ML17067A079

Submittal of 10 CFR 50.46 - 30-Day and Annual Report

ML17067A079
Person / Time
Site:	Watts Bar
Issue date:	03/08/2017
From:	Simmons P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML17067A079 (17)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, TN 37402 March 8, 2017 10 cFR 50 4 10 cFR 50.46 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License NPF-90 and NPF-96 NRC Docket Nos. 50-390 and 50-391

Subject:

10 GFR 50.46 Day and Annua! Report for Watts Bar Nuclear Plant Units 1 and2

Reference:

TVA Letter to NRC, CNL-16-057, "10 CFR 50.46 - Annual Report for Watts Bar, Units 1 and2," dated March 18,2016 [M116081A248]

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 and2, Emergency Core Cooling System (ECCS) evaluation model. This report is required in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.46, "Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors,"

paragraph (aX3Xii).

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 Peak Cladding Temperature (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.

The enclosure also serves as the 30-day report in accordance with 10 CFR 50.46(a)(3)(ii),

which states that a holder of an operating license or construction permit is required to report changes and errors atfecting an ECCS evaluation modelto the NRC within 30 days when the cumulative sum of the absolute magnitudes of resulting PCT changes exceeds 50"F. The licensee is also required to include with the report, a proposed schedule for providing a

U.S. Nuclear Regulatory Commission Page 2 March 8, 2017 reanalysis or taking other action as may be needed to show compliance with the 10 CFR 50.46 requirements. Westinghouse, who performs the LOCA analysis for WBN, submitted a list of changes and errors to the LOCA analysis to TVA on February 8,2017. All the submitted changes and errors result in a 0"F change in PCT, but because the accumulated changes and errors from previous years are more than 50oF, a 30-day report is required.

As presented in this report, compliance with 10 CFR 50.46 requirements is demonstrated by the calculated PCT for both WBN units remaining below the 2200"F limit. Therefore, TVA has concluded that no proposed schedule for providing a reanalysis or other action is required. No further actions are needed to show compliance with 10 CFR 50.46 requirements.

There are no new regulatory commitments in this letter. Please address any questions regarding this response to Gordon Arent at (423) 365-2004.

Paul Simmons Site Vice President Watts Bar Nuclear Plant

Enclosure:

Watts Bar Nuclear Plant, 10 CFR 50.46 30-Day and Annual Report for 2016 cc (Enclosure):

NRC Regional Administrator - Region ll NRC Senior Resident lnspector - Watts Bar Nuclear Plant Division of Radiological Health - State of Tennessee

U.S. Nuclear Regulatory Commission Page 3 March 8, 2017 DCB Enclosures bcc (w/o Enclosures):

G. P. Arent M. A. Balduzzi J. M. Casner T. M. Conners S. M. Connors D. M. Czufin R. E. Detwiler S. M. Douglas B. M. Duckett B. M. Finn E. K. Henderson J. T. Polickoski A. E. Robinson-Givens E. D. Schrull J. W. Shea P. R. Simmons S. A. Vance K. T. Walsh 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 30-Day and Annual Report for 20i6 ln accordance with the reporting requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.46(a)(3)(ii), the Tennessee Valley Authority (T\\/A) 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 (ECCS) evaluation models forWBN Units 1 and 2. This report describes the changes and errors affecting the calculated peak cladding temperature (PCT) since the last analysis of record was submitted to the Nuclear Regulatory Commission (NRC).

TVA submitted the last 10 CFR 50.46 annual report for WBN Units 1 and2 to the NRC on March 18, 2016 (Reference 1).

Table 1 lists the changes and errors in the large break LOCA (LBLOCA) analysis for WBN Unit 1 since the analysis of record (AOR) and the associated effect on PCT. Table 2 lists the changes and errors in the small break LOCA (SBLOCA) analyses for WBN Unit 1 since the AOR and the associated effect on PCT. The changes that were not previously identified in Reference 1 are described in the notes to Tables 1 and 2.

