ML17174B290

From kanterella
Jump to navigation Jump to search
2017 NEI Risk-Informed Regulation and Fire Protection Fire Forum Slides
ML17174B290
Person / Time
Issue date: 06/26/2017
From: Michael Cheok, Mary Drouin, Jonathan Evans, Anders Gilbertson, Matthew Humberstone, Markhenry Salley, Brett Titus, Jennifer Whitman
NRC/NRR/DRA, NRC/RES/DRA
To:
Nuclear Energy Institute
Frumkin D
References
Download: ML17174B290 (146)
v • d • e


Text

NRC Support of Risk-Informed Regulation NEI Risk Informed Regulation Forum June 26, 2017 Mike Cheok Director Division of Risk Analysis Office of Nuclear Regulatory Research

=

Background===

Commission Policy statement on use of PRA Approach for using PRAs in plant specific changes (RG 1.174 and application specific RGs)

Approach for determining technical adequacy of PRAs (RG 1.200, NUREG-1855) 2

We are Now More Advanced Analytical improvements support more advanced risk-informed initiatives Risk insights have enhanced reactor safety and improved decision-making Investments in infrastructure, capacity, and methods are underway to address technical and cultural challenges 3

PRA Models Have Improved Industry models have improved in scope, technical adequacy, and level of detail NRC SPAR models have also improved in these areas.

4

Risk Insights have Improved Safety SBO risk reduced Maintenance Rule, NFPA 805, the ROP and risk informed ISI, etc. have also improved safety Insights from Fire PRAs are driving safety improvements Mitigation of beyond design basis equipment, also known as FLEX equipment are now in use 5

The NRC is Reviewing Several Major Risk-Informed Initiatives Tornado Missile Risk Evaluator PRA Method Vetting Panel Technical Specifications Task Force (TSTF) 505:

risk-informed completion times (4b)

TSTF-425: risk-informed surveillance frequencies (5b) 50.69: risk-informed structure, system, or component (SSC) categorization 6

7 Risk-Informed Inservice Inspection 50.69 SSC Categorization 5b, Risk-Informed Surveillance Frequencies NFPA-805, Risk-Informed Fire Protection 4b, Risk-Informed Completion Times Required scope, level of

detail, technical robustness, and plant representation Greater reliance on PRA More flexibility for licensee More complex staff review PRA Must Be Suitable for the Application

NRC is Upgrading the Infrastructure Needed to Support RIDM Facts and Observations (F&O) independent assessment process Improved guidance (e.g., Regulatory Guide 1.174 update)

Interactions with industry to improve LAR consistency and quality 8

We are Collaborating to Improve PRA Realism Improving fire PRA methods Seeking stakeholder input on human error probability estimates and common-cause failure modeling Potential methods for modeling credit of FLEX equipment and RCP seals Enhancing probabilistic flooding hazard analyses 9

We are Improving PRA Capacity in the NRC The NRC Grow Your Own program Support from other NRC Offices and from contractors Risk-Informed Thinking workshops 10

Process Updates to Support a Risk-Informed Culture Enhanced review guidance and office procedures place greater emphasis on using risk insights Greater collaboration between PRA specialists and traditional reviewers 11

Key Documents in Support of Risk-Informed Decisionmaking NEI Risk Informed Regulation Forum June 26, 2017 Mary Drouin, Anders Gilbertson Division of Risk Analysis Office of Nuclear Regulatory Research

OUTLINE Status and Plans for:

RG 1.174, REV. 3

  • Draft published as Draft Guide (DG) - 1285

- Originally published for comment in 2012

  • NRC resumed development of DG in March 2016
  • Revised DG-1285 was published* in April 2017, for a 45-day public review and comment period that concluded on May 22
  • NRC has received and is in the process of resolving public comments 3

RG 1.174, REV. 3

  • Major changes include:

- Enhanced guidance on defense-in-depth (DID)

- Language on large early release frequency for new reactors

- Language on containment performance expectations for new reactors

- A stronger tie to guidance on uncertainty in NUREG-1855

- Language on combining risk results (i.e., risk aggregation)

- Emphasis on acceptance guideline boundaries as gradual transitions

- Language on DID from relevant guidance documents 4

RG 1.174, REV. 3 - NEXT STEPS

  • Aug/Sept 2017: ACRS Subcommittee and Full Committee reviews/meetings
  • February 2018: RG finalized for publication
  • March 2018: Anticipated final issuance of RG 1.174, Revision 3 5

RG 1.200 Provides NRC regulatory position on:

  • Consensus PRA standards and industry PRA programs
  • Demonstrating acceptable PRA used to support a regulatory application
  • Documentation to support a regulatory submittal 6

RG 1.200, REV 2 RG currently endorses:

  • NEI 05-04 (Process for Performing Follow-on PRA Peer Reviews Using the ASME PRA Standard, Rev 2)

NEW AND REVISED STANDARDS AND GUIDANCE

  • Level 2 PRA standard - out for trial use
  • Low Power and Shutdown standard - out for trial use
  • Non-LWR PRA standard - out for trial use
  • Seismic PRA - in ballot process, to be issued as a Code Case
  • Level 3 PRA - in ballot process, to be issued for trial use
  • Advanced LWR PRA standard - expected issuance for trial use in 2017
  • New edition to Level 1/LERF PRA standard - expected in 2018 8

NEW AND REVISED STANDARDS AND GUIDANCE (Continued)

  • NEI Peer Review Guidance 12-13 on external hazards PRA
  • Appendices to NEI Peer Review Guidance addressing resolution of Facts and Observations (F&Os) - issued Feb 2016
  • NEI guidance 16-04 on new methods - draft issued Feb 2016 (update to be issued in mid-to-late summer 2017) 9

RG 1.200, REV 3 - PATH FORWARD

  • Issue a series of Draft Guides (DG)

- As standards are issued, DG will be issued providing a draft staff position

  • Public review and comment period would be open over the entire time
  • Allows for trial use of standards to be piloted before finalizing RG
  • Incorporate lessons learned from past decade
  • Rev 3 tentative schedule

- Draft Guide: 2018

- Final RG: 2019 10

Best Practices and Common Pitfalls Division of Risk Assessment Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission

2 Best Practices

  • Looking at previous submittals (e.g.

coordinating committees)

  • On-going communication with NRC staff
  • Audits/Observations

3 Best Practices

- Familiarizes staff with licensees strategy and goals for LAR

- Allows for clarifications to reduce acceptance review pitfalls

  • Looking at previous submittals (e.g.

coordinating committees)

- Helps licensee anticipate and address common RAIs

- Minimizes deviations from acceptable approaches/templates

4 Best Practices

  • On-going communication with NRC staff

- Having PRA personnel engage NRC staff

- Raises chances of efficient resolution to RAIs (i.e. reduces need for multiple RAIs)

  • Audits/Observations

- Assist with NRC review on complex or pilot reviews

5 Common Pitfalls with PRA reviews

  • Peer-reviewed PRA
  • F&Os
  • Applicability of External Hazards
  • Scope of review

6 Common Pitfalls with PRA reviews

  • Outdated Peer-reviewed PRA

- Peer-Reviewed internal events needed to support all applications

  • Complex sequence of gap assessment(s) and focused scope peer review(s) undesirable

- Peer-Reviewed Fire PRA should be used when one exists

- All hazards require technically adequate disposition consistent with application

7 Common Pitfalls with PRA reviews (contd)

  • F&Os

- Resolution of all F&Os should summarize technical issue

- Fixing documentation should summarize method that was documented

- Licensee summarization of F&O sometimes too short and hard to interpret

- Reported resolution should refer to application specific needs, if inapplicable need explanation about why inapplicable.

8 Common Pitfalls with PRA reviews (contd)

  • F&Os (contd)

- F&Os can only be closed out (and excluded from NRC LAR submittal) by:

  • A peer-review
  • F&O closure review per the acceptable process

- F&Os resolved with an upgrade still need a peer review

- Potentially obviates the need for a more in-depth review

9 Common Pitfalls with PRA reviews (contd)

  • Applicability of External Hazards

- Discussing IPEEE without addressing new hazard information since completing IPEEE

- Addressing impact on baseline risk without addressing impact on application specific change-in-risk

10 Common Pitfalls with PRA reviews (contd)

  • Scope of review

- Providing inapplicable or unclear risk results (e.g. providing delta risk using average maintenance instead of incremental risk for one-time TS changes)

- Providing multiple sensitivity study results without an comprehensive final result

- Deviating from acceptable approaches without fully describing new approach

11 Looking towards Future

  • Applications with greater reliance on PRA (NFPA-805, TSTF-505) warrant step improvement in PRA, PRA review, and documentation of PRA review.
  • Post approval PRA maintenance for living programs

- Methods new to licensee/plant need peer-review

- Methods new to industry need NRC acceptance

Review Process for Risk-Informed TSTF Reviews Jennifer Whitman, Acting Chief Technical Specifications Branch Office of Nuclear Reactor Regulation 2017 NEI Risk-Informed Regulation and Fire Protection Forum

There have been 8 risk-informed technical specification initiatives.

