ML15310A088

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Submittal of 10 CFR 50.46 Annual Report
ML15310A088
Person / Time
Site: Limerick  Constellation icon.png
Issue date: 11/06/2015
From: Jim Barstow
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML15310A088 (12)


Text

Exelon Generation November 6, 2015 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Units 1 and 2 200 Exelon Way Kennett Square. PA 19348 www.exetoncorp.com 10 CFR 50.46 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

References:

1) Letter from J. Barstow (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report,"

dated November 7, 2014 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 designs through November 7, 2014.

Since the Reference 1 report was issued, no vendor notifications of an Emergency Core Cooling System (ECCS) model error/change applicable to LGS, Units 1 and 2, have been issued. Also, no ECCS-related changes or modifications have occurred at LGS, Units 1 and 2, that affect the assumptions of the ECCS analyses.

It should be noted that since the Reference 1 report, LGS Unit 2 has unloaded all bundles of the GE14 fuel type from the core. Therefore, only the GNF2 fuel type is reported on.

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 updated 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.

U.S. Nuclear Regulatory Commission Limerick Generating Station, Units 1 and 2 1 O CFR 50.46 Annual Report November 6, 2015 Page 2 There are no regulatory commitments in this letter.

If you have any questions, please contact Glenn Stewart at 610-765-5529.

Respectfully, d~~

James Barstow Director - 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 R. R. Janati, Bureau of Radiation Protection

ATTACHMENT 1 Peak Cladding Temperature Rack-Up Sheet Limerick Generating Station, Unit 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 November 6, 2015

Peak Cladding Temperature Rack-Up Sheet, LGS Unit 1 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 PLANT NAME:

ECCS EVALUATION MODEL:

REPORT REVISION DATE:

CURRENT OPERATING CYCLE:

Limerick Unit 1 SAFER/GESTR-LOCA 11/6/15 1Q ANALYSIS OF RECORD CALCULATIONS Page 1of2

1. "Limerick Generating Station, Units 1 and 2 SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis," NEDC-32170P, Rev. 2, May 1995.
2. "Limerick Generating Station Units 1 and 2 ECCS-LOCA Evaluation for GE14," GE-NE-J 1103793-09-01 P, March 2001.
3. "Limerick Generating Station Units 1 and 2 GNF2 ECCS-LOCA Evaluation,"

0000-0111-9078-RO, February 2011

4. "Summary of GEH Transient Anticipated Operational Occurrences (AOO) and Loss of Coolant Accident (LOCA) Analyses with Respect to ASD Modification in Limerick Generating Station Units 1 and 2," 0000-0129-8688-R1, Revision 1, May 2011.

Fuels Analyzed in Calculations and in Operation: GE14 and GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure (GE14/GNF2): Battery Failure Limiting Break Size and Location (GE14/GNF2): Double-Ended Guillotine in a Recirculation Suction Pipe Reference Peak Cladding Temperature (PCT) - GE14: 1670°F Reference Peak Cladding Temperature (PCT) - GNF2: 1880°F

Peak Cladding Temperature Rack-Up Sheet, LGS Unit 1 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 MARGIN ALLOCATION A.

PRIOR LOCA MODEL ASSESSMENTS 1 O CFR 50.46 Report dated December 18, 2002 (See Note 1) 1 O CFR 50.46 Report dated December 16, 2003 (See Note 2) 1 O CFR 50.46 Report dated December 3, 2004 (See Note 3) 1 O CFR 50.46 Report dated December 1, 2005 (See Note 4) 1 O CFR 50.46 Report dated December 1, 2006 (See Note 5) 1 O CFR 50.46 Report dated November 30, 2007 (See Note 6) 1 O CFR 50.46 Report dated November 24, 2008 (See Note 7) 1 O CFR 50.46 Report dated November 24, 2009 (See Note 8) 1 O CFR 50.46 Report dated November 24, 201 O (See Note 9) 1 O CFR 50.46 Report dated November 23, 2011 (See Note 1 O) 1 O CFR 50.46 Report dated November 9, 2012 (See Note 11) 10 CFR 50.46 Report dated December 12, 2012 (See Note 12) 1 O CFR 50.46 Report dated November 8, 2013 (See Note 13) 10 CFR 50.46 Report dated November 7, 2014 (See Note 14)

Net PCT (GE14)

Net PCT (GNF2)

B.