Table 3 lists the changes and errors in the LBLOCA analysis for WBN Unit 2 since the AOR and the associated effect on PCT. Table 4 lists the changes and errors in the SBLOCA analyses for WBN Unit 2 since the 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 1 and 2from the last annual report.

This report also serves as the 30-day report in accordance with 10 CFR 50.46(aX3)(ii), which states that a holder of an operating license or construction permit is required to report changes and errors affecting an ECCS evaluation model to the NRC within 30 days when the cumulative sum of the absolute magnitudes of resulting PCT changes exceeds 50"F. The licensee is also required to include with the report, a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with the 10 CFR 50.46 requirements. Westinghouse, who performs the LOCA analysis for WBN, submitted a list of changes and errors to the LOCA analysis to TVA on February 8,2017. All the submitted changes and errors result in a 0'F change in PCT, but because the accumulated changes and errors from previous years are more than 50"F, a 30-day report is required.

As presented in this report, compliance with 10 CFR 50.46 requirements is demonstrated by the calculated PCT for both WBN units remaining below the 2200'F limit. Therefore, TVA has concluded that no proposed schedule for providing a reanalysis or other action is required.

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ENCLOSURE TENNESSEE VALLEY AUTHORIW WATTS BAR NUCLEAR PLANT UNITS 1 and2 DOCKET NOs. 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 30-Day and Annual Report tor2016 Table 1 Watts Bar Unit 1 LBLOCA Year Description Reflood 1 Reflood 2 Note Reference APCT

("F) laecrl

("F)

APCT

("F) lancrl

("F) 1 998 BE LBLOCA AOR PCT 1 656 1892 3

1 999 Vessel Channel DX Error 56 56

-4 4

4 2000 I ncreased Accum ulator Room Tem perature Evaluation 4

4 4

4 4

2000 1.4o/o Uprate Evaluation 12 12 12 12 4

2000 Accu m u lator Li ne/Press urizer Surge Line Data Evaluation

-37 37

-131 131 4

2000 MONTECF Decay Heat Uncertainty Error 4

4 4

4 5

2001 WBN Specific LBLOCA Vessel Geometry 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

8 I

8 7

2004 lncreased Stroke Time for ECCS Valves 0

0 0

0 8

2004 Revised Blowdown Heatup U ncertainty Distribution 5

5 5

5 8

2006 Replacement Steam Generators (D3 to 68AXP)

-50 50

-10 10 9

2006 HOTSPOTTM Fue! Relocation Error 0

0 65 65 I

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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 30-Day and Annual Report for 2016 Table 1 Watts Bar Unit 1 LBLOGA Year Description Reflood 1 Reflood 2 Note Reference APCT

("F) lmcrl

("F)

APCT

('F) lancrl

("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 zlRLOrM Claddinq 0

0 0

0 13 2013 HOTSPOTTM lteration Algorithm for Calculation lnitial Fuel Pellet Average Temperature 0

0 0

0 13 2013 WCOBRA/TRACTM Automated Restart Process Logic Error 0

0 0

0 13 2013 Rod lnternal Pressure Calculation Error 0

0 0

0 13 2013 Elevations for Heat Slab Tem perature I nitialization 0

0 0

0 14 2013 Heat Transfer Mode! 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 E3of14

ENCLOSURE TEN NESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET NOs. 50-390 and 50-391 Watts Bar Nuclear PIant, 10 CFR 50.46 30-Day and Annual Report for 2016 Table 1 Watts Bar Unit I LBLOCA Year Description Reflood 1 Reflood 2 Note Reference APCT

("F) lrncrl

("F)

APCT

("F)

Iancrl

("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 peratures 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 M u lti plier Distri butions

-40 40

-85 85 14 2013 HOTSPOT Burst Strain Error 20 20 70 70 15 2014 General Computer Code Maintenance 0

0 0

0 20 2014 Revised Uncertainty in LBLOCA Monte Carlo Simulations 0

0 0

0 20 2016 General Code Maintenance 0

0 0

0 1

2016 CIad Oxidation Calculation 0

0 0

0 2

2016 LOTIC2 Net Free Volume Direction of Conservatism and lce Melt Condition 0

0 0

0 3

2016 LOTIC2 Calculation of the Thermodynam ic Properties of Air 0

0 0

0 4

2016 lncreased Safety lnjection Time Delay with Offsite Power Available 0

0 0

0 5

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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 30-Day and Annual Report for 20i6 Notes

1. Various changes have been made to enhance the usability of codes and to streamline future LBLOCA 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.

