ML23045A286
| ML23045A286 | |
| Person / Time | |
|---|---|
| Issue date: | 03/14/2023 |
| From: | Mike Franovich Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| Download: ML23045A286 (1) | |
Text
Advances in RIDM: Past, Present, Future Technical Session T5 Michael X. Franovich Director, Division of Risk Assessment Office of Nuclear Reactor Regulation
2 Agenda History of Risk-Informed Decision-Making Risk-Informed Guidance Development/A Graded Approach International Cooperation LIC-504: High Energy Arcing Faults Emergency Planning Zone Sizing - SMRs
1957 1975 1984 1986 1985 1988 WASH-1400 The Reactor Safety Study WASH-740 Safety Goal Policy Statement GL-88-20, Individual Plant Examination (IPE) for Severe Accident Vulnerabilities, NUREG-1560 Three Mile Island Chernobyl NUREG-1150 Severe Accident Policy Statement 1979
§50.62 ATWS Rule
§50.63 SBO Rule 1978 3
NUREG-0396 Emergency Response Plans
- Not to Scale
1991 2017-Present GL-88-20, Vol.
4, IPE for External Events 2001 9-11 Attacks
§50.65 Maintenance Rule Fukushima Daiichi NTTF Flooding NTTF Seismic 2011 SECY 98-144, Risk-Informed Performance Based Regulation 1998 4
RIDM Initiatives 1995 PRA Policy Statement RG 1.174 Key Principles 2004 RG 1.200 PRA Acceptability
- Not to Scale
Risk-informed Operating Reactor Programs Have Informed New and Advanced Reactor Guidance Development (A Graded Approach)
LMP Safety Classification Safety-Related Non-Safety-Related with Special Treatment Non-Safety-Related with No Special Treatment 10 CFR 50.69 Risk-Informed Categorization RISC-I: Safety-Related, Safety Significant RISC-II: Nonsafety-Related, Safety Significant RISC-III: Safety-Related, Low Safety Significant RISC-IV: Nonsafety-Related, Low Safety Significant NuScale SSC Classification A1: Safety-Related, Risk-Significant A2: Safety-Related, Not Risk-Significant B1: Nonsafety-Related, Risk-Significant B2: Nonsafety-Related, Not Risk-Significant 5
NRC International Strategy IAEA No. SSR-2/1, Safety of Nuclear Power Plants: Design IAEA No. SSG-3, Development and Application of Level 1 Probabilistic Safety Assessment for Nuclear Power Plants IAEA TECDOC-1980, Application of a Graded Approach in Regulating Nuclear Installations 6
Advance risk management concepts through international standards and guidance for graded approaches in licensing and oversight of operating and new reactors
Developed as a lessons learned from Davis-Besse reactor vessel head degradation Provides a structured process to document decisions for issues that may warrant prompt regulatory actions Provides guidance to apply integrated decision-making including risk, defense-in-depth, and safety margins considerations Has been used frequently for a range of emergent plant-specific and generic issues 7
LIC-504: Integrated Decision-Making Process for Emergent Issues
10-6 10-3 10-5 10-4 LIC-504 Graded Recommendations - examples Change in CDF Regulatory Intensity 10-7 Spectrum of Regulatory Options Immediate regulatory action Formal backfit analysis ( 10-4 )
50.54(f) letters Bulletin Information Notice/Outreach Smart inspection samples No Actions Use RIDM - Not numbers alone 8
LIC-504: High Energy Arcing Faults (HEAF) 9 2007-2008: First international examination 2013: NEA/OECD FIRE program HEAFs are often risk significant with complicated shutdowns 2014-2016: International Test Program NRC observed potential for new failure mechanisms and larger damage states 2021: Integrated Decision-Making Process for Emergent Issues NRC used the LIC-504 process for disposition using new methods Risk Insights Informed NRC Actions Final Regulatory Decision - no new requirements Extensive Outreach to Stakeholders: public webinar, industry forums, and NRC Information Notice (pending)
Incorporation of Insights into NRC Oversight Activities
RIDM in Emergency Planning Zone Sizing 10 Emergency Planning Zones (EPZs)
EPZ = area within which prompt protective actions may be necessary in the event of a radiological release NRC regulation on size of plume exposure pathway:
10 miles for light-water reactors >250 MWth Case-by-case basis for reactors <250MWth Drivers for Risk-Informed EPZ Sizing Maturity of PRA technical acceptability guidance Different risk profile compared to operating reactors Emergency Plans for 10-mile EPZ can include many states, counties, townships, schools, hospitals, Coast Guard, evacuation plans, emergency drills, etc.
Novel approach provides regulatory stability Provides design-and site-specific seismic screening threshold value(s) consistent with technical basis in NUREG-0396
- Results in a complete spectrum of accidents and avoids extremely unlikely seismic accelerations Addresses multi-module risk Uses quantified seismic sequences because they can be dominant contributor to plant risk and EPZ sizing Compatible with risk metrics other than CDF or LERF Conclusions from Risk-Informed Approach for Emergency Planning Zone Sizing (SMRs) 11
12 Key Messages NRC supports and advances risk-informed decision making (RIDM) through its programs and activities to help enhance safety and focus resources on what is most safety significant. Additional opportunities exist for future initiatives.
NRC is leveraging the use of risk assessment approaches in RIDM in a manner that complements Defense-in-Depth, Safety Margins, Engineering Judgment, and Enterprise Risk.
The NRC has built a strong foundation in risk-informed guidance and tools and is continuing to develop innovative approaches, including leveraging international cooperation, to increase the use of risk-informed decisionmaking.
Technical Session T5 Building on a Strong Foundation: A Voyage through Risk Informed Decision-Making Advances in RIDM: Past, Present, Future Points of Contact Stacey.Rosenberg@nrc.gov Senior Reliability and Risk Analyst Division of Risk Assessment, NRR Alissa.Neuhausen@nrc.gov Reliability and Risk Analyst Division of Risk Assessment, NRR 13
Acronyms CDF Core Damage Frequency LERF Large Early Release Frequency NTTF Near Term Task Force SSC LMP Licensing Modernization Project Structures, Systems, Components SMR Small Modular Reactor