ML20267A442

Enhancement of PRA Technology for Applications: a Regulatory Research Perspective

ML20267A442
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Issue date:	09/29/2020
From:	Office of Nuclear Regulatory Research
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Nathan Siu
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Enhancement of PRA Technology for Applications:

A Regulatory Research Perspective*

Nathan Siu and Mehdi Reisi Fard Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission IAEA Technical Meeting on the Enhancement of Methods, Approaches and Tools for Development and Application of Probabilistic Safety Assessments September 29-October 2, 2020

• The views expressed in this presentation are not necessarily those of the U.S. Nuclear Regulatory Commission

Outline

• Role of regulatory research at NRC

• Comments on potential PSA technology* TM Organizer Questions enhancements

• Why it is important to consider the

- Dynamic PSA subject from a PSA research

- Combinations of hazards perspective?

- Portable equipment

• What is the current

- Development of SAMGs national/international status of

- Level 3 PSA practice/experience?

- Software reliability and modelling

• What are the current challenges

- Incorporation of ageing aspects and open issues?

- Treatment of uncertainties**

• In this presentation Technology = {methods, models, tools, data}

2 **Added to organizer list

ROLE OF REGULATORY R&D 3

Role of Regulatory R&D Ultimate NRC Regulatory R&D: Purpose Purpose and Considerations Adapted from NUREG-2150 NRC/RES TSOs Multiple Multiple Applications Universities Actors Stakeholders Analyses (incl. reviews)

Industry (A)

R&D needs, wants, Other Agencies priorities International Methods, Models, Tools, Databases, Technology Multiple (capabilities)

Resources Uses Standards, Technical analyses

- People Guidance, (T)

Technology development

- Funds Tests/experiments

- Infrastructure

- Information Surveys/reviews Foundational Knowledge (K) Context Multiple Products 4

Role of Regulatory R&D NRC Regulatory R&D: More Considerations Multiple regulatory functions (and decision types)

Risk-informed decision making Time Scale Near Term Long Term (User Need) (Future-Focused)

Current Trends Not just reactors 5

Role of Regulatory R&D Some Trends

• Market forces

- Increased number of applications

- Increased credit for capabilities (e.g., FLEX)

- Greater role in design (e.g., LMP)

• Novel designs, technologies, and operational concepts Photo courtesy of NEA Halden Reactor Project

• Improving analysis capabilities

- Computational resources

- Smart technologies (e.g., content analytics) Challenge :

Be Ready!

• Changing workforce (KSAs, preferences) 6

A:

Analyses Analyses (for application)

• Why it is important to consider the subject from a T: Technology Technology (provides capability)

PSA research perspective?

• What is the current status of practice/experience? K: Knowledge Knowledge (provides context)

• What are the challenges and open issues?

COMMENTS ON POTENTIAL PRA TECHNOLOGY ENHANCEMENTS 7

Dynamic PSA

• Importance (Benefits)

• Analyses (anticipated, potential) Long history (starting with fast rx)

• Advanced reactor design approvals

• Operating reactor risk-informed applications (e.g., FLEX, security)

• External hazards scenarios (e.g., flooding)

• Severe accidents

• Technology Not always complicated

• Improved realism (fewer modelling approximations)

• Reduced completeness uncertainties (e.g., EOCs, passive systems)

• Improved synergy (other fields, educational trends) Computational capabilities + investments (e.g.,

A. Amendola and G. Reina, Event Sequences and J.M. Lanore, et al, Progress in Methodology for Probabilistic Assessment of Accidents: Timing of

• DOE, TSOs, universities) => time to reap benefits?

Accident Sequences," ANS/ENS Intl Mtg Probabilistic Knowledge Consequence Spectrum: A Methodology for Probabilistic Transient Analysis," Nuclear Technology, 77, 297-315(1981). Risk Assessment, Port Chester, NY, 1981.

• Improved insights

• Current status

• U.S.

• Technology development TAF

• Multiple demonstrations

• International: some applications T. J. McIntyre and N. Siu, "Electric Power Recovery at TMI-1, A Simulation Model," ANS/ENS Intl Topical Mtg Thermal Reactor Safety, San Diego, California, February 2-6, 1986.

• Challenges

• Communication and perception

• Investment requirements, cost/benefit

• Cultural resistance See also draft white paper (ML19066A390) and presentation from 2019 IAEA workshop 8

(ML19248C656)

Combination of Hazards

• Importance (Benefits)

Treatment of consecutive events

• Analyses (ongoing)

• Current risk-informed applications (specific (and pre-conditioning)?

combinations)

• Technology

• Improved realism (correlation of hazards)

• Reduced completeness uncertainties

• Improved synergy with natural hazards community

• Knowledge

• Additional/improved insights https://commons.wikimedia.org/wiki/File:Storms_Lothar_and_Martin_december_1999.png

• Current status (U.S.)

