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Overview of NRC’s Probabilistic Flood Hazard Assessment Research Program

Fire and External Hazards Analysis BranchDivision of Risk Analysis

Office of Nuclear Regulatory Research

Meredith Carr Ph.D., P.E.meredith.carr@nrc.gov

Overview• Objectives• Key Challenges• Main Themes• Current Projects• Future Work

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PFHA Research Objectives• Support development of risk‐informed licensing and oversight 

guidance and tools for assessing flooding hazards and consequences– Addresses significant gap in probabilistic basis for external hazards

• Seismic and wind hazard assessments currently have probabilistic basis  

• Support both new reactor licensing and oversight of operating reactors– Design basis flood hazard assessments for new facilities

• 10 CFR Part 50 ‐ traditional construction permits and operating licenses

• 10 CFR Part 52 ‐ early site permits (ESPs), combined operating licenses (COLs)

– Operating reactor oversight program (ROP)• Significance determination process (SDP) analyses for evaluating deficiencies 

related to flood protection at operating facilities

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2

PRA?

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Protected?

∙∙∙Magnitude

Load Intensity

Failure Probab

ilityFlood Protection Feature

No Impact

Mitigation

ImpactsSuccess?

No

No

Yes

Yes

Procedures and Manual Actions

Hazard Curves : Quantitative probabilistic assessment

of flood hazard(s)

Fragility Curves :Quantitative Reliability of Passive and 

Active Flood Protection Features

Human Reliability Assessment (HRA) issues with flood protection and/or mitigation procedures

Fragility

Hazard

To Plant Internal Model

Risk-informed Assessment of Flooding Hazards and Consequences

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Key Challenges• Interested in range of annual exceedance probabilities (AEPs) 

from moderately rare to extreme floods

– Full hazard curves needed

• Aleatory and epistemic uncertainties

– AEPs in the range 1e‐4 to 1e‐6 desired

• Large uncertainties

• Component fragility and human reliability information is sparse

• Flooding impacts exhibit cliff‐edge effects

• Complexity

– Coincident and correlated mechanisms

– Associated effects 

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Protected?

∙∙∙

Load Intensity

Failure Probab

ility

Flood Protection Feature 

Failure Model

Miti‐gation

ImpactsSuccess?

No

No

Yes

Yes

Procedures, Manual Actions

Fragility Curves

, , ,∙∙∙

Magnitude

HazardCurves

Internal Plant Model

potential impacts of dynamic and 

nonstationary processes

Reliability of Flood Protection and Plant 

Response

Improved Modeling Methods

PFHA Frameworks

Leverage Available Flooding Information 

Phase 2 and Phase 3 Activities

Main Research Themes

No Impact

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Leverage Available Flood Information Technical Basis for Extending Frequency Analysis Beyond Current

Consensus Limits– Contractor: U.S. Bureau of Reclamation (USBR)– NRC PM: Joseph Kanney

Research to Develop Guidance on Extreme Precipitation Frequency in Orographic Regions

– Contractor: USBR– NRC PM: Joseph Kanney

• Guidance on Application of State-of-Practice Flood Frequency Analysis Methods and Tools

– Contractor: U.S. Geological Survey (USGS)– NRC PM: Meredith Carr

• Development of Flood Hazard Information Digests for NPP Sites– Contractor: Idaho National Laboratory (INL)– NRC PM: Meredith Carr

• Detailed TN River Paleoflood Study– Contractor: USGS– NRC PM: Mark Fuhrmann 7

Leverage Available Flood Information Technical Basis for Extending Frequency Analysis Beyond Current

Consensus Limits– Contractor: U.S. Bureau of Reclamation (USBR)– NRC PM: Joseph Kanney

Research to Develop Guidance on Extreme Precipitation Frequency in Orographic Regions

– Contractor: USBR– NRC PM: Joseph Kanney

• Guidance on Application of State-of-Practice Flood Frequency Analysis Methods and Tools

– Contractor: U.S. Geological Survey (USGS)– NRC PM: Meredith Carr

• Development of Flood Hazard Information Digests for NPP Sites– Contractor: Idaho National Laboratory (INL)– NRC PM: Meredith Carr

• Detailed TN River Paleoflood Study– Contractor: USGS– NRC PM: Mark Fuhrmann 8

Leverage Available Flood Information Technical Basis for Extending Frequency Analysis Beyond Current

Consensus Limits– Contractor: U.S. Bureau of Reclamation (USBR)– NRC PM: Joseph Kanney

Research to Develop Guidance on Extreme Precipitation Frequency in Orographic Regions

