ML19011A422
| ML19011A422 | |
| Person / Time | |
|---|---|
| Issue date: | 01/16/2019 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| Nathan Siu 415-0744 | |
| Shared Package | |
| ML19011A416 | List:
|
| References | |
| Download: ML19011A422 (25) | |
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RIDM in the Nuclear IndustryLecture 1-21 Key TopicsRange of stakeholders and perspectivesKey policy drivers for risk-informed regulationRange and types of risk-informed applicationsGeneral characteristics of nuclear power plant (NPP) risk-informed decision making (RIDM)General characteristics of NPP probabilistic risk assessment (PRA) and role in RIDM2Overview ResourcesFederal Register, Vol. 60, p. 42622 (60 FR 42622), August 16, 1995.DecisionmakingNUREG-2201, U.S. Nuclear Regulatory Commission, September 2016.Organisationfor Economic Co-Development of Probabilistic Safety Assessment: An Overview of the NEA/CSNI/R (2012)11, Nuclear Energy Agency, Paris, France, 2012, (Available from: http://www.oecd-nea.org/nsd/docs/indexcsni.html)Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Regulatory Guide 1.174, Revision 3, January 2018. (ADAMS ML17317A256)3Overview Other ReferencesOperation of Nuclear Power Plants; Policy Statement; Correction Federal Register, Vol. 51, p. 30028 (51 FR 30028), August 21, 1986.-https://www.nrc.gov/about-nrc/regulatory/risk-informed/rpp.html-Informed Regulation at the U.S. Nuclear -Informed Decision-Reactor Regulation Office Instruction LIC-504, Revision 4, June 2, 2014. (ADAMS ML14035A143)F.E. Haskin, A.L. Camp, S.A. Hodge, and D.A. Powers, NUREG/CR-6042, Revision 2, March 2002.4Overview Stakeholders in NPP RIDM -Organizational Stakeholders can:have a role (including support) in decision making processbe affected by decisionsStakeholder roles, beliefs, and backgrounds, can affect views on risk assessment as well as views on the appropriate use of risk information in support of decision making5IndustryRegulatorsOther Government AgenciesTechnical Support OrganizationsConsensus Standards OrganizationsInternational OrganizationsAcademiaNon-Governmental OrganizationsGeneral PublicStakeholders Stakeholders in NPP RIDM -Functional 6StakeholdersDevelopersAnalysts/ReviewersUsers External Flooding : A Really Big PictureSparse data and concerns with extrapolation => mechanistic analysisDaunting scaleRegional analysisHuman actions Besides flooding level: duration, debris, dynamic forces, warning timeMulti-site impactsorganizations7Stakeholders Policy Driver: Safety Goal Policy Statement (1986)Qualitative health objectivesIndividuals should bear no significant additional risktechnologies, should not be a significant addition to other societal risksQuantitative health objectives (QHOs)Prompt fatality risk for an average, nearby individual < 0.1% risks from all other accidentsCancer fatality risk for population in area) < 0.1% cancer fatality risks from all other causesSurrogate risk measuresPrompt fatality: LERF < 10-5/ryLatent cancer: CDF < 10-4/ry8Applications Policy Driver: PRA Policy Statement (1995)Policies:Increase use of PRA technology to the extent supported by the state of the art and data.Complement deterministic approach, support defense-in-depth philosophyReduce unnecessary conservatism, support additional requirements as appropriateAnalyses should be as realistic as practicable; data should be publicly available for reviewsubsidiary objectivesExpected Benefits:(1)Considers broader set of potential challenges (2)Helps prioritize challenges(3)Considers broader set of defenses9Applications RIDM NRC Examples10Applications 11ApplicationsRuleRequires monitoring of in-scope SSC performance to identify and address maintenance related issuesassess and manage the increase in risk that may result from the proposed maintenance activitiesRisk-informed and performance-basedOutcome: widely viewed as a success NEI: Improved equipment reliability and plat performanceproblems so as to prevent them from becoming *Seehttps://allthingsnuclear.org/dlochbaum/nrcs-nuclear-maintenance-rule Changes in Plant Licensing Basis (RG 1.174)Voluntary changes: licensee requests, NRC reviewsSmall risk increases may be acceptableChange