ML23226A111

10 CFR 50.46 Annual Report

ML23226A111
Person / Time
Site:	Peach Bottom
Issue date:	08/14/2023
From:	David Helker Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
Download: ML23226A111 (1)

Text

200ExelonWay KennettSquare,PA19348 www.ConstellationEnergy.com 10 CFR 50.46 August 14, 2023 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station, Units 2 and 3 Subsequent Renewed Facility Operating License Nos. DPR-44 and DPR-56 NRC Docket Nos. 50-277 and 50-278

Subject:

10 CFR 50.46 Annual Report

Reference:

Letter from David P. Helker (Constellation Energy Generation, LLC) to the U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 12, 2022 The purpose of this letter is to transmit the 10 CFR 50.46 reporting information for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3. The previous 10 CFR 50.46 report for PBAPS, Units 2 and 3, (Reference) provided the cumulative Peak Cladding Temperature (PCT) errors for the most recent fuel designs through August 12, 2022.

Since the last report (Reference), one new Notification Letter 2023-01 was issued which documents an error in the application of the SAFER evaluation model. The error was estimated to have a zero-degree impact upon the GNF2 and GNF3 PCT. Notification Letter 2023-01 has been incorporated into the Peach Bottom 2023 annual report as shown in Attachments 1 through 5. Both PBAPS Unit 2 and Unit 3 operate with GNF2 and GNF3 fuel. For this report, the PCT value for GNF2 fuel is 1962oF and the PCT value for GNF3 fuel is 2040oF.

There are no regulatory commitments in this letter.

If you have any questions concerning this letter, please contact Richard Gropp at richard.gropp@constellation.com.

Respectfully, David P. Helker Sr. Manager, Licensing Constellation Energy Generation, LLC

U.S. Nuclear Regulatory Commission Peach Bottom Atomic Power Station, Units 2 and 3 10 CFR 50.46 Report August 14, 2023 Page 2 Attachments:

1. Peach Bottom Unit 2 l SAFER/PRIME l GNF2 Fuel 10 CFR 50.46 Report

2. Peach Bottom Unit 2 l SAFER/PRIME l GNF3 Fuel 10 CFR 50.46 Report

3. Peach Bottom Unit 3 l SAFER/PRIME l GNF2 Fuel 10 CFR 50.46 Report

4. Peach Bottom Unit 3 l SAFER/PRIME l GNF3 Fuel 10 CFR 50.46 Report

5. Assessment Notes 10 CFR 50.46 Report cc:

w/Attachments USNRC Region I, Regional Administrator USNRC Senior Resident Inspector, PBAPS USNRC Project Manager, PBAPS W. DeHaas, Pennsylvania Bureau of Radiation Protection S. Seaman, State of Maryland



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Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 GNF2 Peak Cladding Temperature Rack-Up Sheet for PBAPS Unit 2 Page 1 of 1

PLANT NAME:

Peach Bottom Atomic Power Station, Unit 2 ECCS EVALUATION MODEL:

SAFER/PRIME REPORT REVISION DATE:

07/26/2023 EVALUATION MODEL VENDOR:

GNF/GEH CURRENT OPERATING CYCLE:

25 ANALYSIS OF RECORD CALCULATIONS

1. Project Task Report, Exelon Generation Company LLC, Peach Bottom Atomic Power Station, Units 2 & 3 MELLLA+ Task T0407: ECCS-LOCA Performance, 0000-0162-2354-R0, Revision 0, (PLM 000N0296 Revision 0), December 2013.

Fuels Analyzed in Calculations and in Operation:

GNF2 Limiting Fuel Type:

GNF2 Limiting Single Failure:

Battery Failure Limiting Break Location:

Recirculation Discharge Line Limiting Break Size 0.05 ft2 (Small Break)

Reference Peak Cladding Temperature (PCT) for GNF2 Fuel:

1920°F MARGIN ALLOCATION A. PRIOR LOCA ASSESSMENTS (Note 1) 10 CFR 50.46 Report dated August 15, 2014 (Note 1.1)

GNF2: PCT = 5°F 10 CFR 50.46 Report dated August 10, 2016 (Note 1.2)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 10, 2017 (Note 1.3)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 10, 2018 (Note 1.4)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 12, 2019 (Note 1.5)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 12, 2020 (Note 1.6)

GNF2: PCT = 0°F 10 CFR 50.46 Report (30-Day Report) dated November 05, 2020 (Note 1.7)

GNF2: PCT = 37°F 10 CFR 50.46 Report dated August 12, 2021 (Note 1.8)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 12, 2022 (Note 1.9)

GNF2: PCT = 0°F Net PCT GNF2: 1962°F B. CURRENT LOCA ASSESSMENTS (Note 2)

Total PCT Change from Current Assessments (Note 2)

