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Results
Other: ML111640211, ML111861529, ML111890408, ML111890413, ML112130165, ML112350873, ML112350883, ML112630673, ML112630676, ML112770237, ML112770246, ML112770251, ML113050623, ML113060606, ML113060615, ML113060623, ML113210411, ML113330116
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MONTHYEARML1104105052011-02-10010 February 2011 2/22/11 Notice of Forthcoming Public Meeting with STP Nuclear Operating Co., Units 1 & 2, to Discuss Risk-informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor Sump Performance, Resolution Option Approach Project stage: Meeting ML1107700052011-04-0505 April 2011 Summary of Meeting with STP Nuclear Operating Company to Discuss a Risk-informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Option Approach for South Texas, Units 1 and 2 Project stage: Meeting ML1113302442011-05-16016 May 2011 Notice of Meeting with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 and 2 Project stage: Meeting ML1114706522011-05-16016 May 2011 Correction 06/02/2011 Notice of Meeting with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 Project stage: Meeting ML11157A0102011-06-0202 June 2011 STP Nuclear Operating Company, Licensee Handouts, 6/2/2011 Meeting Risk-Informed GSI-191 Closure Plan for GSI-191 Resolution Project stage: Meeting ML1116401602011-06-21021 June 2011 Summary of Meeting with STP Nuclear Operating Company Regarding Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance; Resolution Approach for South Texas, Units 1 and 2 (TAC ME5358-ME5 Project stage: Meeting ML1116402112011-06-24024 June 2011 Notice of Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 & 2 Project stage: Other ML1118903912011-07-0606 July 2011 Email Additional Materials for Teleconference on 7/7/11 with STP to Discuss Risk Informed GSI-191 Project stage: Meeting ML1118904082011-07-0606 July 2011 Licensee Handout Loca Frequencie Approach and Example Application Project stage: Other ML1118904132011-07-0606 July 2011 Licensee Slide Regarding Questions on LOCA Frequency Analysis and Responses to Comments Project stage: Other ML1118904202011-07-0606 July 2011 Licensee Slide from 7/7/11 Meeting with STP Nuclear Project stage: Meeting ML1118903762011-07-0707 July 2011 Email Licensee Slides for 7/7/11 Teleconference with STP to Discuss Risk Informed GSI-191 Project stage: Meeting ML1118903802011-07-0707 July 2011 Licensee Slides, LOCA Initiating Event Frequencies and Uncertainties(Draft) Project stage: Draft Other ML1118615292011-07-12012 July 2011 Notice of Conference Call with STP Nuclear Operating Company to Discuss Risk-informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 and 2 Project stage: Other ML1120707292011-07-26026 July 2011 Meeting Notice with South Texas Project, Units 1 and 2 - Licensee Slides Computational Fluid Dynamics Validation Plan Project stage: Meeting ML1120707072011-07-26026 July 2011 Meeting Notice with South Texas Project, Units 1 and 2 - Licensee Slide Models and Methods Used for Casa Grande Project stage: Meeting ML1121301822011-08-0202 August 2011 Meeting Notice with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 and 2 (TAC ME5358-ME5359 Project stage: Meeting ML1119500942011-08-0404 August 2011 Summary of Meeting with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 and 2 Project stage: Meeting ML1121301652011-08-19019 August 2011 7/26/11 - Summary of Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 an Project stage: Other ML1123508732011-08-22022 August 2011 Models and Methods Used for Casa Grande Project stage: Other ML1123508832011-08-22022 August 2011 LOCA Initiating Event Frequencies and Uncertainties Status Report Project stage: Other ML1125101482011-09-15015 September 2011 Notice of Meeting by Conference Call with STP Nuclear Operating Co. to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 and 2 Project stage: Meeting ML1126306732011-09-20020 September 2011 Email, NRC Staff Questions, Loss-of-Coolant Accident Frequency Analysis, Resolution Approach for Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance. Project stage: Other ML1126306762011-09-20020 September 2011 NRC Staff Questions, Loss-of-Coolant Accident Frequency Analysis, Resolution Approach for Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance. Project stage: Other ML1127702372011-09-30030 September 2011 LOCA Frequencies for STP GSI-191( Final) Project stage: Other ML1127701702011-10-0303 October 2011 E-mail Licensee Handouts for 10/3/11 Public Meeting Project stage: Meeting ML1127701762011-10-0303 October 2011 Licensee Handouts from 10/3/11 Meeting STP LOCA Frequency Project stage: Meeting ML1127702032011-10-0303 October 2011 Licensee Slides from 10/3/11 Meeting LOCA Frequencies, Final Results Project stage: Meeting ML1127702302011-10-0303 October 2011 E-mail Documents for 10/3/11 Teleconference Project stage: Meeting ML1127702462011-10-0303 October 2011 E-mail Questions Associated with LOCA Frequency Analysis Project stage: Other ML1127702512011-10-0303 October 2011 STP Responses to Questions Associated with LOCA Frequency Analysis Project stage: Other ML1124114192011-10-0404 October 2011 8/22/11 Summary of Meeting with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 and 2 (TAC M Project stage: Meeting ML1127901512011-10-11011 October 2011 Notice of Meeting by Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 & Project stage: Meeting ML1127900992011-10-11011 October 2011 Notice of Meeting by Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas, Units 1 an Project stage: Meeting ML1130606232011-10-20020 October 2011 Technical Review of STP LOCA Frequency Estimation Methodology Project stage: Other ML1130506322011-10-26026 October 2011 Licensee Handouts from November 1, 2011 Meeting with STP Nuclear Operating Company on GSI-191 Project stage: Meeting ML1130506232011-10-26026 October 2011 Alion- Expected Impact of Chemical Effects on GSI-191 Risk Informed Evaluation for South Texas Project Project stage: Other ML1130606152011-10-31031 October 2011 LOCA Frequencies for STP Nuclear Operating Company GSI-191 Project stage: Other ML1128401142011-10-31031 October 2011 10/3/11 Summary of Meeting Via Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas Project stage: Meeting ML1129701092011-11-0101 November 2011 Notice of Meeting Via Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor Sump Performance, Resolution Approach for South Texas, Units 1 & 2 Project stage: Meeting ML1132104112011-11-0101 November 2011 Revised Notice of by Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Project stage: Other ML1130606062011-11-0202 November 2011 Questions Associated with Loss-of-Coolant Accident (LOCA) Frequency Analysis Project stage: Other ML1133301162011-11-29029 November 2011 Email, 11/1/2011 Pre-Licensing Conference Call to Discuss the Topic of Expected Impact of Chemical Effects on GSI-191 Risk-Informed Evaluation, Phenomena Identification and Ranking Table Items (TAC ME5358-ME5359) Project stage: Other ML1131201292011-11-29029 November 2011 Summary of 11/1/11 Meeting by Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance,Resolution Approach for South Texas, Un Project stage: Meeting ML1133505632011-12-0101 December 2011 Licensee Presentation from 12/1/11 Meeting Via Conference Call to Discuss Risk-Informed GSI-191,Assessment of Debris Accumulation on Pressurized Water Reactor Sump Performance Project stage: Meeting ML1131801962011-12-0505 December 2011 Summary of Meeting with STP Nuclear Operating Company Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas Units 1 and 2 Project stage: Meeting ML1134300872011-12-23023 December 2011 Summary of 12/1/11 Meeting by Conference Call with STP Nuclear Operating Company to Discuss Risk-Informed GSI-191, Assessment of Debris Accumulation on Pressurized-Water Reactor (PWR) Sump Performance, Resolution Approach for South Texas Un Project stage: Meeting 2011-05-16
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Category:Report
MONTHYEARNOC-AE-230040, Supplement to Proposed Alternate Frequency to Containment Unbonded Post-Tensioning System Inservice Inspection (Relief Request RR-ENG-4-06)2023-12-14014 December 2023 Supplement to Proposed Alternate Frequency to Containment Unbonded Post-Tensioning System Inservice Inspection (Relief Request RR-ENG-4-06) ML23243B0562023-08-31031 August 2023 Supplemental Information to Application for Order Approving Indirect Transfer of Control of Licenses ML23229A4992023-08-17017 August 2023 Supplement to Proposed Alternate Frequency to Containment Unbonded Post-Tensioning System Inservice Inspection (Relief Request RR-ENG-4-06) NOC-AE-21003841, Request for Relief from ASME Section Xl Code Requirements for Weld Examinations (Relief Request RR-ENG-3-25)2021-09-23023 September 2021 Request for Relief from ASME Section Xl Code Requirements for Weld Examinations (Relief Request RR-ENG-3-25) ML21266A4262021-09-23023 September 2021 Request for Relief from ASME Section Xl Code Requirements for Weld Examinations (Relief Request RR-ENG-3-25) NOC-AE-21003816, Commitment Change Summary Report2021-06-30030 June 2021 Commitment Change Summary Report ML21182A2412021-06-30030 June 2021 Commitment Change Summary Report ML17019A0032017-07-11011 July 2017 Attachment 2 to Safety Evaluation - In-Vessel Thermal-Hydraulic Analysis, Issuance of Amendment Nos. 212 and 198 - Risk-Informed Approach to Resolve Generic Safety Issue 191 NOC-AE-17003468, 10 CFR 50.46 Thirty-Day Report of Significant ECCS Model Changes2017-05-10010 May 2017 10 CFR 50.46 Thirty-Day