ML22140A324

franovichm-hv-t8-r1

ML22140A324
Person / Time
Issue date:	03/10/2022
From:	Mike Franovich NRC/NRR/DRA
To:	Office of Nuclear Reactor Regulation
References
Download: ML22140A324 (13)

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Safety Improvements Using Risk Insights Technical Session T8 Michael X. Franovich Director, Division of Risk Assessment Office of Nuclear Reactor Regulation

AGENDA Historical Background Derecho Analysis High Energy Arc Fault (HEAF)

New Reactors 2

Meeting the Challenge of Becoming a More Modern Risk-Informed Regulator

• Risk assessment technology continues to mature and is used increasingly in regulatory matters to support safety decisions.

• Risks are dynamic. Effective risk management relies on vigilant assessment and use of operating experience.

• Risk technology and insights complement traditional defense in depth to achieve an acceptable level of residual risk.

• Transformation is in progress to further risk-inform.

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Value Added Pursue a common understanding of risk ( and +) and communication of risk information across the agency.

Continual

• Enhanced decisionmaking, more efficient use of resources, and reduction of unnecessary burden Learning Objectives of the Commission policy on probabilistic risk assessment (PRA)

• Improved mission delivery, reduced costs, and Organization focused corrective actions towards key risks Objectives of the Office of Management and Budget policy requiring enterprise risk management

• Agile, adaptive, and enhanced efficiency NRC Futures Assessment 4

Major Policies Shaping Risk-Informed Thinking for the NRC Individual Plant Examinations The use of PRA technology should be (IPE) for Severe Accident Vulnerabilities increased in all regulatory matters to the extent TMI Accident (GL 88-20, NUREG-1560) supported by the state-of-the-art in PRA Policy PRA methods and data and in a manner Severe Accident Shutdown / Statement that complements the NRC's deterministic Policy Statement Low Power approach and supports the NRC's traditional (NUREG-1449) defense-in-depth philosophy.

X 1980 1990 1975 1985 1995 1998 ATWS Indian Point Safety Goal IPE of (NUREG-0460) & Zion Policy Statement External Events Probabilistic (GL 88-20 Supp. 4, Risk-Informed, Safety Studies NUREG-1742) Performance-Based Regulation Station Blackout (NUREG-1032) Severe Accident Risks SECY-98-144 Reactor Safety Study (NUREG-1150)

(WASH-1400) 5

Integrated Decisionmaking Principles

3. Sufficient safety margins are maintained

4. Changes in risk are small and

2. Change is consistent with consistent with NRC Safety Goal defense-in-depth philosophy Policy Statement Integrated Decisionmaking

1. Change meets current (RG 1.174) 5. Monitor change regulations unless specifically with performance measurement related to a requested exemption strategies All elements of Integrated Decisionmaking should be considered more than just the numbers alone.

Integrated Decisionmaking is a place for critical thinking and dialogue. 6

Background on the LIC-504 Process LIC-504 (ADAMS Accession No. ML19253D401) was created to address recommendations in the Government Accountability Office (GAO) report, GAO-04-415, Nuclear RegulationNRC Needs to More Aggressively and Comprehensively Resolve Issues Related to the Davis-Besse Nuclear Power Plants Shutdown, issued 2004 The major revision of LIC-504 (Rev. 5, 2020) included several significant changes prompted by previous uses of the process (e.g., considering enterprise risk and exposure to workers, guidance on how to consider risk significance to recommend generic communications).

1. Determine whether prompt regulatory actions are necessary.

LIC-504 2. Use best available information to develop risk-informed recommendations for evaluations result management consideration; specifically including the following:

in two distinct Use conservative assumptions in the absence of information Use best available information outcomes: Rely on performance monitoring (NUREG/CR-1855) to address uncertainties The way LIC-504 teams develop recommendations has evolved to accommodate some key elements of the Be riskSMART (NUREG/KM-0016) framework. 7

Example 1LIC-504 Duane Arnold Derecho PROBLEM:

• Derecho highlighted a combined event not modeled in PRAs (weather-related loss of offsite power (LOOP) coincident with potential loss of emergency service water); potential for generic issue with previously unknown risk.

APPROACH:

• Using LIC-504 guidelines, determine whether prompt regulatory actions (i.e., orders to shut down or impose compensatory measures) were needed.

SOLUTION:

• Communicate risk insights within the NRC and with industry.

• Update Standardized Plant Analysis Risk (SPAR) models to improve realism and review team recommendations for further updates.

KEY TAKEAWAYS:

• Review the combined event effects and generate risk-informed recommendations that could help enhance plant safety and future regulatory processes. 8

Example 2Aluminum High Energy Arc Fault PROBLEM:

• Path forward on risk posed by aluminum HEAFs. San Onofre 4160 V (2001)

APPROACH:

• Evaluate operating experience.

• Improve modeling of aluminum HEAFs.

• Mitigate the impact from aluminum HEAFs.

• Develop the strategies for a risk-informed resolution (Be riskSMART).

• Continue communication and outreach.

SOLUTION:

• Perform LIC-504 review and communicate risk insights.

KEY TAKEAWAYS:

• Plants are safe; however, HEAF events are credible.

• Use LIC-504 to continue to identify any potential safety issues that may be applicable to operating light-water reactors and develop risk-informed options to disposition them.

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Example 3New ReactorsNuScale PROBLEM:

• Review inadvertent actuation block (IAB) valves and consider passive components and applicability of the single-failure criterion (SFC).

APPROACH

• SFC is one element of a defense-in-depth approach.

• SECY-05-0138, Risk-Informed and Performance-Based Alternatives to the Single-Failure Criterion (ADAMS Accession No. ML051950619)

(1) Eliminate unlikely sequences and postulated single failure (2) Risk-inform based upon safety significance (3) Take a blended approach of diversity, redundancy, and unreliability SOLUTION:

• Assess options (including regulatory certainty and timeliness) through SECY-19-0036, Application of the Single Failure Criterion to NuScale Power LLCs Inadvertent Actuation Block Valves, (ADAMS Accession No. ML19060A081).

• Conduct review using risk-informed decisionmaking (RIDM) and the 1995 PRA Policy Statement as directed by the Commission in SRM-SECY-19-0036 (ADAMS Accession No. ML19183A408).

KEY TAKEAWAYS:

• SRM-SECY-19-0036 provides direction on the appropriate application and interpretation of both regulatory requirements in 10 CFR Part 50 and risk-informed principles for the NuScale IAB valve. The NRC has some discretion, in fact- or application-specific circumstances, to decide when to apply SFC. The NuScale decision is similar to those in previous Commission documents that addressed the use of SFC and clarified when to apply it. 10

Three Key Messages The NRC supports and advances RIDM through its programs and activities to help enhance safety and focus resources on what is most safety significant.

The NRC is leveraging the use of risk assessment approaches in RIDM in a manner that complements defense in depth, Continual safety margins, engineering judgment, and enterprise risk.

Learning The NRC is continuing to increase the use of risk insights through Be riskSMART and other initiatives to expand the use Organization of PRA technology to other business lines to further support other regulatory matters.

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Questions?

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Points of Contact Antonios.Zoulis@nrc.gov Branch Chief, Division of Risk Assessment, NRR Lundy.Pressley@nrc.gov Reliability and Risk Analyst Division of Risk Assessment, NRR 13