GNF2: PCT = 0°F Cumulative PCT Change from Current Assessments GNF2: lPCTl = 0°F Net PCT GNF2: 1962°F







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Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 GNF3 Peak Cladding Temperature Rack-Up Sheet for PBAPS Unit 2 Page 1 of 1

PLANT NAME:

Peach Bottom Atomic Power Station, Unit 2 ECCS EVALUATION MODEL:

SAFER/PRIME REPORT REVISION DATE:

07/26/2023 EVALUATION MODEL VENDOR:

GNF/GEH CURRENT OPERATING CYCLE:

25 ANALYSIS OF RECORD CALCULATIONS

1. Peach Bottom Atomic Power Station Units 2 & 3 GNF3 ECCS-LOCA Evaluation, 005N9630-R0, Revision 0, April 2021.

Fuels Analyzed in Calculations and in Operation:

GNF3 Limiting Fuel Type:

GNF3 Limiting Single Failure:

Battery Failure Limiting Break Location:

Recirculation Discharge Line Limiting Break Size 0.05 ft2 (Small Break)

Reference Peak Cladding Temperature (PCT) for GNF3 Fuel:

2040°F MARGIN ALLOCATION A. PRIOR LOCA ASSESSMENTS (Note 1)

No prior LOCA Model Assessments have been provided as this is the first time the reference Analysis of Record is being reported. (See Note 1)

N/A Net PCT GNF3: 2040°F B. CURRENT LOCA ASSESSMENTS (Note 2)

Total PCT Change from Current Assessments (Note 2)

GNF2: PCT = 0°F Cumulative PCT Change from Current Assessments GNF2: lPCTl = 0°F Net PCT GNF3: 2040°F





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Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 GNF2 Peak Cladding Temperature Rack-Up Sheet for PBAPS Unit 3 Page 1 of 1

ANALYSIS OF RECORD CALCULATIONS

1. Project Task Report, Exelon Generation Company LLC, Peach Bottom Atomic Power Station, Units 2 & 3 MELLLA+ Task T0407: ECCS-LOCA Performance, 0000-0162-2354-R0, Revision 0, (PLM 000N0296 Revision 0), December 2013.

Fuels Analyzed in Calculations and in Operation:

GNF2 Limiting Fuel Type:

GNF2 Limiting Single Failure:

Battery Failure Limiting Break Location:

Recirculation Discharge Line Limiting Break Size 0.05 ft2 (Small Break)

Reference Peak Cladding Temperature (PCT) for GNF2 Fuel:

1920°F MARGIN ALLOCATION A. PRIOR LOCA ASSESSMENTS (Note 1) 10 CFR 50.46 Report dated August 15, 2014 (Note 1.1)

GNF2: PCT = 5°F 10 CFR 50.46 Report dated August 10, 2016 (Note 1.2)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 10, 2017 (Note 1.3)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 10, 2018 (Note 1.4)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 12, 2019 (Note 1.5)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 12, 2020 (Note 1.6)

GNF2: PCT = 0°F 10 CFR 50.46 Report (30-Day Report) dated November 05, 2020 (Note 1.7)

GNF2: PCT = 37°F 10 CFR 50.46 Report dated August 12, 2021 (Note 1.8)

GNF2: PCT = 0°F 10 CFR 50.46 Report dated August 12, 2022 (Note 1.9)

GNF2: PCT = 0°F Net PCT GNF2: 1962°F B. CURRENT LOCA ASSESSMENTS (Note 2)

Total PCT Change from Current Assessments (Note 2)

GNF2: PCT = 0°F Cumulative PCT Change from Current Assessments GNF2: lPCTl = 0°F Net PCT GNF2: 1962°F PLANT NAME:

Peach Bottom Atomic Power Station, Unit 3 ECCS EVALUATION MODEL:

SAFER/PRIME REPORT REVISION DATE:

07/26/2023 EVALUATION MODEL VENDOR:

GNF/GEH CURRENT OPERATING CYCLE:

24







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Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 GNF3 Peak Cladding Temperature Rack-Up Sheet for PBAPS Unit 3 Page 1 of 1

PLANT NAME:

Peach Bottom Atomic Power Station, Unit 3 ECCS EVALUATION MODEL:

SAFER/PRIME REPORT REVISION DATE:

07/26/2023 EVALUATION MODEL VENDOR:

GNF/GEH CURRENT OPERATING CYCLE:

24 ANALYSIS OF RECORD CALCULATIONS

1. Peach Bottom Atomic Power Station Units 2 & 3 GNF3 ECCS-LOCA Evaluation, 005N9630-R0, Revision 0, April 2021.

Fuels Analyzed in Calculations and in Operation:

GNF3 Limiting Fuel Type:

GNF3 Limiting Single Failure:

Battery Failure Limiting Break Location:

Recirculation Discharge Line Limiting Break Size 0.05 ft2 (Small Break)

Reference Peak Cladding Temperature (PCT) for GNF3 Fuel:

2040°F MARGIN ALLOCATION A. PRIOR LOCA ASSESSMENTS (Note 1) 10 CFR 50.46 Report dated August 12, 2022 (Note 1.9)

GNF3: PCT = 0°F Net PCT GNF3: 2040°F B. CURRENT LOCA ASSESSMENTS (Note 2)

Total PCT Change from Current Assessments (Note 2)

GNF3: PCT = 0°F Cumulative PCT Change from Current Assessments GNF3: lPCTl = 0°F Net PCT GNF3: 2040°F









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Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 Assessment Notes for PBAPS Page 1 of 5

1. Prior LOCA Assessments The last 50.46 annual report submitted to the U.S. Nuclear Regulatory Commission (NRC) was on August 12, 2022 (Reference 1). This report documents a GNF2 fuel Net PCT of 1962°F; a Licensing Basis PCT of 1920°F from the analysis of record report, and a total PCT adder of +42°F at Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3. The report also documents a GNF3 fuel Net PCT of 2040°F; a Licensing Basis PCT of 2040°F, and a total PCT adder of 0°F at PBAPS Unit 3. GNF3 fuel was introduced into the PBAPS Unit 2 Cycle 25 core in addition to the existing GNF2 fuel. All 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. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 12, 2022.]

1.1. Prior LOCA Assessment - 2014 The referenced letter reported four vendor notifications that were received.

1. 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.

2. 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 Emergency Core Cooling System (ECCS) flow credited as reaching the core. Correction of this error resulted in a +10°F Peak Cladding Temperature (PCT) change for GNF2 fuel.

3. 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 pressure drop calculation was applied without regard to droplet condition resulting in a PCT of -10°F for GNF2 fuel.

4. The forth notification addressed an incorrect pressure head representation when defining the Counter Current Flow Limitation (CCFL). Correction of this error resulted in a +5°F PCT change for GNF2 fuel.

Note that the 10 CFR 50.46 notifications discussed in the referenced report are applicable to the Unit 2 and Unit 3 MELLLA+ LOCA analysis and the net effect of these notifications is +5°F

[

Reference:

Letter from James Barstow (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 15, 2014.]

Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 Assessment Notes for PBAPS Page 2 of 5

1.2. Prior LOCA Assessment - 2016 The referenced letter reported that Peach Bottom Unit 2 and Unit 3 implemented Maximum Extended Load Line Limit Analysis Plus (MELLLA+) for which a new LOCA analysis was performed. Unit 2 and Unit 3 transitioned to MELLLA+ operation mid-cycle in April 2016 and May 2016, respectively. The error notifications reported in Assessment Note 1.1 are applicable to the Peach Bottom 2 and 3 MELLLA+ LOCA analysis. The notifications were issued subsequent to the performance of the MELLLA+ LOCA analysis, but prior to its implementation.

[

Reference:

Letter from James Barstow (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 10, 2016.]

1.3. Prior LOCA Assessment - 2017 The referenced letter reported two vendor notifications regarding ECCS modeling changes/errors applicable to PBAPS (Notifications 2017-01 and 2017-02). These notifications described issues related to the improper modelling of lower tie plate leakage for the GNF2 fuel design and changes to modeling of the fuel rod plenum for 10x10 fuel. Correction of these errors each resulted in a 0°F PCT change for GNF2 fuel.

The referenced letter reported a change in the Level 3 setpoint. The impact of this change on the Loss of Coolant Accident (LOCA) analysis was assessed in GNF Report 003N4534-R0, "Peach Bottom Level 3 Analytical Limit Reduction," dated May 25, 2016, which concluded that there is no impact on the licensing basis PCT for PBAPS.

[

Reference:

Letter from David T. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 10, 2017.]

1.4. Prior LOCA Assessment - 2018 The referenced letter reported no changes/errors against the PBAPS LOCA Analysis of Record during this reporting period.

[

Reference:

Letter from David T. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 10, 2018.]

1.5. Prior LOCA Assessment - 2019 The referenced letter reported no changes/errors against the PBAPS LOCA Analysis of Record during this reporting period.

[

Reference:

Letter from David T. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 12, 2019.]

Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 Assessment Notes for PBAPS Page 3 of 5

1.6. Prior LOCA Assessment - 2020 The referenced letter reported two vendor notifications:

Notification 2019-05 identified 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 zero-degree upon the GNF2 PCT.

Notification 2020-01 identified that the PRIME code contained errors in irradiation growth after a breakaway neutron fluence, 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 zero-degree impact upon the GNF2 PCT.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 12, 2020.]