Report of Significant ECCS Model Changes ML16302A0152016-10-20020 October 2016 South Texas Project, Units 1 & 2 - Supplement 3 to Revised Pilot Submittal and Requests for Exemptions and License Amendment for a Risk-Informed Approach to Address Generic Safety Issue (GSl)-191 and Respond to Generic Letter (GL) 2004-02 NOC-AE-16003345, LTR-PAFM-16-11-NP, Revision 0, Technical Justification to Support Extended Volumetric Examination Interval for South Texas, Unit 2 Reactor Vessel Inlet Nozzle to Safe End Dissimilar Metal Welds.2016-03-31031 March 2016 LTR-PAFM-16-11-NP, Revision 0, Technical Justification to Support Extended Volumetric Examination Interval for South Texas, Unit 2 Reactor Vessel Inlet Nozzle to Safe End Dissimilar Metal Welds. NOC-AE-15003249, Submittal of 10 CFR 50.46 Thirty-Day Report of Significant ECCS Model Changes and Annual Report2015-06-0909 June 2015 Submittal of 10 CFR 50.46 Thirty-Day Report of Significant ECCS Model Changes and Annual Report ML14357A1362015-01-22022 January 2015 Review of Analysis of Capsule Withdrawal Schedule from Reactor Vessel Radiation Surveillance Program NOC-AE-14003190, Attachment 2 to NOC-AE-14003190 - ALION-REP-STP-8998-14, Strainer Test Plan in Support of STP Pilot Risk-Informed GSI-191 Pilot Licensing Application2014-10-30030 October 2014 Attachment 2 to NOC-AE-14003190 - ALION-REP-STP-8998-14, Strainer Test Plan in Support of STP Pilot Risk-Informed GSI-191 Pilot Licensing Application ML14344A5462014-10-30030 October 2014 Attachment 1 to NOC-AE-14003190 - Alion REP-STP-8998-13, Strainer Test Plan in Support of STP Pilot Risk-Informed GSI-191 Pilot Licensing Application Executive Summary NOC-AE-14003178, Update Foreign Ownership, Control, or Influence (FOCI)2014-09-17017 September 2014 Update Foreign Ownership, Control, or Influence (FOCI) NOC-AE-14003161, Engineering Report 1060, Rev. 1, Meter Factor Calculation & Accuracy Assessment for South Texas Project Units 1 & 2.2014-08-31031 August 2014 Engineering Report 1060, Rev. 1, Meter Factor Calculation & Accuracy Assessment for South Texas Project Units 1 & 2. ML14260A4382014-08-31031 August 2014 Engineering Report ER-1059, Rev. 1, Bounding Uncertainty Analysis for Thermal Power Determination at South Texas Project Units 1 & 2 Using LEFM System. NOC-AE-14003101, Enclosure 1 to Enclosure 6 Concerning Second Set of Responses to April 2014, Requests for Additional Information Regarding STP Risk-Informed GSI-191 Application2014-06-25025 June 2014 Enclosure 1 to Enclosure 6 Concerning Second Set of Responses to April 2014, Requests for Additional Information Regarding STP Risk-Informed GSI-191 Application ML14168A2682014-05-0101 May 2014 Texas Pollutant Discharge Elimination System Major Amendment with Renewal Application for a Major Facility Tpdes Permit No. WQ000190800 NOC-AE-14003103, University of Texas White Paper, Means of Aggregation and NUREG-1829: Geometric and Arithmetic Means, Rev. 3, Enclosure 2 to Attachment 12014-04-18018 April 2014 University of Texas White Paper, Means of Aggregation and NUREG-1829: Geometric and Arithmetic Means, Rev. 3, Enclosure 2 to Attachment 1 ML14087A0782014-04-15015 April 2014 Staff Assessment of the Seismic Walkdown Report Supporting Implementation of Near-Term Task Force Recommendation 2.3 Related to Fukushima Dai-Ichi Nuclear Power Plant Accident (TAC MF0178 & MF0179) NOC-AE-14003114, Seismic Hazard and Screening Report (CEUS Sites), Response NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai..2014-03-31031 March 2014 Seismic Hazard and Screening Report (CEUS Sites), Response NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai.. NOC-AE-14003082, Alternate Source Term Dose Analysis: an Estimate of Risk Attributed to GSI-191, Attachment 32014-03-11011 March 2014 Alternate Source Term Dose Analysis: an Estimate of Risk Attributed to GSI-191, Attachment 3 NOC-AE-13003067, Supplement to Seismic Walkdown Summary Report of Items Classified as Inaccessible2014-02-27027 February 2014 Supplement to Seismic Walkdown Summary Report of Items Classified as Inaccessible ML14072A0832014-02-24024 February 2014 CHLE-010, Chle Tank Test Results for Blended and NEI Fiber Beds with Aluminum Addition, Revision 3 ML14072A0872014-02-24024 February 2014 CHLE-016, Calculated Material Release to Estimate Chemical Effects, Revision 3 ML14072A0862014-02-24024 February 2014 CHLE-015, Summary of Chemical Effects Testing in 2012 for STP GSI-191 License Submittal, Revision 4 ML14072A0802014-02-24024 February 2014 CHLE-006, STP Material Calculations, Revision 2 ML14072A0822014-02-23023 February 2014 CHLE-008, Debris Bed Preparation & Formation Test Results, Revision 4 ML14072A0792014-02-22022 February 2014 CHLE-020, Test Results for 10-Day Chemical Effects Test Simulating LBLOCA Condition (T5), Revision 