2. A closely-related group of errors were discovered in the software that calculates high temperature oxidation in the LBLOCA analyses.

The LOTIC2 code calculates the minimum containment pressure transient for LBLOCA analyses. An error in the LOTIC2 code and an error in the application of the LOTIC2 code were discovered and corrected. The first enor concerned the direction of conservatism for the modeled compartment net free volumes. While it has been assumed that larger compartment volumes would lead to the calculation of a conseruatively low containment backpressure, it was discovered that modelling minimum lower compartment and dead ended compartment volumes could result in the calculation of a lower backpressure. The second error concerned the calculation of heat transferred to the ice, where it was determined that an incorrect reference temperature was being used that could impact heat removed by the ice when the rate of steam condensation in the ice compartment exceeded the rate of steam entering from the lower compartment.

The LOTIC2 code calculates the minimum containment pressure transient for LBLOCA analyses. An error was discovered in the calculation of specific enthalpy and specific internal energy for air in the LOTIC2 code. The calculations omitted Fahrenheit to Rankine conversions when using specific heat and temperature to calculate the enthalpy of air, resulting in enthalpy and internal energy values that were smaller than the correct values.

The Safety !njection (Sl) delay time with offsite power available was increased by five seconds to account for the time it may take transformer load taps to change during a degraded voltage event coincident with a LOCA.

3.

4.

5.

Year Description Reflood 1 Reflood 2 Note Reference APCT

('F)

Irecrl

("F)

APCT

("F)

Inecrl

("F)

Updated (net) Iicensing basis PCT AORPCT+fAPCT 1832 1 865 Cumulative sum of PGT changes I lancrl 430 433 E5of14

ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET NOs. 50-390 and 50-391 Watts Bar Nuclear Plant, {0 CFR 50.46 30-Day and Annual Report for 2016 Table 2 Watts Bar Unit 1 SBLOCA Year Description SBLOCA APGT

("F)

SBLOGA I APCr I

("F)

Note Reference 2006 SBLOCA AOR PCT 1132 16 2013 NOTRU M P-EMrM Eval uation of Fuel Pellet TCD 0

0 13 2014 General Computer Code Maintenance 0

0 20 2014 Fuel Rod Gap Conductance Error 0

0 20 2014 Radiation Heat Transfer Model Error 0

0 20 2014 SBLOCTA Pre-DNB Cladding Surface Heat Transfer Coefficient Calculation 0

0 20 2014 Evaluation of 8-inch Axial Blankets 0

0 20 2015 General Computer Code Maintenance 0

0 1

2015 Auxiliary Feedwater (AFW)

Temperature lncrease During Cold Leg Recirculation 0

0 1

2016 Plant-Specific Upper Head Geometric Data 0

0 1

2016 Increased Containment Spray FIow Rate and Reduced RWST Useable Volume 0

0 2

Updated (net) Iicensing basis PCT AORPCT+fAPCT 1132 E6of14

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 30-Day and Annual Report for 2016 Cumulative sum of PCT changes I lrecr!

0 Notes:

1. The upper head geometric data used in the SBLOCA analysis was found to not be reflective of the actual upper head design.

2. The SBLOCA analysis modeled flow from one train of containment spray as a mechanism to deplete the Refueling Water Storage Tank (RWST). The standard SBLOCA methodology considers the actuation of all available containment spray pumps to minimize the time at which the switchover to sump recirculation occurs. Additionally, the RWST inventory used in the analysis included credit for volume that would be injected during the manual operator actions required to complete the switchover from ECCS injection to sump recirculation. The standard SBLOCA methodology models a more conservative (smaller) volume that represents the RWST inventory between the minimum initial level and the initiation of the switchover to sump recirculation.

