CNL-16-057, Transmittal of l0 CFR 50.46 Annual Report

Transmittal of l0 CFR 50.46 Annual Report

ML16081A248
Person / Time
Site:	Watts Bar
Issue date:	03/18/2016
From:	Walsh K T Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-16-057
Download: ML16081A248 (15)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, TN 37402 cNL-16-057 March 18, 2016 10 cFR s0.4 10 cFR 50 .46 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License NPF-90 NRC Docket No. 50-390 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391

Subject:

l0 CFR 50.46 - Annual Report for Watts Bar Nuclear Plant Units 1 and 2

Reference:

1. TVA Letter to NRC, CNL-'I5-053, '10 CFR 50.46 Day and Annual Report for Watts Bar, Units 1 and 2," dated March 30, 2015 [ML150984124]

The purpose of this letter is to provide the annual report of changes and errors to the calculated peak cladding temperature (PCT) for the Watts Bar Nuclear Plant (WBN) Units 1 and 2, Emergency Core Cooling System (ECCS) evaluation model. This report is required in accordance with Title 10 of the Code of Federal Regulafibns

('10 CFR) 50.46, "Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors," paragraph (a)(3Xii).

The Tennessee Valley Authority (TVA) submitted the last 10 CFR 50.46 annual report for WBN Units 1 and 2 to the Nuclear Regulatory Commission (NRC) in the referenced letter. As indicated in the enclosure, there are no changes to the current updated (net) licensing basis PCT for the WBN Unit 1 large break loss of coolant accident (LBLOCA) and the updated (net)licensing basis PCT for the WBN Unit 1 small break loss of coolant accident (SBLOCA).Similarly, there are no changes to the current updated (net) licensing basis PCT for the WBN Unit 2 LBLOCA and the updated (net) licensing basis PCT for the WBN Unit 2 SBLOCA.There are no new regulatory commitments in this letter. Please address any questions regarding this response to Mr. Gordon Arent at 423-365-2004.

U.S. Nuclear Regulatory Commission cNL-16-057 Page 2 March 18,2016 K. T. Walsh Site Vice President Watts Bar Nuclear Plant

Enclosure:

Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 cc (Enclosures):

NRC RegionalAdministrator - Region ll NRC Senior Resident lnspector - Watts Bar Nuclear Plant, Unit 1 NRC Senior Resident lnspector - Watts Bar Nuclear Plant, Unit 2 Division of Radiological Health - State of Tennessee Respectfully, U.S. Nuclear Regulatory Commission cNL-16-057 Page 3 March 18, 2016 DCB Enclosures bcc (w/o Enclosures):

G. P. Arent M. A. Balduzzi G. A. Boerschig C. Carey J. M. Casner T. M. Conners S. M. Connors D. M. Czufin D. L. Daniels K. D. Dietrich S. M. Douglas B. M. Duckett B. M. Finn J. P. Grimes E. K. Henderson G. E. Pry E. D. Schrull J. W. Shea P. R. Simmons M. D. Skaggs S. A. Vance K. T. Walsh, Sr.N. A. Welch B. A. Wetzel P. R. Wilson ECM ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 ANd 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 ln accordance with the reporting requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.46(aX3)(ii), the Tennessee Valley Authority (TVA) is providing the following summary of the limiting design basis loss of coolant accident (LOCA) analysis results established using the current Watts Bar Nuclear Plant WBN) Emergency Core Cooling System evaluation models for WBN Units 1 and 2. This report describes the changes and errors affecting the calculated peak cladding temperatures (PCTs) since the last analysis of record was submitted to the Nuclear Regulatory Commission (NRC).TVA submitted the last 1 0 CFR 50.46 annual report for WBN Units 1 and 2 to the NRC on March 30, 2015 (Reference 1).Table 1 lists the changes and errors in the large break LOCA (LBLOCA) analysis for WBN Unit 1 since the last analysis of record (AOR) and the associated effect on PCT. For 2015, there were no new changes or errors to report for the LBLOCA analysis.

