ML13095A182

Braidwood Station and Byron Station - Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors

ML13095A182
Person / Time
Site:	Byron, Braidwood
Issue date:	04/05/2013
From:	Gullott D M Exelon Generation Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
RS-13-090
Download: ML13095A182 (15)

Text

4300 Winfield Road Warrenville, IL 60555 Exeton Generation(., RS-13-09010 CFR 50.46 April 5, 2013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF

-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455

Subject:

Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors

References:

1)Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. NRC,"Annual 10 CFR 50.46 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors," dated April 6, 2012 2)Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S. NRC, Byron and Braidwood Stations, Unit 1, "ECCS Evaluation Model Error -

10 CFR 50.46 Report," dated May 21, 2012 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 Braidwood and Byron Stations, Units 1 and 2.

The attachments describe the changes in accumulated peak cladding temperature (PCT) since the previous annual report submitted in Reference 1 and the 30

-day report submitted in Reference 2.The 30-day report provided the estimated impact of thermal conductivity degradation on the large break loss of coolant accident (LBLOCA)analysis for Braidwood Station, Unit 1 and Byron Station, Unit 1.

The 90 O F penalties in the small break loss of coolant accident (SBLOCA)analysis for Byron and Braidwood Stations, Units 1 and 2 were initially reported in notifications made on May 10 and November 19, 2007, and on April 11, 2008. There has since been no assessment of an additional penalty greater than 0 OF PCT.Therefore, the conclusion previously stated in the 10 CFR 50.46 notifications, that re-analysis for SBLOCA is not needed, continues to apply.

630 657 2000 Office A ; 1 U'" Exelon Generation@

RS-13-090 April 5, 2013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455 4300 Winfield Road Warrenville.

IL 60555 630 657 2000 Office 10 CFR 50.46

Subject:

Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors

References:

1) Letter from D. M. Gullott (Exelon Generation Company, LLC) to U. S. NRC, "Annual 10 CFR 50.46 Report of the Emergency Core Cooling System Evaluation Model Changes and Errors,* dated April 6, 2012 2) Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S. NRC, Byron and Braidwood Stations, Unit 1, "ECCS Evaluation Model Error-10 CFR 50.46 Report," dated May 21, 2012 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 Braidwood and Byron Stations, Units 1 and 2. The attachments describe the changes in accumulated peak cladding temperature (PCT) since the previous annual report submitted in Reference 1 and the 30-day report submitted in Reference

2. The 30-day report provided the estimated impact of thermal conductivity degradation on the large break loss of coolant accident (LBLOCA) analysis for Braidwood Station, Unit 1 and Byron Station, Unit 1. The 90 OF penalties in the small break loss of coolant accident (SBLOCA) analysis for Byron and Braidwood Stations, Units 1 and 2 were initially reported in notifications made on May 10 and November 19, 2007, and on April 11, 2008. There has since been no assessment of an additional penalty greater than 0 OF PCT. Therefore, the conclusion previously stated in the 10 CFR 50.46 notifications, that re-analysis for SBLOCA is not needed, continues to apply.

April 5, 2013 U. S. Nuclear Regulatory Commission Page 2 There are no regulatory commitments contained in this submittal. Should you have any questions concerning this letter, please contact Richard W. McIntosh at (630) 657-2816.

Respectfully, David M.Gullott Manager - Licensing Exelon Generation Company, LLC Attachments:

1)Braidwood and Byron Stations, Units 1 and 2 - 10 CFR 50.46 Report 2)Braidwood and Byron Stations, Units 1 and 2 - 10 CFR 50.46 Report Assessment Notes cc:NRC Regional Administrator, Region III NRC Senior Resident Inspector, Braidwood Station NRC Senior Resident Inspector, Byron Station NRR Project Manager, Braidwood and Byron Stations Illinois Emergency Management Agency - Division of Nuclear Safety April 5, 2013 U. S. Nuclear Regulatory Commission Page 2 There are no regulatory commitments contained in this submittal.

Should you have any questions concerning this letter, please contact Richard W. Mcintosh at (630) 657-2816.

Respectfully, /2fJ/Maf!!7-----.

David M. Gullott Manager -Licensing Exelon Generation Company, LLC Attachments:

1) Braidwood and Byron Stations, Units 1 and 2 -10 CFR 50.46 Report 2) Braidwood and Byron Stations, Units 1 and 2 -10 CFR 50.46 Report Assessment Notes cc: NRC Regional Administrator, Region 1\1 NRC Senior Resident Inspector, Braidwood Station NRC Senior Resident Inspector, Byron Station NRR Project Manager, Braidwood and Byron Stations Illinois Emergency Management Agency -Division of Nuclear Safety ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Braidwood Station Unit 1 ECCS EVALUATION MODEL:Small Break Loss of Coolant Accident (SBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 17 ANALYSIS OF RECORD (AOR)

Evaluation Model: NOTRUMP Calculation:

Westinghouse CN-LIS-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location: 2-inch Break in the Bottom of the Cold Leg Reference Peak Cladding Temperature (PCT)PCT = 1624.0°F MARGIN ALLOCATION A.PRIOR LOSS OF COOLANT ACCIDENT (LOCA)

MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1)

APCT = 0 OF 10 CFR 50.

46 report dated April 18, 2002 (Note 2)

APCT = 0 OF 10 CFR 50.46 report dated April 14, 2003 (Note 3)APCT = 0 OF 10 CFR 50.46 report dated April 14, 2004 (Note 4)APCT = 35 OF 10 CFR 50.46 report dated April 14, 2005 (Note 5)APCT = 0 OF 10 CFR 50.46 report dated April 14, 2006 (Note 6)APCT = 0 OF 10 CFR 50.46 report dated April 13, 2007 (Note 7)APCT = 0 OF 10 CFR 50.46 report dated June 22, 2007 (Note 9)APCT = 0 OF 10 CFR 50.46 report dated November 19, 2007 (Note 10)APCT = 90 OF 10 CFR 50.46 report dated April 11, 2008 (Note 11)APCT = 0 OF 10 CFR 50.46 report dated April 9, 2009 (Note 12)

APCT = 0 OF 10 CFR 50.46 report dated April 8, 2010 (Note 13)APCT = 0 OF 10 CFR 50.46 report dated April 6, 2011 (Note 15)

APCT = 0 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)

APCT = 0 °F NET PCT PCT = 1749.0°F B.CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity De g radation (Note 24)

