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MONTHYEARCNL-21-026, License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03)2021-08-0505 August 2021 License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03) Project stage: Request ML21239A0712021-08-27027 August 2021 Acceptance of License Amendment Request to Adopt TSTF-505, Revision 2 Project stage: Acceptance Review ML21246A0532021-09-15015 September 2021 Regulatory Audit in Support of Review of the Application to Adopt Risk-Informed Extended Completion Times RITSTF Initiative 4B Project stage: Approval CNL-21-001, Application to Modify the Technical Specification Table 3.3.1-1, Reactor Trip System Instrumentation (SQN-TS-21-01)2021-11-29029 November 2021 Application to Modify the Technical Specification Table 3.3.1-1, Reactor Trip System Instrumentation (SQN-TS-21-01) Project stage: Request ML21336A3942021-12-0101 December 2021 NRR E-mail Capture - Audit Questions for Sequoyah Units 1 and 2 - LAR to Adopt TSTF-505, Revision 2 (L-2021-LLA-0145) Project stage: Approval ML22035A0182022-02-0303 February 2022 NRR E-mail Capture - Audit Questions (Eeb follow-up) for Sequoyah Units 1 and 2 LAR to Adopt TSTF-505, Revision 2 (L-2021-LLA-0145) Project stage: Approval ML22046A2742022-02-15015 February 2022 NRR E-mail Capture - Audit Question (Snsb 02) for Sequoyah Units 1 and 2 LAR to Adopt TSTF-505, Revision 2 (L-2021-LLA-0145) Project stage: Approval ML22125A1422022-03-22022 March 2022 1 and 2 - March 22, 2022 e-mail - Sequoyah TSTF-505 LAR Supplemental Information Project stage: Approval ML22108A2822022-04-27027 April 2022 Summary of Regulatory Audit Regarding the License Amendment Request to Revise TS to Adopt TSTF 505, Rev. 2, Provide Risk-Informed Extended Completion Times RITSTF Initiative 4b Project stage: Other CNL-22-023, Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf2022-04-28028 April 2022 Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf Project stage: Supplement ML22118A3332022-04-28028 April 2022 Submittal of Sequoyah Nuclear Plant, Units 1 and 2 - Updated Final Safety Analysis Report Amendment 30 Project stage: Request CNL-22-034, Second Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03)2022-05-13013 May 2022 Second Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03) Project stage: Supplement ML22146A3322022-05-26026 May 2022 NRR E-mail Capture - Request for Additional Information Related to Sequoyah Nuclear Plant'S LAR to Adopt TSTF-505 Project stage: RAI CNL-22-069, Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf.2022-07-0101 July 2022 Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf. Project stage: Response to RAI ML22196A0732022-07-15015 July 2022 NRR E-mail Capture - (External_Sender) State Notification for Sequoyah Units 1 and 2 Amendment Issuance - TSTF-505 RICT (L-2021-LLA-0145) Project stage: Other ML22210A1182022-08-24024 August 2022 Issuance of Amendment Nos. 358 and 352 Regarding Technical Specifications Task Force Traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4B Project stage: Approval ML22259A2042022-09-29029 September 2022 Correction to Amendment Nos. 358 and 352 Regarding Technical Specifications Task Force Traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4B Project stage: Other 2022-03-22
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Category:Letter type:CNL
MONTHYEARCNL-24-017, Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure and Emergency Preparedness Department Procedure Revisions2024-01-17017 January 2024 Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure and Emergency Preparedness Department Procedure Revisions CNL-23-068, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-12-21021 December 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation CNL-23-036, Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-02 and WBN-TS-23-08)2023-12-18018 December 2023 Application to Revise Function 5 of Technical Specification Table 3.3.2-1, Engineered Safety Feature Actuation System Instrumentation, for the Sequoyah Nuclear Plant and Watts Bar Nuclear Plant (SQN-TS-23-02 and WBN-TS-23-08) CNL-23-067, Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2023-11-27027 November 2023 Central Emergency Control Center Emergency Plan Implementing Procedure Revisions CNL-23-061, Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revision2023-09-20020 September 2023 Tennessee Valley Authority - Central Emergency Control Center Emergency Plan Implementing Procedure Revision CNL-23-059, Supplement to Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2, Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-2023-09-20020 September 2023 Supplement to Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Units 1 and 2, Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-03 CNL-23-057, Central Emergency Control Center Emergency Plan Implementing Procedure Revisions. Includes CECC-EPIP-1, Revision 76 and CECC-EPIP-9, Revision 642023-09-0505 September 2023 Central Emergency Control Center Emergency Plan Implementing Procedure Revisions. Includes CECC-EPIP-1, Revision 76 and CECC-EPIP-9, Revision 64 CNL-23-028, Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-03 and WBN-TS-23-06)2023-08-0202 August 2023 Application to Revise Technical Specifications to Adopt TSTF-567-A, Revision 1, Add Containment Sump TS to Address GSI-191 Issues (SQN-TS-23-03 and WBN-TS-23-06) CNL-23-055, Tennessee Valley Authority - Emergency Preparedness Department Procedure Revision. Includes EPDP-3, Revision 3, Emergency Plan Exercises and Preparedness Drills2023-07-25025 July 2023 Tennessee Valley Authority - Emergency Preparedness Department Procedure Revision. Includes EPDP-3, Revision 3, Emergency Plan Exercises and Preparedness Drills CNL-23-053, Tennessee Valley Authority - Radiological Emergency Plan