RS-08-053, Annual & Thirty Day Reports of the Emergency Core Cooling System Evaluation Model Changes & Errors Required by 10 CFR 50.46, Acceptance Criteria for Emergency Core Cooling Systems..
| ML081020797 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 04/11/2008 |
| From: | Simpson P Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RS-08-053 | |
| Download: ML081020797 (14) | |
Text
wwwexeloncorp .com Exel6n Nuclear Fxelon Generation 4300 Winfield Road Warrenville, I L 60555 10 CFR 50.46 RS-08-053 April 11, 2008 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 and Thirty Day Reports of the Emergency Core Cooling System Evaluation Model Changes and Errors Required by 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors" References : 1 . Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S.
Nuclear Regulatory Commission, "Plant Specific ECCS Evaluation Change-10 CFR 50.46 Report," dated May 10, 2007
- 2. Letter from P. R . Simpson (Exelon Generation Company, LLC) to U. S .
Nuclear Regulatory Commission, "Plant Specific ECCS Evaluation Change -
10 CFR 50.46 Report," dated November 19, 2007 In accordance with 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors," Exelon Generation Company, LLC (EGC) is submitting the attached information to fulfill the annual report for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2. The report also fulfills the 30-day reporting requirements for Byron Station Unit 1 and Braidwood Station Unit 2 due to peak cladding temperature (PCT) assessments of 90°F for the small break loss of coolant accident (SBLOCA) analyses .
Specifically, a PCT increase of 90°F has been evaluated for the SBLOCA as a result of Generic Safety Issue (GSI)-191 modifications that are being made during the Spring 2008 Byron Station Unit 1 and Braidwood Station Unit 2 refueling outages . The modifications involve replacement of Safety Injection system throttle valves, which result in ECCS flow changes. As a result of these modifications, the calculated PCT for the Byron Station Unit 1 SBLOCA is now 1749.0°F and the calculated PCT for the Braidwood Station Unit 2 SBLOCA is now 1755 .0°F . Both of these units remain within the acceptance criteria set forth in 10 CFR 50.46. Therefore; additional reanalysis is not required .
April 11, 2008 U. S. Nuclear Regulatory Commission Page 2 This same 90°F increase in PCT for the SBLOCA as a result of GSI-191 modifications for Byron Station Unit 2 and Braidwood Station Unit 1 were reported in Reference 1 and Reference 2, respectively . Attachment 1 provides updated information regarding the PCT values for the limiting SBLOCA and LBLOCA evaluations for Braidwood Station and Byron Station . contains a detailed description for each change or error reported .
There are no regulatory commitments contained in this letter . If you have any questions concerning this letter, please contact David Chrzanowski at (630) 657-2816 .
Patrick R . Simpson Manager - Licensing : Peak Cladding Temperature Rack-Up Sheets : Assessment Notes
Attachment 1 Byron and Braidwood Units 1 and 210 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Braidwood Station Unit 1 ECCS EVALUATION MODEL: Small Break Loss of Coolant Accident (SBLOCA)
