ML24271A013
| ML24271A013 | |
| Person / Time | |
|---|---|
| Issue date: | 09/27/2024 |
| From: | Coyne K NRC/RES/DRA |
| To: | |
| References | |
| Download: ML24271A013 (1) | |
Text
An Over view of Current Risk-Informed Decision-Making Research Activities at the US Nuclear Regulatory Commission
Kevin Coyne US Nuclear Regulatory Commission Kevin.Coyne@nrc. gov Outline
- NRC s Risk Informed Decision Making Objectives
- Key Research Activities
- Operating Experience Data
- PSA Standards Activities
- Fire Research
- Advanced Reactors
- Forward Looking Activities
- Conclusions and Questions PSA Research Objectives
- Support the reactor oversight and operating experience programs;
- Remove obstacles to the implementation of risk-informed regulation (e. g., licensing activities);
- Expand the use of PSA and risk evaluation to encompass advanced reactor designs; and
- Support continuous advancement in the PSA state-of-the-art a n d state-of-practice Standardized Plant Analysis Risk (SPAR)
Models
- SPrisk assessment models that use standardized modeling AR models are plant-specific, NRC-developed, probabilistic conventions and industry averaged data
- Standardization increases efficiency of
- data updates,
- generating risk insight reports, and
- analysis of conditions across multiple plant models
- Currently maintain 67 SPcurrently operating U.S. nuclear plants. AR models, representing all
- All include Level 1 PRA modeling (core damage frequency) for internal hazards, high winds, and seismic hazards.
- Tw e n t y -three models include fire PRA modelling
- Six models for new reactors designs (e. g., ABWR, US EPR, APWR).
SAPHIRE Computer Code
- Systems Analysis Programs for Hands(SAPHIRE) computer code is used to develop and run the SP-on Integrated Reliability Evaluations AR models
- Developed by Idaho National Laboratorymaintained under a quality assurance program, under sponsorship of the NRC, and
- Includes modern fault tree/event tree capabilities as well as additional features that support NRC event and condition assessment (ECA) activities:
- Efficiently calculated changes in core damage frequency
- Enhanced common cause failure modelling
- SAPHIRE recent activities have focused on:
- improve computational speed,
- enhancement of large early release calculational capabilities,
- success path quantification for high failure probabilities, and
- development of a cloud-based SAPHIRE code
- More information available here: nrc/regulatory/research/obtainingcodes.html#6https://www.nrc.gov/about-Accident Sequence Precursor (ASP) Program
- Determines risk significance of two broad categories of reactor operational events:
- Degraded plant conditions characterized by the unavailability or degradation of equipment in the absence of a specific initiating event, or
- The occurrence of an initiating event (e.g., a reactor trip) with or without any other degraded plant conditions
- Program initiated in 1979 following issuance of WASH-1400
- As noted in NUREG/CR-0400, it is important that potentially significant sequences and precursors be subjected to the kind of analysis contained in WASH -1400
- Provides an input for NRC performance metrics Accident Sequence Precursor (ASP) Program
- Risk metric of interest is either the change core damage probability (CDP) (for degraded plant conditions) or the conditional core damage probability (CCDP) (for an initiating event)
- A precursor is defined as a CDP greater than or equal to 10-6 or an initiating event with a CCDP greater than 10-6 or the CCDP of a non-recoverable loss of feedwater or condenser heat sink (whichever is larger)
- Several categories of precursors are trended, including: losses of offsite power, initiating events, degraded conditions, and BWR/PWR trends
- More information available here: nrc/regulatory/research/asp.htmlhttps://www.nrc. gov/about-Accident Sequence Precursor (ASP) Program Operating Experience Data
- In collaboration with Idaho National Laboratoryand publishes operating experience (OpE) data consistent with our PRA, the NRC collects, analyzes, Policy Statement
- A key input for OpE data is provided by the Institute for Nuclear Power Operation (INPO) under their Industry Reporting and Information System (IRIS)
- Plant identifiers are removed and industry average data is published on a public website (https://nrcoe.inl. gov/)
- The industry averaged data is analyzed periodically to develop:
- updated reliability parameter estimates for use in SPAR models
- initiating events trends and insights;
- component and system studies;
- and common cause failure insights.
