ML19011A421
| ML19011A421 | |
| Person / Time | |
|---|---|
| Issue date: | 01/16/2019 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| Nathan Siu 415-0744 | |
| Shared Package | |
| ML19011A416 | List:
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| References | |
| Download: ML19011A421 (22) | |
Text
What is RIDM?
Lecture 1-1 1
Overview Key Topics
- Practical purpose of risk assessment
- Triplet definition of risk
- Difference between risk-informed and risk-based decision making 2
Overview Resources
- G. Apostolakis, et al., A Proposed Risk Management Regulatory Framework, NUREG-2150, U.S. Nuclear Regulatory Commission, April 2012.
- International Nuclear Safety Group, A Framework for an Integrated Risk Informed Decision Making Process, INSAG-25, International Atomic Energy Agency, 2011.
- National Research Council, Understanding Risk: Informing Decisions in a Democratic Society, P.C. Stern and H.V. Fineberg (eds), National Academies Press, 1996.
- U.S. Nuclear Regulatory Commission, White paper on risk-informed and performance-based regulation, SECY-98-144, June 22, 1998.
- S. Kaplan and B.J. Garrick, On the quantitative definition of risk, Risk Analysis, 1, 11-37(1981).
- N. Siu, et al., Probabilistic Risk Assessment and Regulatory Decisionmaking: Some Frequently Asked Questions, NUREG-2201, U.S. Nuclear Regulatory Commission, September 2016.
- M. Drouin, et al., Glossary of Risk-Related Terms in Support of Risk-Informed Decisionmaking, NUREG-2122, U.S. Nuclear Regulatory Commission, November 2013.
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Risk assessment purpose An Unexpected Research Result As part of an international research program, NRC-supported experimentalists intentionally create electrical faults in medium voltage switchgear to determine the potential consequences. The resulting explosions appear to be reasonably consistent with (or even bounded by) current models. Then one day 4
Risk assessment purpose HEAF Video OECD/NEA High Energy Arcing Fault (HEAF) Program Phase 1 Project information: http://www.oecd-nea.org/jointproj/heaf.html 5
Risk assessment purpose Sample Decision Options A. Stop the experiments until the relevance to field conditions is confirmed and the regulatory applications are clarified B. Continue the current experiments while alerting the industry and other stakeholders of preliminary findings C. Shut down all plants with similar switchgear 6
Risk assessment purpose Power HEAF Generation Accident? Loss Probability Potential Outcomes FA1 N None pA1 FA2 Y Major pA2 FB1 N Minor pB1 S
FB2 Y Major pB2 Notes: FC1 N Major pC1
- Outcomes are simplified for illustration
- Probabilities and consequences for Option B depend on industry response to alert
- Probabilities and consequences for Option C recognize possibility of accidents while FC2 Y Major pC2 shutdown 7
Risk assessment purpose Observations
- Worst case (a HEAF-induced Risk assessment is a set of accident and major losses of tools, not an end in itself.
power) is possible (albeit The limited resources unlikely) for all three options available should be spent to
- Selection of the best alternative generate information that requires consideration of likelihood and consequence, helps risk managers to i.e., risk choose the best possible Risk assessment is a useful course of action among the tool for decision support available options.
The scope, approach, level of detail, etc. of the risk - National Research Council, 1994 assessment depend on the needs of the decision problem 8
Risk definition Dictionary Definitions of Risk
- 1. The chance of injury, damage, or loss; a dangerous chance; a hazard.
- 2. In insurance, (a) the chance of loss; (b) the degree of probability of loss; (c) the amount of possible loss to the insuring company; (d) a person or thing with reference to the risk involved in insuring him or it; (e) the type of loss that a policy offers (e.g., fire risk).
=> Consideration of likelihood OR consequences 9
Risk definition Common Scalar Definition Risk x
- Includes effects of likelihood and consequences
- Purely quantitative
- Enables simple scalar comparisons
- Average value, equates
- Low-probability/high-consequence
- High-probability/low-consequence 10
Risk definition Low-Probability/High Consequence vs. High-Probability/Low Consequence National Transportation Safety Board, 2016.