Table 2 lists the changes and errors in the small break LOCA (SBLOCA) analyses for WBN Unit 1 since the last AOR and the associated effect on PCT. The changes that were not previously identified in Reference 1 are described in the notes to Tables 1and2.Table 3 lists the changes and errors in the LBLOCA analysis for WBN Unit 2 since the last AOR and the associated effect on PCT. For 2015, there were no new changes or errors to report for the LBLOCA analysis.

Table 4 lists the changes and errors in the SBLOCA analyses for WBN Unit 2 since the last AOR and the associated effect on PCT. The changes that were not previously identified in Reference 1 are described in the notes to Tables 3 and 4.The updated (net) licensing basis PCT for the LBLOCA and SBLOCA remain unchanged for WBN Units l and2from the last annual report.cNL-16-057 E1of12 ENCLOSURE TEN NESSEE VALLEY AUTHORIW WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 1 Watts Bar Unit 1 LBLOCA Year Description Reflood 1 Reflood 2 Note Reference APCT ("F)Iancrl ("F)APCT ("F)lmcrl ("F)1 998 BE LBLOCA AOR PCT 1 656 1892 3 1 999 Vessel Channe! DX Error 56 56-4 4 4 2000! ncreased Accumulator Room Tem perature Evaluation 4 4 4 4 4 2000 1.4% Uprate Evaluation 12 12 12 12 4 2000 Accu m u lator Line/Pressu rizer Surse Line Data Evaluation

-37 37-131 131 4 2000 MONTECF Decay Heat Uncertainty Error 4 4 4 4 5 2001 WBN Specific LBLOCA Vessel Geometrv lnput Errors 0 0 0 0 6 2003 lnput Error Resulting in lncomplete Solution Matrix 60 60 0 0 7 2003 Tavg Bias Error 8 I 8 8 7 2004 lncreased Stroke Time for ECCS Valves 0 0 0 0 I 2004 Revised Blowdown Heatup U ncertai nty Distri butio n 5 5 5 5 I 2006 Replacement Steam Generators (D3 to 68AXP)-50 50-10 10 I 2006 HOTSPOTTM Fuet Relocation Error 0 0 65 65 9 CNL-16-057 E2of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable I Watts Bar Unit I LBLOCA Year Description Reflood 1 Reflood 2 Note Reference APCT ('F)Imcrl ("F)APCT ("F)lmcrl ('F)2012 PMID/PBOT Violation Evaluation 20 20 20 20 10, 11 2012 TCD and Peaking Factor Burndown 114 114 15 15 10, 11 2013 WCOBRA/TRACTM History File Dimension Error 0 0 0 0 12 2013 General Code Maintenance 0 0 0 0 13 2013 HOTSPOTTM Burst Temperature Calculation for ZIRLo'M Claddinq 0 0 0 0 13 2013 HOTSPOTTM lteration Algorithm for Calculation lnitial Fuel Pellet Average Temperature 0 0 0 0 13 2013 WCO BRA/TRACTM Auto mate d Restart Process Loqic Error 0 0 0 0 13 2013 Rod lnternal Pressure Calculation Error 0 0 0 0 13 2013 Elevations for Heat Slab Temperature I nitialization 0 0 0 0 14 2013 Heat Transfer Model Error Corrections 0 0 0 0 14 2013 Correction to Heat Transfer Node lnitialization 0 0 0 0 14 2013 Mass Conservation Error Fix 0 0 0 0 14 2013 Correction to Split Channel Momentum Equation 0 0 0 0 14 cNL-16-057 E3ot12 ENCLOSURE TEN NESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 1 Watts Bar Unit I LBLOCA Year Description Reflood I Reflood 2 Note Reference APCT ("F)Imcrl ("F)APCT ("F)lmcrl ("F)2013 Heat Transfer Logic Correction for Rod Burst Calculation 0 0 0 0 14 2013 Changes to Vessel Superheated Steam Properties 0 0 0 0 14 2013 Update to Metal Density Reference Tem peratu res 0 0 0 0 14 2013 Decay Heat Model Error Corrections 0 0 0 0 14 2013 Correction to the Pipe Exit Pressure Drop Error 0 0 0 0 14 2013 WCOBRA/TRAC File Dimension Error Correction 0 0 0 0 14 2013 Revised Heat Transfer Mu ltiplier Distributions

