ML22235A651
ML22235A651 | |
Person / Time | |
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Issue date: | 09/01/2022 |
From: | Office of Nuclear Regulatory Research |
To: | |
N. DiFrancesco | |
References | |
Download: ML22235A651 (37) | |
Text
oo~***P #N uclearResearch Supporting Decision-Making Performing Comprehensive Advancing Probabilistic Risk with Modeling and Simulation Technical Analysis Assessment
/4..eword
- NuclearResearch We invite you to explore the U.S. Nuclear Regulatory Commission's Research Prospectus for Fiscal Years 2022 through 2024.
THESE ARE EXCITING TIMES FOR RESEARCH. Our research results support the safety decisions our agency is making today. We are also preparing the agency for the future through our research of new and emerging technologies and r
Ra, ~iftel(aa.
Director technical advances. Such technologies and advances include accident tolerant fuels, advanced reactor designs, artificial intelligence, human-machine interface, advanced manufacturing techniques, to name but a few. To conduct our research activities, the Office of Nuclear Regulatory Research maintains an expert staff and collaborates with many domestic and international partners. We appreciate your interest and welcome your feedback on our research program.
' ' No research without action, gte;/4alfie Coffilf Deputy Director no action without research.
-Dr. Kurt Lewin, Founder of Modern Social Psychology
/ Offi<::e of Nuclear Regulatory Research Current FY 2022
$8SM 203 RESEARCH FULL-TIME EQUIVALENT BUDGET STAFF Research by the Numbers FY 2021 MAJOR RESEARCH INTERNATIONAL PROGRAMS AGREEMENTS RECENT NUREGS COMPUTER CODE USERS NEW AND REVISED UNIVERSITY-LED, MISSION-REGULATORY GUIDES RELATED GRANTS
/ Abbreviated Terms Al artificial intelligence ASP accident sequence precursor ATF accident-tolerant fuel FAST Fuel Analysis under Steady-state and Transients FFR future focused research FY fiscal year HEAF high energy arcing fault HRA human reliability analysis IDHEAS Integrated Human Event Analysis System LWR light-water reactor M mi 11 ion MACCS MELCOR Accident Sequence Code System ML machine learning NRC U.S. Nuclear Regulatory Commission NUREG NRC technical report designation Organisation for Economic Co-Operation and OECD/NEA Development, Nuclear Energy Agency OpE operating experience PARCS Purdue Advanced Reactor Core Simulator PRA probabilistic risk assessment Radiation Protection Computer Code Analysis and RAMP Maintenance Program RE I RS Radiation Exposure Information and Reporting System RG regulatory guide Systems Analysis Programs for Hands-on Integrated SAP HIRE Reliability Evaluations SCALE Standardized Computer Analyses Licensing Evaluation SPAR standardized plant analysis risk TRACE TRAC/RELAP Advanced Computational Engine UNLP University Nuclear Leadership Program 4
Prospectus Contents FUTURE FOCUSED ADVANCED REACTORS RESEARCH RESEARCH SYSTEMS ANALYSIS ENGINEERING RISK ANALYSIS RESEARCH RESEARCH RESEARCH
- N uclearResearch 5
/ 4oking Ahead Increasing Interest FFR&UNLP PROGRAMS
- NuclearResearch Positive Feedback The FFR Program provides a vehicle to position the NRC to be ready for future state-of-the-art technologies and their potential regulatory impacts. It opens new areas of foundational knowledge on key topics.
The UNLP inspires researchers at U.S. institutions to develop innovative ideas that benefit the NRC mission and the broader nuclear community.
6
> In the first 3 years of the FFR program, $1.8M has been awarded for external support services. Sustained interest in the program may mean an increased allocation in the budgeted amount for FY 2023.
> FFR projects are generally completed in 3 years or less.
> Example projects that are at or nearing completion include Dynamic Probabilistic Analysis, Systems-Theoretic Accident Model and Processes-Based Methods for Digital Nuclear Safety System Evaluation, Digital Twins-Regulatory Viability, and Automation Tool Mapping.
UNLP Highlights
> In FY 2020, the first year of the program, 54 institutions submitted over 160 proposals. In a highly competitive review process, the NRC selected 15 proposals to receive research and development grants totaling $7 .3M .