CURRENT LOCA MODEL ASSESSMENTS None (See Note 15)

Total PCT change from current assessments (GE14)

Total PCT change from current assessments (GNF2)

Cumulative PCT change from current assessments (GE14)

Cumulative PCT change from current assessments (GNF2)

Net PCT lGE14)

Net PCT lGNF2)

Page 2 of 2 GE14 L1PCT = 10°F GE14 L1PCT = -5°F GE14 L1PCT = 0°F GE14 L1PCT = 0°F GE14 L1PCT = 0°F GE14 L1PCT = 0°F GE14 i'.1PCT = 0°F GE14 i'.1PCT = 0°F GE14 L1PCT = 0°F GE14 L1PCT = 50°F GNF2 i'.1PCT = 50°F GE14 i'.1PCT = 0°F GNF2 L1PCT = 0°F GE14 i'.1PCT = 65°F GNF2 L1PCT = 45°F GE14 i'.1PCT = 0°F GNF2 L1PCT = 0°F GE14 L1PCT = 10°F GNF2 i'.1PCT = 10°F 1800 °F 1985 °F GE14 L1PCT = 0°F GNF2 i'.1PCT = 0°F IL1PCT = 0 °F IL1PCT = 0 °F I I i'.1PCT I = 0 °F I I i'.1PCT I = 0 °F 1800 °F 1985 °F

ATTACHMENT 2 Peak Cladding Temperature Rack-Up Sheet Limerick Generating Station, Unit 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 November 6, 2015

Peak Cladding Temperature Rack-Up Sheet, LGS Unit 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 PLANT NAME:

ECCS EVALUATION MODEL:

REPORT REVISION DATE:

CURRENT OPERATING CYCLE:

Limerick Unit 2 SAFER/G ESTR-LOCA 11/6/15 H

ANALYSIS OF RECORD CALCULATIONS Page 1 of 1

1. "Limerick Generating Station, Units 1 and 2 SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis," NEDC-32170P, Rev. 2, May 1995.
2. "Limerick Generating Station Units 1 and 2 GNF2 ECCS-LOCA Evaluation,"

0000-0111-9078-RO, February 2011.

Fuels Analyzed in Calculations and in Operation: GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure (GNF2): Battery Failure Limiting Break Size and Location (GNF2): Double-Ended Guillotine in a Recirculation Suction Pipe Reference Peak Cladding Temperature (PCT) - GNF2: 1880°F MARGIN ALLOCATION A.

PRIOR LOCA MODEL ASSESSMENTS 1 O CFR 50.46 Report dated November 23, 2011 (See Note 10)

GNF2 tiPCT = 50°F 1 O CFR 50.46 Report dated November 9, 2012 (See Note 11)

GNF2 tiPCT = 0°F 1 O CFR 50.46 Report dated December 12, 2012 (See Note 12)

GNF2 tiPCT = 45°F 1 O CFR 50.46 Report dated November 8, 2013 (See Note 13)

GNF2 tiPCT = 0°F 10 CFR 50.46 Report dated November 7, 2014 (See Note 14)

GNF2 tiPCT = 10°F Net PCT (GNF2) 1985 °F B.

CURRENT LOCA MODEL ASSESSMENTS None (See Note 15)

GNF2 tiPCT = 0°F Total PCT change from current assessments (GNF2)

ItiPCT = 0 °F Cumulative PCT change from current assessments (GNF2)

I I tiPCT I = 0 °F Net PCT lGNF2l 1985 °F Assessment Notes Limerick Generating Station, Units 1 and 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 November 6, 2015

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015

1.