-40 40-85 85 14 2013 HOTSPOT Burst Strain Error 20 20 70 70 15 2014 General Computer Code Maintenance 0 0 0 0 1 2014 Revised Uncertainty in LBLOCA Monte Carl Simulations 0 0 0 0 1 Updated (net) Iicensing basis PCT AORPCT+fAPCT 1832 I 865 Gumulative sum of PCT changes I !ancrl 430 433 cNL-16-057 E4of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and 2 DOGKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 2 Watts Bar Unit { SBLOCA Year Description SBLOCA APCT ("F)SBLOCA I APcr I ("F)Note Reference 2006 SBLOCA AOR PCT 1132 16 2013 NOTRU M P-E MrM Evaluation of Fuel Pellet TCD 0 0 13 2014 General Computer Code Maintenance 0 0 1 2014 Fuel Rod Gap Conductance Error 0 0 1 2014 Radiation Heat Transfer Model Error 0 0 1 2014 SBLOCTA Pre-DNB Cladding Surface Heat Transfer Coefficient Calculation 0 0 1 2014 Evaluation of 8-inch Axial Blankets 0 0 1 2015 General Computer Code Maintenance 0 0 1 2015 Auxiliary Feedwater (AFW)Temperature lncrease During Cold Leg Recirculation 0 0 2 Updated (net) Iicensing basis PCT AORPCT+fAPCT 1132 Cumulative sum of PCT changes r lmcrl 0 cNL-16-057 E5of12 Notes: 1.2.ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 GFR 50.46 Annual Report for 2015 Various changes have been made to enhance the usability of codes and to streamline future analyses.

Examples of these changes include modifying input variable definitions, units and defaults; improving the input diagnostic checks; enhancing the code output;optimizing active coding; and eliminating inactive coding.The WBN Unit 1 and WBN Unit 2 AFW temperature during cold leg recirculation may reach a temperature of 130'F. This temperature is an increase in the AFW temperature modeled in the SBLOCA analyses of record. However, there is no effect on the SBLOCA analysis results.cNL-16-057 E6of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 3 Watts Bar Untt2 LBLOCA Year Description LBLOCA APCT ("F)LBLOCA lmcrl ('F)Note Reference 2413 LBLOCA AOR PCT 1 766 17 2013 Elevations for Heat Slab Temperatu re I n itialization 0 0 19 2013 Heat Transfer Model Error Corrections 0 0 19 2013 Correction to Heat Transfer Node lnitialization 0 0 19 2013 Mass Conservation Error Fix 0 0 19 2013 Correction to Split Channel Momentum Equation 0 0 19 2013 Heat Transfer Logic Correction for Rod Burst Calculation 0 0 19 2013 Changes to Vessel Superheated Steam Properties 0 0 19 2013 Update to Metal Density Reference Tem peratu res 0 0 19 2013 Decay Heat Model Error Corrections 0 0 19 2013 Correction to the Pipe Exit Pressure Drop Error 0 0 19 2013 WCOBRA/TRAC File Dimension Error Correction 0 0 19 2013 Revised Heat Transfer Multiplier Distributions

-55 55 19 2013 Initial Fuel Pellet Average Tem perature U ncertainty Calculation 0 0 19 2013 HOTSPOT Burst Strain Error 0 0 15 CNL-16-057 ET of 12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUGLEAR PLANT UNITS 1 and2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Year Description LBLOCA APCT ('F)LBLOCA lancrl ('F)Note Reference 2014 Cold Leg Accumulator Injection Lines Hydraulic Resistance Chanqes 0 0 2 2014 General Computer Code Maintenance 0 0 1 2014 Errors in Decay Group Uncertainty Factors 0 0 1 2014 Treatment of Burnup Effects on Thermal Conductivity Degradation 0 0 1 Updated (net) Iicensing basis PCT (AORPCT+fAPCT) 1711 Cumulative sum of PCT changes I lmcrl 55 CNL-16-057 E8of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 4 Watts Bar Unit 2 SBLOCA Year Description SBLOCA APGT ("F)SBLOCA Imcrl ("F)Note Reference 2010 SBLOCA AOR PCT 1184 18 2014 Cold Leg Accumulator lnjection Lines Hydraulic Resistance Changes 0 0 2 2014 General Computer Code Maintenance 0 0 1 2014 Fuel Rod Gap Conductance Error 0 0 1 2014 Radiation Heat Transfer Model Error 0 0 1 2014 SBLOCTA Pre-DNB Cladding Surface Heat Transfer Coefficient Calculation 0 0 1 2015 General Computer Code Maintenance 0 0 1 2015 AFW Temperature I ncrease During Cold Leg Recirculation 0 0 2 Updated (net) Iicensing basis PCT (AORPCT+fAPCT) 1184 Cumulative sum of PCT changes I lmcrl 0 0 cNL-16-057 E9of12 Notes: 1.ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Various changes have been made to enhance the usability of codes and to streamline future analyses.