Revisions2023-07-18018 July 2023 Tennessee Valley Authority - Radiological Emergency Plan Revisions CNL-23-049, Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan .2023-06-26026 June 2023 Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan . CNL-23-042, Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2023-05-16016 May 2023 Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions CNL-23-032, Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Unit 1 and 2, Nuclear Quality Assurance Plan, TVA-NQA-PLN89-A, Revision 412023-04-27027 April 2023 Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Unit 1 and 2, Nuclear Quality Assurance Plan, TVA-NQA-PLN89-A, Revision 41 CNL-23-030, Tennessee Valley Authority - Hydrologic Engineering Center River Analysis System Project Milestone Status Update2023-04-27027 April 2023 Tennessee Valley Authority - Hydrologic Engineering Center River Analysis System Project Milestone Status Update CNL-23-033, Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revision2023-04-24024 April 2023 Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revision CNL-23-029, Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2023-04-11011 April 2023 Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions CNL-23-012, Revision to the Application to Revise Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (TS-19-02)2023-04-11011 April 2023 Revision to the Application to Revise Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (TS-19-02) CNL-23-023, Annual Insurance Status Report2023-03-30030 March 2023 Annual Insurance Status Report CNL-23-024, TVA Guarantee of Payment of Deferred Premiums - 2022 Annual Report2023-03-29029 March 2023 TVA Guarantee of Payment of Deferred Premiums - 2022 Annual Report CNL-23-022, Decommissioning Funding Status Report2023-03-29029 March 2023 Decommissioning Funding Status Report CNL-23-021, Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2023-03-0808 March 2023 Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions CNL-22-037, Application to Revise Technical Specifications to Adopt TSTF-541-A, Add Exceptions to Surveillance Requirements for Valves and Dampers Locked in the Actuated Position (BFN TS-533)2023-01-31031 January 2023 Application to Revise Technical Specifications to Adopt TSTF-541-A, Add Exceptions to Surveillance Requirements for Valves and Dampers Locked in the Actuated Position (BFN TS-533) CNL-23-003, Browns Nuclear Plant, Units 1, 2 & 3; Sequoyah Nuclear Plant, Units 1 & 2; and Watts Bar Nuclear Plant, Units 1 & 2 - Organizational Topic Report TVA-NPOD89-A2023-01-30030 January 2023 Browns Nuclear Plant, Units 1, 2 & 3; Sequoyah Nuclear Plant, Units 1 & 2; and Watts Bar Nuclear Plant, Units 1 & 2 - Organizational Topic Report TVA-NPOD89-A CNL-23-011, Steam Generator Tube Inspection Report to Reflect TSTF-577 Reporting Requirements2023-01-18018 January 2023 Steam Generator Tube Inspection Report to Reflect TSTF-577 Reporting Requirements CNL-23-009, Response to Request for Additional Information Request to Revise Technical Specification 3.4.122023-01-0404 January 2023 Response to Request for Additional Information Request to Revise Technical Specification 3.4.12 CNL-23-008, Tennessee Valley Authority Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2022-12-22022 December 2022 Tennessee Valley Authority Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions CNL-22-106, Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revision. Includes CECC EPIP-14, Revision 38, Nuclear Emergency Public Information Organization and Operat2022-11-28028 November 2022 Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revision. Includes CECC EPIP-14, Revision 38, Nuclear Emergency Public Information Organization and Operatio CNL-22-099, Tennessee Valley Authority - Hydrologic Engineering Center River Analysis System Project Milestone Status Update2022-10-31031 October 2022 Tennessee Valley Authority - Hydrologic Engineering Center River Analysis System Project Milestone Status Update CNL-22-104, Correction to Response to Request for Additional Information Regarding Sequoyah Nuclear Plant, Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RV-022022-10-31031 October 2022 Correction to Response to Request for Additional Information Regarding Sequoyah Nuclear Plant, Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RV-02 CNL-22-098, Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions. Includes CECC EPIP-7, Rev. 45 & CECC EPIP-8, Rev. 552022-10-17017 October 2022 Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions. Includes CECC EPIP-7, Rev. 45 & CECC EPIP-8, Rev. 55 CNL-22-084, Response to Request for Additional Information Regarding License Amendment Request to License Amendment Request to Modify Approved 10 CFR 50.69 Categorization Process (SQN-TS-21-07)2022-09-16016 September 2022 Response to Request for Additional Information Regarding License Amendment Request to License Amendment Request to Modify Approved 10 CFR 50.69 Categorization Process (SQN-TS-21-07) CNL-22-085, Response to Request for Additional Information Regarding Sequoyah Nuclear Plant (Sqn), Units 1 and 2 and Watts Bar Nuclear Plant (Wbn), Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Al2022-09-0202 September 2022 Response to Request for Additional Information Regarding Sequoyah Nuclear Plant (Sqn), Units 1 and 2 and Watts Bar Nuclear Plant (Wbn), Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alte CNL-22-053, Response to Request for Additional Information Regarding Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis - Second Partial Response to Additional Requ2022-08-22022 August 2022 Response to Request for Additional Information Regarding Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis - Second Partial Response to Additional Reques