> In FY 2021, nearly 100 proposals were submitted, and the NRC selected 11 proposals to receive research and development grants totaling $4.5M .
7
/ 4oking Ahead ADVANCED REACTORS
- NuclearResearch Research on advanced reactors facilitates the NRC's readiness for non-LWR licensing reviews.
The Near-Term Implementation Action Plan is the vehicle to execute the NRC's vision to safely achieve effective and efficient non-LWR mission readiness. Research efforts support development of computer codes and knowledge, guidance, and industry codes and standards for regulatory reviews.
8
oking Ahead Develop two demonstration plant models for system Fy2 2/ >
and source term analysis for non-LWRs Complete MACCS radionuclide properties on atmospheric transport and dosimetry
> Issue trial-use RG 1.247
> Complete final RG endorsing American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section Ill, Division 5, including Alloy 617
> Complete review of MACCS capabilities for reviewing tritium Fy 231/ releases to the environment
> Complete scalable reactor operator licensing review guidance
> Complete computational tool for confirmatory analyses of graphite component integrity
> Complete trial RGs for risk-informed, performance-based seismic design and seismic isolation $6.4M FY24 > Update two demonstration plant models for system analysis 1/ > Develop risk-informed decision-making guidance for non-LWRs
> Develop scalable human factors engineering and reactor operator licensing guidance
> Develop methodology and evaluation tools for digital twin applications and enabling technologies 9
Building the NRC's analytical capability and expertise FOCUS AREAS
> Fuels and Neutronics Analysis
> Thermal Hydraulics Analysis
> Accident Progression and Source Term Analysis
> Consequence Analysis
> Radiation Protection Research 10
/4.tems Analysis Research ADVANCED T
Code development to support advanced nuclear technologies, including ATF, high burnup and high-Sfale assay low-enriched uranium fuels and non-LWRs, in addition to code enhancements for LWRs.
INTERNATIONAL FUELS & NEUTRONICS Participation in ANALYSIS various OECD/NEA projects to obtain data and investigate
- NuclearResearch fuel and cladding behavior.
Fuels and neutronics research provides the technical bases for SOFTWARE risk-informed regulatory decision-making. e Development of staff expertise in reactor The FAST code enables confirmatory physics phenomena, studies for new fuel designs, including including criticality ATF and high burnup fuels. The SCALE and shielding, and code can analyze neutronics-related analyses of phenomena (e.g., nuclear data advanced fuel libraries, depletion and activation, designs.
criticality and shielding, and sensitivity and uncertainty analysis) and is used to initialize other NRC safety codes.
11
/4.tems Analysis Research FY22 > Annual release of computer codes for LWR and
/ non-LWR applications
> Workshops for molten salt and sodium reactors
> Issuance of research information letter on fuel fragmentation, relocation, and dispersal
> Spent fuel storage and transportation for ATF
> Ann~al ~el ease of computer codes for LWR and non-LWR Fy 231/ applications
> Completion of the first phase of the OECD/NEA Framework for Irradiation Experiments (four joint experimental programs)
> In-house familiarity with U.S. Department of Energy computer codes
$6.SM
> Ann~al ~elease of computer codes for LWR and non-LWR Fy 241/ appl1cat1ons
> Studsvik Cladding Integrity Program experiments
> SCALE bundle experiments studying ATF cladding materials at the QUENCH facility in Germany
> Spent fuel storage and transportation phenomena identification and ranking tables for ATF 12
/4.tems Analysis Research SOFTWARE The TRACE and PARCS computer codes are maintained, developed, and distributed for performing best estimate thermal hydraulic and neutronics reactor systems analysis.
EXPERIMENTS THERMAL HYDRAULICS D Participation in ANALYSIS international experimental programs enables
- NuclearResearch the NRC to obtain validation data at low cost. These data are then assessed to Thermal hydraulics research enhance code leads to the development of predictions.
computer codes that can INDEPENDENT simulate the behavior of nuclear reactors.
The TRACE and PARCS computer The TRACE and PARCS computer codes codes support are used for confirmatory analyses of independent existing and new reactor designs to technical basis support regulatory decision-making. development. They Like other modern reactor system are used for codes, they depend upon empirical confirmatory correlations that have been analyses to support developed from detailed experiments safety and security over decades of domestic and regulatory decision-international research. making.