Prior LOCA Assessment Page 1of4 The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported GE LOCA errors related to a SAFER core spray sparger elevation error and a SAFER bulk water level error. The PCT impact for the new errors was determined to be 15°F and -5°F, respectively, for GE14 fuel. The total PCT impact of these errors was determined to be 10°F for GE14 fuel.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Reporting Requirements," dated December 18, 2002.]

2.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported a GE LOCA error related to a SAFER Level/Volume Table error. The PCT impact for the new error was determined to be -5°F for GE14 fuel.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Reporting Requirements," dated December 16, 2003.]

3.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported GE LOCA errors related to a GESTR file interpolation error, a SAFER computer platform change, a WEVOL S1 volume error, a SAFER separator pressure drop error and a new heat source. The PCT impact for the new errors was determined to be 0°F for each error. The total PCT impact of these errors on GE14 fuel was determined to be 0°F.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated December 3, 2004.]

4.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2005 reporting period.

[

Reference:

Letter from Pamela B. Cowan (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated December 1, 2005.]

5.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported a newly discovered sensitivity to the assumed axial power shape for small break LOCA cases. This sensitivity may result in higher calculated PCT values for top-peaked

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 Page 2 of 4 axial power shapes. Due to this sensitivity, the calculated small break PCT for Limerick was higher than the previously calculated value. However, the Licensing Basis PCT (based on large break) remained the same. Therefore, the PCT impact of the new power shape sensitivity was determined to be 0°F for GE14 fuel.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report"" dated December 1, 2006.]

6.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2007 reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 30, 2007.]

7.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2008 reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 24, 2008.]

8.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2009 reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 24, 2009.]

9.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 201 O reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated November 24, 201 O.]

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 1 O.

Prior LOCA Assessment Page 3 of 4 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. The assessment notes above (Notes 1-9) are not applicable to GNF2 fuel. 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 11 ).

Also discussed in the referenced letter are two vendor notifications of Emergency Core Cooling System (ECCS) model error/changes for GE14 and 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. Correction of this error resulted in a PCT increase of 45°F for both the GE14 fuel and 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.

Correction of this error resulted in a PCT increase of 5°F for both the GE14 fuel and GNF2 fuel.

[

Reference:

Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 23, 2011.]

11.

Prior LOCA Assessment 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 O were applied to Unit 1 as Prior LOCA Model Assessments.

[

Reference:

Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 9, 2012.]

12.

Prior LOCA Assessment The referenced letter provided an annual 50.46 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

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 Page 4 of 4 remains GESTR based and will not be PRIME based until the ECCS-LOCA analysis is re-performed using PRIME.

[

Reference:

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.J

13.

Prior LOCA Assessment 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:

Letter from James Barstow (Exelon Generation Company, LLC (EGG)) to U.S.

NRG, "10 CFR 50.46 Annual Report," dated November 8, 2013.J

14.

Prior LOCA Assessment 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. Correction of this error resulted in a 0°F PCT change to both GE14 and 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. Correction of this error resulted in a 10°F PCT change to both GE14 and 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 resulting in a PCT of +20°F to both GE14 and GNF2 fuel. The fourth notification addressed an incorrect pressure head representation when defining the counter current flow limitation (CCFL). Correction of this error resulted in a -20°F PCT change to both GE14 and GNF2 fuel.

[

Reference:

Letter from James Barstow (Exelon Generation Company, LLC (EGG)) to U.S.

NRG, "10 CFR 50.46 Annual Report," dated November 7, 2014.J

15.

Current LOCA Assessment No vendor 50.46 change/error notifications have been received since the last annual report. In addition, since the last annual report, Limerick Unit 2 has unloaded all bundles of the GE 14 fuel type from the core.