CNL-22-077, Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2022-08-11011 August 2022 Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions CNL-22-030, Application to Revise Technical Specification 3.4.12, Low Temperature Overpressure Protection System for Sequoyah Nuclear Plant (SQN-TSC-22-01) and TS 3.4.12 Cold Overpressure Mitigation System for Watts Bar Nuclear Plant (WBN-TS-22-03)2022-07-27027 July 2022 Application to Revise Technical Specification 3.4.12, Low Temperature Overpressure Protection System for Sequoyah Nuclear Plant (SQN-TSC-22-01) and TS 3.4.12 Cold Overpressure Mitigation System for Watts Bar Nuclear Plant (WBN-TS-22-03) CNL-22-080, Request for Enforcement Discretion from the Requirements of Technical Specification 3.5.2, ECCS - Operating2022-07-22022 July 2022 Request for Enforcement Discretion from the Requirements of Technical Specification 3.5.2, ECCS - Operating CNL-22-081, Supplement to Sequoyah Nuclear Plant, Unit 1, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RP-122022-07-21021 July 2022 Supplement to Sequoyah Nuclear Plant, Unit 1, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RP-12 CNL-22-079, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RP-122022-07-20020 July 2022 American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RP-12 CNL-22-071, Supplement to Application to Revise Technical Specifications to Adopt TSTF-577, Revised Frequencies for Steam Generator Tube Inspections (SQN-TS-21-03 and WBN-TS-21-08)2022-07-13013 July 2022 Supplement to Application to Revise Technical Specifications to Adopt TSTF-577, Revised Frequencies for Steam Generator Tube Inspections (SQN-TS-21-03 and WBN-TS-21-08) CNL-22-039, Application to Revise Technical Specifications to Adopt TSTF-554-A, Revision 1, Revise Reactor Coolant Leakage Requirements (BFN TS-537) (SQN-21-05) (WBN-TS-21-04)2022-07-13013 July 2022 Application to Revise Technical Specifications to Adopt TSTF-554-A, Revision 1, Revise Reactor Coolant Leakage Requirements (BFN TS-537) (SQN-21-05) (WBN-TS-21-04) CNL-22-069, Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf.2022-07-0101 July 2022 Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf. CNL-22-070, Status Regarding the Improved Flood Mitigation System Project2022-06-30030 June 2022 Status Regarding the Improved Flood Mitigation System Project CNL-22-062, Response to Request for Additional Information Regarding American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RV-022022-06-28028 June 2022 Response to Request for Additional Information Regarding American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RV-02 CNL-22-008, and Watts Bar Nuclear Plant - Application to Revise Technical Specifications to Adopt TSTF-529, Clarify Use and Application Rules (BFN-TS-541, SQN-TS-21-09, and WBN-TS-22-002)2022-06-13013 June 2022 and Watts Bar Nuclear Plant - Application to Revise Technical Specifications to Adopt TSTF-529, Clarify Use and Application Rules (BFN-TS-541, SQN-TS-21-09, and WBN-TS-22-002) CNL-22-064, Response to Request for Additional Information Regarding Tennessee Valley Authority License Amendment Request to Revise Emergency Plan Implementing Procedure Regarding Seismic Event Emergency Action Level Change2022-06-0909 June 2022 Response to Request for Additional Information Regarding Tennessee Valley Authority License Amendment Request to Revise Emergency Plan Implementing Procedure Regarding Seismic Event Emergency Action Level Change CNL-22-068, Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions2022-06-0808 June 2022 Tennessee Valley Authority - Radiological Emergency Plan and Central Emergency Control Center Emergency Plan Implementing Procedure Revisions CNL-22-047, Central Emergency Control Center Emergency Plan Implementing Procedure and Emergency Preparedness Department Procedure Revisions2022-05-23023 May 2022 Central Emergency Control Center Emergency Plan Implementing Procedure and Emergency Preparedness Department Procedure Revisions CNL-22-034, Second Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03)2022-05-13013 May 2022 Second Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03) CNL-22-027, Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Unit 1 and 2, Nuclear Quality Assurance Plan, TVA-NQA-PLN89-A, Revision 40 - Annual Update and Proposed Changes to Revision 402022-04-28028 April 2022 Clinch River, Sequoyah, Units 1 and 2, Watts Bar, Unit 1 and 2, Nuclear Quality Assurance Plan, TVA-NQA-PLN89-A, Revision 40 - Annual Update and Proposed Changes to Revision 40 CNL-22-023, Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf2022-04-28028 April 2022 Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf 2024-01-17
[Table view] Category:Response to Request for Additional Information (RAI)
MONTHYEARML24004A0402024-01-0303 January 2024 Response to NRCs November 8, 2023, Request for Additional Information - Related to Independent Spent Fuel Storage Installation ML23117A1162023-04-27027 April 2023 Response to Follow-up Questions to TVAs Response to NRCs Request for Supplemental Information (Rsi) Related to August 4, 2022, Sequoyah ISFSI Exemption Request CNL-23-009, Response to Request for Additional Information Request to Revise Technical Specification 3.4.122023-01-0404 January 2023 Response to Request for Additional Information Request to Revise Technical Specification 3.4.12 ML22353A0662022-12-19019 December 2022 Response to Request for Supplemental Information (D-RSI) Request for Exemption from Non-Destruction-Examination Compliance CNL-22-084, Response to Request for Additional Information Regarding License Amendment Request to License Amendment Request to Modify Approved 10 CFR 50.69 Categorization Process (SQN-TS-21-07)2022-09-16016 September 2022 Response to Request for Additional Information Regarding License Amendment Request