• Some methods developed and used, included in PRA Role of stochastic simulation?

standards and guidance

• Participation in international activities

• Challenges

• Efficient identification and prioritization

• Data augmentation (simulation?)

• Communication (discipline-specific frameworks -

what is a hazard? Area of responsibility when Hurricane tracks adapted from University of Wisconsin-Milwaukee performing analyses?) (https://web.uwm.edu/hurricane-models/models/archive/)

Emergency response based on data from National Hurricane Center:

(https://www.nhc.noaa.gov/1992andrew.html) 9

Portable Equipment

• Importance (Benefits) Task-Based Simulation: Old Idea, Recent Applications

• Analyses (ongoing)

• FLEX applications

• Other non-safety related equipment

• Technology

• Improved HRA for ex-MCR activities (possibly including task-based simulation)

• Improvements (practice, methods?) in constructing informed priors (potential)

• Knowledge

• Improved insights M.T. Lawless, K.R. Laughery, and J.J. Persensky, Using Micro Saint to Predict Performance in a

• Current status (U.S.)

Nuclear Power Plant Control Room: A Test of Validity and Feasibility, NUREG/CR-6159, 1995.

• Strong interest, many applications (e.g., NOED, CRM, SDP, licensing actions, NTTF 2.1 seismic PRA)

• Further applications being developed

• Improved HRA demonstration (IDHEAS)

• Challenges

• Reliability data

• HRA (e.g., granularity/aggregation, quantification)

S. Fogarty, Approaches and Tools to Quantifying Facility Security Risk, INMM Workshop on Risk-Informed Security , Stone Mountain, GA, February 11-12, 2014.

See also presentation from 2019 IAEA workshop (ML19248C655) 10

Development of SAMGs

• Importance (Benefits) SOARCA Assessment of B.5.b Measures

• Technology

• Improved HRA for post-core damage

• Severe-accident induced cascading failures

• Knowledge

• Additional/improved insights (e.g., to prioritize severe accident R&D)

• Current status (U.S.)

• Some changes identified during FLEX implementation

• Challenges

• Multi-source dependencies

• HRA

• Appropriate realism (scope, avoiding Game Over)

D. Collins, et al., Modeling Potential Reactor Accident Consequences, NUREG/BR-0359 Rev. 1, 2012. (ML12347A049) 11

Level 3 PSA

• Importance (Benefits)

• Analyses

• Demonstration of LMP for operating plants Level 3 PRA Project Scope

• Regulatory analysis guidance revisions (potential)

• Technology

• Developments in selected areas (e.g., multi-source PRA)

• Knowledge

• Improved insights regarding safety margins

• Improved insights for performing analyses (risk, feasibility of and benefits from future Level 3 studies)

• Improved staff capabilities for performing and reviewing PRAs

• Current status (U.S.)

• Reference plant state-of-practice study ongoing

• Challenges

• Broad scope Integration across all sources, hazards Resources 12

Software Reliability and Modeling

• Importance (Benefits)

• Analyses WGRISK Benchmarking Study

• Licensing digital upgrades

• Approving new designs

• Technology

• Improved hazard identification

• Reduced completeness uncertainties

• Improved synergy with I&C community

• Knowledge

• Improved insights

• Current status

• U.S.

• Technology development (e.g., integration of STAMP/STPA with conventional PRA)

• International

• Activities include WGRISK benchmarking study

• Challenges M. Porthin, et al., Comparative application of digital I&C modeling approaches for PSA,

• Software CCF International Topical Meeting on Probabilistic Safety Assessment (PSA 2019), Charleston, SC, April 28-May 3, 2019.

• Data 13

Incorporation of Ageing Aspects

• Importance (Benefits) Analysis technology exists

• Technology

• Capabilities should regulatory need arise As good as new

• Knowledge Blending mechanistic and statistical perspectives

• Improved insights changes PRA approach?

• Current status (U.S.)

• Long history of R&D, no recent work

• Challenges Importance of burn-in?

• Data

• Physics of failure modeling

• Other trends, e.g.,

• Technology (NDE, prognostics, ) D. Rudland and C. Harrington, xLPR Pilot Study Report, NUREG-2110, 2012. (ML12145A470)

• Workforce

• Fleet (unique reactors)

• Incorporation in PRA Standards 14

Treatment of Uncertainties Model uncertainties can be characterized; consensus

• Importance (Benefits) approach for quantification?

• Analyses

• All risk-informed applications (operating reactors and new designs)

• Technology

• Improved characterization methods

• Improved synergy with other technical communities From static (handoff) to dynamic (interaction)?

• Knowledge

• Improved insights

• Current status (U.S.)

• Established methods and guidance

• Improvements being considered in R&D planning Adapted from NUREG-2156

• Challenges

• Quantitative assessment (model and completeness uncertainties), particularly for new designs

• Communication 15