REPORT REVISION DATE : 03/03/08 CURRENT OPERATING CYCLE: 14 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" Low Tavg 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 (see note 1) APCT = 0°F 10 CFR 50.46 report dated April 18, 2002 (see note 2) APCT = 0°F 10 CFR 50.46 report dated April 14, 2003 (see note 3) APCT = 0°F 10 CFR 50.46 report dated April 14, 2004 (see note 4) APCT = 35°F 10 CFR 50.46 report dated April 14, 2005 (see note 5) APCT = 0°F 10 CFR 50.46 report dated April 14, 2006 (see note 6) APCT = 0°F 10 CFR 50.46 report dated April 13, 2007 (see note 7) APCT = 0 °F 10 CFR 50 .46 report dated June 22, 2007 (see note 9) APCT = 0°F 10 CFR 50.46 report dated November 19, 2007 (see note 10) APCT = 90°F NET PCT PCT = 1749 .0°F B. CURRENT LOCA MODEL ASSESSMENTS NOTRUMP - SBLOCA General Code Maintenance (see note 12) APCT = 0°F NOTRUMP - SBLOCA Pump Weir Resistance Modeling (see note APCT = 0°F 13 Total PCT change from current assessments Y- APCT = 0°F Cumulative PCT change from current assessments Y APCT = 0°F NET PCT PCT = 1749 .0°F
Attachment 1 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Braidwood Station Unit 1 ECCS EVALUATION MODEL: Large Break Loss of Coolant Accident (LBLOCA)
REPORT REVISION DATE : 03/03/08 CURRENT OPERATING CYCLE : 14 AOR Evaluation Model: CQD (1996)
Calculation : Westinghouse CN-LIS-00-7, September 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: Guillotine break in the Cold Leg Reference PCT PCT = 2044 .0°F MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50 .46 report dated June 11, 2001 (see note 1) APCT = 12°F 10 CFR 50 .46 report dated April 18, 2002 (see note 2) APCT = 0°F 10 CFR 50 .46 report dated April 14, 2003 (see note 3) APCT = 0°F 10 CFR 50 .46 report dated April 14, 2004 (see note 4) APCT = 0°F 10 CFR 50 .46 report dated April 14, 2005 (see note 5) APCT = 5°F 10 CFR 50.46 report dated April 14, 2006 (see note 6) APCT = 0°F 10 CFR 50.46 report dated April 13, 2007 (see note 7) APCT = 0°F 10 CFR 50.46 report dated June 22, 2007 (see note 9) APCT = 20°F 10 CFR 50.46 report dated November 19, 2007 (see note 10) APCT = 0°F NET PCT PCT = 2081 .0°F B. CURRENT LOCA MODEL ASSESSMENTS Axial Power Shape Distribution Violation (see note 14) 4PCT = 80°F Total PCT change from current assessments E APCT = 80°F Cumulative PCT change from current assessments Y- I APCT = 80°F NET PCT PCT = 2161 .0°F
Attachment 1 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Braidwood Station Unit 2 ECCS EVALUATION MODEL: SBLOCA REPORT REVISION DATE: 03/03/08 CURRENT OPERATING CYCLE: _14*
- Cycle 14 to start May 2008 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" Low Tavg 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 (see note 1) APCT = 3°F 10 CFR 50.46 report dated April 18, 2002 (see note 2) APCT = 0°F 10 CFR 50.46 report dated April 14, 2003 (see note 3) APCT = 0°F 10 CFR 50.46 report dated April 14, 2004 (see note 4) APCT = 35°F 10 CFR 50.46 report dated April 14, 2005 (see note 5) APCT = 0°F 10 CFR 50.46 report dated April 14, 2006 (see note 6) APCT = 0°F 10 CFR 50.46 report dated April 13, 2007 (see note 7) APCT = 0°F 10 CFR 50.46 report dated June 22, 2007 (see note 9) APCT = 0°F NET PCT PCT = 1665.0°F B. CURRENT LOCA MODEL ASSESSMENTS ECCS Flow Change Evaluation (see note 11) APCT = 90°F NOTRUMP - SBLOCA General Code Maintenance (12) APCT = 0°F NOTRUMP - SBLOCA Pump Weir Resistance Modeling (see note APCT = 0°F 13 Total PCT change from current assessments I APCT = 90°F Cumulative PCT change from current assessments I I Y APCT = 90°F NET PCT PCT = 1755.0°F
Attachment 1 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Braidwood Station Unit 2 ECCS EVALUATION MODEL: LBLOCA REPORT REVISION DATE: 03/03/08 CURRENT OPERATING CYCLE: _14"
