIS OF RECORD CALCULATIONS
Limerick Generating Station Units 1 and 2 GNF2 ECCS-LOCA Evaluation, 0000-0111-9078-R0, February 2011.=
Fuels Analyzed in Calculations and in Operation: GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure (GNF2): Battery Failure Limiting Break Location: Recirculation Suction Line Limiting Break Size: Double-Ended Guillotine Break
Reference Peak Cladding Temperature (PCT): 1880°F
MARGIN ALLOCATION
A. PRIOR LOCA MODEL ASSESSMENTS
10 CFR 50.46 Report dated November 23, 2011 (See Note 1.1)= GNF2 PCT = +50°F 10 CFR 50.46 Report dated November 09, 2012 (See Note 1.2)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated December 12, 2012 (See Note 1.3)= GNF2 PCT = +45°F=
10 CFR 50.46 Report dated November 08, 2013 (See Note 1.4)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated November 07, 2014 (See Note 1.5)= GNF2 PCT = +10°F=
10 CFR 50.46 Report dated November 06, 2015 (See Note 1.6)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated November 04, 2016 (See Note 1.7)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated November 06, 2017 (See Note 1.8)= GNF2 PCT = +30°F=
10 CFR 50.46 Report dated November 06, 2018 (See Note 1.9)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2019 (See Note 1.10)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2020 (See Note 1.11)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2021 (See Note 1.12)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 29, 2022 (See Note 1.13)= GNF2 PCT = 0°F=
10 CFR 50.46 Report dated October 30, 2022 (See Note 1.14)= GNF2 PCT = 0°F=
Net PCT (GNF2) 2015 °F
B. CURRENT LOCA MODEL ASSESSMENTS
Total PCT Change from Current Assessments (See Note 2)= GNF2 PCT = 0°F=
Cumulative PCT Change from Current Assessments= GNF2 lPCTl = 0°F=
Net PCT (GNF2) 2015 °F ATTACHMENT 4
10 CFR 50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors
Assessments as of October 29, 2024
GNF3 Peak Cladding Temperature Rack-Up Sheet
Limerick Generating Station, Unit 2 Report of the Emergency Core Cooling System Attachment 4 Evaluation Model Changes and Errors Page 1 of 1 Assessments as of October 29, 2024 GNF3 Peak Cladding Temperature Rack-Up Sheet, LGS Unit 2
PLANT NAME: Limerick Unit 2 ECCS EVALUATION MODEL: SAFER/PRIME-LOCA REPORT REVISION DATE: 10/29/2024 CURRENT OPERATING CYCLE: 18
ANALYSIS OF RECORD CALCULATIONS
Limerick Generating Station Units 1 and 2 GNF3 ECCS-LOCA Evaluation, 005N3990 Rev 0, December 2020.
Fuels Analyzed in Calculations and in Operation: GNF3 Limiting Fuel Type: GNF3 Limiting Single Failure (GNF3): Battery Failure Limiting Break Location: Recirculation Suction Line Limiting Break Size: Double-Ended Guillotine Break
Reference Peak Cladding Temperature (PCT): 1940°F
MARGIN ALLOCATION
A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 Report dated October 29, 2021 (See Note 1.12) GNF3 PCT = 0°F 10 CFR 50.46 Report dated October 29, 2022 (See Note 1.13) GNF3 PCT = 0°F 10 CFR 50.46 Report dated October 30, 2023 (See Note 1.14) GNF3 PCT = 0°F Net PCT (GNF3) 1940 °F
B. CURRENT LOCA MODEL ASSESSMENTS Total PCT Change from Current Assessments (See Note 2) GNF3 PCT = 0°F Cumulative PCT Change from Current Assessments GNF3 lPCTl = 0°F
Net PCT (GNF3) 1940 °F Attachment 5
10 CFR 50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors
Assessments as of October 29, 2024
Assessment Notes
Limerick Generating Station, Units 1 and 2
Report of the Emergency Core Cooling System Attachment 5 Evaluation Model Changes and Errors Page 1 of 5 Assessments as of October 29, 2024 Assessment Notes, LGS, Units 1 and 2
- 1. Prior LOCA Assessments
The last 10 CFR 50.46 annual report submitted to the NRC was on October 29, 2022 (Reference 1). This report documents a GNF2 fuel Net PCT of 2015°F, a Licensing Basis PCT of 1880°F from the analysis of record report, and a total PCT adder of +135°F at Limerick Generating Station (LGS), Units 1 and 2. The report also documents a GNF3 fuel Net PCT of 1940°F, a Licensing Basis PCT of 1940°F, and a total PCT adder of 0°F at Limerick Generating Station (LGS) Units 1 and 2. In addition to the existing GNF2 fuel, GNF3 fuel was introduced into the LGS Unit 1 core beginning in Cycle 20 and into the LGS Unit 2 core beginning in cycle 16. All of the listed prior LOCA assessments below are documented in the referenced letter.
[Reference 1: Letter from David P. Helker (Constellation Energy Generation, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report, dated October 29, 2022.]