to License Amendment Request to Modify Approved 10 CFR 50.69 Categorization Process (SQN-TS-21-07) CNL-22-085, Response to Request for Additional Information Regarding Sequoyah Nuclear Plant (Sqn), Units 1 and 2 and Watts Bar Nuclear Plant (Wbn), Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Al2022-09-0202 September 2022 Response to Request for Additional Information Regarding Sequoyah Nuclear Plant (Sqn), Units 1 and 2 and Watts Bar Nuclear Plant (Wbn), Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alte CNL-22-053, Response to Request for Additional Information Regarding Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis - Second Partial Response to Additional Requ2022-08-22022 August 2022 Response to Request for Additional Information Regarding Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis - Second Partial Response to Additional Reques CNL-22-069, Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf.2022-07-0101 July 2022 Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - Ritstf. CNL-22-062, Response to Request for Additional Information Regarding American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RV-022022-06-28028 June 2022 Response to Request for Additional Information Regarding American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RV-02 CNL-22-064, Response to Request for Additional Information Regarding Tennessee Valley Authority License Amendment Request to Revise Emergency Plan Implementing Procedure Regarding Seismic Event Emergency Action Level Change2022-06-0909 June 2022 Response to Request for Additional Information Regarding Tennessee Valley Authority License Amendment Request to Revise Emergency Plan Implementing Procedure Regarding Seismic Event Emergency Action Level Change CNL-21-024, Partial Response to Additional Request for Information Re Application to Revise Updated Final Safety Analysis Report Re Changes to Hydrologic Analysis (TS-19-02)2021-06-15015 June 2021 Partial Response to Additional Request for Information Re Application to Revise Updated Final Safety Analysis Report Re Changes to Hydrologic Analysis (TS-19-02) CNL-21-039, Response to Request for Additional Information Re Application to Modify Technical Specification to Allow for Transition to Westinghouse RFA-2 Fuel (SQN-TS-20-09)2021-05-0505 May 2021 Response to Request for Additional Information Re Application to Modify Technical Specification to Allow for Transition to Westinghouse RFA-2 Fuel (SQN-TS-20-09) CNL-20-082, Partial Response to Request for Additional Information Regarding Application to Revise Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis (TS-19-02)2020-11-10010 November 2020 Partial Response to Request for Additional Information Regarding Application to Revise Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis (TS-19-02) CNL-20-076, Response to Request for Additional Information Re Application to Revise Sequoyah Nuclear Plant (SQN) Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency (SQN-TS-20-01)2020-09-23023 September 2020 Response to Request for Additional Information Re Application to Revise Sequoyah Nuclear Plant (SQN) Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency (SQN-TS-20-01) CNL-20-057, Tennessee Valley Authority - Application to Revise Sequoyah Nuclear Plant Units 1 & 2 Updated FSAR Changes to Hydrologic Analysis - Partial Response to Additional Request for Additional Information (TS-19-02)2020-08-12012 August 2020 Tennessee Valley Authority - Application to Revise Sequoyah Nuclear Plant Units 1 & 2 Updated FSAR Changes to Hydrologic Analysis - Partial Response to Additional Request for Additional Information (TS-19-02) ML20196L6892020-07-16016 July 2020 TVA Non-Proprietary Slides for Open Session of July 16, 2020, Partially Closed Public Meeting to Discuss Sequoyah License Amendment Request CNL-20-032, Response to Request for Additional Information (TS-19-02) Application to Revise Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis2020-05-14014 May 2020 Response to Request for Additional Information (TS-19-02) Application to Revise Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis CNL-20-026, Supplement to Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (TS-19-02)2020-02-18018 February 2020 Supplement to Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (TS-19-02) CNL-19-119, Response to Request for Additional Information Regarding Sequoyah Nuclear Plant, Unit 1 Exigent License Amendment Request to Revise Technical Specification 4.2.2, Control Rod Assemblies (SQN-TS-19-05)2019-11-19019 November 2019 Response to Request for Additional Information Regarding Sequoyah Nuclear Plant, Unit 1 Exigent License Amendment Request to Revise Technical Specification 4.2.2, Control Rod Assemblies (SQN-TS-19-05) CNL-19-061, Seismic Probabilistic Risk Assessment for Sequoyah Nuclear Plant, Units 1 and 2 - Response to NRC Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task2019-10-18018 October 2019 Seismic Probabilistic Risk Assessment for Sequoyah Nuclear Plant, Units 1 and 2 - Response to NRC Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Fo ML19231A2082019-08-19019 August 2019 Response to Request for Information Regarding Unit 2 Cycle 22 - 180-Day Steam Generator Tube Inspection Report CNL-19-068, Response to Request for Additional Information Regarding the Sequoyah Nuclear Plant (SQN) Units 1 and 2 and Watts Bar Nuclear Plant (WBN) Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for2019-07-22022 July 2019 Response to Request for Additional Information Regarding the Sequoyah Nuclear Plant (SQN) Units 1 and 2 and Watts Bar Nuclear Plant (WBN) Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for .. CNL-19-057, Response to Request for Additional Information Regarding American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Inservice