13 0
/4.tems Analysis Research FY22 > Complete TRACE Version 5, Patch 7
/ > Complete the ARTHUR experimental program
> Complete two plant models to be ready for emergent licensing needs
> Complete TRACE Version 5, Patch 8 FY 231/,Complete TRACE assessment cases for the ATLAS-3 experimental program
> Continue to provide regulatory support for the review of research reactors and a radioisotope production facility
> Complete two plant models to be ready for emergent licensing needs $6.lM FY > Complete TRACE Version 5, Patch 9 241/ > Complete the ETHARINUS experimental program
> Continue to provide regulatory support for the review of research reactors and a radioisotope production facility
> Complete two plant models to be ready for emergent licensing needs 14
/4.tems Analysis Research SOFTWARE Code modernization and readiness for advanced nuclear technology applications, including ATF, high burnup and high-assay low-enriched uranium fuels, non-LWRs, and small modular reactors.
ACCIDENT INTERNATIONAL PROGRESSION &
Participation in SOURCE TERM ANALYSIS various OECD/NEA projects to obtain data for code
- NuclearResearch verification and validation.
Research to develop, validate, and maintain state-of-the-art tools for SOFTWARE severe accident and source term analysis.
Using MELCOR to maintain staff The MELCOR computer code is used to expertise in new support safety issue resolution and technologies.
risk-informed decision-making.
MELCOR is a system-level code that simulates the entire spectrum of accidents and phenomena from initiation to core degradation and fission product release from the fuel and transport to the containment and the outside environment.
15
/4.tems Analysis Research FY22 > Ann~al ~elease of MELCOR for LWR and non-LWR
/ applications
> Annual technical meetings on Cooperative Severe Accident Research Program
> Workshops for molten salt and sodium reactors
> Source term analysis for chromium-coated ATF
> Non-LWR fuel cycle demonstration calculations
> Ann~al ~elease of MELCOR for LWR and non-LWR Fy 231/ applications
> Annual technical meetings on Cooperative Severe Accident Research Program
> Modernization of the core code models
> OECD/NEA experimental programs and data analysis
> Fusion reactor demonstration project
$2.SM
> Ann~al ~elease of MELCOR for LWR and non-LWR Fy 241/ appl1cat1ons
> Annual technical meetings on Cooperative Severe Accident Research Program
> Modernization of the radionuclide and transport code models
> OECD/NEA experimental programs and data analysis 16
/4.tems Analysis Research SOFTWARE Develop and apply the MACCS computer code to model the Dr-y Dep,osition offsite consequences
\ \ \\ from hypothetical
\ lnhal Clouds severe accidents at nuclear power plants.
l Groundshine INTERNATIONAL CONSEQUENCE Leverage research ANALYSIS from international organizations and other Federal
- NuclearResearch agencies to continually improve the MACCS code.
Research to develop and apply accident consequence codes to evaluate offsite consequences from EMERGENCY hypothetical severe accidents. B Provide insights to support Consequence analysis supports methodology and risk-informed decision-making by guidance for evaluating the public health effects and determining economic costs of mitigation actions for severe accidents and assists in emergency planning emergency planning. The analyses also zone sizes for provide input to cost-benefit studies and nuclear power support plant-specific evaluations of plants.
severe accident mitigation alternatives required for environmental assessments.
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/4.tems Analysis Research FY2 2 > Issue protective action recommendations scoping
/ study report
> Complete MACCS radionuclide properties on atmospheric transport and dosimetry
> Complete initial evaluation of consequences from non-LWR source term demonstration calculations using MACCS
> Continue the evaluation of consequences from non-LWR Fy 231/ source term demonstration calculations using MACCS
> Develop screening analysis to inform the level of detail needed for severe accident mitigation design alternative and severe accident mitigation alternative analyses for new and non-LWR applications
> Complete Level 3 PRA consequence analysis reports for the $2.SM remaining reactor accident analyses
> Complete review of MACCS capabilities for reviewing tritium Fy241/ releases to the environment
> Continue the evaluation of consequences from non-LWR source term demonstration calculations using MACCS
> Address WinMACCS graphical user interface obsolescence 18
/4.tems Analysis Research SOFTWARE Develop and maintain RAMP computer codes in RAMP the areas of nuclear power plant licensing and siting, decommissioning, atmospheric transport and dispersion, and emergency response.
