Recent Guidance Developed for Post-Fukushima Activities in the US Presented by Annie Kammerer January 23, 2013
Presentation Contents • Overview of the NTTF activities • EPRI SPID Guidance • ISG on the NRC SMA method • Status of Seismic Walkdowns • NEI proposed augmented approach 2
Near Term Task Force (NTTF) 3
NTTF Activities • 50.54(f) RFI Letter issued March 12, 2012 • Enclosure 1: Seismic hazard and risk reevaluation • Enclosure 3 Seismic Walkdowns 4
Seismic NTTF Overview Walkdowns to assure plants are meeting licensing basis and to look for potential seismic 11/2012 Completed except delayed equipment that requires outages 2.3 Walkdowns (+outages) issues. Reports due November 2012. Some equipment delayed until outage. Ongoing 9/2013 Hazard evaluation due in 18 months for NPPs Hazard (CEUS) within the CEUS SSC model area. 3 years for western US NPPs performing SSHAC level 3 3/2015 evaluation studies. Plant-specific site response. (WUS) Risk results due 3-4 years after hazard. SMAs Risk only allowed for small exceedance levels. 3 years 2.1 after hazard SPRAs allowed for all exceedances, but evaluation required for large exceedances. Near term Regulatory After receiving the information from the SPRA Depends and SMA analyses, the NRC will determine on findings Actions appropriate regulatory actions. 10 year Rulemaking Rulemaking to require a reevaluation every 10 Long term 2.2 timeline years. update 5
R2.1 Overall Approach PHASE 2 PHASE 1 STAGE 1 STAGE 2 Interact with Industry Screen & Prioritize on Hazard and Risk NRC makes Regulatory October 2013 Plants for Risk Completed Evaluation Guidance Decisions as Needed Evaluation (SPID) * Safety Enhancements * Backfit Analysis Licensees Conduct * Modify Plant License Licensees Conduct September 2013 Seismic Hazard Risk Evaluation Reevaluation NRC evaluates new October 2013 NRC Evaluates Risk hazard and near-term Evaluation (already doing actions indpendent calcs) 6
Seismic Response Timeline March 2012 50.54(f) letter sent CEUS Hazard September 2013 Report/Interim Actions CEUS SSC WUS Hazard March 2015 Report/Interim Actions Model Already WUS sites must CEUS Higher Developed October 2016 Priority Risk do Site-Specific Assessment NUREG 2115 due SSHAC Level 3 CEUS Risk October 2017 Assessments PSHA studies due -leads to longer WUS Higher April 2018 Priority Risk start time Assessment due WUS Risk April 2019 Assessments due 7
Seismic Response Timeline Challenges • Number of plants screening into SPRA may be higher than original estimates leading to problems with limited resources on both sides • Options being considered – NEI has proposed augmented approach (shown at the end of the presentation) – After preliminary discussions, NRC requested a white paper with details on proposal 8
EPRI Screening, Prioritization and Implementation Guidance (SPID) • EPRI 1025287 • Objective was to develop guidance to allow licensees to address the 50.54(f) letter in a uniform, technically sound and optimized way • Publically available and finalized November 2012 9
EPRI SPID • NRC in the process of endorsing • Developed through strong interaction between Industry and NRC experts through more than a dozen public meetings • All positions have a technical basis and several studies were conducted to support positions • In depth review against the ANS standard performed to assure that the positions allow for use of SPRA for risk-informed applications 10
EPRI SPID Some key participants • Industry: Kimberly Keithline, Greg Hardy, Bob Kennedy, John Richards, Kelly Merz, Divakar Bhargava, Robin McGuire, Walt Silva, Don Moore, Bob Whorton, Stewart Lewis • NRC: Nilesh Chokshi, Jon Ake, Cliff Munson, Bob Budnitz, Ravi Ravendra, and Annie Kammerer • Others were involved in specific topics (see acknowledgements page) 11
EPRI SPID Ch1: Purpose and Approach Ch2: Seismic Hazard Development Ch3: GMRS Comparison and Screening Ch4: Seismic Hazard and Screening Report Ch5: Prioritization Ch6: Risk Evaluations Ch7: Spent Fuel Pool Integrity Evaluation 12
EPRI SPID Appx A: Control Point Appx B: Development of Site Specific Amplification factors Appx C: Sensitivity Studies to Develop Criteria for Analyzing Rock-Founded Structures as Fixed-Base Models Appx D: Sensitivity of Computed Annual Probability of Failure PF to Assumed Logarithmic Standard Deviation β Used in Hybrid Method with Capacities Defined by 1% Failure Probability Capacity C 1 13