Examples of these changes include modifying input variable definitions, units and defaults; improving the input diagnostic checks; enhancing the code output;optimizing active coding; and eliminating inactive coding.The WBN Unit 1 and WBN Unit 2 AFW temperature during cold leg recirculation may reach a temperature of 130"F. This temperature is an increase in the AFW temperature modeled in the SBLOCA analyses of record. However, there is no effect on the SBLOCA analysis results.2.cNL-16-057 E 10of12 ENCLOSURE TENNESSEE VALLEY AUTHORIW WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015

References:

1 . Letter from TVA to NRC, CNL-15-053, '10 CFR 50.46 Day and Annual Report for Watts Bar, Units 1 and2," dated March 30,2015 [ML15098A124]

2. Letter from TVA to NRC, CNL-15-034, "10 CFR 50.46 Day Report for Watts Bar, Unit 2" dated February 6, 2015 [M115037A725]

3. WCAP-14839, Revision 1, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Nuclear Plant," September 1998 4. Letter from TVA to NRC, "Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Annual Notification and Reporting for 2000," dated October 26,2000 [ML003764646]

5. Letter from TVA to NRC, 'Watts Bar Nuclear Plant (VVBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Revised Annual Notification Report for 2000," dated September 7,2001 [ML012570290]

6. Letter from TVA to NRC, 'Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes - Annua! Notification and Reporting for 2001," dated April 3, 20021MLO210704041

7. Letter from TVA to NRC, "Watts Bar Nuclear Plant (WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Revised Annual Notification and Reporting for 2003," dated April 19, 2004 [M1041130196]

8. Letter from TVA to NRC, "Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes - Annual Notification and Reporting for 2004," dated April 19, 2005 [M10511201641

9. Letter from TVA to NRC, 'Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Annual Notification and Reporting for 2006," dated July 3, 2007 [ML071860388]

10. Letter from TVA to NRC, "Supplement to 10 CFR 50.46 Day Special Report," dated February 13, 2013 [ML1 3046A002]1 1 . Letter from TVA to NRC, '10 CFR 50.46 Day Special Report," dated October 18,2012 lML12296pc54l

12. Letter from TVA to NRC, '10 CFR 50.46 Day Report for Watts Bar Unit 1," dated March 19, 2013 [ML1 3080A405]13. Letter from TVA to NRC, '10 CFR 50.46 Day and Annual Report for 2012," dated April 25, 2013 [M113120A005]

CNL-16-057 E 11 of 12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 GFR 50.46 Annual Report for 2015 14. Letter from TVA to NRC, "10 CFR 50.46 - 30 day Report for Watts Bar, Unit 1," dated August 28, 2013 [MLl 32674034]15. Letter from TVA to NRC, CNL-14-035, '10 CFR 50.46 - 30 day Report for Watts Bar, Units 1 and 2," dated February 28,2014. [ML14064A431]

16. WTV-RSG-06-015, "LOCA & Non-LOCA Analysis Summary for Replacement Steam Generator," February 2006 17. WCAP-I7093-P, Revision 1, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Unit 2 Nuclear Plant Using the ASTRUM Methodology," June 2013 18. WBT-D-1460, "Final Small Break LOCA Summary Report forWBN Unit 2," January 2010 19. Letter from TVA to NRC, 'Watts Bar Nuclear Plant, Unit 2 - Emergency Core Cooling System Evaluation Model Changes - 30 Day Report - 10 CFR 50.46 Notification," dated August 28, 2013. [ML1 32464076]cNL-16-057 E 12of12 Tennessee Valley Authority, 1101 Market Street, Chattanooga, TN 37402 cNL-16-057 March 18, 2016 10 cFR s0.4 10 cFR 50 .46 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License NPF-90 NRC Docket No. 50-390 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391