CONSOLIDATION RADIATION PROTECTION RESEARCH Gain RAMP computer code flexibility,
- NuclearResearch efficiencies, and increased user-friendliness by Research for radiation consolidating protection, dose similar dose assessment codes.
assessment, emergency response, and monitoring of INTERNATIONAL radiation exposures for occupational safety.
Leverage global experti.se a d This research promotes computer research results to code development under RAMP. It improve the RAMP also supports regulatory decisions computer codes.
affecting radiation protection through development of the abnormal occurrence report for Congress, REIRS, and occupational health RGs.
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/4.tems Analysis Research FY2 2 > Issue annual abnormal occurrence report for
/ Congress
> Issue annual REIRS report
> Complete atmospheric transport and dispersion module for the RAMP consolidated computer code FY 23 > Issue annual abnormal occurrence report for Congress 1/ > Issue annual REIRS report
> Issue RG 8.39, Revision 2, "Release of Patients Administered Radioactive Material"
$4.3M FY24 > Issue annual abnormal occurrence report for Congress 1/ > Issue annual REIRS report
> Complete consolidated RAMP computer code including the consolidated control room habitability, source term, and environmental pathways modules and user interface 20
Delivering technology and engineering solutions to make the NRC a modern, risk-informed regulator FOCUS AREAS
> Seismic, Geotechnical, and Structural
> Instrumentation, Electrical, and Cybersecurity
> Materials Performance 21
/ 4gineering Research Hazard Analysis SEISMIC, GEOTECHNICAL, & Data Analysis STRUCTURAL
- NuclearResearch Performance assessment of nuclear power plant Long-Term structures.
Operation The performance of structures in nuclear installations is an essential aspect of their safety and security.
Safety-related systems, structures, and components must be designed to ensure performance of their intended safety functions under design-basis events as required by NRC regulations.
22
/
Engineering Research Seismic site response-Senior Seismic Hazard Analysis Committee Level 2 study Research information letter on aging of posttensioned concrete containment vessels with emphasis on concrete creep and creep rupture Risk-informed, performance-based seismic safety and seismic isolation for advanced reactors Seismic source characterization and ground-motion model updates Three-dimensional physics-based ground motion study
$4.3M Irradiation-assisted concrete degradation FY2ly Harvesting irradiated concrete materials Prestressed concrete containment aging Probabilistic liquefaction model development 23
/ 4gineering Research Instrumentation &
Control INSTRUMENTATION, ELECTRICAL, & Engineering CVBERSECURITY
- NuclearResearch Research into digital instrumentation and control systems, cybersecurity, and Safety electrical engineering.
Enables the safe use of new technologies in nuclear facilities, while also ensuring system security and data integrity. Also evaluates the potential degradation of electrical components and aging of cables in the existing fleet of nuclear power plants.
24
/
Engineering Research Research on potential cyber risks from wireless technologies in risk-significant networks Regulatory assessment of attack surface definitions, characterizations, and tools to assist cybersecurity Evaluation of the effectiveness of systems-theoretic accident model and processes-based methods for system hazard identification Evaluation of methodologies and results of hazard analyses for digital instrumentation and control systems Cybersecurity-focused overview of novel technology implementations in nuclear power plants Electrical cable condition monitoring assessment reports Criteria for determining the safety of wireless technologies at nuclear power plants $3.SM Zero trust paradigm for cybersecurity in nuclear power plants Characterizing cybersecurity using Al/ML for safety, control, and cyber protection systems Contributions to Institute of Electrical and Electronics Engineers and International Electrotechnical Commission standards (all FYs)
Ongoing research regarding condition monitoring of cables at nuclear power plants 25
/ 4gineering Research Emerging Applications Defense In Depth MATERIALS PERFORMANCE 1111 Software Tools
- NuclearResearch Assessment of materials performance for manufacturing and long-term plant operations to ensure component integrity.
Preparing for review of advanced and Evaluation manufacturing technology applications and industry proposals related to nondestrutctive examination. Also facilitates risk-informed decision-making for component integrity assessments and addresses the impacts of material degradation for long-term operation.