EPRI SPID • Ch2: Seismic Hazard Development – Uses modern PSHA with newly developed models – Provides guidance on how to develop site response factors account for uncertainties for sites with old geotechnical data (new site investigations were not required) – “approach 3” in NUREG/CR-6728 used – Site response approach provided in detail in Appendix B – Control point clarified 14
EPRI SPID Ch4: Seismic Hazard and Screening Report – Provides template for licensees Ch5: Prioritization – General information as NRC staff will develop approach Ch7: Spent Fuel Pool Integrity Evaluation – Significant amount of information and provides a general approach for individual NPPs. Work is on-going to find optimizations across sites. 15
Seismic Flowchart Based on chart provided in 50.54(f) letter Attachment 1
Evaluation Methods & Screening • Current practices for hazard evaluations – CEUS-SSC & SSHAC Level 3 for WUS to develop new hazard curves (GMRS) • Methods for plant evaluations – SMA or SPRA for small exceedances of SSE – SPRA for NPPs with GMRS beyond 1.3xSSE (1 to 10 Hz) – Exceedances in the high frequency range (beyond 10 Hz) to be addressed through component testing program – Allowances for narrow band exceedances (3.2.1.2) – Allowances for very low hazard sites with exceedances in <1Hz range (addressed on an SSC basis, 3.2.1.1)
2.1 Seismic Screening High Frequency Evaluation Seismic PRA needed GMRS > SSE only at GMRS > 1.3*SSE btwn 1 to 10 Hz frequencies above 10 Hz
2.1 Seismic Screening Low frequency exceedance for Specific rules for narrow band very low hazard sites allowed to do exceedances are provided SSC-specific margins review 0.8 SSE or IPEEE HCLPF 0.7 0.6 0.5 Acceleration (g) 0.4 0.3 0.2 0.1 0 0.1 1 10 100 Frequency (Hz)
SPID Positions for SPRA and SMA • The following SPID topics apply to both SPRA and NRC SMA - High frequency test program - Screening of component - Use of the CDFM and Separation of Variables methods for fragility curve development - Use of existing structural models - Scaling of in-structure response spectra - Use of fixed-based models for soft rock sites With the enhancements in the NRC-SMA method and use of the above positions the differences between SMA & SPRA are narrowing
SPID Approach to Screening and High Frequency Exceedances High frequency only exceedances being treated through large testing program
SPID Approach to High Frequency Exceedances • Testing program being conducted to demonstrate large capacities where exist (very (tables maxed out) • EPRI Testing program developed in consultation with NRC staff, including in 2012 workshop • Work plan available through NRC public meeting minutes (August or Sept 2012)
SPID Approach to High Frequency Exceedances • Phase 1: Pilot study – Completed in summer 2012 – Looked at multiple load types – Took sampling of different types of equipment in EPRI 1015109 • Phase 2: Production Testing – To cover large number of components with loading informed by Phase 1 results
SPID Approach to High Frequency Exceedances • EPRI 1015109 High-frequency equipment list – Electro-mechanical relays (e.g., control relays, time delay relays, protective relays) – Circuit breakers (e.g., molded case and power breakers – low and medium voltage) – Control switches (e.g., benchboard, panel, operator switches) – Process switches and sensors (e.g., pressure, temperature, flow, limit/position) – Electro-mechanical contactors (e.g., MCC starters) – Auxiliary contacts (e.g., for MCCBs, fused disconnects, contactors/starters) – Transfer switches (e.g., low and medium voltage switches with instrumentation) – Potentiometers (without locking devices) – Digital/solid state devices (mounting and connections only)
SPID Approach to High Frequency Exceedances • Also considers failure modes – Inadvertent change of state – Contact chatter – Change in output signal or set-point – Electrical connection discontinuity or intermittency (e.g., insufficient contact pressure) – Mechanical connection loosening – Mechanical misalignment/binding (e.g., latches, plungers) – Cyclic strain effects (e.g., cracks in solder joints) – Wiring not properly restrained – Inadequately secured mechanical fasteners and thumb screw connections
SPID Approach to SSC Screening
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