Subject:

l0 CFR 50.46 - Annual Report for Watts Bar Nuclear Plant Units 1 and 2

Reference:

1. TVA Letter to NRC, CNL-'I5-053, '10 CFR 50.46 Day and Annual Report for Watts Bar, Units 1 and 2," dated March 30, 2015 [ML150984124]

The purpose of this letter is to provide the annual report of changes and errors to the calculated peak cladding temperature (PCT) for the Watts Bar Nuclear Plant (WBN) Units 1 and 2, Emergency Core Cooling System (ECCS) evaluation model. This report is required in accordance with Title 10 of the Code of Federal Regulafibns

('10 CFR) 50.46, "Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors," paragraph (a)(3Xii).

The Tennessee Valley Authority (TVA) submitted the last 10 CFR 50.46 annual report for WBN Units 1 and 2 to the Nuclear Regulatory Commission (NRC) in the referenced letter. As indicated in the enclosure, there are no changes to the current updated (net) licensing basis PCT for the WBN Unit 1 large break loss of coolant accident (LBLOCA) and the updated (net)licensing basis PCT for the WBN Unit 1 small break loss of coolant accident (SBLOCA).Similarly, there are no changes to the current updated (net) licensing basis PCT for the WBN Unit 2 LBLOCA and the updated (net) licensing basis PCT for the WBN Unit 2 SBLOCA.There are no new regulatory commitments in this letter. Please address any questions regarding this response to Mr. Gordon Arent at 423-365-2004.

U.S. Nuclear Regulatory Commission cNL-16-057 Page 2 March 18,2016 K. T. Walsh Site Vice President Watts Bar Nuclear Plant

Enclosure:

Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 cc (Enclosures):

NRC RegionalAdministrator - Region ll NRC Senior Resident lnspector - Watts Bar Nuclear Plant, Unit 1 NRC Senior Resident lnspector - Watts Bar Nuclear Plant, Unit 2 Division of Radiological Health - State of Tennessee Respectfully, U.S. Nuclear Regulatory Commission cNL-16-057 Page 3 March 18, 2016 DCB Enclosures bcc (w/o Enclosures):

G. P. Arent M. A. Balduzzi G. A. Boerschig C. Carey J. M. Casner T. M. Conners S. M. Connors D. M. Czufin D. L. Daniels K. D. Dietrich S. M. Douglas B. M. Duckett B. M. Finn J. P. Grimes E. K. Henderson G. E. Pry E. D. Schrull J. W. Shea P. R. Simmons M. D. Skaggs S. A. Vance K. T. Walsh, Sr.N. A. Welch B. A. Wetzel P. R. Wilson ECM ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 ANd 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 ln accordance with the reporting requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.46(aX3)(ii), the Tennessee Valley Authority (TVA) is providing the following summary of the limiting design basis loss of coolant accident (LOCA) analysis results established using the current Watts Bar Nuclear Plant WBN) Emergency Core Cooling System evaluation models for WBN Units 1 and 2. This report describes the changes and errors affecting the calculated peak cladding temperatures (PCTs) since the last analysis of record was submitted to the Nuclear Regulatory Commission (NRC).TVA submitted the last 1 0 CFR 50.46 annual report for WBN Units 1 and 2 to the NRC on March 30, 2015 (Reference 1).Table 1 lists the changes and errors in the large break LOCA (LBLOCA) analysis for WBN Unit 1 since the last analysis of record (AOR) and the associated effect on PCT. For 2015, there were no new changes or errors to report for the LBLOCA analysis.

Table 2 lists the changes and errors in the small break LOCA (SBLOCA) analyses for WBN Unit 1 since the last AOR and the associated effect on PCT. The changes that were not previously identified in Reference 1 are described in the notes to Tables 1and2.Table 3 lists the changes and errors in the LBLOCA analysis for WBN Unit 2 since the last AOR and the associated effect on PCT. For 2015, there were no new changes or errors to report for the LBLOCA analysis.