- Cycle 14 to start May 2008 AOR Evaluation Model : CQD (1996)
Calculation : Westinghouse CN-LIS-00-7, September 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: Guillotine break in the Cold Leg Reference PCT PCT = 2088.0°F MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (see note 1) OPCT = 12°F 10 CFR 50.46 report dated April 18, 2002 (see note 2) APCT = 0°F 10 CFR 50 .46 report dated April 14, 2003 (see note 3) APCT = 0°F 10 CFR 50.46 report dated April 14, 2004 (see note 4) APCT = 0°F 10 CFR 50.46 report dated April 14, 2005 (see note 5) APCT = 5°F 10 CFR 50.46 report dated April 14, 2006 (see note 6) OPCT = 0°F 10 CFR 50.46 report dated April 13, 2007 (see note 7) OPCT = 0°F 10 CFR 50.46 report dated June 22, 2007 (see note 9) J APCT = 55°F NET PCT PCT = 2160.0°F B. CURRENT LOCA MODEL ASSESSMENTS Axial Power Shape Distribution Violation (see note 14) APCT = 8°F Total PCT change from current assessments Y- APCT = 8°F Cumulative PCT change from current assessments Y APCT = 8°F 1 NET PCT PCT = 2168.0°F
Attachment 1 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Boron Station Unit 1 ECCS EVALUATION MODEL: SBLOCA REPORT REVISION DATE: 03/03/08 CURRENT OPERATING CYCLE: _16*
- Cycle 16 to start April 2008 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" Low Tavg 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 (see note 1) APCT = 0°F 10 CFR 50.46 report dated April 18, 2002 (see note 2) APCT = 0°F 10 CFR 50.46 report dated April 14, 2003 (see note 3) APCT = 0°F 10 CFR 50.46 report dated April 14, 2004 (see note 4) OPCT = 35°F 10 CFR 50.46 report dated April 14, 2005 (see note 5) APCT = 0°F 10 CFR 50.46 report dated April 14, 2006 (see note 6) APCT = 0°F 10 CFR 50 .46 report dated April 13, 2007 (see note 7) APCT = 0°F 10 CFR 50 .46 report dated June 22, 2007 (see note 9) APCT = 0°F NET PCT PCT = 1659.0°F B. CURRENT LOCA MODEL ASSESSMENTS ECCS Flow Change Evaluation (see note 11) OPCT = 90°F NOTRUMP - SBLOCA General Code Maintenance (see note 12) APCT = 0°F NOTRUMP - SBLOCA Pump Weir Resistance Modeling (see note APCT = 0°F 13 Total PCT change from current assessments Y- APCT = 90°F Cumulative PCT change from current assessments Y OPCT = 90°F NET PCT PCT = 1749.0°F
Attachment 1 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Boron Station Unit 1 ECCS EVALUATION MODEL: LBLOCA REPORT REVISION DATE: 03/03/08 CURRENT OPERATING CYCLE: _16*
- Cycle 16 to start April 2008 AOR Evaluation Model : COD (1996)
Calculation : Westinghouse CN-LIS-00-7, September 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 : Guillotine break in the Cold Leg Reference PCT PCT = 2044 .0°F MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50 .46 report dated June 11, 2001 (see note 1) APCT = 12°F 10 CFR 50.46 report dated April 18, 2002 (see note 2) APCT = 0°F 10 CFR 50.46 report dated April 14, 2003 (see note 3) APCT = 0°F 10 CFR 50.46 report dated April 14, 2004 (see note 4) OPCT = 0°F 10 CFR 50.46 report dated April 14, 2005 (see note 5) APCT = 5°F 10 CFR 50.46 report dated April 14, 2006 (see note 6) APCT = 0°F 10 CFR 50.46 report dated April 13, 2007 (see note 7) APCT = 0°F 10 CFR 50.46 report dated June 22, 2007 (see note 9) APCT = 20°F NET PCT PCT = 2081 .0*F B. CURRENT LOCA MODEL ASSESSMENTS Axial Power Shape Distribution Violation (see note 14) APCT = 80°F Total PCT change from current assessments Z APCT = 80°F Cumulative PCT change from current assessments Y APCT = 80°F NET PCT PCT = 2161 .0°F