1.1. Prior LOCA Assessment - 2011
The referenced letter provided an annual 50.46 report for Units 1 and 2. The referenced letter discussed the introduction of the GNF2 fuel design to the Limerick Unit 2 core. Subsequent to the referenced letter, the GNF2 fuel design was introduced to the Unit 1 core and the errors discussed in this note also apply to Unit 1 (See Note 1.2).
Also discussed in the referenced letter are two vendor notifications of Emergency Core Cooling System (ECCS) model error/changes for GNF2 fuel applicable to Limerick. The errors/changes are summarized below.
The first error involved the way input coefficients were used to direct the deposition of gamma radiation energy produced by the fuel. The impact of this error is estimated to be +45°F for GNF2 fuel.
The second error involved the contribution of heat from gamma ray absorption by the channel.
The gamma ray absorption by the channel was found to have been minimized. The impact of this error is estimated to be +5°F for GNF2 fuel.
[Reference 1.1: Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, 10 CFR 50.46 Annual Report, dated November 23, 2011.]
1.2. Prior LOCA Assessment - 2012
The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2012 reporting period.
GNF2 fuel was introduced into the Unit 1 core during Reload 14 (Cycle 15) outage. The ECCS model error/changes discussed in Note 1.1 were applied to Unit 1 as Prior LOCA Model Assessments.
[Reference 1.2: Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, 10 CFR 50.46 Annual Report, dated November 9, 2012.]
Report of the Emergency Core Cooling System Attachment 5 Evaluation Model Changes and Errors Page 2 of 5 Assessments as of October 29, 2024 Assessment Notes, LGS, Units 1 and 2
1.3. Prior LOCA Assessment - 2012 (30-day report)
The referenced letter provided a 50.46 30-day report for Units 1 and 2. To address inaccuracies in fuel pellet thermal conductivity as a function of exposure, commonly referred to as thermal conductivity degradation (TCD); GEH replaced the GESTR-LOCA model with a newer model, PRIME. The most dominant effect impacting PCT is from the way the PRIME fuel properties treat thermal conductivity, which results in a higher fuel stored energy. The PCT impact identified in the referenced letter reflects the difference between the existing GESTR analysis PCT and a conservatively postulated PCT if the analysis was performed with the PRIME model. The ECCS-LOCA analysis methodology remains GESTR based and will not be PRIME based until the ECCS-LOCA analysis is re-performed using PRIME.
[Reference 1.3: Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, 10 CFR 50.46 30-Day Report, dated December 12, 2012.]
1.4. Prior LOCA Assessment - 2013
The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2013 reporting period.
[Reference 1.4: Letter from James Barstow (Exelon Generation Company, LLC (EGC)) to U.S.
NRC, 10 CFR 50.46 Annual Report," dated November 8, 2013.]
1.5. Prior LOCA Assessment - 2014
The referenced letter reported four vendor notifications that were received. The first notification addressed several accumulated updates to the SAFER04A model. The code maintenance changes had an individually and collectively insignificant effect on calculated peak cladding temperature. The impact of this error is estimated to be 0°F for GNF2 fuel. The second notification was for a correction to a logic error that was isolated, occurring with an indication that the expected systems mass diverged from the calculated actual system mass. This error affected the ECCS flow credited as reaching the core. The impact of this error is estimated to be +10°F for GNF2 fuel. The third notification addressed an error with the imposed minimum pressure differential (p) for droplet flow above a two-phase level in the core. This error could have offered an inappropriate steam cooling benefit above the core two phase level. To correct this error an explicit core p calculation was applied without regard to droplet condition. The impact of this error is estimated to be +20°F for GNF2 fuel. The fourth notification addressed an incorrect pressure head representation when defining the counter current flow limitation (CCFL). The impact of this error is estimated to be -20°F for GNF2 fuel.
[Reference 1.5: Letter from James Barstow (Exelon Generation Company, LLC (EGC)) to U.S.
NRC, 10 CFR 50.46 Annual Report," dated November 7, 2014.]
Report of the Emergency Core Cooling System Attachment 5 Evaluation Model Changes and Errors Page 3 of 5 Assessments as of October 29, 2024 Assessment Notes, LGS, Units 1 and 2
1.6. Prior LOCA Assessment - 2015
The referenced letter provided an annual 50.46 report for LGS, Units 1 and 2. There were no errors reported for the 2015 reporting period. The referenced letter notes that LGS Unit 2 has unloaded all bundles of the GE14 fuel type from the core.
[Reference 1.6: Letter from James Barstow (Exelon Generation Company, LLC (EGC)) to U.S.
NRC, 10 CFR 50.46 Annual Report," dated November 6, 2015.]
1.7. Prior LOCA Assessment - 2016
The referenced letter notes that LGS Unit 1 has unloaded all bundles of the GE14 fuel type from the core. There were no errors reported for the 2016 reporting period.
[Reference 1.7: Letter from James Barstow (Exelon Generation Company, LLC (EGC)) to U.S.
NRC, 10 CFR 50.46 Annual Report," dated November 4, 2016.]