Table 4 lists the changes and errors in the SBLOCA analyses for WBN Unit 2 since the last AOR and the associated effect on PCT. The changes that were not previously identified in Reference 1 are described in the notes to Tables 3 and 4.The updated (net) licensing basis PCT for the LBLOCA and SBLOCA remain unchanged for WBN Units l and2from the last annual report.cNL-16-057 E1of12 ENCLOSURE TEN NESSEE VALLEY AUTHORIW WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 1 Watts Bar Unit 1 LBLOCA Year Description Reflood 1 Reflood 2 Note Reference APCT ("F)Iancrl ("F)APCT ("F)lmcrl ("F)1 998 BE LBLOCA AOR PCT 1 656 1892 3 1 999 Vessel Channe! DX Error 56 56-4 4 4 2000! ncreased Accumulator Room Tem perature Evaluation 4 4 4 4 4 2000 1.4% Uprate Evaluation 12 12 12 12 4 2000 Accu m u lator Line/Pressu rizer Surse Line Data Evaluation

-37 37-131 131 4 2000 MONTECF Decay Heat Uncertainty Error 4 4 4 4 5 2001 WBN Specific LBLOCA Vessel Geometrv lnput Errors 0 0 0 0 6 2003 lnput Error Resulting in lncomplete Solution Matrix 60 60 0 0 7 2003 Tavg Bias Error 8 I 8 8 7 2004 lncreased Stroke Time for ECCS Valves 0 0 0 0 I 2004 Revised Blowdown Heatup U ncertai nty Distri butio n 5 5 5 5 I 2006 Replacement Steam Generators (D3 to 68AXP)-50 50-10 10 I 2006 HOTSPOTTM Fuet Relocation Error 0 0 65 65 9 CNL-16-057 E2of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable I Watts Bar Unit I LBLOCA Year Description Reflood 1 Reflood 2 Note Reference APCT ('F)Imcrl ("F)APCT ("F)lmcrl ('F)2012 PMID/PBOT Violation Evaluation 20 20 20 20 10, 11 2012 TCD and Peaking Factor Burndown 114 114 15 15 10, 11 2013 WCOBRA/TRACTM History File Dimension Error 0 0 0 0 12 2013 General Code Maintenance 0 0 0 0 13 2013 HOTSPOTTM Burst Temperature Calculation for ZIRLo'M Claddinq 0 0 0 0 13 2013 HOTSPOTTM lteration Algorithm for Calculation lnitial Fuel Pellet Average Temperature 0 0 0 0 13 2013 WCO BRA/TRACTM Auto mate d Restart Process Loqic Error 0 0 0 0 13 2013 Rod lnternal Pressure Calculation Error 0 0 0 0 13 2013 Elevations for Heat Slab Temperature I nitialization 0 0 0 0 14 2013 Heat Transfer Model Error Corrections 0 0 0 0 14 2013 Correction to Heat Transfer Node lnitialization 0 0 0 0 14 2013 Mass Conservation Error Fix 0 0 0 0 14 2013 Correction to Split Channel Momentum Equation 0 0 0 0 14 cNL-16-057 E3ot12 ENCLOSURE TEN NESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 1 Watts Bar Unit I LBLOCA Year Description Reflood I Reflood 2 Note Reference APCT ("F)Imcrl ("F)APCT ("F)lmcrl ("F)2013 Heat Transfer Logic Correction for Rod Burst Calculation 0 0 0 0 14 2013 Changes to Vessel Superheated Steam Properties 0 0 0 0 14 2013 Update to Metal Density Reference Tem peratu res 0 0 0 0 14 2013 Decay Heat Model Error Corrections 0 0 0 0 14 2013 Correction to the Pipe Exit Pressure Drop Error 0 0 0 0 14 2013 WCOBRA/TRAC File Dimension Error Correction 0 0 0 0 14 2013 Revised Heat Transfer Mu ltiplier Distributions

