RS-21-020, Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station

Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station

ML21050A242
Person / Time
Site:	LaSalle
Issue date:	02/18/2021
From:	Demetrius Murray Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-21-020
Download: ML21050A242 (9)

Text

4300 Winfield Road Warrenville, IL 60555 Exelon Generation 630 657 2000 Office RS-21-020 10 CFR 50.46 February 19, 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington , DC 20555-0001 LaSalle County Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374

Subject:

Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station

Reference:

Letter from D. Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station," dated March 9, 2020 In accordance with 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors," paragraph (a)(3)(ii), Exelon Generation Company, LLC (EGC) is submitting the attached information to fulfill the annual reporting requirements for LaSalle County Station (LSCS) , Units 1 and 2. The attachments describe the changes in accumulated peak cladding temperature (PCT) since the previous annual report submitted in the referenced letter.

There are no regulatory commitments contained in this submittal. Should you have any questions concerning this letter, please contact Mr. Jason Taken at (630) 657-3660.

~

Dwi Murray Sr. Manager - Licensing Exelon Generation Company, LLC Attachments:

1) LaSalle County Station, Units 1 and 2 - 10 CFR 50.46 Report

2) LaSalle County Station, Units 1 and 2 - 10 CFR 50.46 Report Assessment Notes

February 19, 2021 U.S. Nuclear Regulatory Commission Page 2 cc: NRC Regional Administrator, Region Ill NRC Senior Resident Inspector, LaSalle County Station Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT 1 LaSalle County Station, Units 1 and 2 10 CFR 50.46 Report PLANT NAME: LaSalle County Station (LSCS). Units 1 & 2 ECCS EVALUATION MODEL: SAFER/PRIME LOCA REPORT REVISION DATE: February 8. 2021 CURRENT OPERATING CYCLES: L1C19 and L2C18 ANALYSES OF RECORD

1) General Electric Hitachi (GEH) Calculation 0000-0121-8990-RO, "LaSalle County Station GNF2 ECCS-LOCA Evaluation," GEH Nuclear Energy, January 2012

2) GNF Document Number 002N3086 .1, "Technical Evaluation to Support Introduction of GNF3 Lead Use Assemblies (LUAs) in LaSalle County Station, Unit 2," Global Nuclear Fuel, December 2014 Fuel Types: GNF2. GNF3 LUAs Limiting Single Failure: High Pressure Core Spray Diesel Generator Failure Limiting Break Size & Location: Recirculation Pump Suction Line Break <0.08 ft2 in small break)

Reference Peak Cladding Temperature (PCT): GNF2: 1540°F GNF3 LUAs: 1550°F Page 1 of 2

ATTACHMENT 1 LaSalle County Station, Units 1 and 2 10 CFR 50.46 Report MARGIN ALLOCATION A PRIOR LOCA MODEL ASSESSMENTS GNF2: b.PCT 00F 10 CFR 50.46 Report dated March 7, 2012 (Note 1)

GNF3 LUA: N/A GNF2: b.PCT 0°F 10 CFR 50.46 Report dated March 7, 2013 (Note 2)

GNF3 LUA: N/A GNF2: b.PCT 00F 10 CFR 50.46 Report dated March 7, 2014 (Note 3)

GNF3 LUA: N/A GNF2: b.PCT -5°F 10 CFR 50.46 Report dated March 6, 2015 (Note 4)

GNF3 LUA: b.PCT = 0°F GNF2: b.PCT 00F 10 CFR 50.46 Report dated March 7, 2016 (Note 5)

GNF3 LUA: b.PCT = 0°F GNF2: b.PCT 00F 10 CFR 50.46 Report dated March 7, 2017 (Note 6)

GNF3 LUA: b.PCT = 0°F GNF2: b.PCT 00F 10 CFR 50.46 Report dated March 7, 2018 (Note 7)

GNF3 LUA: b.PCT = 0°F GNF2: b.PCT 0°F 10 CFR 50.46 Report dated March 7, 2019 (Note 8)

GNF3 LUA: b.PCT = 0°F GNF2: b.PCT 00F 10 CFR 50.46 Report dated March 9, 2020 (Note 9)

GNF3 LUA: b.PCT = 0°F GNF2: 1535°f Net PCT GNF3 LUA: 1550°F B. CURRENT LOCA MODEL ASSESSMENTS GNF2: Lb.PCT 25°F Total PCT Change from Current Assessments (Note 10)