1.8. Prior LOCA Assessment - 2017
The referenced letter reported two vendor notifications regarding Emergency Core Cooling System (ECCS) modeling changes/errors applicable to LGS. These notifications described issues related to the improper modelling of lower tie plate leakage for the GNF2 fuel design (2017-01) and changes to modeling of the fuel rod plenum for 10x10 fuel (2017-02), respectively. The impact of the 2017-01 error is estimated to be +30°F for GNF2 fuel. The impact of the 2017-02 error is estimated to be 0°F for GNF2 fuel.
[Reference 1.8: Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report," dated November 6, 2017.]
1.9. Prior LOCA Assessment - 2018
The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2018 reporting period.
[Reference 1.9: Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report," dated November 6, 2018.]
1.10. Prior LOCA Assessment - 2019
The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2019 reporting period.
[Reference 1.10: Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report," dated October 29, 2019.]
Report of the Emergency Core Cooling System Attachment 5 Evaluation Model Changes and Errors Page 4 of 5 Assessments as of October 29, 2024 Assessment Notes, LGS, Units 1 and 2
1.11. Prior LOCA Assessment - 2020
The referenced letter provided an annual 50.46 report for Units 1 and 2. There were three errors reported for the 2020 reporting period.
Notification 2019-05 identifies that the upper and lower limits for the SAFER code forward and backward bypass leakage were coded incorrectly for the control rod guide tube to control rod drive housing interface backward leakage path. The error was estimated to have a zero-degree impact upon the GNF2 fuel licensing basis PCT.
Notification 2020-01 identifies that the PRIME code contained errors in Zircaloy irradiation growth after a breakaway neutron fluence, Zircaloy thermal conductivity applied to the zirconium barrier for cladding temperature drop, and gap conductance during pellet-cladding gap closure. The errors were estimated to have a zero-degree impact upon the GNF2 fuel licensing basis PCT.
Notification 2020-03 identifies that the Analysis of Record (AOR) did not utilize the bounding dome pressure. The dome pressure of 1063 psia was used in the AOR; instead of the more bounding Technical Specification LCO value of 1068 psia. The error was estimated to have a zero-degree impact upon the GNF2 fuel licensing basis PCT.
[Reference 1.11: Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report," dated October 29, 2020.]
1.12. Prior LOCA Assessment - 2021
The referenced letter provided an annual 50.46 report for Units 1 and 2. There were two errors reported for the 2021 reporting period.
Notification 2021-01 identifies an error in the fuel rod stress and perforation model due to an incorrect value used for the fuel pellet to plenum spring conductance input. The error was a result of an incorrect conversion from SI units in preparing the input for SAFER analyses. The error was estimated to have a zero degree impact upon the GNF2 fuel PCT.
Notification 2021-02 identifies an error in the inner cladding surface roughness value in the gap conductance model. An inconsistency was identified between the roughness value used in the fuel performance model PRIME and the input to the SAFER and TRACG calculations. The error was estimated to have a zero degree impact upon the GNF2 fuel PCT.
These Notifications were only applicable to the analysis of record documented in Attachments 1 and 3. The analysis of record documented in Attachment 2 and 4 was performed with corrected models and therefore these notifications were not applicable.
[Reference 1.12: Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report," dated October 29, 2021.]
Report of the Emergency Core Cooling System Attachment 5 Evaluation Model Changes and Errors Page 5 of 5 Assessments as of October 29, 2024 Assessment Notes, LGS, Units 1 and 2
1.13. Prior LOCA Assessment - 2022
The referenced letter provided an annual 50.46 report for Units 1 and 2. There was one error reported for the 2022 reporting period; however, a notification letter was not received.
The referenced letter included Constellation Issue Report 4508795, which was written to document a change to GNFs SAFER ECCS Evaluation Model for a decay heat input used in nominal calculations that occurred in 2011. The updated DH model is a best estimate decay heat curve based on the 1979 ANS 5.1 standard and considers SIL 636. This change was discovered during review of the GNF3 New Fuel Introduction and additional vendor assessments estimated an impact of 0°F upon the GNF2 PCT. This change was already incorporated into the initial GNF3 LOCA evaluation and, therefore, has no impact on the GNF3 LOCA analysis of record.
No additional ECCS related changes or modifications occurred at LGS that affected the assumptions in the GNF2 or GNF3 LOCA analysis of record.
[Reference 1.13: Letter from David P. Helker (Constellation Energy Generation, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report, dated October 29, 2022.]
1.14. Prior LOCA Assessment - 2023
The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2018 reporting period.
[Reference 1.14: Letter from David P. Helker (Constellation Energy Generation, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report, dated October 30, 2023.]
- 2. Current LOCA Assessment
The last Limerick Generating Station 10 CFR 50.46 Annual Report was submitted to the U.S.
NRC on October 30, 2023. Since the previous 10 CFR 50.46 report (Reference in Assessment Note 1.14) there have been no changes to the net PCT, Licensing Basis PCT, or PCT adder for GNF2 and GNF3 fuel.