ML20303A013
| ML20303A013 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 10/29/2020 |
| From: | David Helker Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML20303A013 (11) | |
Text
200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.46 October 29, 2020 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:
- 1. Letter from D. Helker (Exelon Generation Company, LLC) to U.S.
Nuclear Regulatory Commission, 10 CFR 50.46 Annual Report, dated October 29, 2019.
- 2. Notification Letter 2019-05, SAFER Lower Limit on Differential Pressure for Bypass Leakage, dated October 23, 2019.
- 3. Notification Letter 2020-01, PRIME Coding Errors for Zircaloy Irradiation Growth and Zr Barrier Thermal Conductivity as input to ECCS LOCA Analyses, dated April 14, 2020.
- 4. Notification Letter 2020-03, Dome Pressure Input Change to Span Range of Tech Spec LCO, dated October 9, 2020.
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 1) provided the cumulative Peak Cladding Temperature (PCT) errors for the most recent fuel design through October 29, 2019.
Since the Reference 1 report, three vendor notifications regarding Emergency Core Cooling System (ECCS) modeling changes/errors applicable to LGS, Units 1 and 2, have been issued (References 2, 3, and 4). These notifications identified that: (1) 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; (2) 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; and (3) the
Limerick Generating Station, Units 1 and 2 10 CFR 50.46 Annual Report October 29, 2020 Page 2 dome pressure of 1063 psia was used in the Analysis of Record instead of the more bounding Technical Specification Limiting Condition for Operation value of 1068 psia.
These errors were estimated to have a zero-degree impact upon the GNF2 licensing basis Peak Cladding Temperature (PCT). Therefore, the total net PCT value of 2015oF reported in the 2019 annual report is unchanged for this report.
Three attachments are included with this letter that provide the current LGS, Units 1 and 2, 10 CFR 50.46 status. Attachments 1 and 2 (Peak Cladding Temperature Rack-Up Sheet) provide information regarding the PCT for the limiting Loss of Coolant Accident (LOCA) analysis evaluations for LGS, Units 1 and 2, respectively. Attachment 3, Assessment Notes, contains a detailed description for each change or error reported.
There are no regulatory commitments in this letter.
If you have any questions, please contact Glenn Stewart at 610-765-5529.
Respectfully, David P. Helker Sr. Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC Attachments:
- 1) Peak Cladding Temperature Rack-Up Sheet (Limerick Generating Station, Unit 1)
- 2) Peak Cladding Temperature Rack-Up Sheet (Limerick Generating Station, Unit 2)
- 3) Assessment Notes (Limerick Generating Station, Units 1 and 2) cc: USNRC Region I, Regional Administrator USNRC Senior Resident Inspector, LGS USNRC Project Manager, LGS W. DeHaas, Pennsylvania Bureau of Radiation Protection
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, 2020 Peak Cladding Temperature Rack-Up Sheet Limerick Generating Station, Unit 1
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Page 1 of 1 Assessments as of October 29, 2020 Peak Cladding Temperature Rack-Up Sheet, LGS Unit 1 PLANT NAME:
Limerick Unit 1 ECCS EVALUATION MODEL:
SAFER/GESTR-LOCA REPORT REVISION DATE:
10/29/2020 CURRENT OPERATING CYCLE:
19 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 Net PCT (GNF2) 2015 °F B.
CURRENT LOCA MODEL ASSESSMENTS Total PCT Change from Current Assessments (See Note 2)
GNF 2 PCT = 0 °F Cumulative PCT Change from Current Assessments GNF2 PCT = 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, 2020 Peak Cladding Temperature Rack-Up Sheet Limerick Generating Station, Unit 2
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Page 1 of 1 Assessments as of October 29, 2020 Peak Cladding Temperature Rack-Up Sheet, LGS Unit 2 PLANT NAME:
Limerick Unit 2 ECCS EVALUATION MODEL:
SAFER/GESTR-LOCA REPORT REVISION DATE:
10/29/2020 CURRENT OPERATING CYCLE:
16 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 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 PCT = 0°F Net PCT (GNF2) 2015 °F
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, 2020 Assessment Notes Limerick Generating Station, Units 1 and 2
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Page 1 of 4 Assessments as of October 29, 2020 Assessment Notes, LGS, Units 1 and 2
- 1.
Prior LOCA Assessments The last 10 CFR 50.46 annual report submitted to NRC was on October 29, 2019 (Reference 1).
This report documents a Total Net PCT of 2015°F. All of the listed prior LOCA assessments below are documented in the referenced letter.
[Reference 1: Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. NRC, 10 CFR 50.46 Annual Report," dated October 29, 2019.]
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.]
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
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Page 2 of 4 Assessments as of October 29, 2020 Assessment Notes, LGS, Units 1 and 2 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.]
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.]
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Page 3 of 4 Assessments as of October 29, 2020 Assessment Notes, LGS, Units 1 and 2 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.]
- 2. Current LOCA Assessment The following 50.46 notifications were received from the fuel vendor since the last (2019) annual report (Reference 1.10) submitted to the NRC.
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 licensing basis PCT.
Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Page 4 of 4 Assessments as of October 29, 2020 Assessment Notes, LGS, Units 1 and 2 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 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 licensing basis PCT.
Therefore, the total net PCT value of 2015oF reported in the 2019 annual report is unchanged for this report.