APCT = 0 OF Total PCT change from current assessments E APCT = 0 OF Cumulative PCT change from current assessments APCT 1=0-17 NET PCT Page 1 of 8 PCT = 1749.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Braidwood Station Unit 1 ECCS EVALUATION MODEL: REPORT REVISION DATE: Small Break Loss of Coolant Accident (SBLOCAl 04/05/13 CURRENT OPERATING CYCLE: 17 ANALYSIS OF RECORD (AOR) Evaluation Model: NOTRUMP Calculation:

Westinghouse CN-LiS-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

2-inch Break in the Bottom of the Cold Leg Reference Peak Cladding Temperature (PCT) PCT = 1624.0°F MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1) of 10 CFR 50.46 report dated April 18, 2002 (Note 2) of 10 CFR 50.46 report dated April 14, 2003 (Note 3) of 10 CFR 50.46 report dated April 14, 2004 (Note 4) of 10 CFR 50.46 report dated April 14, 2005 (Note 5) 10 CFR 50.46 report dated April 14, 2006 (Note 6) 0 OF 1 0 CFR 50.46 report dated April 13, 2007 (Note 7) of 10 CFR 50.46 report dated June 22, 2007 (Note 9) 10 CFR 50.46 report dated November 19, 2007 (Note 10) 90°F 10 CFR 50.46 report dated April 11, 2008 (Note 11) 0 of 10 CFR 50.46 report dated April 9, 2009 (Note 12) 0 of 10 CFR 50.46 report dated April 8, 2010 (Note 13)

OF 10 CFR 50.46 report dated April 6, 2011 (Note 15) of 1 0 CFR 50.46 report dated April 6, 2012 (Note 17) of NETPCT PCT = 1749.0°F B. CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity of DeJll"adation (Note 24) Total PCT change from current assessments Cumulative PCT change from current assessments L

1= 0 of NETPCT PCT = 1749.0°F Page 1 of 8 ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Braidwood Station Unit 1 ECCS EVALUATION MODEL:Large Break Loss of Coolant Accident (LBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model:

ASTRUM (2004)

Calculation:

Westinghouse WCAP-16841-P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location: Guillotine break in the Cold Leg Reference PCTPCT =1913.0°F MARGIN ALLOCATION A.PRIOR LOSS OF COOLANT ACCIDENT (LOCA)

MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15, 2011 (Note 14)APCT = 0 OF 10 CFR 50.46 report dated April 6, 2011 (Note 15)APCT = 0 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)APCT = 0 OF 10 CFR 50.46 report dated May 21, 2012 (Note 18)APCT = 44 OF NET PCT PCT = 1957.0°F B.CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19)

APCT = 0 OF HOTSPOT Burst Temperature Calculation for ZIRLO Cladding (Note 20)APCT = 0 OF HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet Average Temperature (Note 21)

APCT = 0 OF WCOBRA/TRAC Automated Restart Process Logic Error (Note 22)

APCT = 0 OF Rod Internal Pressure Calculation (Note 23)

APCT = 0 OF WCOBRA/TRAC Thermal-Hydraulic History File Dimension Used in HSDRIVER (See Note 25)

BPCT = 0 OF Total PCT change from current assessments E APCT = 0 OF Cumulative PCT change from current assessments E APCT= 0 °F NET PCT Page 2 of 8 PCT = 1957.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Braidwood Station Unit 1 ECCS EVALUATION MODEL: REPORT REVISION DATE: Large Break Loss of Coolant Accident (LBLOCA) 04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model: ASTRUM (2004) Calculation:

Westinghouse WCAP-16841-P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

Guillotine break in the Cold Leg Reference PCT PCT = 1913.0°F MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15,2011 (Note 14) APCT=O of 10 CFR 50.46 report dated April 6, 2011 (Note 15) APCT=O of 10 CFR 50.46 report dated April 6, 2012 (Note 17) APCT=O of 10 CFR 50.46 report dated May 21 , 2012 (Note 18) APCT =44 of NETPCT PCT = 1957.0°F B. CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19) APCT=O°F HOTSPOT Burst Temperature Calculation for ZIRLO Cladding APCT=O of (Note 20) HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet APCT=O of Averaae Temperature (Note 21) WCOBRAITRAC Automated Restart Process Logic Error (Note 22) APCT= O°F Rod Internal Pressure Calculation (Note 23) APCT=O of WCOBRAITRAC Thermal-Hydraulic History File Dimension Used in APCT=O of HSDRIVER (See Note 25) Total PCT change from current assessments LAPCT=O°F Cumulative PCT change from current assessments L I APCT 1=0 of NETPCT PCT = 1957.0°F Page 2 of 8 ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Braidwood Station Unit 2 ECCS EVALUATION MODEL:Small Break Loss of Coolant Accident (SBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model:

NOTRUMP Calculation:

Westinghouse CN-LIS-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location: 2-inch Break in the Bottom of the Cold Leg Reference PCTPCT = 1627.0°F MARGIN ALLOCATION A.PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1)

APCT = 3 OF 10 CFR 50.46 report dated April 18, 2002 (Note 2)

APCT = 0 OF 10 CFR 50.46 report dated April 14, 2003 (Note 3)

APCT = 0 OF 10 CFR 50.46 report dated April 14, 2004 (Note 4)

APCT = 35 OF 10 CFR 50.46 report dated April 14, 2005 (Note 5)

APCT = 0 OF 10 CFR 50.46 report dated April 14, 2006 (Note 6)

APCT = 0 OF 10 CFR 50.46 report dated April 13, 2007 (Note 7)

APCT = 0 OF 10 CFR 50.46 report dated June 22, 2007 (Note 9)

APCT = 0 OF 10 CFR 50.46 report dated April 11, 2008 (Note 11)

APCT = 90 OF 10 CFR 50.46 report dated April 9, 2009 (Note 12)

APCT = 0 OF 10 CFR 50.46 report dated April 8, 2010 (Note 13)

APCT = 0 OF 10 CFR 50.46 report dated April 6, 2011 (Note 15)

APCT = 0 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)

APCT = 0 OF NET PCT PCT = 1755.0°F B.CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity De g radation (Note 24)

APCT = 0 OF Total PCT change from current assessments Y- APCT = 0 OF Cumulative PCT change from current assessments Y APCT I= 0 OF NET PCT Page 3 of 8 PCT = 1755.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Braidwood Station Unit 2 ECCS EVALUATION MODEL: REPORT REVISION DATE: Small Break Loss of Coolant Accident (SBLOCAl 04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model: NOTRUMP Calculation:

Westinghouse CN-US-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

2-inch Break in the Bottom of the Cold Leg Reference PCT PCT = 1627.0°F MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1) 3°F 10 CFR 50.46 report dated April 18, 2002 (Note 2) = 0 of 10 CFR 50.46 report dated April 14, 2003 (Note 3) 10 CFR 50.46 report dated April 14, 2004 (Note 4) of 10 CFR 50.46 report dated April 14, 2005 (Note 5) = 0 of 10 CFR 50.46 report dated April 14, 2006 (Note 6) 10 CFR 50.46 report dated April 13, 2007 (Note 7) of 10 CFR 50.46 report dated June 22, 2007 (Note 9) of 10 CFR 50.46 report dated April 11, 2008 (Note 11) 90°F 10 CFR 50.46 report dated April 9, 2009 (Note 12) of 10 CFR 50.46 report dated April 8, 2010 (Note 13) 10 CFR 50.46 report dated April 6, 2011 (Note 15) 10 CFR 50.46 report dated April 6, 2012 (Note 17) 0 of NETPCT PCT = 1755.0°F B. CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity of DeQradation (Note 24) Total PCT change from current assessments Cumulative PCT change from current assessments L I 1=0 of NETPCT PCT = 1755.0°F Page 3 of 8 ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Braidwood Station Unit 2 ECCS EVALUATION MODEL:Large Break Loss of Coolant Accident (LBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model: ASTRUM (2004)

Calculation:

Westinghouse WCAP-1 6841 -P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location: Guillotine break in the Cold Leg Reference PCTPCT = 2041.0°F MARGIN ALLOCATION A.PRIOR LOSS OF COOLANT ACCIDENT (LOCA)

MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15, 2011 (Note 14)

APCT = 0 OF 10 CFR 50.46 report dated April 6, 2011 (Note 15)APCT = 0 OF 10 CFR 50.46 report dated March 19, 2012 (Note 16)APCT = -42 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)APCT = 0 OF NET PCT PCT = 1999.0°F B.CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19)

APCT = 0 OF HOTSPOT Burst Temperature Calculation for ZIRLO Cladding (Note 20)APCT = 0 OF HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet Average Temperature Note 21 APCT = 0 OF WCOBRA/TRAC Automated Restart Process Logic Error (Note 22)

APCT = 0 OF Rod Internal Pressure Calculation (Note 23)

APCT = 0 OF WCOBRA/TRAC Thermal-Hydraulic History File Dimension Used in HSDRIVER (See Note 25)

APCT = 0 OF Total PCT change from current assessments Y- APCT = 0 OF Cumulative PCT change from current assessments Y APCT= 0 OF NET PCT Page 4 of 8 PCT = 1999.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Braidwood Station Unit 2 ECCS EVALUATION MODEL: REPORT REVISION DATE: Large Break Loss of Coolant Accident (LBLOCA) 04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model: ASTRUM (2004) Calculation:

Westinghouse WCAP-16841-P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

Guillotine break in the Cold Leg Reference PCT PCT = 2041.0°F MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15, 2011 (Note 14) L\PCT = 0 of 10 CFR 50.46 report dated April 6, 2011 (Note 15) L\PCT = 0 of 10 CFR 50.46 report dated March 19, 2012 (Note 16) L\PCT = -42 of 10 CFR 50.46 report dated April 6, 2012 (Note 17) L\PCT = 0 of NETPCT PCT = 1999.0°F B. CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19) L\PCT = 0 OF HOTSPOT Burst Temperature Calculation for ZIRLO Cladding L\PCT = 0 OF (Note 20) HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet L\PCT = 0 OF Average Temperature (Note 21) WCOBRAITRAC Automated Restart Process Logic Error (Note 22) L\PCT = 0 of Rod I nternal Pressure Calculation (Note 23) L\PCT = 0 of WCOBRAITRAC Thermal-Hydraulic History File Dimension Used in L\PCT = 0 OF HSDRIVER (See Note 25) Total PCT change from current assessments LL\PCT= 0 OF Cumulative PCT change from current assessments L I L\PCT I = 0 of NETPCT PCT = 1999.0°F Page 40f 8 ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Byron Station Unit 1 ECCS EVALUATION MODEL:Small Break Loss of Coolant Accident (SBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 19 AO R Evaluation Model: NOTRUMP Calculation:

Westinghouse CN-LIS-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location: 2-inch Break in the Bottom of the Cold Leg Reference PCTPCT= 1624.0°F MARGIN ALLOCATION A.PRIOR LOSS OF COOLANT ACCIDENT (LOCA)

MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1)

APCT = 0 OF 10 CFR 50.46 report dated April 18, 2002 (Note 2)

APCT = 0 OF 10 CFR 50.46 report dated April 14, 2003 (Note 3)

APCT = 0 OF 10 CFR 50.46 report dated April 14, 2004 (Note 4)

APCT = 35 OF 10 CFR 50.46 report dated April 14, 2005 (Note 5)

APCT = 0 OF 10 CFR 50.46 report dated April 14, 2006 (Note 6)

APCT = 0 OF 10 CFR 50.46 report dated April 13, 2007 (Note 7)

APCT = 0 OF 10 CFR 50.46 report dated June 22, 2007 (Note 9)

APCT = 0 OF 10 CFR 50.46 report dated April 11, 2008 (Note 11)

APCT = 90 OF 10 CFR 50.46 report dated April 9, 2009 (Note 12)

APCT = 0 OF 10 CFR 50.46 report dated April 8, 2010 (Note 13)

APCT = 0 OF 10 CFR 50.46 report dated April 6, 2011 (Note 15)

APCT = 0 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)

APCT = 0 OF NET PCT PCT = 1749.0°F B.CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity De g radation (Note 24)

APCT = 0 OF Total PCT change from current assessments E APCT = 0 OF Cumulative PCT change from current assessments Y APCT= 0 OF NET PCT Page 5of8 PCT = 1749.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Byron Station Unit 1 ECCS EVALUATION MODEL: REPORT REVISION DATE: Small Break Loss of Coolant Accident (SBLOCAl 04/05/13 CURRENT OPERATING CYCLE: 19 AOR Evaluation Model: NOTRUMP Calculation:

Westinghouse CN-LiS-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

2-inch Break in the Bottom of the Cold Leg Reference PCT PCT = 1624.0°F MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1) LiPCT = 0 of 10 CFR 50.46 report dated April 18, 2002 (Note 2) LiPCT = 0 of 10 CFR 50.46 report dated April 14, 2003 (Note 3) LiPCT = 0 of 10 CFR 50.46 report dated April 14, 2004 (Note 4) LiPCT = 35 of 10 CFR 50.46 report dated April 14, 2005 (Note 5) LiPCT = 0 of 10 CFR 50.46 report dated April 14, 2006 (Note 6) LiPCT = 0 OF 10 CFR 50.46 report dated April 13, 2007 (Note 7) LiPCT = 0 of 10 CFR 50.46 report dated June 22, 2007 (Note 9) LiPCT = 0 of 10 CFR 50.46 report dated April 11, 2008 (Note 11) LiPCT = 90 of 10 CFR 50.46 report dated April 9, 2009 (Note 12) LiPCT = 0 of 10 CFR 50.46 report dated April 8, 2010 (Note 13) LiPCT = 0 of 10 CFR 50.46 report dated April 6, 2011 (Note 15) LiPCT = 0 of 10 CFR 50.46 report dated April 6, 2012 (Note 17) LiPCT = 0 of NETPCT PCT = 1749.0°F B. CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity LiPCT = 0 of Degradation (Note 24) Total PCT change from current assessments L LiPCT = 0 of Cumulative PCT change from current assessments L ILiPCT 1= 0 OF NETPCT PCT = 1749.0°F Page 5 of 8 ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Byron Station Unit 1 ECCS EVALUATION MODEL:Large Break Loss of Coolant Accident (LBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 19 AOR Evaluation Model:

ASTRUM (2004)

Calculation:

Westinghouse WCAP-1 6841-P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type:

VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location: Guillotine break in the Cold Leg Reference PCTPCT =1913.0°F MARGIN ALLOCATION A.PRIOR LOSS OF COOLANT ACCIDENT (LOCA)

MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15, 2011 (Note 14)APCT = 0 OF 10 CFR 50.46 report dated April 6, 2011 (Note 15)APCT = 0 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)

APCT = 0 OF 10 CFR 50.46 report dated May 21, 2012 (Note 18)

APCT = 44 OF NET PCT PCT = 1957.0°F B.CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19)

APCT = 0 OF HOTSPOT Burst Temperature Calculation for ZIRLO Cladding (Note 20)APCT = 0 OF HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet Avera ge Temp erature Note 21 APCT = 0 OF WCOBRA/TRAC Automated Restart Process Logic Error (Note 22)

APCT = 0 OF Rod Internal Pressure Calculation (Note 23)APCT = 0 OF WCOBRAJTRAC Thermal-Hydraulic History File Dimension Used in HSDRIVER See Note 25)

APCT = 0 OF Total PCT change from current assessments APCT = 0 OF Cumulative PCT change from current assessments I APCT= 0 OF NET PCT Page 6 of 8 PCT = 1957.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Byron Station Unit 1 ECCS EVALUATION MODEL: REPORT REVISION DATE: Large Break Loss of Coolant Accident (LBLOCAl 04/05/13 CURRENT OPERATING CYCLE: 19 AOR Evaluation Model: ASTRUM (2004) Calculation:

Westinghouse WCAP-16841-P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

Guillotine break in the Cold Leg Reference PCT PCT = 1913.0°F MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15, 2011 (Note 14) dPCT=O of 10 CFR 50.46 report dated April 6, 2011 (Note 15) dPCT= O°F 10 CFR 50.46 report dated April 6, 2012 (Note 17) dPCT= O°F 10 CFR 50.46 report dated May 21 , 2012 (Note 18) dPCT=44°F NETPCT PCT = 1957.0°F B. CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19) dPCT= 0 OF HOTSPOT Burst Temperature Calculation for ZIRLO Cladding (Note dPCT=O of 20) HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet dPCT=O of Average Temperature (Note 21) WCOBRAITRAC Automated Restart Process Logic Error (Note 22) dPCT=O of Rod Internal Pressure Calculation (Note 23) dPCT=O of WCOBRAITRAC Thermal-Hydraulic History File Dimension Used in dPCT=O of HSDRIVER (See Note 25) Total PCT change from current assessments LdPCT=O of Cumulative PCT change from current assessments L IdPCT 1= 0 of NETPCT PCT = 1957.0°F Page 60f 8 ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Byron Station Unit 2 ECCS EVALUATION MODEL:Small Break Loss of Coolant Accident (SBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model:

NOTRUMP Calculation:

Westinghouse CN-LIS-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure:

Loss of one train of ECCS flow Limiting Break Size and Location: 2-inch Break in the Bottom of the Cold Leg Reference PCTPCT = 1627.0°F MARGIN ALLOCATION A.PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1)APCT = 3 OF 10 CFR 50.46 report dated April 18, 2002 (Note 2

)APCT = 0 OF 10 CFR 50.46 report dated April 14, 2003 (Note 3)APCT = 0 OF 10 CFR 50.46 report dated April 14, 2004 (Note 4)APCT = 35 OF 10 CFR 50.46 report dated April 14, 2005 (Note 5)APCT = 0 OF 10 CFR 50.46 report dated April 14, 2006 (Note 6

)APCT = 0 OF 10 CFR 50.46 report dated April 13, 2007 (Note 7)APCT = 0 OF 10 CFR 50.46 report dated May 10, 2007 (Note 8)APCT = 90 OF 10 CFR 50.

46 report dated June 22, 2007 (Note 9)APCT = 0 OF 10 CFR 50.46 report dated April 11, 2008 (Note 11)APCT = 0 OF 10 CFR 50.46 report dated April 9, 2009 (Note 12)

APCT = 0 OF 10 CFR 50.46 report dated April 8, 2010 (Note 13)APCT = 0 OF 10 CFR 50.46 report dated April 6, 2011 (Note 15)

APCT = 0 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)APCT = 0 OF NET PCT PCT = 1755.0°F B.CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity De g radation (Note 24)

APCT = 0 OF Total PCT change from current assessments E APCT = 0 OF Cumulative PCT change from current assessments E APCT= 0 OF NET PCT Page 7 of 8 PCT = 1755.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Byron Station Unit 2 ECCS EVALUATION MODEL: REPORT REVISION DATE: Small Break Loss of Coolant Accident (SBLOCA) 04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model: NOTRUMP Calculation:

Westinghouse CN-LiS-00-208, December 2000 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

2-inch Break in the Bottom of the Cold Leg Reference PCT PCT = 1627.0°F MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (Note 1) of 10 CFR 50.46 report dated April 18, 2002 (Note 2) of 10 CFR 50.46 report dated April 14, 2003 (Note 3) 10 CFR 50.46 report dated April 14, 2004 (Note 4) of 10 CFR 50.46 report dated April 14,2005 (Note 5) = 0 of 10 CFR 50.46 report dated April 14, 2006 (Note 6) 10 CFR 50.46 report dated April 13, 2007 (Note 7)