Inspection Program, Request for Alternative, 18-ISl-12019-06-19019 June 2019 Response to Request for Additional Information Regarding American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Inservice Inspection Program, Request for Alternative, 18-ISl-1 CNL-19-002, Response to Request for Additional Information Regarding Application to Modify Sequoyah Nuclear Plant Units 1 and 2, Application to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures,.2019-03-21021 March 2019 Response to Request for Additional Information Regarding Application to Modify Sequoyah Nuclear Plant Units 1 and 2, Application to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures,. CNL-19-016, Response to Request for Additional Information on License Amendment Request to Modify Essential Raw Cooling Water Motor Control Center Breakers and to Revise the Updated Final Safety Analysis Report2019-01-30030 January 2019 Response to Request for Additional Information on License Amendment Request to Modify Essential Raw Cooling Water Motor Control Center Breakers and to Revise the Updated Final Safety Analysis Report CNL-18-089, Response to Request for Additional Information Regarding Decommissioning Funding Plan Update for Browns Ferry Nuclear Plant and Sequoyah Nuclear Plant Independent Spent Fuel Storage Installations, Docket Nos. 72-052 and 72-0342018-07-23023 July 2018 Response to Request for Additional Information Regarding Decommissioning Funding Plan Update for Browns Ferry Nuclear Plant and Sequoyah Nuclear Plant Independent Spent Fuel Storage Installations, Docket Nos. 72-052 and 72-034 NL-18-044, Browns Ferry Units 1, 2, and 3; Sequoyah Units 1 and 2; Watts Bar Units 1 and 2 - Tennessee Valley Authority Response to NRC Request for Additional Information Related to Topical Report TVA-NPG-AWA16, TVA Overall Basin Probable Maximum Pre2018-04-19019 April 2018 Browns Ferry Units 1, 2, and 3; Sequoyah Units 1 and 2; Watts Bar Units 1 and 2 - Tennessee Valley Authority Response to NRC Request for Additional Information Related to Topical Report TVA-NPG-AWA16, TVA Overall Basin Probable Maximum Prec CNL-18-044, Tennessee Valley Authority Response to NRC Request for Additional Information Related to Topical Report TVA-NPG-AWA16, TVA Overall Basin Probable Maximum Precipitation.2018-04-19019 April 2018 Tennessee Valley Authority Response to NRC Request for Additional Information Related to Topical Report TVA-NPG-AWA16, TVA Overall Basin Probable Maximum Precipitation. CNL-17-063, Response to Request for Additional Information (RAI) Regarding Application to Modify Technical Specifications Regarding Diesel Generator Steady State Frequency (SQN-TS-14-02)2017-10-26026 October 2017 Response to Request for Additional Information (RAI) Regarding Application to Modify Technical Specifications Regarding Diesel Generator Steady State Frequency (SQN-TS-14-02) CNL-17-104, Response to Request for Additional Information Regarding Proposed Technical Specification Change to Revise the Note Modifying SR 3.8.1.17 of TS 3.8.1 AC Sources - Operating (TS-SQN-16-04)2017-08-0707 August 2017 Response to Request for Additional Information Regarding Proposed Technical Specification Change to Revise the Note Modifying SR 3.8.1.17 of TS 3.8.1 AC Sources - Operating (TS-SQN-16-04) CNL-17-098, Revised Response to NRC Request for Additional Information Related to TVA Fleet License Amendment Request to Adopt NEI 99-01 Revision 6 Emergency Action Levels2017-07-27027 July 2017 Revised Response to NRC Request for Additional Information Related to TVA Fleet License Amendment Request to Adopt NEI 99-01 Revision 6 Emergency Action Levels CNL-17-085, Response to NRC Request for Additional Information Related to TVA Fleet License Amendment Request to Adopt NEI 99-01 Revision 6 Emergency Action Levels2017-07-0707 July 2017 Response to NRC Request for Additional Information Related to TVA Fleet License Amendment Request to Adopt NEI 99-01 Revision 6 Emergency Action Levels CNL-17-039, Response to NRC Request for Information, Per 10CFR50.54(f) Regarding Recommendations 2.1, 2.3 and 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident - Withdrawal of Regulatory..2017-03-10010 March 2017 Response to NRC Request for Information, Per 10CFR50.54(f) Regarding Recommendations 2.1, 2.3 and 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident - Withdrawal of Regulatory.. CNL-16-194, Response to NRC Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accid2016-12-23023 December 2016 Response to NRC Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accid CNL-16-178, Response to Request for Additional Information (RAI) Regarding Application to Modify Technical Specifications Regarding Diesel Generator Steady State Frequency (SQN-TS-14-02)2016-12-23023 December 2016 Response to Request for Additional Information (RAI) Regarding Application to Modify Technical Specifications Regarding Diesel Generator Steady State Frequency (SQN-TS-14-02) CNL-16-196, Revised Response to NRC Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools2016-12-19019 December 2016 Revised Response to NRC Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools CNL-16-123, Response to NRC Request for Additional Information Request for Approval for Use of Alternate Calibration Block Reflector Requirements 16-PDI-52016-07-28028 July 2016 Response to NRC Request for Additional Information Request for Approval for Use of Alternate Calibration Block Reflector Requirements 16-PDI-5 CNL-16-086, Response to Request for Additional Information Technical Specifications 3.7.8 Change - Essential Raw Cooling Water System2016-05-31031 May 2016 Response to Request for Additional Information Technical Specifications 3.7.8 Change - Essential Raw Cooling Water System CNL-15-218, Application to Revise Technical