– Contractor: USBR– NRC PM: Joseph Kanney

• Guidance on Application of State-of-Practice Flood Frequency Analysis Methods and Tools

– Contractor: U.S. Geological Survey (USGS)– NRC PM: Meredith Carr

• Development of Flood Hazard Information Digests for NPP Sites– Contractor: Idaho National Laboratory (INL)– NRC PM: Meredith Carr

• Detailed TN River Paleoflood Study– Contractor: USGS– NRC PM: Mark Fuhrmann 9

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PFHA Frameworks

Technical Basis for Probabilistic Flood Hazard Assessment – Riverine Flooding – Contractor: Pacific Northwest National Laboratory (PNNL)– NRC PM: Joseph Kanney

• Probabilistic Flood Hazard Assessment Framework Development– Contractor: U.S. Army Corps of Engineers (USACE)– NRC PM: Joseph Kanney

• Structured Hazard Assessment Committee Process for Flooding– Contractor: PNNL– NRC PM: Joseph Kanney

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PFHA Frameworks Technical Basis for Probabilistic Flood Hazard

Assessment – Riverine Flooding – Contractor: Pacific Northwest National Laboratory (PNNL)– NRC PM: Joseph Kanney

• Probabilistic Flood Hazard Assessment Framework Development– Contractor: U.S. Army Corps of Engineers (USACE)– NRC PM: Joseph Kanney

• Structured Hazard Assessment Committee Process for Flooding– Contractor: PNNL– NRC PM: Joseph Kanney

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Improved Process Modeling• Numerical Modeling of Local Intense Precipitation

Processes– Contractor: University of California Davis/USGS– NRC PM: Elena Yegorova

• Quantifying Uncertainties in Probabilistic Storm Surge Models

– Contractor: USACE– NRC PM: Joseph Kanney

• Erosion Processes in Embankment Dams– Contractor: USBR– NRC PM: Jacob Philip

• Application of Point Precipitation Frequency Estimates to Watersheds

– Contractor: ORNL– NRC PM: Elena Yegorova

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Improved Process Modeling• Numerical Modeling of Local Intense Precipitation

Processes– Contractor: University of California Davis/USGS– NRC PM: Elena Yegorova

Quantifying Uncertainties in Probabilistic Storm Surge Models– Contractor: USACE– NRC PM: Joseph Kanney

• Erosion Processes in Embankment Dams– Contractor: USBR– NRC PM: Jacob Philip

• Application of Point Precipitation Frequency Estimates to Watersheds– Contractor: ORNL– NRC PM: Elena Yegorova

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Observed 7-day accumulated precipitation field

Maximized 7-day accumulated precipitation field

Maximized 3-day accumulatedprecipitation field

Transposition of Hurricane Isaac (2012)

Reliability of Flood Protection and Plant Response to Flooding Events

• Performance of Flood Penetration Seals at NPPs– Contractor: Fire Risk Management (FRM)– NRC PM: Tom Aird

Effects of Environmental Factors on Manual Actions for Flood Protection and Mitigation at NPPs– Contractor: PNNL– NRC PM: Meredith Carr

Modeling Plant Response to Flooding Events – Contractor: INL– NRC PM: Joseph Kanney

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Reliability of Flood Protection and Plant Response to Flooding Events

• Performance of Flood Penetration Seals at NPPs– Contractor: Fire Risk Management (FRM)– NRC PM: Tom Aird

Effects of Environmental Factors on Manual Actions for Flood Protection and Mitigation at NPPs– Contractor: PNNL– NRC PM: Meredith Carr

Modeling Plant Response to Flooding Events – Contractor: INL– NRC PM: Joseph Kanney

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Dynamic and Nonstationary Processes• Regional Climate Change Projections: Potential

Impacts to Nuclear Facilities– Contractor: PNNL– NRC PM: Elena Yegorova

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Future Work*Technical Basis

• Interfacing Flood Hazard Modeling Outputs with HRA and PRA Models

• Probabilistic Treatment of Coincident and Correlated Hazards and Their Effects

• Application of SHAC-F toCoastal Flooding Hazard Assessments

• Quantifying Uncertainties in Probabilistic Riverine Flood Models

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Future Work*Draft Guidance, Pilot Studies

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• Development of Draft Guidance

• Piloting opportunities– on the hazard only – eg. LIP– also on the full risk – include Plant PRA

• Work with Industry, other Agencies– Inland location, coastal location

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For more information on any of the projects, • Download presentations from the 3rd PFHA

Research Workshop are at: https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML17355A071

• Contact me at meredith.carr@nrc.gov

• Come to the 4th PFHA Research Workshop Jan 29-31, 2019

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