GNF3 LUA: L b.PCT =25°F GNF2: L Jb.PCTI 25°F Cumulative PCT Change from Current Assessments GNF3 LUA: L Jb.PCTI =25°F GNF2: 1560°f Net PCT GNF3 LUA: 1575°f Page 2 of 2

ATTACHMENT 2 LaSalle County Station, Units 1 and 2 10 CFR 50.46 Report Assessment Notes ASSESSMENT NOTES

1. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2012 reporting period. The referenced letter reported the introduction of GNF2 fuel into the LSCS, Unit 1, core . A new LOCA analysis of record for GNF2 fuel was performed by GE Hitachi Nuclear Energy (GEH). No Emergency Core Cooling System (ECCS) related changes or modifications occurred at LSCS that affected the assumptions in the GEH GNF2 LOCA analysis.

[Reference : Letter from David M. Gullett (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "Plant Specific ECCS Evaluation Changes -10 CFR 50.46 Report," dated March 7, 2012]

2. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2013 reporting period . The referenced letter reported the introduction of GNF2 fuel into the LSCS, Unit 2, core. The referenced letter also reported no vendor notifications of ECCS model errors/changes applicable to the GNF2 fuel in LSCS, Units 1 and 2, and reported that no ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH GNF2 LOCA analysis for the GNF2 fuel in LSCS, Units 1 and 2.

[Reference : Letter from David M. Gullett (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 7, 2013]

3. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2014 reporting period . The referenced letter reported no vendor notifications of ECCS model errors/changes applicable to the GNF2 fuel in LSCS, Units 1 and 2, and reported that no ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH GNF2 LOCA analysis for the GNF2 fuel in LSCS, Units 1 and 2.

[Reference : Letter from David M. Gullett (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 7, 2014]

Page 1 of 5

ATTACHMENT 2 LaSalle County Station, Units 1 and 2 10 CFR 50.46 Report Assessment Notes

4. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2015 reporting period. The referenced letter reported four vendor notifications, Notifications 2014-01 through 2014-04, of ECCS model error/changes. The first notification addressed several code maintenance changes to the SAFER04A model, which resulted in a PCT change of 0°F for GNF2. The second notification corrected a logic error, which affects the ECCS flow credited as reaching the core. Correction of this error resulted in a 0°F PCT change for GNF2. 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 can offer an inappropriate steam cooling benefit above the core two phase level. Correction of this error resulted in a PCT change of -10°F for GNF2. The fourth 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.

The referenced letter also reported that no ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH LOCA analysis for the GNF2 fuel in LSCS, Units 1 and 2.

Four (4) GNF3 Lead Use Assemblies (LUAs) were loaded into LSCS, Unit 2, during the LSCS, Unit 2 Reload 15 outage (L2R15) . Notifications 2014-01through2014-04 were included in the determination of the licensing basis PCT for the GNF3 LUAs.

[

Reference:

Letter from David M. Gullatt (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 6, 2015]

5. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2016 reporting period. The referenced letter reported no vendor notifications of ECCS model errors/changes applicable to the GNF2 fuel in LSCS, Units 1 and 2, and reported that no ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH GNF2 LOCA analysis of record for the GNF2 fuel in LSCS, Units 1 and 2.

The referenced letter reported no vendor notifications of ECCS model errors/changes applicable to the GNF3 fuel in LSCS, Unit 2, and that no ECCS related changes or modifications occurred at LSCS, Unit 2, that affected the assumptions in the GEH GNF3 LOCA analysis of record for the GNF3 fuel in LSCS, Unit 2. All ATRIUM-10 fuel was removed from LSCS, Unit 1, during the LSCS, Unit 1 Reload 16(L1 R16) outage prior to startup of LSCS, Unit 1 Cycle 17 (L 1 C17).

[

Reference:

Letter from David M. Gullatt (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "Annual 10 CFR 50.46 Report of Emergency Core Page 2 of 5

ATTACHMENT 2 LaSalle County Station, Units 1 and 2 10 CFR 50.46 Report Assessment Notes Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 7, 2016]

6. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2017 reporting period. The referenced letter reported no vendor notification of the ECCS model errors/changes applicable to the GNF2 or GNF3 fuel in LSCS Units 1 and 2 and reported that no ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH LOCA analyses for GNF2 or GNF3 fuel at LSCS Units 1 and 2.