Attachment 1 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Byron Station Unit 2 ECCS EVALUATION MODEL: SBLOCA REPORT REVISION DATE: 03/03/08 CURRENT OPERATING CYCLE: 14 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" Low Tavg 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 (see note 1) APCT = 3°F 10 CFR 50.46 report dated April 18, 2002 (see note 2) OPCT = 0°F 10 CFR 50.46 report dated April 14, 2003 (see note 3) APCT = 0°F 10 CFR 50.46 report dated April 14, 2004 (see note 4) APCT = 35°F 10 CFR 50.46 report dated April 14, 2005 (see note 5) APCT = 0°F 10 CFR 50.46 report dated April 14, 2006 (see note 6) OPCT = 0°F 10 CFR 50.46 report dated April 13, 2007 (see note 7) APCT = 0°F 10 CFR 50.46 report dated May 10, 2007 (see note 8) APCT == 90°F 0
10 CFR 50 .46 report dated June 22, 2007 (see note 9) OPCT °F NET PCT PCT = 1755.0°F B. CURRENT LOCA MODEL ASSESSMENTS NOTRUMP - SBLOCA General Code Maintenance (see note 11 ) OPCT = 0°F NOTRUMP - SBLOCA Pump Weir Resistance Modeling (see note OPCT = 0°F 12 Total PCT change from current assessments Y_ OPCT = 0°F Cumulative PCT change from current assessments Y APCT = 0°F NET PCT PCT = 1755 .0°F
Attachment 1 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Peak Cladding Temperature Rack-up Sheets PLANT NAME : Byron Station Unit 2 ECCS EVALUATION MODEL: LBLOCA REPORT REVISION DATE : 03/03/08 CURRENT OPERATING CYCLE: 14 AOR Evaluation Model: COD (1996)
Calculation : Westinghouse CN-LIS-00-7, September 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 : Guillotine break in the Cold Leg Reference PCT PCT = 2088.0°F MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated June 11, 2001 (see note 1) APCT = 12°F 10 CFR 50.46 report dated April 18, 2002 (see note 2) APCT = 0°F 10 CFR 50.46 report dated April 14, 2003 (see note 3) OPCT = 0°F 10 CFR 50.46 report dated April 14, 2004 (see note 4) APCT = 0°F 10 CFR 50.46 report dated April 14, 2005 (see note 5) APCT = 5°F 10 CFR 50 .46 report dated April 14, 2006 (see note 6) APCT = 0°F 10 CFR 50.46 report dated April 13, 2007 (see note 7) APCT = 8°F 10 CFR 50.46 report dated May 10, 2007 (see note 8) APCT = 0°F 10 CFR 50.46 report dated June 22, 2007 (see note 9) APCT = 55°F NET PCT PCT = 2168.0°F B. CURRENT LOCA MODEL ASSESSMENTS None APCT = 0°F Total PCT change from current assessments Y- APCT = 0°F Cumulative PCT change from current assessments Y APCT I = 0°F NET PCT PCT = 2168.0°F
Attachment 2 Byron and Braidwood Units 1 and 210 CFR 50.46 Report Assessment Notes 1 . Prior LOCA Model Assessment The 10 CFR 50.46 report dated June 11, 2001, reported new large break loss of coolant accident (LBLOCA) and small break loss of coolant accident (SBLOCA) analyses to support operations at uprated power conditions. The same report assessed the impact from decay heat uncertainty error in Monte Carlo calculations on LBLOCA analysis and the impact from annular axial blankets on SBLOCA analysis . Evaluations for plant conditions and LBLOCA and SBLOCA model changes which resulted in 0°F PCT change were reported . Cycle specific evaluations related to axial power shape distribution envelope violation were reported for the applicable operating cycles .
- 2. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 18, 2002, reported evaluations for LBLOCA and SBLOCA model changes which resulted in 0°F PCT change. Cycle specific evaluations related to axial power shape distribution envelope violation were reported for the applicable operating cycles .
