ML22053A280

Regulatory Information Conference (RIC) RIC 2022 Technical Session T8 - True D - NEI Presentation RIDM Greater than Sum of Its Parts

ML22053A280
Person / Time
Site:	Nuclear Energy Institute
Issue date:	03/31/2022
From:	True D Nuclear Energy Institute
To:	NRC/NRR/DRA/APOB
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Download: ML22053A280 (6)

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Risk-informed Decision-making:

Greater Than the Sum of its Parts Doug True Sr. Vice President Nuclear Energy Institute March 2022

©2022 Nuclear Energy Institute

Safety vs. Risk Regulations based on deterministic requirements provide the foundation for assuring the safety of nuclear power plants Risk Analysis provides a tool to assess the risk that remains even when regulations are followed

• The residual risk is never zero Risk Analysis provides an estimate of the residual risks (aka level of safety) associated with the deterministic requirements Risk Analysis can also assess the risk increment of changes to requirements and/or non-compliances

©2022 Nuclear Energy Institute 2

Conceptual Relationship Between Safety & Risk Lots Example Deterministic Requirement:

Redundancy of Safety Systems Level of Residual Risk Little No One Two Three Four . . . . Twenty-seven Safety Safety Safety Safety Safety Safety Systems Train Trains Trains Trains Trains

©2022 Nuclear Energy Institute 3

Risk-informing Improves Safety Focus on the safety significant issues:

• Allows allocation of resources in the manner that most effectively improves safety

• Incentivizes licensee focus on issues important to safety

• Reduces resources applied to issues of low importance

• Stimulates a net improvement in safety Must account for limitations in risk analysis models (e.g., PRA)

• PRA is a tool that must be used appropriately

• PRA is neither omnipotent, nor omniscient

- Neither is a deterministic approach

©2022 Nuclear Energy Institute 4

Risk-informing Addresses Uncertainty PRA results are the product of a model that contains uncertainties

• PRA does not create those uncertainties, it simply illuminates them Risk-informed Decision-making RG 1.174 outlines an integrated decision-making Defense in framework, in part to address uncertainties in PRA Depth results Current Safety

• PRA is one input Regulations Margins Integrated

• The elements should not be treated separately Decision-making Addressing uncertainties:

• Identify uncertainties that are important to the Performance Small Change decision Monitoring in Risk

• Consider implications for defense-in-depth &

safety margins

• Example: FLEX for post-Fukushima response All safety impacts of the proposed licensing basis changes are evaluated in an integrated manner1

©2022 Nuclear Energy Institute 5 1 - Reg. Guide 1.174

Examples of Risk Insights Improving Safety Regulatory Changes:

• ATWS Rule

• Station Blackout Rule

• Severe accident vents and water addition for BWR Mark I & II Voluntary Changes:

• Fire protection pipe failure impacts all divisions of AC/DC power

• Addition of non-safety feedwater pump

• Procedural changes to enable novel uses of systems

• Operator training on important human actions

©2022 Nuclear Energy Institute 6