WBL-23-013, 10 CFR 50.46 Annual Report for 2022

10 CFR 50.46 Annual Report for 2022

ML23088A213
Person / Time
Site:	Watts Bar
Issue date:	03/29/2023
From:	Anthony Williams Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
WBL-23-013
Download: ML23088A213 (1)

Text

TENNESSEE VALLEY

' AUTHORITY Post Office Box 2000, Spring City, Tennessee 37381 WBL-23-013 March 29, 2023 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 CFR 50.46 -Annual Report for Watts Bar Nuclear Plant Units 1 and 2

References:

1. TVA Letter to NRC, WBL-22-012, "10 CFR 50.46 - Annual Report for Watts Bar Nuclear Plant Units 1 and 2," dated March 2, 2022 (ML22062A002)

2. NRC Letter to TVA, "Watts Bar Nuclear Plant, Units 1 and 2 - Issuance of Amendment Nos. 143 and 50 Regarding Implementation of Full Spectrum' Loss-of-Coolant Accident Analysis {LOCA) and New LOCA-Specific Tritium Producing Burnable Absorber Rod Stress Analysis Methodology (EPID L-2020-LLA-0005)," dated February 26, 2021 (ML21034A169)

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 Regulations (10 CFR) 50.46, "Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors,"

paragraph (a)(3)(ii).

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 Reference 1. The (net) licensing basis PCT for the WBN Unit 2 large break loss of coolant accident (LBLOCA) and small break loss of

U.S. Nuclear Regulatory Commission WBL-23-013 Page 2 March 29, 2023 coolant accident (SBLOCA) PCTs have been revised as the result of implementing the Full Spectrum (FS) Loss of Coolant Accident (LOCA) (FSLOCA) methodology as the LOCA analysis of record for WBN Unit 2, as described in Reference 2. A Reactor Coolant System (RCS)

Average Temperature (Tav9 ) Window has been incorporated into the Unit 2 LOCA analysis, resulting in an 11 °F impact to the updated (net) licensing basis LBLOCA PCT for Unit 2. There are no changes to the updated (net) licensing basis LBLOCA or SBLOCA PCTs for Unit 1.

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 Jonathan Johnson, Site Licensing Manager, at jtjohnson0@tva.gov.

ony L. Williams IV Site Vice President Watts Bar Nuclear Plant

Enclosure:

Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2022 cc (Enclosure):

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

ENCLOSURE Watts Bar Nuclear Plant, 10 CFR 50.46 Annual Report for 2022 In accordance with the reporting requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.46(a)(3)(ii), 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 (ECCS) evaluatio n 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 10 CFR 50.46 annual report for WBN Units 1 and 2 to the NRC in Reference 1 of this Enclosure.

Tables 1 and 3 list the changes and errors in the large break LOCA (LBLOCA) Analysis of Record (AOR) and their associated effects on PCT for WBN Units 1 and 2, respectively.

Tables 2 and 4 list the changes and errors in the small break LOCA (SBLOCA) AOR and their associat ed effect on PCT for WBN Units 1 and 2, respectively. The baseline PCTs for WBN Units 1 and 2 resulted from the adoption of a Westinghouse Full-Spectrum (FS) LOCA (FSLOCA) 1 analysis (Referen ce 2 of this Enclosure) as the LOCA AOR as described in Reference 3 of this Enclosure .

The updated (net) licensing basis PCT for the LBLOCA and SBLOCA remain unchang ed for WBN Unit 1 from the last annual report. The updated (net) licensing basis PCT for the LBLOCA and SBLOCA changed as a result of the implementation of the FSLOCA analysis after the replacement of the Unit 2 Steam Generators during the spring 2022 refueling outage , in addition to the analysis of operation with a Reactor Coolant System (RCS) Average Temperature (Tav ) Window.

9 As presented in this report, compliance with 10 CFR 50.46 requirements is demons trated 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 reanalys is or other action is required.

1 FULL SPECTRUM and FSLOCA are trademarks of Westinghouse Electric Company LLC , or its affiliates and/or subsidiaries.

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ENCLOSURE Table 1 Watts Bar Unit 1 LBLOCA OPA LOOP j~PCTj j6PCTI

~PCT ~PCT (°F)

(OF) (OF) (OF)

Year Description Notes Reference 2020 FSLOCA AOR Baseline 1464 --- 1477 --- 1 3 General Code 2020 0 0 0 0 - -- 1 Maintenance General Code 2021 0 0 0 0 --- 1 Maintenance 2022 Hoop Stress Error 0 0 0 0 2 ---

Generalized Energy Deposition Model 2022 0 0 0 0 3 ---

(GEOM) Energy Non-Conservation General Code 2022 0 0 0 0 4 ---

Maintenance Updated (net) licensing basis PCT

--- 1464 --- 1477 --- --- ---

(AOR PCT + ; 6PCT)

Cumulative sum of PCT

--- changes --- ---

0 0 --- ---

LI ~PCT!