3 ML14072A0882014-02-22022 February 2014 CHLE-018, Results of Bench Tests to Assess Corrosion of Aluminum in STP Containment Conditions, Revision 3 ML14072A0852014-02-22022 February 2014 CHLE-014, T2 LBLOCA Test Report, Revision 3 ML14072A0842014-02-18018 February 2014 CHLE-012, T1 Mbloca Test Report, Revision 4 ML14072A0772014-02-18018 February 2014 CHLE-005, Determination of the Initial Pool Chemistry for the Chle Test, Revision 2 ML14149A4352014-02-14014 February 2014 Project, Units 1 and 2 - ALION-REP-STP-8998-02, Rev. 0, STP Casa Grande Analysis and LAR Enclosure 4-3 RAI Response, Enclosure 1 to Attachment 1 ML14072A0812014-02-13013 February 2014 CHLE-007, Debris Bed Requirements & Preparation Procedures, Revision 4 ML13339A7362014-01-29029 January 2014 Interim Staff Evaluation and Audit Report Relating to Overall Integrated Plan in Response to Order EA-12-049 - Mitigation Strategies ML13354B8332014-01-23023 January 2014 Mega-Tech Services, LLC Technical Evaluation Report Regarding the Overall Integrated Plan for South Texas Project, Units 1 and 2, TAC Nos.: MF0825 and MF0826 NOC-AE-13003070, Response to NRC Request for Reference Document for STP Risk-Informed GSI-191 Application2013-12-23023 December 2013 Response to NRC Request for Reference Document for STP Risk-Informed GSI-191 Application ML13323A1862013-11-12012 November 2013 Enclosure 4-1 - Risk-Informed Closure of GSI-191, Volume 1 ML13323A1912013-11-0606 November 2013 Enclosure 4-3 Risk-Informed Closure of GSI-191, Volume 3, Engineering (Casa Grande) Analysis, Page 212 of 1-122 ML13323A1902013-11-0606 November 2013 Enclosure 4-3 Risk-Informed Closure of GSI-191, Volume 3, Engineering (Casa Grande) Analysis, Cover - Page 211 of 248 ML13323A1892013-10-22022 October 2013 Enclosure 4-2 - Risk-Informed Closure of GSI-191, Volume 2 Probabilistic Risk Analysis ML13323B2092013-10-0404 October 2013 Attachment 12: CHLE-020, Rev. 2, Test Results for a 10-day Chemical Effects Test Simulating LBLOCA Conditions (T5). ML13323B2082013-09-23023 September 2013 Attachment 11: CHLE-019, Rev. 2, Test Results for Chemical Effect Tests Stimulating Corrosion and Precipitation (T3 & T4) ML13323B2072013-09-16016 September 2013 Attachment 10: CHLE-018, Rev. 2, Results of Bench Tests to Assess Corrosion of Aluminum in STP Containment Conditions. NOC-AE-13003019, Submittal of Commitment Change Summary Report for the Period June 21, 2011 Through June 21, 20132013-07-18018 July 2013 Submittal of Commitment Change Summary Report for the Period June 21, 2011 Through June 21, 2013 ML13175A2122013-06-18018 June 2013 Project, Units 1 and 2, Enclosure 4-1 to NOC-AE-13002986, Risk-Informed Closure of GSI-191 Volume 1 Project Summary NOC-AE-13002986, Enclosure 4-3 to NOC-AE-13002986, Risk-Informed Closure of GSI-191 Volume 3 Engineering Casa Grande Analysis, Page 161 of 260 Through End2013-06-0606 June 2013 Enclosure 4-3 to NOC-AE-13002986, Risk-Informed Closure of GSI-191 Volume 3 Engineering Casa Grande Analysis, Page 161 of 260 Through End 2023-08-31
[Table view] Category:Technical
MONTHYEARNOC-AE-230040, Supplement to Proposed Alternate Frequency to Containment Unbonded Post-Tensioning System Inservice Inspection (Relief Request RR-ENG-4-06)2023-12-14014 December 2023 Supplement to Proposed Alternate Frequency to Containment Unbonded Post-Tensioning System Inservice Inspection (Relief Request RR-ENG-4-06) ML23229A4992023-08-17017 August 2023 Supplement to Proposed Alternate Frequency to Containment Unbonded Post-Tensioning System Inservice Inspection (Relief Request RR-ENG-4-06) NOC-AE-21003841, Request for Relief from ASME Section Xl Code Requirements for Weld Examinations (Relief Request RR-ENG-3-25)2021-09-23023 September 2021 Request for Relief from ASME Section Xl Code Requirements for Weld Examinations (Relief Request RR-ENG-3-25) ML21266A4262021-09-23023 September 2021 Request for Relief from ASME Section Xl Code Requirements for Weld Examinations (Relief Request RR-ENG-3-25) ML16302A0152016-10-20020 October 2016 South Texas Project, Units 1 & 2 - Supplement 3 to Revised Pilot Submittal and Requests for Exemptions and License Amendment for a Risk-Informed Approach to Address Generic Safety Issue (GSl)-191 and Respond to Generic Letter (GL) 2004-02 NOC-AE-16003345, LTR-PAFM-16-11-NP, Revision 0, Technical Justification to Support Extended Volumetric Examination Interval for South Texas, Unit 2 Reactor Vessel Inlet Nozzle to Safe End Dissimilar Metal Welds.2016-03-31031 March 2016 LTR-PAFM-16-11-NP, Revision 0, Technical Justification to Support Extended Volumetric Examination Interval for South Texas, Unit 2 Reactor Vessel Inlet Nozzle to Safe End Dissimilar Metal Welds. NOC-AE-14003161, Engineering Report 1060, Rev. 1, Meter Factor Calculation & Accuracy Assessment for South