Specification 6.8.4.h, Containment Leakage Rate Testing Program, (SQN-TS-14-03) (TAC Nos. MF5366 and MF5367), Supplement to Response to Request for Additional Information2015-10-23023 October 2015 Application to Revise Technical Specification 6.8.4.h, Containment Leakage Rate Testing Program, (SQN-TS-14-03) (TAC Nos. MF5366 and MF5367), Supplement to Response to Request for Additional Information CNL-15-171, Application to Revise Technical Specification 6.8.4.h, Containment Leakage Rate Testing Program, (SQN-TS-14-03) - Response to Request for Additional Information2015-09-11011 September 2015 Application to Revise Technical Specification 6.8.4.h, Containment Leakage Rate Testing Program, (SQN-TS-14-03) - Response to Request for Additional Information CNL-15-158, Supplement to TVA Letter, Sequoyah Nuclear Plant - Revision to Commitment No. 28 and Review of Impacts to the SQN Reactor Vessel Internals Aging Management Program Due to Dislodged Reactor Vessel Surveillance Capsules in Unit 1 Reactor.2015-08-0303 August 2015 Supplement to TVA Letter, Sequoyah Nuclear Plant - Revision to Commitment No. 28 and Review of Impacts to the SQN Reactor Vessel Internals Aging Management Program Due to Dislodged Reactor Vessel Surveillance Capsules in Unit 1 Reactor. CNL-15-146, Response to NRC Request for Information Regarding the Review of the License Renewal Application, Set 25 (TAC Nos. MF0481 and MF0482)2015-08-0303 August 2015 Response to NRC Request for Information Regarding the Review of the License Renewal Application, Set 25 (TAC Nos. MF0481 and MF0482) NL-15-158, Supplement to TVA Letter, Sequoyah Nuclear Plant - Revision to Commitment No. 28 and Review of Impacts to the SQN Reactor Vessel Internals Aging Management Program Due to Dislodged Reactor Vessel Surveillance Capsules in Unit 1 Reactor.2015-08-0303 August 2015 Supplement to TVA Letter, Sequoyah Nuclear Plant - Revision to Commitment No. 28 and Review of Impacts to the SQN Reactor Vessel Internals Aging Management Program Due to Dislodged Reactor Vessel Surveillance Capsules in Unit 1 Reactor. CNL-15-136, Response to NRC Request for Additional Information Regarding ASME Request for Relief RP-072015-07-22022 July 2015 Response to NRC Request for Additional Information Regarding ASME Request for Relief RP-07 ML15176A6822015-06-19019 June 2015 Sequoyah Nuclear Plants, Units 1 and 2 Technical Specifications Conversion to NUREG-1431, Rev. 4.0 (SQN-TS-11-10) - Supplement 2. Part 4 of 8 ML15176A6812015-06-19019 June 2015 Sequoyah Nuclear Plants, Units 1 and 2 Technical Specifications Conversion to NUREG-1431, Rev. 4.0 (SQN-TS-11-10) - Supplement 2. Part 3 of 8 ML15176A7482015-06-19019 June 2015 Plants, Units 1 and 2 Technical Specifications Conversion to NUREG-1431, Rev. 4.0 (SQN-TS-11-10) - Supplement 2. Part 8 of 8 ML15176A7402015-06-19019 June 2015 Plants, Units 1 and 2 Technical Specifications Conversion to NUREG-1431, Rev. 4.0 (SQN-TS-11-10) - Supplement 2. Part 7 of 8 ML15176A6792015-06-19019 June 2015 Sequoyah Nuclear Plants, Units 1 and 2 Technical Specifications Conversion to NUREG-1431, Rev. 4.0 (SQN-TS-11-10) - Supplement 2. Part 2 of 8 ML15176A6642015-06-19019 June 2015 Sequoyah Nuclear Plants, Units 1 and 2 Technical Specifications Conversion to NUREG-1431, Rev. 4.0 (SQN-TS-11-10) - Supplement 2. Part 1 of 8 2024-01-03
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1101 Market Street, Chattanooga, Tennessee 37402 CNL-22-069 July 1, 2022 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 50-328
Subject:
Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03) EPID L-2021-LLA-0145
References:
- 1. TVA Letter to NRC, CNL-21-026, License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times---RITSTF Initiative 4b (SQN-TS-20-03), dated August 5, 2021 (ML21217A174)
- 2. TVA Letter to NRC, CNL-22-023, Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (SQN-TS-20-03)
EPID L-2021-LLA-0145, dated April 28, 2022 (ML22118A496)
- 3. TVA Letter to NRC, CNL-22-034, Second Supplement to License Amendment Request to Revise Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times---RITSTF Initiative 4b (SQN-TS-20-03), dated May 13, 2022 (ML22133A238)
- 4. NRC electronic mail to TVA, Request for Additional Information Related to Sequoyah Nuclear Plant's LAR to adopt TSTF-505 (EPID L-2021-LLA-0145),
dated May 26, 2022 (ML22146A332)
By letter dated August 5, 2021 (Reference 1), Tennessee Valley Authority (TVA) requested an amendment to the Sequoyah Nuclear Plant (SQN), Units 1 and 2 Renewed Facility Operating License. The proposed amendment would modify Technical Specifications (TS) requirements to permit the use of Risk-Informed Completion Times (RICT) in accordance with Technical
U.S. Nuclear Regulatory Commission CNL-22-069 Page 2 July 1, 2022 Specifications Task Force (TSTF)-505-A, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF [Risk-Informed TSTF] Initiative 4b. In Reference 2, TVA submitted a supplement to the Reference 1 license amendment request (LAR). In Reference 3, TVA submitted a second supplement to the Reference 1 LAR.
In Reference 4, the Nuclear Regulatory Commission (NRC) issued a request for additional information (RAI) and requested TVA respond by July 11, 2022.
The enclosure to this submittal provides the TVA response to the RAI.
TVA has reviewed the information supporting the no significant hazards consideration and the environmental consideration that was previously provided to the NRC in the referenced LAR.
The additional information provided in this RAI response does not impact the conclusion that the proposed license amendment does not involve a significant hazards consideration. The additional information also does not impact the conclusion that there is no need for an environmental assessment to be prepared in support of the proposed amendment.