26
/
Engineering Research Assessment of electron beam welding and powder metallurgy hot isostatic pressing Evaluation of modeling and simulation for ultrasonic examination predictions Issuance of probabilistic fracture mechanics RG Assessment of irradiated materials test results Release of flaw evaluation software Evaluation of advanced phased array ultrasonic techniques New release of the Fracture Analysis of Vessels-Probabilistic code and upgrades to the Extremely Low Probability of Rupture code Assessment of primary water stress corrosion cracking initiation testing of Alloy 690/52/152 materials
$9.0M Assessment of automated data analysis and ML for FY24/ nondestructive examination Benchmarking of the Fracture Analysis of Vessels-Probabilistic code and the Extremely Low Probability of Rupture code Assessment of primary water stress corrosion cracking initiation testing of Alloy 690/52/152 weld dilution zones, heat affected zones, and weld defects 27
Developing risk-informed solutions to current and anticipated regulatory challenges FOCUS AREAS
> Human Reliability and Organizational Factors
> Operating Experience
> Risk Tools and Studies
> Fire Research and External Hazards Analysis 28
/4,k Analysis Research HUMAN RELIABILITY &
ORGANIZATIONAL FACTORS
- N uclearResearch Provides safety perspectives on the impact of human performance on nuclear power plants and other NRC-licensed facilities.
Improves understanding of complex human, organizational, and system interactions, which will help to ensure the continued safety of Virtually every system ... places "operator error" high on its list nuclear operations of causal factors-generally about with novel 60 to 80 percent of accidents are technologies and attributed to this factor.
advanced concepts of operation.
Use state-of-the-art principles to develop human and
+ ' +
Apply robust scientific basis to develop and improve HRA methods for Leverage domestic and international programs to gain organizational risk analyses data and insights factors guidance 29
/ 4k Analysis Research Enhance HRA method for all nuclear applications: IDHEAS Fy 22 >
for Event and Condition Assessment
/ > Develop new method for performing dependency analysis in HRA applications: IDHEAS-Dependency
> Provide update on the human factors challenges associated with the incorporation of adaptive automation
> Report on the use of cognitive task analysis for human factors engineering reviews
> Complete human factors engineering training program
> Update human factors engineering program review model based on Fy 23 lessons learned from new and advanced reactor reviews 1/ > Develop new method for calculating the effects of time on human error:
IDHEAS-Time
> Publish research information letters on the results of the NRC's human performance test facility experiments Enhance guidance for performing expert elicitations
> Enrich database on human error to support HRA method development: $3.SM IDHEAS-Data
> Update Human-System Interface Design Review Guidelines based on Fy 24 lessons learned from new and advanced reactor reviews 1/ > Develop new method for crediting recovery actions in HRA:
IDHEAS-Recovery
> Enhance technical bases for minimum joint human error probabilities
> Issue guidance for the use of independent safety culture assessments in the nuclear industry 30
/4.k Analysis Research RISK INSIGHTS Evaluates U.S.
nuclear power plant OpE to identify, document, and rank operational events by core damage probability parameters.
PUBLIC WEBPAGE OPERATING Displays on the EXPERIENCE NRC's public webpage trends and insights from
- NuclearResearch initiating events, system and component failures, and common-cause failures.
Evaluation of OpE to gain risk insights, understand DATA ANALYTICS industry performance, and inform NRC risk models.
Collaboration with the U.S. Department The ASP Program evaluates OpE to of Energy to identify precursors to potential evaluate data core damage. OpE data collection analytics and Al/ML and analysis looks for long-term for use to increase component and system performance the effectiveness of trends and is used for initiating NRC OpE event frequencies and failure evaluations.
parameters in the NRC's plant risk models.
31
/ 4k Analysis Research
> Calendar year 2021 ASP analyses and issuance of Fy2 2/ annual ASP report
> SPAR model data parameters update
> Evaluation of initiating and loss of offsite power events
> System and component reliability studies update
> Development and evaluation of component-specific priors for common-cause failures
> Calendar year 2022 ASP analyses and issuance of annual Fy 231/ ASP report
> Evaluation of initiating and loss of offsite power events
> Collection, coding, and provide quality assurance of reactor operating data
> Maintenance and enhancement of the database that houses the long-term OpE data and licensee event reports $4.0M
> Calendar year 2023 ASP analyses and issuance of annual Fy 241/ ASP report
> Evaluation of initiating and loss of offsite power events
> Collection, coding, and provide quality assurance of reactor operating data
> Maintenance and enhancement of the database that houses the long-term OpE data and licensee event reports 32
/4.k Analysis Research RISK MODELS Maintain the NRC's SPAR models for all operating nuclear power plants with the goal of reflecting current designs and operations.