Texas Project Units 1 & 2.2014-08-31031 August 2014 Engineering Report 1060, Rev. 1, Meter Factor Calculation & Accuracy Assessment for South Texas Project Units 1 & 2. ML14260A4382014-08-31031 August 2014 Engineering Report ER-1059, Rev. 1, Bounding Uncertainty Analysis for Thermal Power Determination at South Texas Project Units 1 & 2 Using LEFM System. NOC-AE-14003082, Alternate Source Term Dose Analysis: an Estimate of Risk Attributed to GSI-191, Attachment 32014-03-11011 March 2014 Alternate Source Term Dose Analysis: an Estimate of Risk Attributed to GSI-191, Attachment 3 ML14072A0872014-02-24024 February 2014 CHLE-016, Calculated Material Release to Estimate Chemical Effects, Revision 3 ML14072A0862014-02-24024 February 2014 CHLE-015, Summary of Chemical Effects Testing in 2012 for STP GSI-191 License Submittal, Revision 4 ML14072A0802014-02-24024 February 2014 CHLE-006, STP Material Calculations, Revision 2 ML14072A0832014-02-24024 February 2014 CHLE-010, Chle Tank Test Results for Blended and NEI Fiber Beds with Aluminum Addition, Revision 3 ML14072A0822014-02-23023 February 2014 CHLE-008, Debris Bed Preparation & Formation Test Results, Revision 4 ML14072A0792014-02-22022 February 2014 CHLE-020, Test Results for 10-Day Chemical Effects Test Simulating LBLOCA Condition (T5), Revision 3 ML14072A0852014-02-22022 February 2014 CHLE-014, T2 LBLOCA Test Report, Revision 3 ML14072A0882014-02-22022 February 2014 CHLE-018, Results of Bench Tests to Assess Corrosion of Aluminum in STP Containment Conditions, Revision 3 ML14072A0772014-02-18018 February 2014 CHLE-005, Determination of the Initial Pool Chemistry for the Chle Test, Revision 2 ML14072A0842014-02-18018 February 2014 CHLE-012, T1 Mbloca Test Report, Revision 4 ML14149A4352014-02-14014 February 2014 Project, Units 1 and 2 - ALION-REP-STP-8998-02, Rev. 0, STP Casa Grande Analysis and LAR Enclosure 4-3 RAI Response, Enclosure 1 to Attachment 1 ML14072A0812014-02-13013 February 2014 CHLE-007, Debris Bed Requirements & Preparation Procedures, Revision 4 ML13339A7362014-01-29029 January 2014 Interim Staff Evaluation and Audit Report Relating to Overall Integrated Plan in Response to Order EA-12-049 - Mitigation Strategies ML13354B8332014-01-23023 January 2014 Mega-Tech Services, LLC Technical Evaluation Report Regarding the Overall Integrated Plan for South Texas Project, Units 1 and 2, TAC Nos.: MF0825 and MF0826 NOC-AE-13003070, Response to NRC Request for Reference Document for STP Risk-Informed GSI-191 Application2013-12-23023 December 2013 Response to NRC Request for Reference Document for STP Risk-Informed GSI-191 Application ML13323B2092013-10-0404 October 2013 Attachment 12: CHLE-020, Rev. 2, Test Results for a 10-day Chemical Effects Test Simulating LBLOCA Conditions (T5). ML13323B2082013-09-23023 September 2013 Attachment 11: CHLE-019, Rev. 2, Test Results for Chemical Effect Tests Stimulating Corrosion and Precipitation (T3 & T4) ML13323B2072013-09-16016 September 2013 Attachment 10: CHLE-018, Rev. 2, Results of Bench Tests to Assess Corrosion of Aluminum in STP Containment Conditions. ML13175A2122013-06-18018 June 2013 Project, Units 1 and 2, Enclosure 4-1 to NOC-AE-13002986, Risk-Informed Closure of GSI-191 Volume 1 Project Summary ML13175A2402013-06-0606 June 2013 Project, Units 1 and 2, Enclosure 4-3 to NOC-AE-13002986, Risk-Informed Closure of GSI-191 Volume 3 Engineering Casa Grande Analysis, Page 1 of 260 Through Page 160 of 260 NOC-AE-13002986, Enclosure 4-3 to NOC-AE-13002986, Risk-Informed Closure of GSI-191 Volume 3 Engineering Casa Grande Analysis, Page 161 of 260 Through End2013-06-0606 June 2013 Enclosure 4-3 to NOC-AE-13002986, Risk-Informed Closure of GSI-191 Volume 3 Engineering Casa Grande Analysis, Page 161 of 260 Through End NOC-AE-13002975, Enclosuflooding Hazard Reevaluation Report, Cover Through Page 2.2-462013-03-31031 March 2013 Enclosuflooding Hazard Reevaluation Report, Cover Through Page 2.2-46 ML13079A8082013-03-11011 March 2013 Enclosuflooding Hazard Reevaluation Report, Cover Through Page 2.3-1 Through End ML13323B2012013-01-22022 January 2013 Attachment 7: CHLE-014, Rev. 2, T2 LBLOCA Test Report. ML13323B2042013-01-22022 January 2013 Attachment 9: CHLE-016, Rev. 2, Calculated Material Release to Estimate Chemical Effects. ML13323B2022013-01-15015 January 2013 Attachment 8: CHLE-015, Rev. 3, Summary of Chemical Effects Testing in 2012 for STP GSI-191 License Submittal. ML13323B2002013-01-0909 January 2013 Attachment 6: CHLE-012, Rev. 3, T1 Mbloca Test Report, Figure 53 Through End ML13323B1992013-01-0909 January 2013 Attachment 6: CHLE-012, Rev. 3, T1 Mbloca Test Report, Cover Through Figure 52 ML12335A1842012-11-26026 November 2012 Licensee Documents for December 12, 2012 Public Meeting ML12335A1902012-11-26026 November 