-40 40-85 85 14 2013 HOTSPOT Burst Strain Error 20 20 70 70 15 2014 General Computer Code Maintenance 0 0 0 0 1 2014 Revised Uncertainty in LBLOCA Monte Carl Simulations 0 0 0 0 1 Updated (net) Iicensing basis PCT AORPCT+fAPCT 1832 I 865 Gumulative sum of PCT changes I !ancrl 430 433 cNL-16-057 E4of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and 2 DOGKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 2 Watts Bar Unit { SBLOCA Year Description SBLOCA APCT ("F)SBLOCA I APcr I ("F)Note Reference 2006 SBLOCA AOR PCT 1132 16 2013 NOTRU M P-E MrM Evaluation of Fuel Pellet TCD 0 0 13 2014 General Computer Code Maintenance 0 0 1 2014 Fuel Rod Gap Conductance Error 0 0 1 2014 Radiation Heat Transfer Model Error 0 0 1 2014 SBLOCTA Pre-DNB Cladding Surface Heat Transfer Coefficient Calculation 0 0 1 2014 Evaluation of 8-inch Axial Blankets 0 0 1 2015 General Computer Code Maintenance 0 0 1 2015 Auxiliary Feedwater (AFW)Temperature lncrease During Cold Leg Recirculation 0 0 2 Updated (net) Iicensing basis PCT AORPCT+fAPCT 1132 Cumulative sum of PCT changes r lmcrl 0 cNL-16-057 E5of12 Notes: 1.2.ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 GFR 50.46 Annual Report for 2015 Various changes have been made to enhance the usability of codes and to streamline future analyses.

Examples of these changes include modifying input variable definitions, units and defaults; improving the input diagnostic checks; enhancing the code output;optimizing active coding; and eliminating inactive coding.The WBN Unit 1 and WBN Unit 2 AFW temperature during cold leg recirculation may reach a temperature of 130'F. This temperature is an increase in the AFW temperature modeled in the SBLOCA analyses of record. However, there is no effect on the SBLOCA analysis results.cNL-16-057 E6of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 3 Watts Bar Untt2 LBLOCA Year Description LBLOCA APCT ("F)LBLOCA lmcrl ('F)Note Reference 2413 LBLOCA AOR PCT 1 766 17 2013 Elevations for Heat Slab Temperatu re I n itialization 0 0 19 2013 Heat Transfer Model Error Corrections 0 0 19 2013 Correction to Heat Transfer Node lnitialization 0 0 19 2013 Mass Conservation Error Fix 0 0 19 2013 Correction to Split Channel Momentum Equation 0 0 19 2013 Heat Transfer Logic Correction for Rod Burst Calculation 0 0 19 2013 Changes to Vessel Superheated Steam Properties 0 0 19 2013 Update to Metal Density Reference Tem peratu res 0 0 19 2013 Decay Heat Model Error Corrections 0 0 19 2013 Correction to the Pipe Exit Pressure Drop Error 0 0 19 2013 WCOBRA/TRAC File Dimension Error Correction 0 0 19 2013 Revised Heat Transfer Multiplier Distributions

-55 55 19 2013 Initial Fuel Pellet Average Tem perature U ncertainty Calculation 0 0 19 2013 HOTSPOT Burst Strain Error 0 0 15 CNL-16-057 ET of 12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUGLEAR PLANT UNITS 1 and2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Year Description LBLOCA APCT ('F)LBLOCA lancrl ('F)Note Reference 2014 Cold Leg Accumulator Injection Lines Hydraulic Resistance Chanqes 0 0 2 2014 General Computer Code Maintenance 0 0 1 2014 Errors in Decay Group Uncertainty Factors 0 0 1 2014 Treatment of Burnup Effects on Thermal Conductivity Degradation 0 0 1 Updated (net) Iicensing basis PCT (AORPCT+fAPCT) 1711 Cumulative sum of PCT changes I lmcrl 55 CNL-16-057 E8of12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Iable 4 Watts Bar Unit 2 SBLOCA Year Description SBLOCA APGT ("F)SBLOCA Imcrl ("F)Note Reference 2010 SBLOCA AOR PCT 1184 18 2014 Cold Leg Accumulator lnjection Lines Hydraulic Resistance Changes 0 0 2 2014 General Computer Code Maintenance 0 0 1 2014 Fuel Rod Gap Conductance Error 0 0 1 2014 Radiation Heat Transfer Model Error 0 0 1 2014 SBLOCTA Pre-DNB Cladding Surface Heat Transfer Coefficient Calculation 0 0 1 2015 General Computer Code Maintenance 0 0 1 2015 AFW Temperature I ncrease During Cold Leg Recirculation 0 0 2 Updated (net) Iicensing basis PCT (AORPCT+fAPCT) 1184 Cumulative sum of PCT changes I lmcrl 0 0 cNL-16-057 E9of12 Notes: 1.ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015 Various changes have been made to enhance the usability of codes and to streamline future analyses.