The letter also noted that all ATRIUM-10 fuel was removed from LSCS, Unit 2, prior to the start of LSCS, Unit 2 Cycle 17 (L2C17).

[Reference : Letter from David M. Gullett (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission , "Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 7, 2017]

7. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2018 reporting period. The referenced letter reported two vendor notifications were produced, 2017-01 and 2017-02. Notification 2017-01 describes corrections made to the GNF2 lower tie plate modeling and Notification 2017-02 describes corrections made to the fuel rod upper plenum thermal model. Neither of these corrections resulted in a change in PCT for either GNF2 or GNF3.

[Reference : Letter from David M. Gullett (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 7, 2018]

8. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2019 reporting period. The referenced letter reported no vendor notification of the ECCS model errors/changes applicable to the GNF2 or GNF3 fuel in LSCS Units 1 and 2 and reported that no ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH LOCA analyses for GNF2 or GNF3 fuel at LSCS, Units 1 and 2.

[Reference : RS-19-020 , Letter from David M. Gullett (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission , "Annual 10 CFR 50.46 Report of Emergency Page 3 of 5

ATTACHMENT 2 LaSalle County Station, Units 1 and 2 10 CFR 50.46 Report Assessment Notes Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 7, 2019]

9. Prior LOCA Assessment The referenced letter provided the annual 10 CFR 50.46 report for LSCS, Units 1 and 2, for the 2020 reporting period. The referenced letter reported one vendor notification of ECCS model errors/changes applicable to the GNF2 fuel in LSCS, Units 1 and 2 and the GNF3 LUAs in LSCS, Unit 2, issued in Notification 2019-05. Notification 2019-05 describes the driving differential pressure for the lower limit for the control rod guide tube to control rod driving housing interface backward leakage path that was found to be incorrect in SAFER. A SAFER version correcting this error was executed on representative plants and confirmed the software code and error had no impact on the plant ECCS LOCA evaluations, and reported a 0°F impact of PCT.

No ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH GNF2 LOCA analysis of record for the GNF2 fuel in LSCS, Units 1 and 2. No ECCS related changes or modifications occurred at LSCS, Unit 2, that affected the assumptions in the GEH GNF3 LOCA analysis of record for the GNF3 fuel in LSCS, Unit 2.

[Reference : RS-20-024, Letter from Dwi Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station,"

dated March 9, 2020]

10. Current LOCA Assessment Since the last annual 10 CFR 50.46 report, two vendor notifications of ECCS model errors/changes applicable to the GNF2 fuel in LSCS, Units 1 and 2, were issued in Notifications 2020-01 and 2020-02. Notification 2020-01 describes errors in the Zircaloy irradiation growth model, Zircaloy thermal conductivity for the Zr barrier, and gap conductance model in their PRIME code. The estimated PCT impact for this notification is 0°F. Notification 2020-02 describes an updated impact evaluation for one of the issues reported in Notification 2014-01. This update is regarding the SAFER code error regarding the subcooled water level in the downcomer region, more specifically for small break LOCA scenarios where a two-phase level is established in this region . The estimated PCT impact for this notification is 25°F.

Since the last annual 10 CFR 50.46 report, one vendor notification of ECCS model errors/changes applicable to the GNF3 LUAs in LSCS, Unit 2 has been issued.

Notification 2020-02 only lists GNF2 as the affected fuel, however after a review of Analyses of Record No. 2 of Attachment 1 it was concluded that the GNF3 LUAs PCT is based on GNF2 PCT (Analyses of Record No. 1 of Attachment 1). Therefore, the estimated GNF2 impact of 25°F is conservatively included for the GNF3 LUAs as well.

Page 4 of 5

ATTACHMENT 2 LaSalle County Station, Units 1 and 2 10 CFR 50.46 Report Assessment Notes No ECCS related changes or modifications occurred at LSCS that affected the assumptions in the GEH GNF2 LOCA analysis of record for the GNF2 fuel in LSCS, Units 1 and 2. No ECCS related changes or modifications occurred at LSCS, Unit 2, that affected the assumptions in the GEH GNF3 LOCA analysis of record for the GNF3 fuel in LSCS, Unit 2.

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