O°F 1 0 CFR 50.46 report dated May 10, 2007 (Note 8) 90 OF 10 CFR 50.46 report dated June 22, 2007 (Note 9) 10 CFR 50.46 report dated April 11, 2008 (Note 11) of 10 CFR 50.46 report dated April 9, 2009 (Note 12) 10 CFR 50.46 report dated April 8, 2010 (Note 13) 10 CFR 50.46 report dated April 6, 2011 (Note 15) 10 CFR 50.46 report dated April 6, 2012 (Note 17)

NETPCT PCT = 1755.0°F B. CURRENT LOCA MODEL ASSESSMENTS NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity . Degradation (Note 24) Total PCT change from current assessments L = 0 OF Cumulative PCT change from current assessments L

1= 0 OF NETPCT PCT = 1755.0°F Page 7 of 8 ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report PLANT NAME:Byron Station Unit 2 ECCS EVALUATION MODEL:Large Break Loss of Coolant Accident (LBLOCA)

REPORT REVISION DATE:04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model:

ASTRUM (2004)

Calculation:

Westinghouse WCAP-1 6841-P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location: Guillotine break in the Cold Leg Reference PCTPCT = 2041.0°F MARGIN ALLOCATION

A.PRIOR LOSS OF COOLANT ACCIDENT (LOCA)

MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15, 2011 (Note 14)

APCT = 0 OF 10 CFR 50.

46 report dated April 6, 2011 (Note 15)APCT = 0 OF 10 CFR 50.46 report dated March 19, 2012 (Note 16)APCT = -42 OF 10 CFR 50.46 report dated April 6, 2012 (Note 17)

APCT = 0 OF NET PCT PCT = 1999.0°F B.CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19)

APCT = 0 OF HOTSPOT Burst Temperature Calculation for ZIRLO Cladding (Note 20)APCT = 0 OF HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet Average Temperature Note 21 APCT = 0 OF WCOBRA/TRAC Automated Restart Process Logic Error (Note 22)

APCT = 0 OF Rod Internal Pressure Calculation (Note 23)

APCT = 0 OF WCOBRA/TRAC Thermal-Hydraulic History File Dimension Used in HSDRIVER See Note 25)

APCT = 0 OF Total PCT change from current assessments Y- APCT = 0 OF Cumulative PCT change from current assessments Y APCT I= 0 OF NET PCT Page 8 of 8 PCT = 1999.0°F PLANT NAME: ATTACHMENT 1 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Byron Station Unit 2 ECCS EVALUATION MODEL: REPORT REVISION DATE: Large Break Loss of Coolant Accident (LBLOCA) 04/05/13 CURRENT OPERATING CYCLE: 17 AOR Evaluation Model: ASTRUM (2004) Calculation:

Westinghouse WCAP-16841-P, November 2007 Fuel: VANTAGE+ 17 x 17 Limiting Fuel Type: VANTAGE+ 17 x 17 Limiting Single Failure: Loss of one train of ECCS flow Limiting Break Size and Location:

Guillotine break in the Cold Leg Reference PCT PCT = 2041.0°F MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS 10 CFR 50.46 report dated March 15, 2011 (Note 14) APCT=O°F 10 CFR 50.46 report dated April 6, 2011 (Note 15). APCT=O of 10 CFR 50.46 report dated March 19,2012 (Note 16) APCT= -42 of 10 CFR 50.46 report dated April 6, 2012 (Note 17) APCT=O of NETPCT PCT = 1999.0°F B. CURRENT LOCA MODEL ASSESSMENTS General Code Maintenance (Note 19) APCT=O°F HOTSPOT Burst Temperature Calculation for ZIRLO Cladding APCT=O OF (Note 20) HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet APCT=O°F Average Temperature(Note

21) WCOBRAfTRAC Automated Restart Process Logic Error (Note 22) APCT=O of Rod Internal Pressure Calculation (Note 23) APCT=O OF WCOBRAfTRAC Thermal-Hydraulic History File Dimension Used in APCT = 0 of HSDRIVER (See Note 25) Total PCT change from current assessments LAPCT=O°F Cumulative PCT change from current assessments L IAPCT 1= 0 OF NETPCT PCT = 1999.0°F Page 8 of 8 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 1.Prior LOCA Model Assessment The 10 CFR 50.46 report dated June 11, 2001 reported new small break loss of coolant accident (SBLOCA) analyses to support operations at uprated power conditions. The same report assessed the impact from annular axial blankets on SBLOCA analysis, which determined a 0°F PCT penalty for Units 1 and a 3°F PCT penalty for Units 2. Evaluations for plant conditions and SBLOCA model changes which resulted in 0 OF PCT change were reported.2.Prior LOCA Model AssessmentThe 10 CFR 50.46 report dated April 18, 2002 reported evaluations for SBLOCA model changes which resulted in 0 OF PCT change.

3.Prior LOCA Model AssessmentThe 10 CFR 50.46 report dated April 14, 2003 reported evaluations for SBLOCA model changes which resulted in 0 OF PCT change.

4.Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2004 reported evaluations for a SBLOCA assessment related to NOTRUMP bubble rise/drift flux model inconsistency corrections, which resulted in 35 OF PCT assessment.

5.Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2005 reported evaluations for SBLOCA model changes which resulted in 0 OF PCT change. Assembly N10S was reconstituted with two stainless steel filler rods during Braidwood Unit 1 Refueling Outage 11. This assembly is reloaded into the core and is in use during Braidwood Unit 1 Cycle 12 operation. The introduction of up to five stainless steel filler rods has been evaluated and shown to have no impact on SBLOCA analysis. The estimated PCT effect is 0°F. This assembly was discharged during Reload 12.

6.Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2006 reported evaluations for SBLOCA NOTRUMP General Code Maintenance which resulted in 0 OF change.

7.Prior LOCA Model AssessmentThe 10 CFR 50.46 report dated April 13, 2007 reported evaluations for SBLOCA model changes and errors.

The report documented general code maintenance for NOTRUMP, AXIOM lead test assembly evaluation and NOTRUMP refined break spectrum, which resulted in 0 OF PCT impact.

Page 1 of 5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 1. Prior LOCA Model Assessment The 10 CFR 50.46 report dated June 11, 2001 reported new small break loss of coolant accident (SBLOCA) analyses to support operations at uprated power conditions.

The same report assessed the impact from annular axial blankets on SBLOCA analysis, which determined a O°F PCT penalty for Units 1 and a 3°F PCT penalty for Units 2. Evaluations for plant conditions and SBLOCA model changes which resulted in 0 OF PCT change were reported.

2. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 18, 2002 reported evaluations for SBLOCA model changes which resulted in 0 of PCT change. 3. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2003 reported evaluations for SBLOCA model changes which resulted in 0 of PCT change. 4. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2004 reported evaluations for a SBLOCA assessment related to NOTRUMP bubble rise/drift flux model inconsistency corrections, which resulted in 35 OF PCT assessment.

5. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2005 reported evaluations for SBLOCA model changes which resulted in 0 of PCT change. Assembly N1 OS was reconstituted with two stainless steel filler rods during Braidwood Unit 1 Refueling Outage 11. This assembly is reloaded into the core and is in use during Braidwood Unit 1 Cycle 12 operation.

The introduction of up to five stainless steel filler rods has been evaluated and shown to have no impact on SBLOCA analysis.

The estimated PCT effect is O°F. This assembly was discharged during Reload 12. 6. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2006 reported evaluations for SBLOCA NOTRUMP General Code Maintenance which resulted in 0 OF change. 7. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 13, 2007 reported evaluations for SBLOCA model changes and errors. The report documented general code maintenance for NOTRUMP, AXIOM lead test assembly evaluation and NOTRUMP refined break spectrum, which resulted in 0 OF PCT impact. Page 1 of 5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 8.Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated May 10, 2007 applicable to Byron Unit 2 reported an assessment of the emergency core cooling system (ECCS), which evaluated changes in ECCS flow during the recirculation phase due to Generic Safety Issue (GSI) -191 related safety injection (SI) throttle valve replacements. The evaluation of recirculation phase ECCS flow changes relative to impact on the current Analysis of Record (AOR) was performed for the SBLOCA. Based on the NOTRUMP and SBLOCTA calculations performed for Byron Unit 2, a conservative, bounding PCT assessment of +90°F was applied to the current Byron Unit 2 SBLOCA PCT.

9.Prior LOCA Model Assessment A 30-day report was submitted to the NRC dated June 22, 2007 to report an error in the HOT SPOT Code which did not impact the SBLOCA analysis.

The 30-day report also reported minor errors with the reactor vessel data collections that potentially affected the vessel inlet and outlet fluid volume, metal mass, and surface area. The corrected values were evaluated for impact, and a 0

°F penalty was assessed for Byron Units 1 and 2, and Braidwood Units 1 and 2, SBLOCA analysis.

10.Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated November 19, 2007 applicable to Braidwood Unit 1 reported an assessment of the ECCS, which evaluated changes in ECCS flow during the recirculation phase due to GSI-1 91 related SI throttle valve replacements. The evaluation of recirculation phase ECCS flow changes relative to impact on the current AOR was performed for the SBLOCA. Based on the NOTRUMP and SBLOCTA calculations performed for Braidwood Unit 1, a conservative, bounding PCT assessment of +90°F was applied to the Braidwood Unit 1 SBLOCA PCT.

11.Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 11, 2008 reported evaluations for loss of coolant accident (LOCA) model changes and errors. Applicable to Braidwood Unit 2 and Byron Unit 1, the ECCS assessment evaluated changes in ECCS flow during the recirculation phase due to GSI-191 related safety injection SI throttle valve replacements. A conservative, bounding PCT assessment of +90°F was applied to the Braidwood Unit 2 and Byron Unit 1 SBLOCA PCTs. The report also documented general code maintenance for SBLOCA and

evaluation for pump weir resistance modeling for SBLOCA analyses, which resulted in 0 OF PCT impact.

12.Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 9, 2009 reported evaluations for LOCA model changes and errors.

The report documents general code maintenance for SBLOCA, errors in reactor vessel lower plenum surface area calculations, discrepancies in metal mass from drawings, and an evaluation of AREVA Lead Use Assemblies.

All of which have a 0 OF PCT penalty associated with them.

Page 2 of 5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 8. Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated May 10, 2007 applicable to Byron Unit 2 reported an assessment of the emergency core cooling system (ECCS), which evaluated changes in ECCS flow during the recirculation phase due to Generic Safety Issue (GSI) -191 related safety injection (51) throttle valve replacements.

The evaluation of recirculation phase ECCS flow changes relative to impact on the current Analysis of Record (AOR) was performed for the SBLOCA. Based on the NOTRUMP and SBLOCTA calculations performed for Byron Unit 2, a conservative, bounding PCT assessment of +90°F was applied to the current Byron Unit 2 SBLOCA PCT. 9. Prior LOCA Model Assessment A 30-day report was submitted to the NRC dated June 22, 2007 to report an error in the HOT SPOT Code which did not impact the SBLOCA analysis.

The 30-day report also reported minor errors with the reactor vessel data collections that potentially affected the vessel inlet and outlet fluid volume, metal mass, and surface area. The corrected values were evaluated for impact, and a O°F penalty was assessed for Byron Units 1 and 2, and Braidwood Units 1 and 2, SBLOCA analysis.

10. Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated November 19, 2007 applicable to Braidwood Unit 1 reported an assessment of the ECCS, which evaluated changes in ECCS flow during the recirculation phase due to GSI-191 related Sl throttle valve replacements.

The evaluation of recirculation phase ECCS flow changes relative to impact on the current AOR was performed for the SBLOCA. Based on the NOTRUMP and SBLOCTA calculations performed for Braidwood Unit 1, a conservative, bounding PCT assessment of +90°F was applied to the Braidwood Unit 1 SBLOCA PCT. 11. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 11, 2008 reported evaluations for loss of coolant accident (LOCA) model changes and errors. Applicable to Braidwood Unit 2 and Byron Unit 1, the ECCS assessment evaluated changes in ECCS flow during the recirculation phase due to GSI-191 related safety injection 51 throttle valve replacements.

A conservative, bounding PCT assessment of +90°F was applied to the Braidwood Unit 2 and Byron Unit 1 SBLOCA PCTs. The report also documented general code maintenance for SBLOCA and evaluation for pump weir resistance modeling for SBLOCA analyses, which resulted in 0 of PCT impact. 12. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 9, 2009 reported evaluations for LOCA model changes and errors. The report documents general code maintenance for SBLOCA, errors in reactor vessel lower plenum surface area calculations, discrepancies in metal mass from drawings, and an evaluation of AREVA Lead Use Assemblies.

All of which have a 0 OF PCT penalty associated with them. Page 2 of 5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 13.Prior LOCA Model AssessmentThe 10 CFR 50.46 report dated April 8, 2010 reported no evaluations for SBLOCA model changes which resulted in O OF PCT change.