Exelon Generation November 6, 2015 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Units 1 and 2 200 Exelon Way Kennett Square. PA 19348 www.exetoncorp.com 10 CFR 50.46 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

References:

1) Letter from J. Barstow (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report,"

dated November 7, 2014 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 designs through November 7, 2014.

Since the Reference 1 report was issued, no vendor notifications of an Emergency Core Cooling System (ECCS) model error/change applicable to LGS, Units 1 and 2, have been issued. Also, no ECCS-related changes or modifications have occurred at LGS, Units 1 and 2, that affect the assumptions of the ECCS analyses.

It should be noted that since the Reference 1 report, LGS Unit 2 has unloaded all bundles of the GE14 fuel type from the core. Therefore, only the GNF2 fuel type is reported on.

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 updated 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.

U.S. Nuclear Regulatory Commission Limerick Generating Station, Units 1 and 2 1 O CFR 50.46 Annual Report November 6, 2015 Page 2 There are no regulatory commitments in this letter.

If you have any questions, please contact Glenn Stewart at 610-765-5529.

Respectfully, d~~

James Barstow Director - 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 R. R. Janati, Bureau of Radiation Protection

ATTACHMENT 1 Peak Cladding Temperature Rack-Up Sheet Limerick Generating Station, Unit 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 November 6, 2015

Peak Cladding Temperature Rack-Up Sheet, LGS Unit 1 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 PLANT NAME:

ECCS EVALUATION MODEL:

REPORT REVISION DATE:

CURRENT OPERATING CYCLE:

Limerick Unit 1 SAFER/GESTR-LOCA 11/6/15 1Q ANALYSIS OF RECORD CALCULATIONS Page 1of2

1. "Limerick Generating Station, Units 1 and 2 SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis," NEDC-32170P, Rev. 2, May 1995.
2. "Limerick Generating Station Units 1 and 2 ECCS-LOCA Evaluation for GE14," GE-NE-J 1103793-09-01 P, March 2001.
3. "Limerick Generating Station Units 1 and 2 GNF2 ECCS-LOCA Evaluation,"

0000-0111-9078-RO, February 2011

4. "Summary of GEH Transient Anticipated Operational Occurrences (AOO) and Loss of Coolant Accident (LOCA) Analyses with Respect to ASD Modification in Limerick Generating Station Units 1 and 2," 0000-0129-8688-R1, Revision 1, May 2011.

Fuels Analyzed in Calculations and in Operation: GE14 and GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure (GE14/GNF2): Battery Failure Limiting Break Size and Location (GE14/GNF2): Double-Ended Guillotine in a Recirculation Suction Pipe Reference Peak Cladding Temperature (PCT) - GE14: 1670°F Reference Peak Cladding Temperature (PCT) - GNF2: 1880°F

Peak Cladding Temperature Rack-Up Sheet, LGS Unit 1 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 MARGIN ALLOCATION A.

PRIOR LOCA MODEL ASSESSMENTS 1 O CFR 50.46 Report dated December 18, 2002 (See Note 1) 1 O CFR 50.46 Report dated December 16, 2003 (See Note 2) 1 O CFR 50.46 Report dated December 3, 2004 (See Note 3) 1 O CFR 50.46 Report dated December 1, 2005 (See Note 4) 1 O CFR 50.46 Report dated December 1, 2006 (See Note 5) 1 O CFR 50.46 Report dated November 30, 2007 (See Note 6) 1 O CFR 50.46 Report dated November 24, 2008 (See Note 7) 1 O CFR 50.46 Report dated November 24, 2009 (See Note 8) 1 O CFR 50.46 Report dated November 24, 201 O (See Note 9) 1 O CFR 50.46 Report dated November 23, 2011 (See Note 1 O) 1 O CFR 50.46 Report dated November 9, 2012 (See Note 11) 10 CFR 50.46 Report dated December 12, 2012 (See Note 12) 1 O CFR 50.46 Report dated November 8, 2013 (See Note 13) 10 CFR 50.46 Report dated November 7, 2014 (See Note 14)

Net PCT (GE14)

Net PCT (GNF2)

B.