There are no new regulatory commitments contained in this submittal.
In accordance with Title 10 of the Code of Federal Regulations 50.91, Notice for Public Comment; State Consultation, a copy of this supplement is being provided to the Tennessee Department of Environment and Conservation.
Please address any questions regarding this submittal to Stuart L. Rymer, Senior Manager, Fleet Licensing, at slrymer@tva.gov.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 1st day of July 2022.
Respectfully, Digitally signed by Rearden, Pamela S Date: 2022.07.01 09:10:38 -04'00' James Barstow Vice President, Nuclear Regulatory Affairs and Support Services Enclosure Response to Request for Additional Information cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant NRC Project Manager - Sequoyah Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation
Enclosure Response to Request for Additional Information NRC Introduction
Background
On August 5, 2021, the Tennessee Valley Authority (the licensee) submitted a license amendment request (LAR) to revise technical specifications to adopt risk-informed completion times in accordance with TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b (ADAMS Accession No. ML21217A174). As part of the NRC staff evaluation of this LAR, a virtual Regulatory Audit was conducted from September 2021 through March 2022 (ADAMS Accession No. ML22108A282). The LAR was supplemented on April 28, 2022 (ADAMS Accession No. ML22118A496), and May 13, 2022 (ADAMS Accession No. ML22133A238).
Regulatory Basis Section 2.3 of Regulatory Guide (RG) 1.174, Revision 3, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis (ADAMS Accession No. ML17317A256), describes acceptability of a probabilistic risk assessment (PRA). The PRA analysis used to support an application is measured in terms of its appropriateness with respect to scope, level of detail, conformance with the technical elements, and plant representation. RG 1.200, Revision 2 (ADAMS Accession No. ML090410014),
provides detailed guidance on technical acceptability of a PRA used to support risk-informed applications.
Request for Additional Information APLC-RAI-1 In its April 28, 2022, response to APLA Audit Question 07, the licensee explained that a revised state-of-knowledge correlation (SOKC) analysis is unnecessary because the point estimate values are within 2 percent of the calculated mean values from the current one top multi-hazard model (OTMHM) seismic PRA (SPRA) model. The licensee provided a comparison of seismic core damage frequency (SCDF) and seismic large early release frequency (SLERF) between the mean and point estimate values in the SPRA submittal made in its October 18, 2019, response to the NRCs post-Fukushima actions (ADAMS Accession No. ML19291A003) and current OTMHM SPRA. The results show that the mean and point estimate values are within 2 percent of each other in the OTMHM SPRA model, while these values are different by more than 2 times in the SPRA submittal in response to the NRCs post-Fukushima actions. The licensee explained that this substantial change was due to the correction of an error in the quantification of the SPRA stating that the error was made by not correctly setting a single parameter used by the UNCERT computer code (@POINTCALC) in calculating mean values, and that the error significantly affected how the mean values were calculated. However, the licensee did not provide any details on the error, the basis for its substantial impact on the quantification results, and why such an impact is expected due to correction of the error.
In addition, the NRC staffs review and discussion during the regulatory audit for the LAR appears to indicate that the OTMHM model does not support uncertainty analysis. Further, in Section 5 of Enclosure 2 to the LAR, the licensee stated that the SQN SPRA Facts and Observations (F&O) Independent Assessment and Focused-Scope Peer Review was performed from February 4 - 8, 2019. Since the licensee submitted its SPRA in response to NRCs post CNL-22-069 E1 of 4
Enclosure Fukushima actions on October 18, 2019, it appears that the change made to correct the quantification error was not part of the SPRA that was peer reviewed.
The NRC staffs experience reviewing SPRAs is that the SPRA mean values and point estimates are appreciably different, primarily due to the uncertainty in the hazard curve and, in certain cases, select fragilities. For example, Case numbers 18 and 19 in Table 5-7 of the licensees October 18, 2019, response to the NRCs post-Fukushima actions demonstrates the large difference in SCDF and SLERF is due to the uncertainty in the seismic hazard. An additional example is a recent peer reviewed SPRA supporting a 10 CFR 50.69 application, which demonstrated that the uncertainty mean is about 30 percent higher than the point estimate for both SCDF and SLERF.
Based on above observations, please address the following:
a) Provide an explanation of the error that was corrected which resulted in the changes to the mean and point estimate SCDF and SLERF values in the OTMHM SPRA model compared to the SPRA submitted in response to the NRCs post-Fukushima actions.
The explanation should discuss why, given the uncertainty in the seismic hazard, the correction of the error resulted in a large change in the mean value and why such a change is to be expected.
b) Clarify whether the OTMHM model supports quantification of parametric uncertainty for the seismic PRA, including the uncertainty in the seismic hazard curve as well as the fragility groups. If it does, explain the process for parametric uncertainty analysis, including the uncertainty in the seismic hazard curve, employed for the OTMHM model compared to the SPRA submitted in response to the NRCs post-Fukushima actions. If it does not, provide an explanation of how the mean and point estimates can be compared using the OTMHM SPRA model.
c) Justify why the change does not constitute a PRA upgrade per the definition in the 2009 ASME/ANS PRA Standard, as endorsed in RG 1.200, Revision 2, and therefore, require a focused-scope peer review.