2012 Licensee Documents for December 12, 2012 Public Meeting ML13025A1382012-10-31031 October 2012 STP GSI-191 Bypass Sensitivity Report - Water Conductivity Added ML12243A4742012-08-30030 August 2012 Email - Risk-Informed Approach to GSI-191, STP Cfd Data Analysis Report - Bypass Test Protocol ML13323B1982012-08-19019 August 2012 Attachment 5: CHLE-010, Rev. 2, Chle Tank Test Results for Blended and NEI Fiber Beds with Aluminum Addition. ML13323B1912012-08-14014 August 2012 Attachment 2: CHLE-006, Rev. 1, STP Material Calculations. NOC-AE-13003040, Attachment 1: CHLE-005, Rev. 1, Determination of the Initial Pool Chemistry for the Chle Test.2012-08-13013 August 2012 Attachment 1: CHLE-005, Rev. 1, Determination of the Initial Pool Chemistry for the Chle Test. ML13323B1942012-08-11011 August 2012 Attachment 3: CHLE-007, Rev. 3, Debris Bed Requirements and Preparation Procedures. ML13323B1962012-06-12012 June 2012 Attachment 4: CHLE-008, Rev. 3, Debris Bed Preparation and Formation Test Results. ML1206100682012-02-28028 February 2012 Southtexas Project, Units 1 and 2 - Test Plan for STP High Temperature Vertical Loops Testing ML1205408162012-02-23023 February 2012 Experimental Setup for Chle Test Equipment ML1205406672012-02-22022 February 2012 Casa Grande Summary ML1205407272012-02-0909 February 2012 Actions Taken to Resolved Pirt Items 2023-08-17
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Letter Report Technical Review of STP LOCA Frequency Estimation Methodology By Ali Mosleh Prepared for South Texas Project Electric Generation Station October 20, 2011
- 1. INTRODUCTION This letter report summarizes the results of an independent limited scope technical review of the Development of LOCA Initiating Event Frequencies for South Texas Project (STP)
[1] Two rounds of review were preformed, first on an earlier draft (dates August, 2011),
and later on the draft final report (dated September 2011). Throughout the process clarifications were sought from the authors of the report, and suggestions were made on the technical approach, results, and report content. Key recommendations made in this process were addressed by the authors and are reflected in the final report [1].
The scope of the review was limited to (a) LOCA Frequency Estimation Model, (b) interpretation and use of NUREG-1829 [2] information, and (c) other key assumptions and computational steps utilized to generate the numerical results. In the following sections we first provide an overview of the basic elements of reports methodology for estimating STP LOCA frequencies and offer general comments on the methodology and its basic assumptions. Next we provide specific comments on the steps of the methodology and their implementation. Finally we provide an overall assessment and key conclusions of this review.
- 2. LOCA FREQUENCY ESTIMATION MODEL OVERVIEW The scope of the current STP LOCA study is to estimate the frequency of LOCAs initiated at or near the location of pipe and nozzle welds. The report indicates that future work would include LOCAs due to pipe failures at other locations and non-pipe related failures in the RCS pressure boundary.
2.1 Basic Estimation Model The reports model for estimating the frequency of a LOCA of a given size is given by the following equations:
F(LOCAx ) = mi ix i (1)
- where, ix = ik P(Rx Fik )I ik k (2) 1
(x refers to the various break size ranges such as those used in NUREG-1829 to describe the 6 LOCA categories). The terms in equations 1 and 2 are defined in the following table
[1].
A point estimate for the failure rate per weld due to a mechanism k is given by nik nik ik = =
ik fik N iTi (3) where Different locations are characterized and assigned rupture frequencies based on 45 combinations of system type, weld type, degradation mechanisms, and pipe size. The estimation process is a bottom-up approach building the LOCA estimates by combining various contributing components, failure mechanisms, and conditional probabilities.
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2.2 Comments and Observations The general decomposition formula (Equation 2) used by the report to estimate LOCA frequencies follows known principles of the calculus of probability. The formula represents the widely used constant failure rate model, but similar to the approach taken by NUREG-1829, an approximate way of allowing aging effects is introduced by applying factors to increase failure rates from one period in plant life to another.
A key advantage of this formulation is that it enables the consideration of known susceptibilities to the damage mechanisms in quantification of the failure rates and conditional probabilities. It allows tailoring the probabilities for component-specific vulnerabilities to various degradation mechanisms.