CURRENT LOCA MODEL ASSESSMENTS None (See Note 15)

Total PCT change from current assessments (GE14)

Total PCT change from current assessments (GNF2)

Cumulative PCT change from current assessments (GE14)

Cumulative PCT change from current assessments (GNF2)

Net PCT lGE14)

Net PCT lGNF2)

Page 2 of 2 GE14 L1PCT = 10°F GE14 L1PCT = -5°F GE14 L1PCT = 0°F GE14 L1PCT = 0°F GE14 L1PCT = 0°F GE14 L1PCT = 0°F GE14 i'.1PCT = 0°F GE14 i'.1PCT = 0°F GE14 L1PCT = 0°F GE14 L1PCT = 50°F GNF2 i'.1PCT = 50°F GE14 i'.1PCT = 0°F GNF2 L1PCT = 0°F GE14 i'.1PCT = 65°F GNF2 L1PCT = 45°F GE14 i'.1PCT = 0°F GNF2 L1PCT = 0°F GE14 L1PCT = 10°F GNF2 i'.1PCT = 10°F 1800 °F 1985 °F GE14 L1PCT = 0°F GNF2 i'.1PCT = 0°F IL1PCT = 0 °F IL1PCT = 0 °F I I i'.1PCT I = 0 °F I I i'.1PCT I = 0 °F 1800 °F 1985 °F

ATTACHMENT 2 Peak Cladding Temperature Rack-Up Sheet Limerick Generating Station, Unit 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 November 6, 2015

Peak Cladding Temperature Rack-Up Sheet, LGS Unit 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 PLANT NAME:

ECCS EVALUATION MODEL:

REPORT REVISION DATE:

CURRENT OPERATING CYCLE:

Limerick Unit 2 SAFER/G ESTR-LOCA 11/6/15 H

ANALYSIS OF RECORD CALCULATIONS Page 1 of 1

1. "Limerick Generating Station, Units 1 and 2 SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis," NEDC-32170P, Rev. 2, May 1995.
2. "Limerick Generating Station Units 1 and 2 GNF2 ECCS-LOCA Evaluation,"

0000-0111-9078-RO, February 2011.

Fuels Analyzed in Calculations and in Operation: GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure (GNF2): Battery Failure Limiting Break Size and Location (GNF2): Double-Ended Guillotine in a Recirculation Suction Pipe Reference Peak Cladding Temperature (PCT) - GNF2: 1880°F MARGIN ALLOCATION A.

PRIOR LOCA MODEL ASSESSMENTS 1 O CFR 50.46 Report dated November 23, 2011 (See Note 10)

GNF2 tiPCT = 50°F 1 O CFR 50.46 Report dated November 9, 2012 (See Note 11)

GNF2 tiPCT = 0°F 1 O CFR 50.46 Report dated December 12, 2012 (See Note 12)

GNF2 tiPCT = 45°F 1 O CFR 50.46 Report dated November 8, 2013 (See Note 13)

GNF2 tiPCT = 0°F 10 CFR 50.46 Report dated November 7, 2014 (See Note 14)

GNF2 tiPCT = 10°F Net PCT (GNF2) 1985 °F B.

CURRENT LOCA MODEL ASSESSMENTS None (See Note 15)

GNF2 tiPCT = 0°F Total PCT change from current assessments (GNF2)

ItiPCT = 0 °F Cumulative PCT change from current assessments (GNF2)

I I tiPCT I = 0 °F Net PCT lGNF2l 1985 °F Assessment Notes Limerick Generating Station, Units 1 and 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 November 6, 2015

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015

1.