14.Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated March 15, 2011 reported a new large break BELOCA (ASTRUM) analysis to support operations for Byron and Braidwood Units 1 and 2.

The same report assessed the impact from several errors, issues, and code enhancements.

Each of these errors/

issues/code enhancements had a 0 OF PCT impact with a net 0 OF PCT impact.15.Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 6, 2011 reported no evaluations for the LBLOCA model. For the SBLOCA model, the following errors, changes, corrections or enhancements were reported. Two errors relating to urania-gadolinia pellet thermal conductivity calculation, two errors relating to pellet crack and dish volume calculation, a discrepancy involving the treatment of vessel average temperature uncertainty, and general code maintenance were reported for the SBLOCA model. All of these issues were determined to have an estimated impact of 0°F.

16.Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated March 19, 2012 applicable to Braidwood Unit 2 and Byron Unit 2 reported an assessment of thermal conductivity degradation (TCD) with an associated peaking factor burndown and a design input change consisting of a reduction inupper bound steam generator tube plugging, a reduction in nominal upper bound nominal vessel average temperature, and an increase in the assumed containment pressure boundary condition. As a result, the estimated effect of the TCD with burndown was determined to be +148°F and the estimated effect of the design input changes was determined to be -190°F. These two assessments are coupled together via their evaluations of burnup effects which include TCD, peaking factor burndown and design input changes. Therefore, the combined effect of these two changes results in a net change in the reported LBLOCA PCT for Braidwood Unit 2 and Byron Unit 2 of -42°F.

17.Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 6, 2012 reported evaluations for LOCA model changes and errors. The report documents general code maintenance for both SBLOCA and LBLOCA, errors in Radiation Heat Transfer Logic for SBLOCA, and an error in the Maximum Fuel Rod Time Step Logic for SBLOCA. All of which have a 0 OF PCT penalty associated with them.

Page 3of5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 13. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 8, 2010 reported no evaluations for SBLOCA model changes which resulted in 0 of PCT change. 14. Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated March 15, 2011 reported a new large break BELOCA (ASTRUM) analysis to support operations for Byron and Braidwood Units 1 and 2. The same report assessed the impact from several errors, issues, and code enhancements.

Each of these errors/issues/code enhancements had a 0 OF PCT impact with a net 0 of PCT impact. 15. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 6, 2011 reported no evaluations for the LBLOCA model. For the SBLOCA model, the following errors, changes, corrections or enhancements were reported.

Two errors relating to urania-gadolinia pellet thermal conductivity calculation, two errors relating to pellet crack and dish volume calculation, a discrepancy involving the treatment of vessel average temperature uncertainty, and general code maintenance were reported for the SBLOCA model. All of these issues were determined to have an estimated impact of O°F. 16. Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated March 19, 2012 applicable to Braidwood Unit 2 and Byron Unit 2 reported an assessment of thermal conductivity degradation (TCD) with an associated peaking factor burndown and a design input change consisting of a reduction in upper bound steam generator tube plugging, a reduction in nominal upper bound nominal vessel average temperature, and an increase in the assumed containment pressure boundary condition.

As a result, the estimated effect of the TCD with burndown was determined to be +148°F and the estimated effect of the design input changes was determined to be -190°F. These two assessments are coupled together via their evaluations of burnup effects which include TCD, peaking factor burndown and design input changes. Therefore, the combined effect of these two changes results in a net change in the reported LBLOCA PCT for Braidwood Unit 2 and Byron Unit 2 of -42°F. 17. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 6, 2012 reported evaluations for LOCA model changes and errors. The report documents general code maintenance for both SBLOCA and LBLOCA, errors in Radiation Heat Transfer Logic for SBLOCA, and an error in the Maximum Fuel Rod Time Step Logic for SBLOCA. All of which have a 0 OF PCT penalty associated with them. Page 3 of 5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 18.Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated May 21, 2012 applicable to Braidwood Unit 1 and Byron Unit 1 reported an assessment of TCD with an associated peaking factor burndown, an analysis input change consisting of a reduction in conservatism in analyzed FQ values and an increase in the assumed containment pressure boundary condition. As a result, the estimated effect of the TCD with burndown was determined to be +110°F and the estimated effect of the analysis input changes was determined to be -66°F. These two assessments are coupled together via their evaluations of burnup effects which include TCD, peaking factor burndown and analysis input changes. Therefore, the combined affect of these two changes results in a net change in the reported LBLOCA PCT for Braidwood Unit 1 and Byron Unit 1 of +44°F.

19.Current LOCA Model Assessment - General Code Maintenance (LBLOCA)Various changes have been made to enhance the usability of the codes, to streamline future analyses, and to help preclude errors in analyses. This includes items such as modifying input variable definitions, units, and defaults; improving the input diagnostic checks; enhancing the code output; optimizing active coding; and, eliminating inactive coding. The nature of these changes leads to an estimated PCT impact of 0°F.

20.Current LOCA Model Assessment - HOTSPOT Burst Temperature Calculation for ZIRLO Cladding (LBLOCA)

A problem was identified in the calculation of the burst temperature for ZIRLOO cladding in the HOTSPOT code when the cladding engineering hoop stress exceeds 15,622 psi. This problem results in either program failure or an invalid extrapolation of the burst temperature vs. engineering hoop stress table. The evaluation of existing analyses demonstrated no impact on the overall PCT results, leading to an estimated effect of 0°F.

21.Current LOCA Model Assessment-HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet Average Temperature (LBLOCA)The HOTSPOT code has been updated to incorporate the following corrections to the iteration algorithm for calculating the initial fuel pellet average temperature: (1) bypass the iteration when the input value satisfies the acceptance criterion; (2) prevent low-end extrapolation of the gap heat transfer coefficient; (3) prevent premature termination of the iteration that occurred under certain conditions; and (4) prevent further adjustment of the gap heat transfer coefficient after reaching the iteration limit. Sample calculations and

engineering judgment lead to an estimated PCT impact of 0°F.

22.Current LOCA Model Assessment -

WCOBRA/TRAC Automated Restart Process Logic Error (LBLOCA)A minor error was identified in the WCOBRA/TRAC Automated Restart Process (WARP) logic for defining the Double-Ended Guillotine (DEG) break tables. The error has been

evaluated for impact on current licensing-basis analysis results and will be incorporated into the plant-specific analyses on a forward-fit basis. These errors were evaluated to have a negligible impact on the large break LOCA analysis results, leading to an estimated PCT impact of 0°F.