Operating Experience Data
Loss of Offsite Power Initiating Event Frequency and Recovery Time Trend PSA Standards Activities
- U.S. law requires that federal agencies emphasize where possible the use of standards developed by private, consensus organizations.
- Tconsensus standards developed by ASME and ANS o meet this requirement, the NRC leverages PSA under the Joint Committee on Nuclear Risk Management (JCNRM)
- Regulatory Guide (RG) 1.200 NRC staff positions, the use of national consensus uses a combination of standards, and peer reviews form the basis of establishing PRA acceptability.
- This approach helps to obviate the need for an indepth review of the base PSA by the NRC staff when -
reviewing licensing actions PSA Standards - Current Status
- Anticipate inclusion in the next revision of RG 1.200:
- ASME/ANS RA-S-1.1 -2024 - Level 1/Large Early Release Frequency (LERF)
- ASME/ANS RA-S-1.2 -2024 - Level 2 PRA
- ASME/ANS RA-during preconstruction and preoperational stagesS-1.5 - Level 1/Level 2 PRA standard for advanced LWRs
- ASME/ANS RA-power and shutdownS-1.6 - The Level 1/LERF PRA standard addresses low-
- Lower priority:
- ASME/ANS RA-S-1.3: Level 3 PRA standard
- ASME/ANS RA-S-1.7: Level 1/Level 2/Level 3 PRA standard for multi-unit PRA models Fire Research Activities
- Recent focus on developing enhanced methods to address high energy arcing faults (in cooperation with EPRI, NIST, SNL, and OECD)
- N U R EG -2262/EPRI 3002025942 improves realism in several areas:
- electrical fault clearing times
- improved technical basis for zones of influence,
- improved estimates for cable fragilityand,
- mitigation credit for electrical raceway fire barrier systems.
New LWR and Non-LWR Advanced Reactor Research In support of new approaches to advanced reactor licensing (e. g., use of the Licensing Modernization Project approach described in NEI 18-04), several activities are ongoing or planned:
- Risk metrics for advanced non-LWR reactors
- Identification of data sources for non-LWR reactor designs
- Development of guidance for addressing uncertainties, and
- Building knowledge and experience with PRA modelling challenges unique to new and advanced reactors (e. g., passive systems)
Continuous Advancement -
Level 3 PRA Project
- Project is for a multihazards. Includes spent fuel and dry cask storage.- unit site and covers all modes of operation and all
- Objectives include: (1) reflect technical advancements since the completion N U R EG -1150, (2) extract new risk insights to enhance decision -making, (3) enhance the staff s PRA capabilities, and (4) obtain insights into the costs of developing Level 3 PRA models.
- Accomplishments include:
- Piloting Level 2 and Level 3 PRA Standards and Peer Reviews
- Piloting streamlined expert elicitation guidance (ISLOCA)
- Significant knowledge management enhancement for agency staff
- The staff anticipates issuing the remaining project reports for public comment in 2024 and 2025.
Continuous Advancement -
For ward Looking Activities
The NRC maintains an active Future Focused Research Program -
several projects are associated with PSA areas of interest:
- Dynamic PRA (DPRA) Study (complete) - Literature sur veys, workshops, and an application of a DPRA tool to a reactor application.
- Apply the Licensing Modernization Project Methodology on an Operating Reactor (complete) - This project applied results from the ongoing Level 3 PRA project to gain experience with the operating Loverall LMP methodology and to identify key risk-insights on WR reactor technology.
- A Performance Monitoring Strategy to Enhance Consistency in Risk-Informed Decision-Making (ongoing) - focused on identifying sources of variability in reactor oversight decision making.
- Preparing Risk Assessment for Hydrogen Production and Use (ongoing) - update and improve the realism of PRA methodology to better assesses risks associated with hydrogen at applications at nuclear power plants.
Questions?