1.7. Prior LOCA Assessment - 2020 (30-Day Report)

The referenced letter reported two vendor notifications:

Notification Letter (NL) 2020-02 documented that the vendor impact evaluation performed in NL 2014-01 was incorrect, and NL 2020-02 provides an updated impact evaluation for one of the issues reported in NL 2014-01. NL 2014-01 (Assessment Note 1.1) reports several changes, one of which is regarding the SAFER code error regarding the subcooled water level in the downcomer. Per NL 2020-02, the impact evaluation performed for 2014-01 was inaccurate, especially for postulated LOCA scenarios where a two-phase level establishes in the downcomer, an expected response for small recirculation line break scenarios. The PBAPS LOCA analysis is small break limited as documented in Attachments 1 and 2, and hence, NL 2020-02 impacted the PBAPS LOCA analysis.

NL 2020-02 was issued by the vendor as a new notification with a PCT impact of 35oF. This was the first NL for PBAPS since the 2020 annual report (Assessment Note 1.6), and the absolute value of the reported impact was less than 50oF; therefore, typically this NL wouldnt have required a thirty-day reporting per 10CFR50.46(a)(3)(ii). However, as documented in NL 2020-02, while this notification did not alter the SAFER code used in the PBAPS LOCA evaluation (Attachments 1 and 2), it did alter the PCT impact from the SAFER code change as reported in NL 2014-01. Therefore, NL 2020-02 effectively amended NL 2014-01 for PBAPS.

Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 Assessment Notes for PBAPS Page 4 of 5

Since NL 2020-02 notification effectively amended 2014-01, the thirty-day reporting requirement was evaluated based upon the conditions applicable when notification 2014-01 was initially issued. Assessment Note 1.1 documents four notifications reported on August 15, 2014. Those four notifications were:

2014-01 = 0°F, 2014-02 = 10°F, 2014-03 = -10°F, and, 2014-04 = 5°F.

with a total impact of 25°F (= 0 + 10 + l-10l + 5). When the reported 2014-01 value (0°F) is corrected with the updated value from NL 2020-02 (35°F), the total impact becomes 60°F (= 35

+ 10 + l-10l + 5), which is larger than the 50°F significance threshold defined in 10CFR50.46(a)(3)(i) for thirty-day reporting. Therefore, this thirty-day report was prepared for PBAPS for NL 2020-02.

Notification 2020-03 identified that the dome pressure input used for Appendix K calculations in the current LOCA analysis of record (Attachments 1 and 2) did not cover operation allowed by Technical Specifications 3.4.10. A PCT impact of +2°F was reported in NL 2020-03 for correcting the dome pressure input used in the analysis.

As described in the description of NL 2020-02, this thirty-day report was prepared for NL 2020-02 received on 10/07/2020. However, since NL 2020-03 was issued within the thirty-day reporting timeframe for NL 2020-02, this thirty-day report also addressed NL 2020-03 for complete and accurate reporting.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Emergency Core Cooling System (ECCS) Loss of Coolant Accident (LOCA) 10 CFR 50.46 30-Day Report," dated November 05, 2020.]

1.8. Prior LOCA Assessment - 2021 The referenced letter reported three vendor notifications:

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 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 PCT.

Annual Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of July 26, 2023 Assessment Notes for PBAPS Page 5 of 5

Notification 2021-03 identifies that an incorrect Low-Pressure Coolant Injection (LPCI) flow rate value at a high pressure point was used in the input to the SAFER calculations. The error was estimated to have a zero-degree impact upon the GNF2 PCT.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, 10 CFR 50.46 Annual Report, dated August 12, 2021.]

1.9. Prior LOCA Assessment - 2022 Issue Report 4508795 reports that a change in 2011 was made to the decay heat (DH) input used in nominal calculations for the SAFER evaluation model. 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.

[

Reference:

Letter from David P. Helker (Constellation Energy Generation, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 12, 2022.]

2. Current LOCA Assessment Since the previous 10 CFR 50.46 report (Reference in Note 1.9) there has been one change.

Notification Letter 2023-01 identifies an error in the application of the SAFER evaluation model.

Potential voids in ECCS piping could delay water entering the core, or spargers, which could impact the Peak Cladding Temperature (PCT). ECCS piping is typically filled with liquid water from the system injection valve to the vessel. The system pressure is often above the low pressure ECCS pump shutoff head while the system injection valve is opening for small breaks. When this is true, no flow can pass through the final check valve. A delay in ECCS injection caused by a potential void in the ECCS piping after the final check valve is considered reportable under interpretation of 10 CFR 50.46 because it may impact the small break PCT result. The error was estimated to have a zero-degree impact upon the GNF2 and GNF3 PCT.

No additional ECCS related changes or modifications occurred at PBAPS that affected the assumptions in the GNF2 or GNF3 LOCA analysis of record.