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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 30-Day and Annual Report for 2016 Table 3 Watts Bar Unit ?LBLOCA Year Description LBLOCA APCT

('F)

LBLOCA lapcrl

("F)

Note Reference 2013 LBLOCA AOR PCT 1 766 17 2013 Elevations for Heat Slab Tem perature I nitialization 0

0 19 2013 Heat Transfer Model Error Corrections 0

0 19 2013 Correction to Heat Transfer Node Initialization 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 WCOBRAITRAC File Dimension Error Correction 0

0 19 2013 Revised Heat Transfer Multiplier Distributions

-55 55 19 2013 Initial Fuel Pellet Average Tem peratu re U ncertai nty Calculation 0

0 19 2013 HOTSPOT Burst Strain Error 0

0 15 E8of14

ENCLOSURE TENNESSEE VALLEY AUTHORIry WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET NOs. 50-390 and 50-391 watts Bar Nuclear PIant, 10 cFR 50.46 30-Day and Annual Report for 2016 Year Description LBLOCA APCT

("F)

LBLOCA laecrl

("F)

Note Reference 2014 Cold Leg Accumulator Injection Lines Hydraulic Resistance Changes 0

0 2

2014 General Computer Code Maintenance 0

0 20 2014 Errors in Decay Group Uncertainty Factors 0

0 20 2014 Treatment of Burnup Effects on Thermal Conductivity Degradation 0

0 20 2016 General Code Maintenance 0

0 1

2016 CIad Oxidation Calculation 0

0 2

2016 Use of Steam Tables in Upper Head Fluid Tem perature Calculations 0

0 3

2016 Lower Support Plate Heat Conductor Surface Area 0

0 4

2016 LOTIC2 Net Free Volume Direction of Conservatism and lce Melt Condition 0

0 5

2016 LOTIC2 Calculation of the Thermodynam ic Properties of Air 0

0 6

Updated (net) licensing basis PCT (AORPCT+fAPCT) 1711 Gumulative sum of PGT changes I lrpcrl 55 Notes:

1. Various changes have been made to enhance the usability of codes and to streamline future LBLOCA 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.

2. A closely-related group of errors were discovered in the software program that calculates high temperature oxidation in the LBLOCA analyses.

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3.

ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNTTS 1 and 2 DOCKET NOs. 50-390 and 50-391 watts Bar Nuclear Plant, 10 cFR 50.46 30-Day and Annual Report for 2016 The initial, steady-state upper head fluid temperature is calculated by interpolating in steam tables based on the pressure and specific enthalpy of the upper head fluid. The steady-state calculation was found to use the steam table applicable to steam when it should have been using the steam table applicable to subcooled water.

A modeling error in the lower support plate heat conductor over-estimates the heat transfer surface area of the lower support plate.

The LOTIC2 code calculates the minimum containment pressure transient for LBLOCA analyses. An error in the LOTIC2 code and an error in the application of the LOTIC2 code were discovered and corrected. The first error concerned the direction of conservatism for the modeled compartment net free volumes. While it has been assumed that larger compartment volumes would lead to the calculation of a conservatively low containment backpressure, it was discovered that modelling minimum lower compartment and dead ended compartment volumes could result in the calculation of a lower backpressure. The second error concerned the calculation of heat transferred to the ice, where it was determined that an incorrect reference temperature was being used that could impact heat removed by the ice when the rate of steam condensation in the ice compartment exceeded the rate of steam entering from the lower compartment.

The LOTIC2 code calculates the minimum containment pressure transient for LBLOCA analyses. An error was discovered in the calculation of specific enthalpy and specific internal energy for air in the LOTIC2 code. The calculations omitted Fahrenheit to Rankine conversions when using specific heat and temperature to calculate the enthalpy of air, resulting in enthalpy and internal energy values that were smaller than the correct values.

4.

5.

6.