SOFTWARE RISK TOOLS&
Use the SAPHIRE STUDIES computer code to support the development of the
- NuclearResearch agency's SPAR models.
Timely, realistic, and repeatable risk assessments to support NRC licensing, RISK ASSESSMENT rulemaking, oversight, and OpE evaluation activities.
Provide living Level 1, 2, and 3 Risk tools support projects such as PRA models to Level 3 PRA, which is a sitewide, support enhanced full-scope PRA that includes all risk-informed radioactive sources for a two-unit decision-making and reference pressurized-water reactor. analyses of emerging This project is advancing the state technologies.
of practice in areas such as human reliability, multiunit risk, severe accidents, and more.
33
/ 4k Analysis Research FY2 2 > SAPHIRE updates to add user-requested features
/ > Hundreds of requested SPAR model changes to support event and condition assessments
> SPAR dashboard for expanded access to risk insights from SPAR models for nonrisk experts
> Level 3 PRA project internal reports for reactor low power and shutdown, spent fuel pool, and dry cask storage
> Draft NUREGs for comment on reactor, at-power, internal events and internal floods, and dry cask storage
> SAPHIRE Version 9.0 with cloud-based capabilities FY 23~ / > Hundreds of requested SPAR model changes to support event and
/ condition assessments
> Expanded SPAR model capabilities in external hazards, diverse and flexible coping strategies, and HRA
> Level 3 PRA project internal report for integrated site risk
> Draft NUREGs for comment on reactor, at-power, internal fires, $4.4M seismic and high winds; reactor, low power and shutdown; and spent fuel pools
> Integration of IDHEAS for Event and Condition Assessment into Fy 24 SAPHIRE as a replacement for SPAR-H 1/ > Hundreds of requested SPAR model changes to support event and condition assessments
> Enhancements to SAPHIRE and SPAR models to assess time-sensitive and quickly changing conditions
> Draft Level 3 PRA NUREGs for comment on integrated site risk and project summary 34
/4,k Analysis Research FIRE RESEARCH & EXTERNAL HAZARDS ANALYSIS
- N uclearResearch Research to develop the tools, methods, and data for analyzing risks from fire and external hazards.
NRC regulations require each operating nuclear unit to be capable of performing safe shutdown and maintenance of the reactor when challenged by a fire or other natural hazards.
We learn from every natural disaster.
Whether it's a fire or a flood, we Research enhances learn something from it so we can realism in fire and respond to the better.
other external hazard PRAs to support risk-informed decision-making.
L Analyze fire + A s s e s s potential r i s + Systematically hazards and the of external flooding assess new natural impact on reactor and the impact on hazard information safety in a reactor safety in a and its impacts on probabilistic probabilistic existing estimates framework framework 35
/ 4k Analysis Research
> In cooperation with the Electric Power Research Institute, Fy 22 develop an improved methodology for assessing fire risk
/ including HEAFs
> Lead the OECD/NEA testing program for HEAF
> Perform fire PRA model refinements to improve PRA realism; update methods in NUREG/CR-6850
> Develop draft probabilistic flood hazard assessment guidance
> Maintain the NRC's Natural Hazard Information Digest
> Host annual workshops and knowledge management training Co~plete testing and publish results from the OECD/NEA HEAF Fy2 31/ >
testing program
> Perform fire PRA model refinements to improve PRA realism; update methods in NUREG/CR-6850, including the development of low power and shutdown risk for fire PRAs
> Publish draft probabilistic flood hazard assessment regulatory guidance for public comment Maintain and expand the NRC's Natural Hazard Information Digest
$2.4M
> Host annual workshops and knowledge management training Continue to develop tools, methods, and data to improve realism in Fy241/ >
fire PRAs, including updates based on fire frequency and OpE
> Publish final probabilistic flood hazard assessment regulatory guidance
> Maintain and expand the NRC's Natural Hazard Information Digest
> Research extreme weather events, such as cold-air outbreaks and high winds, in the context of climate change and their potential hazards for nuclear power plants
> Host annual workshops and knowledge management training 36
Operating Reactors Nuclear Materials