- 3. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2003, reported evaluations for LBLOCA and SBLOCA model changes which resulted in 0°F PCT change. Cycle specific evaluations related to axial power shape distribution envelope violation were reported for the applicable operating cycles .
- 4. Prior LOCA Model Assessment The 10 CFR 50 .46 report dated April 14, 2004, reported evaluations for LBLOCA model changes which resulted in 0°F PCT change. A SBLOCA assessment related to NOTRUMP bubble rise/drift flux model inconsistency corrections, which resulted in 35°F PCT assessment, was reported . Cycle specific evaluations related to axial power shape distribution envelope violation were reported for the applicable operating cycles .
- 5. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2005, reported evaluations for LBLOCA model changes, which resulted in a 5°F PCT change due to the Revised Blowdown Heatup Uncertainty Calculation . 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 LBLOCA and SBLOCA analyses . The estimated PCT effect is 0°F. This assembly will be discharged during Reload 12 and will not be resident in the core for Braidwood Unit 1 Cycle 13. Cycle specific evaluations related to axial power shape distribution envelope violation were reported for the applicable operating cycles .
Attachment 2 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Assessment Notes
- 6. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 14, 2006, reported evaluations for LBLOCA model changes, which resulted in a 0°F PCT change due to the Revised Iteration Algorithm for Calculating the Average Fuel Temperature, Pellet Radial Profile, Improved Automation of End of Blowdown Time, Thermodynamic Properties from THERMO, Vessel Unheated Conductor Noding and Containment Relative Humidity Assumption . NOTRUMP General Code Maintenance resulted in 0°F change for SBLOCA . Cycle specific evaluations related to axial power shape distribution envelope violation were reported for the applicable operating cycles .
- 7. Prior LOCA Model Assessment The 10 CFR 50.46 report dated April 13, 2007, reported evaluations for LOCA model changes and errors . The report documented general code maintenance for NOTRUMP, containment heat sink addition evaluation, AXIOM lead test assembly evaluation and NOTRUMP refined break spectrum, which resulted in 0°F PCT impact . Cycle specific evaluations related to axial power shape distribution envelope violation were reported for the applicable operating cycles .
- 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 and LBLOCA . The LBLOCA analysis was unaffected and a 0°F penalty was assessed . 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 HOTSPOT code which resulted in an increase of 55°F in the LBLOCA PCT for Braidwood Unit 2 and Byron Unit 2 and an 20°F LBLOCA PCT increase for Braidwood Unit 1 and Byron Unit 1 . In addition, the 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 . The LBLOCA analyses were not affected by these minor errors .
- 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 Emergency Core Cooling System (ECCS), which evaluated changes in ECCS flow during the recirculation phase due to GSI-191 related SI throttle valve replacements . The evaluation of recirculation phase ECCS flow changes
Attachment 2 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Assessment Notes relative to impact on the current Analysis of Record (AOR) was performed for the small break loss of coolant accident (SBLOCA) and large break loss of coolant accident (LBLOCA) . The LBLOCA analysis was unaffected and a 0°F penalty was assessed .
Based on the NOTRUMP and SBLOCTA calculations performed for Braidwood Unit 1, a conservative, bounding PCT assessment of +90°F was applied to the current Braidwood Unit 1 SBLOCA PCT.
11 . ECCS Flow Change Evaluation 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 . The evaluation of recirculation phase ECCS flow changes relative to impact on the current Analysis of Record (AOR) was performed for the following areas: small break loss of coolant accident (SBLOCA) and large break loss of coolant accident (LBLOCA) .
Large break loss of coolant accident analyses consider a fuel rod temperature transient that is over long before the transfer to ECCS sump recirculation . Therefore, there is no impact on the LBLOCA PCT calculations .
NOTRUMP and SBLOCTA calculations were performed for Braidwood Unit 2 and Byron Unit 1 ; the only input changes consisted of the revised ECCS flows during recirculation.