Prior LOCA Assessment Page 1of4 The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported GE LOCA errors related to a SAFER core spray sparger elevation error and a SAFER bulk water level error. The PCT impact for the new errors was determined to be 15°F and -5°F, respectively, for GE14 fuel. The total PCT impact of these errors was determined to be 10°F for GE14 fuel.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Reporting Requirements," dated December 18, 2002.]

2.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported a GE LOCA error related to a SAFER Level/Volume Table error. The PCT impact for the new error was determined to be -5°F for GE14 fuel.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Reporting Requirements," dated December 16, 2003.]

3.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported GE LOCA errors related to a GESTR file interpolation error, a SAFER computer platform change, a WEVOL S1 volume error, a SAFER separator pressure drop error and a new heat source. The PCT impact for the new errors was determined to be 0°F for each error. The total PCT impact of these errors on GE14 fuel was determined to be 0°F.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated December 3, 2004.]

4.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2005 reporting period.

[

Reference:

Letter from Pamela B. Cowan (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated December 1, 2005.]

5.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. This letter reported a newly discovered sensitivity to the assumed axial power shape for small break LOCA cases. This sensitivity may result in higher calculated PCT values for top-peaked

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 Page 2 of 4 axial power shapes. Due to this sensitivity, the calculated small break PCT for Limerick was higher than the previously calculated value. However, the Licensing Basis PCT (based on large break) remained the same. Therefore, the PCT impact of the new power shape sensitivity was determined to be 0°F for GE14 fuel.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report"" dated December 1, 2006.]

6.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2007 reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 30, 2007.]

7.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2008 reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 24, 2008.]

8.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 2009 reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 24, 2009.]

9.

Prior LOCA Assessment The referenced letter provided an annual 50.46 report for Units 1 and 2. There were no errors reported for the 201 O reporting period.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated November 24, 201 O.]

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 1 O.

Prior LOCA Assessment Page 3 of 4 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. The assessment notes above (Notes 1-9) are not applicable to GNF2 fuel. 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 11 ).

Also discussed in the referenced letter are two vendor notifications of Emergency Core Cooling System (ECCS) model error/changes for GE14 and 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. Correction of this error resulted in a PCT increase of 45°F for both the GE14 fuel and 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.

Correction of this error resulted in a PCT increase of 5°F for both the GE14 fuel and GNF2 fuel.

[

Reference:

Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 23, 2011.]

11.

Prior LOCA Assessment 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 O were applied to Unit 1 as Prior LOCA Model Assessments.

[

Reference:

Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "1 O CFR 50.46 Annual Report," dated November 9, 2012.]

12.

Prior LOCA Assessment The referenced letter provided an annual 50.46 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

Assessment Notes, LGS, Units 1 and 2 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of November 6, 2015 Page 4 of 4 remains GESTR based and will not be PRIME based until the ECCS-LOCA analysis is re-performed using PRIME.

[

Reference:

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.J

13.

Prior LOCA Assessment 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:

Letter from James Barstow (Exelon Generation Company, LLC (EGG)) to U.S.

NRG, "10 CFR 50.46 Annual Report," dated November 8, 2013.J

14.

Prior LOCA Assessment 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. Correction of this error resulted in a 0°F PCT change to both GE14 and 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. Correction of this error resulted in a 10°F PCT change to both GE14 and 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 resulting in a PCT of +20°F to both GE14 and GNF2 fuel. The fourth notification addressed an incorrect pressure head representation when defining the counter current flow limitation (CCFL). Correction of this error resulted in a -20°F PCT change to both GE14 and GNF2 fuel.

[

Reference:

Letter from James Barstow (Exelon Generation Company, LLC (EGG)) to U.S.

NRG, "10 CFR 50.46 Annual Report," dated November 7, 2014.J

15.

Current LOCA Assessment No vendor 50.46 change/error notifications have been received since the last annual report. In addition, since the last annual report, Limerick Unit 2 has unloaded all bundles of the GE 14 fuel type from the core.