Examples of these changes include modifying input variable definitions, units and defaults; improving the input diagnostic checks; enhancing the code output;optimizing active coding; and eliminating inactive coding.The WBN Unit 1 and WBN Unit 2 AFW temperature during cold leg recirculation may reach a temperature of 130"F. This temperature is an increase in the AFW temperature modeled in the SBLOCA analyses of record. However, there is no effect on the SBLOCA analysis results.2.cNL-16-057 E 10of12 ENCLOSURE TENNESSEE VALLEY AUTHORIW WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2015

References:

1 . Letter from TVA to NRC, CNL-15-053, '10 CFR 50.46 Day and Annual Report for Watts Bar, Units 1 and2," dated March 30,2015 [ML15098A124]

2. Letter from TVA to NRC, CNL-15-034, "10 CFR 50.46 Day Report for Watts Bar, Unit 2" dated February 6, 2015 [M115037A725]

3. WCAP-14839, Revision 1, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Nuclear Plant," September 1998 4. Letter from TVA to NRC, "Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Annual Notification and Reporting for 2000," dated October 26,2000 [ML003764646]

5. Letter from TVA to NRC, 'Watts Bar Nuclear Plant (VVBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Revised Annual Notification Report for 2000," dated September 7,2001 [ML012570290]

6. Letter from TVA to NRC, 'Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes - Annua! Notification and Reporting for 2001," dated April 3, 20021MLO210704041

7. Letter from TVA to NRC, "Watts Bar Nuclear Plant (WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Revised Annual Notification and Reporting for 2003," dated April 19, 2004 [M1041130196]

8. Letter from TVA to NRC, "Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes - Annual Notification and Reporting for 2004," dated April 19, 2005 [M10511201641

9. Letter from TVA to NRC, 'Watts Bar Nuclear Plant WBN) Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes Day Report and Annual Notification and Reporting for 2006," dated July 3, 2007 [ML071860388]

10. Letter from TVA to NRC, "Supplement to 10 CFR 50.46 Day Special Report," dated February 13, 2013 [ML1 3046A002]1 1 . Letter from TVA to NRC, '10 CFR 50.46 Day Special Report," dated October 18,2012 lML12296pc54l

12. Letter from TVA to NRC, '10 CFR 50.46 Day Report for Watts Bar Unit 1," dated March 19, 2013 [ML1 3080A405]13. Letter from TVA to NRC, '10 CFR 50.46 Day and Annual Report for 2012," dated April 25, 2013 [M113120A005]

CNL-16-057 E 11 of 12 ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS I and 2 DOCKET Nos . 50-390 and 50-391 Watts Bar Nuclear Plant, 10 GFR 50.46 Annual Report for 2015 14. Letter from TVA to NRC, "10 CFR 50.46 - 30 day Report for Watts Bar, Unit 1," dated August 28, 2013 [MLl 32674034]15. Letter from TVA to NRC, CNL-14-035, '10 CFR 50.46 - 30 day Report for Watts Bar, Units 1 and 2," dated February 28,2014. [ML14064A431]

16. WTV-RSG-06-015, "LOCA & Non-LOCA Analysis Summary for Replacement Steam Generator," February 2006 17. WCAP-I7093-P, Revision 1, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Unit 2 Nuclear Plant Using the ASTRUM Methodology," June 2013 18. WBT-D-1460, "Final Small Break LOCA Summary Report forWBN Unit 2," January 2010 19. Letter from TVA to NRC, 'Watts Bar Nuclear Plant, Unit 2 - Emergency Core Cooling System Evaluation Model Changes - 30 Day Report - 10 CFR 50.46 Notification," dated August 28, 2013. [ML1 32464076]cNL-16-057 E 12of12