(http://www.ntsb.gov/investigations/)
From Traffic Safety Facts: Research Note, U.S. Dept. of Transportation, 2016. 11
Risk definition The Farmer Curve Adapted from Farmer, F.R., Reactor safety and siting: a proposed risk criterion, Nuclear Safety, 8, 539-548(1967).
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Risk definition The Triplet Definition of Risk (Kaplan and Garrick, 1981)
Risk {si , Ci , pi }
Features
- Vector, not scalar
- Qualitative and
- What can go wrong?
quantitative
- What are the consequences?
- Differences across
- How likely is it? accident spectrum 13
Risk definition Other Organizational Definitions
- International Atomic Energy Agency (referring to radiation risks):
detrimental health effects of radiation exposure (including the likelihood of such effects occurring) (IAEA SF-1, 2006)
- Department of Homeland Security: the potential for an adverse outcome assessed as a function of threats, vulnerabilities, and consequences associated with an incident, event, or occurrence (DHS Risk Lexicon, 2010)
- National Aeronautics and Space Administration: the potential for performance shortfalls, which may be realized in the future, with respect to achieving explicitly established and stated performance requirements (NASA/SP-2010-576, 2010)
- Office of Management and Budget: the effect of uncertainty on objectives (OMB Circular A-123, 2016)*
- Text generally refers to risks as sources of risk 14
Risk-informed decision making Deliberative Decision Making NUREG-2150 15
Risk-informed decision making Naturalistic Decision Making
- Recognition-Primed Decision model
- Pattern recognition
- Mental simulation
- Go with first match
- Continue until change is required
- Risk consideration: Will it work?
- Not limited to field G.A. Klein, A recognition-primed decision (RPD) model of rapid decision making, in Decision Making in Action: Models and Methods, G.A. Klein, et al., eds. 1993.
applications 16
Risk-informed decision making Risk-Based vs Risk-Informed Not Not
- Accidents are rare events OK OK Empirical data are sparse Models play central role
- SECY-98-144: A risk-informed limit other approach to regulatory decision- line factors making represents a philosophy whereby risk insights are considered together with other factors to establish requirements that better focus licensee and regulatory attention on design and OK OK operational issues commensurate Risk- Risk-with their importance to public Based Informed health and safety.
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Allocating Resources: Risk-Based?
U.S. Mortalities (2016) 23%
26%
2% S.L. Murphy, et al., "Mortality 2% in the United States, 2017,"
2%
3% NCHS Data Brief, Number 22%
4% 328, November 2018.
5%
5% 6%
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Or Risk-Informed?
U.S. Mortalities (2016)
Other Heart Disease 23%
26%
S.L. Murphy, et al., "Mortality Suicide 2%
2% in the United States, 2017,"
2%
Kidney Disease 3%
22%
NCHS Data Brief, Number 328, November 2018.
Influenza & Pneumonia 4%
5%
Diabetes 5% 6%
Cancer Alzheimer Disease Stroke Chronic Lower Respiratory Diseases Accidents 19
Risk-informed decision making Other Factors for NPP RIDM Defense-in-depth Current regulations Safety margins Integrated Decision Making Monitoring Risk Adapted from RG 1.174 20
Risk-informed decision making RIDM Implications for Risk Assessment
- Decision support
- Use science, but aim is not science
- Subject to economic and time constraints
=> needs to be good enough
- Decisions can be insensitive to some aspects
- Bounding analyses can be sufficient
- Risk is one of a number of inputs to RIDM
- Need to characterize uncertainties
- Risk considerations
- Despite best efforts by designers, operators, etc., risk is never zero => need to search for scenarios that can challenge assumptions
- Recognize weaknesses and implicit assumptions in possibilistic/worst case approaches 21
Risk-informed decision making Risk Assessment vs. Risk Management National Research Council, Understanding Risk: Informing Decisions in a Democratic Society, National Academy Press, 1996.
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