Page 4 of 5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 18. Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated May 21, 2012 applicable to Braidwood Unit 1 and Byron Unit 1 reported an assessment of TCD with an associated peaking factor burndown, an analysis input change consisting of a reduction in conservatism in analyzed FQ values and an increase in the assumed containment pressure boundary condition.

As a result, the estimated effect of the TCD with burndown was determined to be +11 OaF and the estimated effect of the analysis input changes was determined to be -66°F. These two assessments are coupled together via their evaluations of burnup effects which include TCD, peaking factor burndown and analysis input changes. Therefore, the combined affect of these two changes results in a net change in the reported LBLOCA PCT for Braidwood Unit 1 and Byron Unit 1 of +44°F. 19. Current LOCA Model Assessment

-General Code Maintenance (LBLOCA) Various changes have been made to enhance the usability of the codes, to streamline future analyses, and to help preclude errors in analyses.

This includes items such as modifying input variable definitions, units, and defaults; improving the input diagnostic checks; enhancing the code output; optimizing active coding; and, eliminating inactive coding. The nature of these changes leads to an estimated PCT impact of OaF. 20. Current LOCA Model Assessment

-HOTSPOT Burst Temperature Calculation for ZIRLO Cladding (LBLOCA) A problem was identified in the calculation of the burst temperature for ZIRLO cladding in the HOTSPOT code when the cladding engineering hoop stress exceeds 15,622 psi. This problem results in either program failure or an invalid extrapolation of the burst temperature vs. engineering hoop stress table. The evaluation of existing analyses demonstrated no impact on the overall PCT results, leading to an estimated effect of OaF. 21. Current LOCA Model Assessment -HOTSPOT Iteration Algorithm for Calculating the Initial Fuel Pellet Average Temperature (LBLOCA) The HOTSPOT code has been updated to incorporate the following corrections to the iteration algorithm for calculating the initial fuel pellet average temperature:

(1) bypass the iteration when the input value satisfies the acceptance criterion; (2) prevent low-end extrapolation of the gap heat transfer coefficient; (3) prevent premature termination of the iteration that occurred under certain conditions; and (4) prevent further adjustment of the gap heat transfer coefficient after reaching the iteration limit. Sample calculations and engineering judgment lead to an estimated PCT impact of OaF. 22. Current LOCA Model Assessment

-WCOBRAfTRAC Automated Restart Process Logic Error (LBLOCA) A minor error was identified in the WCOBRAffRAC Automated Restart Process (WARP) logic for defining the Double-Ended Guillotine (DEG) break tables. The error has been evaluated for impact on current licensing-basis analysis results and will be incorporated into the plant-specific analyses on a forward-fit basis. These errors were evaluated to have a negligible impact on the large break LOCA analysis results, leading to an estimated PCT impact of OaF. Page 40f 5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 23.Current LOCA Model Assessment - Rod Internal Pressure Calculation (LBLOCA)

Several issues which affect the calculation of rod internal pressure (RIP) have been identified for certain best

-estimate (BE) large break loss of coolant accident (LBLOCA)evaluation models (EMs). These issues include the sampling of RIP uncertainties, updating HOTSPOT to consider the effect of transient RIP variations in the application of the uncertainty, and generating RIPs at a consistent rod power. These issues have been evaluated to estimate the impact on existing LBLOCA analysis results. The effects described above are either judged to have a negligible effect on existing LBLOCA analysis results or have been adequately incorporated into the TCD evaluations, leading to an estimated PCT impact of 0°F.

24.Current LOCA Model Assessment -

NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity Degradation (SBLOCA)An evaluation has been completed to estimate the effect of fuel pellet TCD on PCT for plants in the United States with analyses using the 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP (NOTRUMP-EM). Based on the phenomena and physics of the SBLOCA transient, in combination with limited sensitivity calculations, it is concluded that TCD has a negligible effect on the limiting cladding temperature transient, leading to an estimated PCT impact of 0°F.

25.Current LOCA Model Assessment - WCOBRA/TRAC Thermal-Hydraulic History File Dimension Used in HSDRIVER (LBLOCA)

A problem was identified in the dimension of the WCOBRAITRAC thermal-hydraulic history file used in HSDRIVER. The array that is used to store the information from the WCOBRA/TRAC thermal-hydraulic history file is dimensioned to 3000 in HSDRIVER. It is possible for this file to contain more than 3000 curves. If that is the case, it is possible that the curves would not be used correctly in the downstream HOTSPOT execution. An extent

-of-condition review indicated that resolution of this issue does not impact the PCT calculation for existing LBLOCA analyses. The nature of these changes leads to an estimated PCT impact of 0°F.

Page 5of5 ATTACHMENT 2 Braidwood and Byron Stations, Units 1 and 2 10 CFR 50.46 Report Assessment Notes 23. Current LOCA Model Assessment

-Rod Internal Pressure Calculation (LBLOCA) Several issues which affect the calculation of rod internal pressure (RIP) have been identified for certain best-estimate (BE) large break loss of coolant accident (LBLOCA) evaluation models (EMs). These issues include the sampling of RIP uncertainties, updating HOTSPOT to consider the effect of transient RIP variations in the application of the uncertainty, and generating RIPs at a consistent rod power. These issues have been evaluated to estimate the impact on existing LBLOCA analysis results. The effects described above are either judged to have a negligible effect on existing LBLOCA analysis results or have been adequately incorporated into the TCD evaluations, leading to an estimated PCT impact of OaF. 24. Current LOCA Model Assessment

-NOTRUMP-EM Evaluation of Fuel Pellet Thermal Conductivity Degradation (SBLOCA) An evaluation has been completed to estimate the effect of fuel pellet TCD on PCT for plants in the United States with analyses using the 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP (NOTRUMP-EM).

Based on the phenomena and physics of the SBLOCA transient, in combination with limited sensitivity calculations, it is concluded that TCD has a negligible effect on the limiting cladding temperature transient, leading to an estimated PCT impact of OaF. 25. Current LOCA Model Assessment

-WCOBRAfTRAC Thermal-Hydraulic History File Dimension Used in HSDRIVER (LBLOCA) A problem was identified in the dimension of the WCOBRAfTRAC thermal-hydraulic history file used in HSDRIVER.

The array that is used to store the information from the WCOBRAfTRAC thermal-hydraulic history file is dimensioned to 3000 in HSDRIVER.

It is possible for this file to contain more than 3000 curves. If that is the case, it is possible that the curves would not be used correctly in the downstream HOTSPOT execution.

An of-condition review indicated that resolution of this issue does not impact the PCT calculation for existing LBLOCA analyses.

The nature of these changes leads to an estimated PCT impact of OaF. Page 5 of 5