As a physical model, the decomposition formula views pipe rupture (LOCA) as a two-stage process involving (1) stochastic occurrence of degraded functional conditions, and (2) stochastic rupture events given a degraded condition. The formulation offers a reasonable first order approximation of a physical process model. Similar formulations are seen elsewhere in PRAs for instance in Accident Sequence Precursor (ASP) methodology and some of the popular methods for common cause failure analysis such as the Beta Factor and Binomial Failure Rate methods.
A key advantage of the approach is the ability to make use of existing operational data in various forms, including information on observed degraded states and early stages of pipe and weld failure, as indicators of far less frequent rupture events. In addition, the parameter Iik, (in Equation 2) determined through a previously developed and peer-reviewed Markov model [3], provides the ability to account for the effects of integrity management programs on reducing likelihood of catastrophic failures.
The report makes a number of other modeling assumptions and simplifications during implementation. For instance, various degradations (crack, small leak, leak, etc.) are lumped together as a homogenous class, irrespective of their implied severity (here the probabilistic distance to rupture events). This means that the same conditional rupture probability applies to all degraded states. The effect is overestimation for some (e.g.,
crack) and underestimation for other degraded conditions (e.g., leak), with the expectation that the net effect on rupture rates is negligible and residuals are well-covered by large ranges of uncertainty applied throughout.
Elsewhere the report linearly combines the contributions of various damage mechanisms at a specific piping location, to determine the total LOCA frequency distribution (for each weld /location). This is a first order approximation to a significantly more complex case where synergetic effects of multiple damage mechanisms are considered explicitly.
However, the state of the art in experimental results and theoretical physics of failure models for the synergistic effects of failure mechanisms is quite limited. It can be argued that to a certain extent the net effect of synergistic phenomena are accounted for through the use of actual data in the failure frequency estimation stage. That is, the actual failure events used by the report to estimate failure frequencies include events where one or 3
several physically possible failure mechanisms were at work, even when only a single failure mechanism is declared as the culprit.
- 3. FAILURE RATE DEVELOPMENT STEPS The report provides a list of key steps of the methodology for estimation of the failure rates. Using the same list, we summarize our observations and comments on the methods applied:
1.1 Determination of component and weld types y Outside the scope of this review 1.2 Perform data query for failure counts Outside the scope of this review 1.3 Estimate component exposure Outside the scope of this review 1.4 Develop component failure rate prior distributions for each damage mechanism (DM)
This aspect of the methodology is based on earlier well-established work in EPRI RI-ISI [3], which has been peer reviewed by industry, academia, and NRC. Therefore no detailed review of this part of the methodology was performed in effort. We have noted the reports appropriate use of very wide lognormal distributions, based on existing pipe failure rates, engineering judgment, and use of data.
1.5 Perform Bayes update for each exposure case (combination of weld count case and DM susceptibility case)
This part of the methodology is a standard use of Bayesian updating (mostly with 0 failures) which is well established and accepted in PRAs.
Computations were done with aid of a validated and widely RDAT computer code.
1.6 Develop mixture distribution to combine results for different exposure hypotheses to yield conditional failure rate distributions given STP specific applicable DMs Use of (equally weighted) mixture of distributions to generate a composite distribution for different data assumptions is an accepted (advanced) methodology within the Bayesian framework. The report has applied this methodology in a very systematic and rigorous way.
Mixture distributions are developed using standard Monte Carlo sampling technique and numerical procedures. However, the specifics of the numerical implementation were not subject of this review.
While the process and assumptions are clearly stated (see for example Table 3-1 of the report [1]) the scope of this review did not include an evaluation of the technical basis for assumptions made in the process of estimating population size for each class (weld, pipe segment, etc.) and in engineering 4
assessing the level of susceptibility of each class to various failure mechanisms 1.7 Calculate total failure rate over all applicable damage mechanisms To generate the distribution of total failure rates standard Monte Carlo sampling technique and numerical procedures are used. The numerical implementation however was not a subject of this review.
- 4. CONDITIONAL RUPTURE PROBABILITY ESTIMATION The goal of this part of the methodology is to develop a set of conditional rupture probabilities (CRPs) vs. break size for each component category. CRPs are estimated by anchoring the generic total frequency of each of the six LOCA classes on two distinct sources of NUREG-1829 data [2]: (a) Base case analyses of specific PWR components (hot leg, surge line, HPI line for a specific 3-loop PWR) developed by B.
Lydell using methodology similar to that used by the current study, and (b) Estimates of 9 experts of LOCA frequencies vs. break size for many PWR components for the entire fleet of U.S. PWRs.
The report provides a list of key steps of the methodology for estimation of the CPRs.
Using the same list, we summarize our observations and comments on the methods applied:
2.1 Select components to define conditional rupture probability (CRP) model categories Outside the scope of this review 2.2 Obtain expert reference LOCA distributions from NUREG-1829 (see comments under 2.3) 2.3 Obtain expert multiplier distributions for 40yr LOCA frequencies from NUREG-1829 Some NUREG-1829 experts had provided asymmetric inputs for lower, middle, and upper values, which were inconsistent with lognormal distribution characteristics. NUREG-1829s approach to deal with such cases was to use split lognormal distributions (a synthesis of two half lognormals). The STP approach fits the asymmetric cases to standard lognormal distribution in part to simplify the procedure. Of the three possible alternatives, this reviewer recommended use of Upper and Mid values to determine fit a lognormal distribution. The advantage of this choice is that it preserves the central tendency of the distribution (often the starting point by experts) and keeps the experts upper bound estimate, which carries more risk significance.
