ML22061A137
| ML22061A137 | |
| Person / Time | |
|---|---|
| Issue date: | 02/15/2022 |
| From: | Thomas Aird, Joseph Kanney, Elena Yegorova NRC/RES/DRA |
| To: | |
| Aird, Thomas - 301 415 2442 | |
| Shared Package | |
| ML22061A095 | List:
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| References | |
| Download: ML22061A137 (13) | |
Text
NRC Probabilistic Flood Hazard Assessment Research Program Update Thomas Aird*, Joseph Kanney, Elena Yegorova Fire and External Hazards Analysis Branch Division of Risk Analysis Office of Nuclear Regulatory Research 7th Annual PFHA Research Workshop NRC HQ, Rockville, MD February 15 - 18, 2022 1
Outline
- Objectives, key challenges, approach
- Phase 1 Overview (Technical Basis)
- Phase 2 Projects (Pilot Studies)
- Thoughts on Phase 3 (Guidance) 2
PFHA Research Objectives
- Develop resources, tools and selected guidance to:
- Address significant gap in the technical basis for guidance for probabilistic assessment of external hazards
- Probabilistic: seismic, high winds
- Deterministic: flooding
- Support risk-informed licensing and oversight activities involving assessment of flooding hazards and potential consequences
- Licensing and oversight in operating reactor program
- Design basis flood hazard assessments for new facilities
- Readiness for licensing of advanced reactors 3
Key Challenges
- Hazard Estimation
- Range of annual exceedance probabilities (AEPs)
- Moderately rare to extreme floods
- Multiple flooding mechanisms
- Coincident and correlated mechanisms
- Uncertainty characterization and Magnitude estimation
- Aleatory (e.g., storm recurrence rates)
- Epistemic (e.g., model structure, parameters)
- Fragility Failure Probability
- Information on reliability of flood protection features and procedures is sparse
- Cliff-edge effects Load Intensity 4
Phased Research Approach Phase 1 Phase 2 Phase 3 Inform &
Technical Application Pilot Studies update Guidance Basis Projects
- Phase 1 - Technical Basis Research - Complete
- Climate and precipitation
- Mechanistic, statistical and probabilistic modeling of flooding processes
- Reliability of flood protection features and procedures
- Modeling Frameworks
- Natural Hazard Information Digest (NHID)
- Phase 2 - Pilot Studies - In Progress
- Local Intense Precipitation (LIP) Flooding
- Riverine Flooding - Complete
- Coastal Flooding
- Phase 3 - Develop Guidance - In Progress 5
Phase 1 Technical Basis Research
- Climate Historical trends and future projections for U.S. regions
- Mechanistic, statistical and probabilistic modeling of flooding processes Extreme precipitation Riverine flooding Coastal flooding
- Methods for Estimating Joint Probabilities of Coincident and Correlated Flooding Mechanisms Riverine flooding Coastal flooding
- Reliability of flood protection features and procedures Flood barriers (seals, etc.)
Environmental effects on manual actions
- Modeling Frameworks
- Structured hazard assessment committee process for flooding (SHAC-F)
- Dynamic analysis of flooding events
- USACE HEC-WAT
- Natural hazards information digest (for internal NRC staff use)
- Collect and organize natural hazard information for operating reactors For more details on Phase 1 completion see Digital Exhibit #11 at the 34th Annual Regulatory Information Conference (RIC), March 8-10, 2022:
https://www.nrc.gov/public-involve/conference-symposia/ric/index.html 6
Phase 2: Pilot Studies Objective: Synthesize results from technical basis research
- Multiple flooding mechanism contribution to hazard curves
- Quantify key aleatory variabilities and epistemic uncertainties
- PNNL
- In Progress; completion expected in March 2022
- Riverine Flooding PFHA Pilot
- USACE/HEC
- Completed in January 2022
- Coastal Flooding Pilot PFHA Pilot
- USACE/ERDC/CHL
- In Progress; completion expected in June 2022 7
Phase 2: LIP Pilot Study
- Objectives
- Inform guidance development for probabilistic assessment of site-scale flooding hazards due to local intense precipitation
- Synthesize results from technical basis research
- Incorporate site-scale features (curbs, buildings, drains)
- Key elements
- Point rainfall (aleatory variability) based on NOAA Atlas 14
- Sensitivity study to identify key epistemic uncertainties wrt site features
- Propagation of uncertainties to construct hazard curve families for selected flood hazard metrics (e.g., depth, velocity, duration)
- Monte Carlo simulation with stratified sampling
- More detailed information:
- Presentation 2A-5 (Wednesday at 12:00) 8
Phase 2: Riverine Pilot Study
- Objectives
- Inform guidance development for probabilistic assessment of riverine flooding hazards
- Synthesize results from technical basis research
- Incorporate multiple flooding mechanism contributions to hazard curves
- Key elements
- Stochastic rainfall model (aleatory variability)
- Epistemic uncertainties in hydrologic (runoff and routing), reservoir, and hydraulic models
- Multiple dam failure scenarios
- Propagation of uncertainties to construct hazard curve families for selected flood hazard metrics (e.g., elevation, velocity, duration)
- Monte Carlo simulation approach using HEC-WAT
- More detailed information:
- Presentation 2B-4 (Wednesday at 15:20)
- Posters 3A-4 and 3A-5 (Thursday at 10:00) 9
Phase 2: Coastal Pilot Study
- Objectives
- Inform guidance development for probabilistic assessment of coastal flooding hazards
- Synthesize results from technical basis research
- Incorporate multiple flooding mechanism contributions to hazard curves
- Key elements
- Tropical cyclone rainfall model (aleatory variability)
- Epistemic uncertainties in hydrodynamic (surge),
hydrologic (runoff and routing), and hydraulic models
- Flooding due to surge and rainfall-induced riverine discharge
- Propagation of uncertainties to construct hazard curve families for selected flood hazard metrics (e.g., elevation, velocity)
- USACE Probabilistic Coastal Hazard Assessment (PCHA) framework
- More detailed information:
- Presentation 3B-3 (Thursday at 12:05) 10
Phase 3: PFHA Guidance
- FY 22/FY23: Develop draft guidance based on:
- Technical basis research
- Pilot projects
- User office needs
- Stakeholder & public interests
- FY23: Publish draft guidance for public comment
- FY23: Finalize guidance based on public comment 11
Past Workshops
- NRC Research Information Letter (RIL) 2020-01
- Proceedings of 5th Annual NRC PFHA Research Workshop
- Proceedings of 6th Annual NRC PFHA Research Workshop
- RIL 2022-02 NRC Research Information Letters are available at:
https://www.nrc.gov/reading-rm/doc-collections/index.html#ril 12
Questions?
Contacts:
Joseph.Kanney@nrc.gov Thomas.Aird@nrc.gov Elena.Yegorova@nrc.gov 13