Additional refined break sizes, including non-integer breaks, were selected and evaluated based on PCT results for each initial case in order to capture the worst PCT.
Since beginning-of-life (BOL) PCT results approximately equal to or greater than 1700°F were calculated, burnup studies were performed for the limiting BOL break size. Based on the NOTRUMP and SBLOCTA calculations performed for Braidwood Unit 2 and Byron Unit 1, a conservative, bounding PCT assessment of +90°F was applied to the current Braidwood Unit 2 and Byron Unit 1 SBLOCA PCTs .
- 12. SBLOCA General Code Maintenance Various changes have been made to enhance the usability of the codes 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 estimated PCT impact of these changes is 0°F . These changes do not apply to LBLOCA .
- 13. SBLOCA Pump Weir Resistance Modeling Review of the reactor coolant pump data collections for SBLOCA identified instances of either including a weir resistance for a design without a weir or double counting the weir resistance for a design with a weir . Resolving the identified discrepancies has been evaluated as having a negligible effect on existing results, leading to an estimated PCT impact of 0°F. This does not apply to LBLOCA.
Attachment 2 Byron and Braidwood Units 1 and 2 10 CFR 50.46 Report Assessment Notes
- 14. Axial power Shape Distribution Envelope Violation (PMID,PBOT)
The LBLOCA analysis is performed based on assuming an axial power shape distribution envelope (PMID, PBOT), where PMID is the power in the middle one-third of the core ; and PBOT is the power in the lower one-third of the core. The envelope is pertinent to the BELOCA analysis and is presented as Figure 11-1 of WCAP-15585, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Byron
/Braidwood Units 1 and 2 Nuclear Plant," November 2000 . For every reload cycle Westinghouse verifies that the envelope remains limiting . If there is a violation then a PCT penalty is calculated .
For Braidwood Unit 1 Cycle 14, there was a violation and a PCT penalty of 80°F was calculated, which was first reported for Braidwood Unit 1 Cycle 11 in the 10 CFR 50 .46 notification to the NRC, dated April 14, 2003. The assessment for the Braidwood Unit 1 Cycle 14 does not affect the net PCT.
For Braidwood Unit 2 Cycle 14, there was a violation and a PCT penalty of 8°F was calculated, first reported for Braidwood Unit 2 Cycle 10, in the 10 CFR 50.46 notification to the NRC, dated April 18, 2002 . The assessment for Braidwood Unit 2 Cycle 14 does not affect the net PCT.
For Byron Unit 1 Cycle 16, there was a violation and a PCT penalty of 80°F was calculated, which was first reported for Byron Unit 1 Cycle 13 in the 30-day 10 CFR 50 .46 notification to the NRC dated November 07, 2003. The assessment for Byron Unit 1 Cycle 16 does not affect the net PCT.
For Byron Unit 1 Cycle 16 and Braidwood Unit 2 Cycle 14, two types of violations were identified. For the violations outside of the sampling range shown in Figure 11-1 of WCAP-15585, but inside the response surface shown in Figure 9.2-1 of WCAP-15585, a PCT penalty of 80°F for Byron Unit 1 Cycle 16 and 8°F for Braidwood Unit 2 Cycle 14 was applied. This is the same type of violation as the cycles discussed above.
The second type of violation is for power shapes slightly outside the response surface shown in Figure 9.2-1 of WCAP-15585 . These violations were determined to be non-limiting power shapes and were evaluated by extrapolating the power distribution response surface in order to predict PCT. In all cases, the predicted PCT was non-limiting as compared to the LBLOCA PCT reported in the Attachment 1 LBLOCA PCT sheet. The Westinghouse reload methodology approved by the NRC, WCAP-9272-P-A, "Westinghouse Reload Safety Evaluation Methodology, March 1978," allows evaluation of key parameters slightly out of bounds using conservative quantitative evaluation . The extrapolation methodology used in this evaluation is consistent with the methodology for extrapolating FQ and FAH described in WCAP-12945-P-A .