requests may be combinedDecisions are risk-informed12Applications Reactor Oversight ProgramInspection planningDetermining significance of findingsCharacterize performance deficiencyUse review panel (if required)Obtain licensee perspectiveFinalizePerformance indicators13ApplicationsCDF < 1E-6LERF < 1E-71E-6 < CDF < 1E-51E-7 < LERF < 1E-61E-5 < CDF < 1E-41E-6 < LERF < 1E-5CDF > 1E-4LERF > 1E-5CDF = Core damage frequencyLERF = Large early release frequency Accident Sequence Precursor ProgramProgram recommended by WASH-1400 review group (1978)Provides risk-informed view of nuclear plant operating experienceConditional core damage probability (events)Increase in core damage probability (conditions)Supported by plant-specific Standardized Plant Analysis Risk models14ApplicationsLicensee Event Reports 1969-2017(No significant precursors since 2002)significant(ADAMS ML18130A856)
NPP RIDM Industry ExamplesRisk-informed Licensing Amendment Requests (LARs)Severe Accident Mitigation Alternatives (SAMA)Outage planningEnterprise Risk ManagementAdvanced reactor designs15ApplicationsOMB Circular A-123, 2016 NPP RIDM International ExamplesPeriodic Safety ReviewsPlant improvementsDemonstrating acceptable safety levels16Applications RIDM Process17NUREG-2150NPP RIDM Licensing Basis Changes RG 1.1741818Change meets current regulations unless it is specifically related to a requested exemptionChange is consistent with defense-in-depth philosophyMaintain sufficient safety marginsProposed changes in risk are small and are consistent with the Goal Policy StatementUse performance measurement strategies to monitor changeIntegrated Decision MakingNPP RIDMU.S. Nuclear Regulatory Commission, Risk Assessment in Risk-Informed Decisions on Plant Specific Changes to 1.174, Revision 3, 2018.
CDF Acceptance Guidelines RG 1.1741910-510-610-510-4CDFCDFNPP RIDM Before tripAfter trip1 hour1 day1 week3300 MWt260 MWt50 MWt15 MWt7 MWtNuclear Design 101: How Things WorkelectricityChain reaction controlled/stopped by control rodsHeat generation continues after chain reaction is stopped 20NPP RIDMAdapted from: https://www.nrc.gov/reactors/pwrs.html Nuclear Power Plant Design FeaturesGeneral Design Criteria (10 CFR Part 50, Appendix A)Key safety principlesDefense-in-depthSingle failure criterion and redundancyDiversityRobust structures, separation21NPP RIDMAdapted from: https://www.nrc.gov/reactors/pwrs.html Core Damage Frequency (CDF)22Adapted from: https://www.nrc.gov/reactors/pwrs.htmlFrom NUREG-2122:Core Damage: Sufficient damage that could lead to a release of radioactive material from the core that could affect public health.Frequency: The expected number of occurrences of an event or accident condition expressed per unit of time.**Lecture 3-1 will provide a more precise mathematical definition.NPP RIDM Analysis Challenges and ImplicationsMultiple safety systems and barriers (physical and operational) => multiple failures required to cause core damage => need to treat large numbers of possible combinations of eventsEmpirical data are sparse => need to bring in other forms of evidence (e.g., model predictions, expert judgments)Accidents generally involve multiple phenomena => need to integrate multiple technical disciplinesNeed systematic, scrutable approach to handle these complexities with appropriate treatment of uncertainties23PRA and RIDM Probabilistic Risk Assessment (PRA)Process/model(s) to answer the risk triplet questionsA form of systems analysisExpresses uncertainties in terms of probabilitiesCurrent practices for NPPs tailored to addressRare eventsSparse dataCombinations of failures (including dependencies)Multiple phenomena24PRA and RIDM*The distinction can be arguable on philosophical grounds but has proven useful in practice. See Lecture 3-1 for further discussion.
NPP PRA Distinguishing CharacteristicsLevelsLevel 1 (core/fuel damage)Level 2 (radioactive release)Level 3 (offsite consequences)HazardsInternal events (hardware, human, LOOP)Operating ModeAt powerLow power/shutdownSourcesCoreSpent fuel poolOther (e.g., dry cask storage)25HazardsInitiatingEventsPlant DamageStatesSourceTerm GroupsReleaseCategoriesOffsiteConsequencesLevel 1Level 2Level 3PRA and RIDM