2.4 Determine 40yr LOCA distributions (product of steps 2.2 and 2.3) for each expert, fit to lognormal 5
This is done for each experts estimate prior to aggregation of the result of 9 experts (correct approach among alternatives). The procedure follows basis probability rules for developing distribution of product of lognormally distributed quantities.
2.5 Determine geometric mean of expert distributions from Step 2.4 (lognormal)
The report investigated two approaches for forming composite distributions (a) Mixture Distribution Method (with equal weight for all experts), and (b)
Geometric Mean Method (by taking the geometric means of two parameters of the experts lognormal distributions, medians and range factors). The Geometric Mean method, which is the approach taken by NUREG-1829 was also adopted by the report. In this reviewers opinion, in general the mixture distribution approach to expert opinion aggregation has a stronger technical basis. However, an equally important factor is the engineering assessment by NUREG-1829 and the STP report of the overall suitability of the results produce by each approach.
2.6a Benchmark Lydell Base Case Analysis for selected components 2.6b Determine failure rate distribution for Lydell Base Case analysis in NUREG-1829; fit to lognormal 2.6c Apply Lydell CRP model from Base Case Analysis 2.6d Determine LOCA frequency distribution from Lydell Base Case Analysis Steps 2.6(a)-(d) replicate the steps of previously applied methods, which also provided a reference estimate in NUREG-1829. The steps also parallel many of the steps of ref [1]. As such further review was regarded as unnecessary.
2.7 Determine mixture distribution of NUREG-1829 GM (from Step 2.5) and Lydell LOCA frequency (from Step 2.8) to obtain Target LOCA frequency Distribution for each CRP category component The report has viewed NUREG-1829 expert opinions and Lydells approach as two largely separate sources of information on LOCA frequencies. This reviewer agrees that the overlap of the two sources are less pronounced than the differences in corresponding modeling and quantification approaches. Of possible options for use of these two sources of information, and based on a recommendation form this reviewer, the report has chosen a mixture of distributions based on (1) aggregation of NUREG-1829 expert estimates using geometric mean method, and (2) Lydells results.
2.8 Apply formulas to calculate CRP distributions to be used as prior distributions for each component assigned to each CRP category This step is straightforward conceptually, but requires relatively complex set of steps in carrying the needed Monte Carlo numerical procedures. This review however did not look into the details of computational implementation.
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2.9 For each component in CRP category, perform Bayes update with evidence of failure and rupture counts from service data This step follows standard approach to Bayesian updating (beta prior distribution and binomial likelihood). Updating is done with marginal distributions (beta) of each of the six CRP categories given a failure. The joint distribution of CRPs is a multinomial distribution but separate updating with marginal (beta) distribution for each CRP is a reasonable simplification with no visible impact on results give the low values of CRPs.
- 5.
SUMMARY
AND CONCLUSIONS This report has summarized the results of an independent review of the report on Development of LOCA Initiating Event Frequencies for South Texas Project [1]. The scope of the review was limited to (1) LOCA Frequency Estimation Model, (2) interpretation and use of NUREG-1829 information, and (3) other key assumptions and computational steps used to generate the numerical results. The review process identified a number of improvements on the technical approach and implementation process that were addressed prior issuing the final report by the authors. Examples include (1) addition of a more detailed summary of the methodology and charts explaining its steps, (2), better explanation of assumptions, both in constructing the model and in its numerical implementation, and (3) more consistent application of probabilistic methods in some areas (e.g., approach to synthesis of different sources of information).
Overall the modeling and parameter estimation approaches of the report were found to be sound, acknowledging a number of common approximations and simplifying assumptions, some imposed by the limitations in the state of the art. The report has applied a systematic approach for identifying various sources of uncertainty and quantifying their effects. These include allowing for expert-to-expert and model-to-model variability, and accounting for known sources of aleatory and epistemic uncertainties.
The systematic treatment of uncertainties well as the reports use of relatively broad ranges for distributions of various model parameters, are expected to cover much of the impact of modeling and implementation assumptions, including those that stem from limitations in the state of the art. Further sensitivity analyses can highlight any potential need to fine-tune the impact of assumptions and approximations.
- 6. REFERENCES
- 1. Development of LOCA Initiating Event Frequencies for South Texas Project GSI-191, Final Report for 2011 Work Scope, Revision 1, Developed for South Texas Project Electric Generating Station, by Karl N. Fleming (KNF Consulting Services LLC) and Bengt O. Y. Lydell and Danielle Chrun, Scandpower Risk Management Inc., Oct 2011.
- 2. Tregoning, R., L. Abramson, and P. Scott, Estimating Loss-of-Coolant Accident (LOCA) Frequencies through the Elicitation Process, NUREG-1829, U.S. Nuclear Regulatory Commission, Washington, DC, April 2008.
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- 3. Fleming, K. N. and B. O. Y. Lydell, Database Development and Uncertainty Treatment for Estimating Pipe Failure Rates and Rupture Frequencies, Reliability Engineering and System Safety, 86: 227-246, 2004.
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