E10ot14

ENCLOSURE TEN NESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNITS 1 and2 DOCKET NOs. 50-390 and 50-391 Watts Bar Nuclear Plant, 10 CFR 50.46 30-Day and Annua! Report for 2016 Table 4 Watts Bar Unit 2 SBLOGA Year Description SBLOCA APCT

('F)

SBLOCA lmcrl

("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 20 2014 Fuel Rod Gap Conductance Error 0

0 20 2014 Radiation Heat Transfer Model Error 0

0 20 2014 SBLOCTA Pre-DNB Cladding Surface Heat Transfer Coefficient Calculation 0

0 20 2015 General Computer Code Maintenance 0

0 1

2015 AFW Temperature I ncrease During Cold Leg Recirculation 0

0 1

2016 Plant-Specific Upper Head Geometric Data 0

0 1

2016 Reduced RWST Useable Volume 0

0 2

Updated (net) Iicensing basis PCT (AORPCT+fAPCT) 1184 Cumulative sum of PCT changes I lrecrl 0

0 Notes:

1. The upper head geometric data used in the SBLOCA analysis was found to not be reflective of the actual upper head design.

E11of14

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 30-Day and Annua! Report for 2016

2. The RWST inventory used in the analyses included credit for volume that would be injected during the manual operator actions required to complete the switchover from ECCS injection to sump recirculation. The standard SBLOCA methodology models a more conservative (smaller) volume that represents the RWST inventory between the minimum initial level and the initiation of the switchover to sump recirculation.

E 12ot14

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 30-Day and Annual Report for 2016

References:

1. Letter from TVA to NRC, CNL-16-057, "10 CFR 50.46 - Annual Report for Watts Bar, Units 1 and2," dated March 18,2016 [MLl6081A248]

2. Letter from TVA to NRC, CNL-15-034,"10 CFR 50.46 Day Report for Watts Bar, Unit 2,"

dated February 6, 2015 [ML15037A725]

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 Annuai Notification and Reporting for 2000,'dated October 26,2000 [ML003764646]

5. 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 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 - Annual Notification and Reporting for 2001,'

dated April 3, 2002 [ML021O7O4O4l 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 1 9, 2004 [ML041130196]

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 Annuai Notification and Reporting for 2006," dated July 3, 2007 [ML071BO038B]

10. Letter from TVA to NRC, "Supplement to 10 CFR 50.46 Day Special Report," dated February 13, 2013 [ML13046A002]

1 1. Letter from TVA to NRC, '10 CFR 50.46 Day Special Report," dated October 19,2012

\\ML12296A2541

12. Letter from TVA to NRC,.10 CFR 50.46 Day Report for Watts Bar Unit 1," dated March 19, 2013 [MLl 3080A405]

13. Letter from TVA to NRC, '10 CFR 50.46 Day and Annual Report for 2012," dated April 25, 201 3 [MLl 31 20A005]

7.

8.

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ENCLOSURE TEN NESSEE VALLEY AUTHORIW WATTS BAR NUCLEAR PLANT UNITS 1 and 2 DOCKET NOs. 50-390 and 50-39i Watts Bar Nuclear Plant, 10 CFR 50.46 30-Day and Annual Report for 2016

14. Letter from TVA to NRC, "10 CFR 50.46 - 30 day Report for Watts Bar, Unit 1,' dated August 28, 2013 [ML13267A0341

15. Letter from TVA to NRC, CNL-14-035, "10 CFR 50.46 - 30 day Report for Watts Bar, Units 1 and2," dated February 28,2014. [M114064A431]

16. WTV-RSG-06-015, "LOCA & Non-LOCA Analysis Summary for Replacement Steam Generator," February 2006

17. WCAP-17093-P, Revision 1, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Wafts Bar Unit 2 Nuclear Plant Using the ASTRUM Methodology," June 2013

18. WBT-D-I460, "Final Small Break LOCA Summary Report for WBN 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, 201 3.[ML13246A076]

20. Letter from TVA to NRC, CNL-15-053, '10 CFR 50.46 Day and Annual Report for Watts Bar, Units 1 and 2," dated March 30, 201S [MLlS0g8A124]

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