TVA Response Response to Part a)
The error in the seismic Probabilistic Risk Assessment (SPRA) submittal relates to the configuration of the model database file that the uncertainty software uses to perform the parametric uncertainty analysis. There is a variable in the database that must be changed to allow the uncertainty software to sample the seismic hazard curve and propagate the sample to the discrete seismic hazard bin initiating event basic events. Similarly, the variable must be properly set in order to sample the structures, systems, and components (SSC) fragilities and propagate the sample to the discrete seismic hazard bin fragility basic events. In addition to this change, model refinements reduced the seismic cored damage frequency (CDF) and the seismic large early release frequency (LERF).
In reviewing the calculations performed to respond to APLA Audit Question 07, it was determined that a second error was made in preparing the computer-aided fault tree analysis (CAFTA) database for the UNCERT calculations. According to the FRANX 4.4 User Manual:
CNL-22-069 E2 of 4
Enclosure There are at least two potential approaches to using the @POINTCALC switch to prepare for parametric uncertainty sampling. The two obvious methods are mentioned below (each involves using UNCERT on pre-solved cutsets, a typical CAFTA parametric uncertainty process):
- 1. The first method is to begin by changing the value of @POINTCALC to 0 and then re-quantify the SPRA model, resulting in a different cutset file than the base point estimate quantification. UNCERT parametric uncertainty is then performed on the new cutset file.
- 2. In the second method you begin with the SPRA point estimate cutset file (i.e., the cutset file produced with @POINTCALC set to 1). You then adjust the value of the
@POINTCALC Type Code to 0 in the associated database (invoking the seismic interval initiator and fragility basic events sampling equations) and then use the CAFTA cutset editor to reload this database into the cutset file. UNCERT parametric uncertainty is then performed on the cutset file.
While the @POINTCALC variable was set to 0, the SPRA was not requantified with the updated database (method 1 above) and the CAFTA cutset editor was not used to reload this database into the cutset file (method 2 above). This led to the failure to sample the seismic fragility basic events and seismic bin (initiator) basic events. Since discovery of this error, mean seismic CDF and LERF for each unit have been recalculated and are summarized below:
Seismic PRA Point Estimate Mean Percent Change U1 CDF 4.04E-06 5.61E-06 39%
U1 LERF 3.11E-06 4.02E-06 29%
U2 CDF 3.84E-06 5.48E-06 42%
U2 LERF 2.90E-06 3.70E-06 27%
These results are consistent with what the NRC cited in the RAI as a recent peer reviewed SPRA supporting a 10 CFR 50.69 application, which demonstrated that the uncertainty mean is about 30 percent higher than the point estimate for both seismic CDF and seismic LERF.
The table below shows the updated comparison of the point estimate values to the mean values for the all-hazards (Internal events, internal flooding, internal fire, and seismic) PRA model. It also shows that the mean U1 and U2 CDF and LERF values for the all-hazards PRA model are still below the NRC Safety Goals. Given this, the SOKC is unimportant (i.e., the risk results are below the acceptance guidelines) and does not need to be incorporated into the calculations for the RICT calculations.
All-Hazards Point Percent NRC Safety Mean PRA Estimate Change Goal U1 CDF 7.11E-05 7.36E-05 3% 1.00E-04 U1 LERF 8.12E-06 9.13E-06 12% 1.00E-05 U2 CDF 7.54E-05 7.76E-05 3% 1.00E-04 U2 LERF 8.91E-06 9.74E-06 9% 1.00E-05 CNL-22-069 E3 of 4
Enclosure TVA Response to Part b)
The OTMHM model does support quantification of parametric uncertainty for the seismic PRA, including the uncertainty in the seismic hazard curve as well as the fragility groups.
The process is the same as for the SPRA model submitted in response to the NRCs post-Fukushima actions. This process is described in Section 5.6 of the response to the NRCs post-Fukushima actions (ADAMS Accession No. ML19291A003). The only difference germane to the parametric uncertainty analysis is which software tool was used to produce the electronic cutset file that the uncertainty software utilizes. Outside of that difference, the process to perform the parametric uncertainty analysis (including the need to properly configure the variable as described in the answer to part a) is the same.
Parameter uncertainty relates to the uncertainty in the computation of the input parameter values used to quantify the model (i.e., initiating event frequencies, component failure probabilities and Human Error Probabilities (HEPs)). These uncertainties can be characterized by probability distributions that relate to the degree of belief in their values. A formal propagation of uncertainty is the best way to correctly account for this, and the PRA software UNCERT has the capability to propagate these uncertainties. The uncertainty analysis was performed with UNCERT 10.0, using Monte Carlo sampling and ACUBE processing.
The UNCERT analysis included distributions for seismic bin frequencies. Those distributions were generated by the FRANX code assuming lognormal distributions and estimating error factors (EFs) from the various seismic hazard curves inputted to the code (16th, median, and 84th). Sampling of the individual seismic bin frequencies was performed using the correlated approach.
Seismic failure probability distributions are determined automatically by FRANX given the fragility parameter estimates (Am, R, and U). The seismic failure probability of all components within a given fragility group are correlated in this process. Distributions for HEPs and combination factors were calculated in the Human Reliability Analysis (HRA) Calculator Version 5.2. Distributions for internal events PRA (IEPRA) basic events were left unchanged from the IEPRA model. Component failure random probabilities are correlated though the use of type codes for similar components.
TVA Response to Part c)
This is not a PRA upgrade because no new methodology has been utilized in the parametric uncertainty analysis. The only change was to properly configure the software to allow sampling of the seismic hazard and fragilities and propagation to the associated discrete seismic hazard bin scenario basic events. This was a software configuration error.
CNL-22-069 E4 of 4