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ENCLOS URE Table 2 Watts Bar Unit 1 SBLOCA Year Description SBLOCA SBLOCA Note Reference

~PCT (°F) I ~PCT! (°F) 2020 FSLOCA AOR Baseline 978 --- 1 3 2020 General Code Maintenance 0 0 --- 1 2021 General Code Maintenance 0 0 --- 1 2022 Hoop Stress Error 0 0 2 ---

2022 GEOM Energy Non-Conservation 0 0 3 ---

2022 General Code Maintenance 0 0 4 ---

Updated (net) licensing basis PCT

--- 978 --- --- ---

(AOR PCT + 2 ~PCT)

Cumulative sum of PCT changes

--- ~ I ~PCTI --- 0 --- ---

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ENCLOSURE Table 3 Watts Bar Unit 2 LBLOCA OPA LOOP L\PCT IL\PCTI IL\PCTI (OF) L\PCT (°F)

(OF) (OF)

Year Description Notes Reference 2020 FSLOCA AOR Baseline 1464 --- 1477 --- 1 3 General Code 2020 0 0 0 0 4 ---

Maintenance General Code 2021 0 0 0 0 4 ---

Maintenance 2022 Tavg Window 11 11 11 11 5 - --

2022 Hoop Stress Error 0 0 0 0 2 ---

GEOM Energy Non-2022 0 0 0 0 3 ---

Conservation General Code 2022 0 0 0 0 4 ---

Maintenance Updated (net) licensing basis PCT

--- 1475 --- 1488 --- - -- ---

(AOR PCT + ) L\PCT)

Cumulative sum of PCT

--- changes --- ---

11 11 --- ---

L I L\PCTI WBL-23-013 E4 of 7

ENCLOS URE Table 4 Watts Bar Unit 2 SBLOCA Year Description SBLOCA SBLOCA Note Reference

~PCT (°F) I ~PCT! (°F) 2020 FSLOCA AOR Baseline 978 --- 1 ---

2020 General Code Maintena nce 0 0 4 ---

2021 General Code Maintena nce 0 0 4 ---

2022 Tav 9 Window 0 0 5 ---

2022 Hoop Stress Error 0 0 2 ---

2022 GEOM Energy Non-Cons ervation 0 0 3 ---

2022 General Code Maintena nce 0 0 4 -- -

Updated (net) licensing basis PCT

--- 978 --- --- ---

(AOR PCT + ; ~PCT)

Cumulative sum of PCT changes

--- L 1 ~PCTI --- 0 --- ---

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ENCLOSURE Notes for Tables 1 through 4:

1. The analysis of record PCT reflects correction of a gamma energy redistribution error as it was included in the original submittal to adopt FSLOCA for WBN Units 1 and 2.

2. For two instances within the cladding rupture logic, the elastic deformation model hoop stress variable was used instead of the hoop stress variable intended for cladding creep deformation and rupture models. The error was evaluated to have a negligible impact on the calculated results, leading to an estimated PCT impact of 0°F.

3. The Generalized Energy Deposition Model (GEOM), described in Section 9.6.2 of WCAP-16996 Revision 1, was discovered to exhibit a non-conservation of deposited energy whereas a small fraction of redistributed energy was not being included in the core balance rods. The energy deposited to the hot rod and hot assembly was confirmed to be conserved and correct.

The error was estimated to have a PCT impact of 0°F.

4. Various changes have been made to enhance the usability of codes and to streamline future analyses. Examples of these changes include 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.

5. A quantitative evaluation was performed to demonstrate that FSLOCA EM analyses contain sufficient margin to the 50.46 acceptance criteria to accommodate implementation of the Tavg window. The Region I uncertainty analysis and Region II uncertainty analysis using LOOP were re-executed mapping the sampled Tavg values from the original Tavg sampling range to the expanded Tavg window implementation range . The estimated effect of Tavg window implementation on Region I analysis is 0°F. The estimated effect for the Region II analyses is 11 °F.

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ENCLOSURE References :

1. TVA Letter to NRC, "10 CFR 50.46 - Annual Report for Watts Bar Nuclear Plant Units 1 and 2, "

dated March 2, 2022 (ML22062A002)

2. WCAP-18437-P, "Engineering Summary Report of the Watts Bar Units 1 and 2 Loss-of-Coolant Accident (LOCA) Analysis with the FULL SPECTRUM LOCA (FSLOCA) Methodo logy," dated April 3, 2019.

3. NRC Letter to TVA, "Watts Bar Nuclear Plant, Units 1 and 2 - Issuance of Amendm ent Nos. 143 and 50 Regarding Implementation of Full Spectrum' Loss-of-Coolant Accident Analysis (LOCA) and New LOCA-Specific Tritium Producing Burnable Absorber Rod Stress Analysis Methodology (EPID L-2020-LLA-0005)," dated February 26, 2021 (ML21034A169)

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