1 End States 5

Surveillance requirements 2

Missed Surveillances 3.0.3 6

Entry into 3.0.3 3

Flexibility in Mode Restraints 7

Non-TS Operability Requirements 4

Completion Times 8

Criterion 4 of 50.36 See SECY 15-0135, Item 5, ML15243A474 2

Initiative 4b, will be used for the context of this discussion.

1 End States 5

Surveillance requirements 2

Missed Surveillances 3.0.3 6

Entry into 3.0.3 3

Flexibility in Mode Restraints 7

Non-TS Operability Requirements 4

Completion Times 8

Criterion 4 of 50.36 3

The more complex travelers have included industry report to support them. Example 4b 4

Following approval of the report, a traveler is submitted with a model LAR.

5

The NRC will develop a SE for the traveler and a model SE for plant LARs.

6

Finally, the NRC will develop a plant specific SE for each LAR.

7

Both the traveler review and LAR review process address risk-informed submittals.

Traveler Review LIC-600 Under review LAR Review LIC-101 Recently Updated ML16061A451 8

LIC-600 treats risk-information similar to other review areas.

TBD 9

LIC-600 will be issued to include insights related to unsuspending a traveler.

TSTF-505 issued TSTF-505 suspended TSTF-505 revised LIC-600 revision issued 10

Risk related review, per LIC-101, depends on the use of risk information in LAR.

Uses risk-informed guidance, 1.174, 1.177, RG 1.200, 1.201 or 1.205 Sufficient deterministic information, but supplemental risk information is provided Completely consistent with deterministic requirements Risk-informed review Limited risk review No risk review See page 34 of 59 of Appendix B of LIC-101, Revision 5 11

If there is risk information there will be a risk review even for CLIIPs.

Uses risk-informed guidance, 1.174, 1.177, RG 1.200, 1.201 or 1.205 Sufficient deterministic information, but supplemental risk information is provided Risk-informed review Limited risk review Risk review even for consolidated line item improvement program (CLIIPed) changes.

12

Risk-informed technical specification changes remains a priority for the NRC staff.

13

NRC Staff Expectations on PRA Technical Adequacy Documentation in Support of Risk-Informed Applications Division of Risk Assessment Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission

2 Risk-Informed Inservice Inspection 50.69 SSC Categorization 5b, Risk-Informed Surveillance Frequencies NFPA-805, Risk-Informed Fire Protection 4b, Risk-Informed Completion Times Required scope, level of

detail, technical robustness, and plant representation PRA Must Be Suitable for the Application
  • Greater reliance on PRA
  • More flexibility for licensee
  • More complex staff review

3 PRA Technical Adequacy Overview

  • Staff review of

- F&Os

- Application specific key assumptions

- Applications specific (change-in-risk) methods

  • Application Specific guidance documents sometimes provide additional guidance (RG 1.201, NEI 04-10 Revision 1, etc.)
  • Guidance aims to assure the quality and uniformity of staff reviews

4 Internal Events PRA

  • Submit PRA quality information based on RG 1.200, Revision 2

- Peer-Reviewed against 2009 ASME/ANS PRA Standard with RG 1.200 clarifications

  • Submit all peer review F&Os applicable to the parts of the PRA required for the application

- address the impact of those F&Os on the application

5 External Hazards

  • Use of an External Event or Fire PRA

- Licensee should identify hazard contribution to the application

- Use RG 1.200 to support the technical adequacy of the methods

- Submit all F&Os

6 External Hazards (other than fire)

  • Use of non-PRA method for external events

- Submittals would not use RG 1.200 to support the technical adequacy of the methods

- Explanation of contribution of risk of excluded external hazards (both to total and to application change in risk)

  • Demonstration of insignificant contribution or
  • Estimate of bounding contribution

- Individual Plant Examination of External Events generally acceptable to support screening after update to current plant conditions and hazards

7 F&O Closure

  • Original option to conduct a focused or full scope peer review
  • New F&O closure process provides one acceptable option to close F&Os (ML17079A427)

- Plans to incorporate it into the next revision to RG.1200

- NRC is planning to conduct periodic sample audits on licensee

- F&O resolutions containing PRA upgrades cannot be closed by this process

  • Closure process potentially obviates the need for a more in-depth review

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ImprovingFirePRARealismwith QualityResearch MarkHenrySalleyP.E.

Chief,FireandExternalHazardsAnalysisBranch U.S.NuclearRegulatoryCommission June2628,LeMeridienCharlotte,NC markhenry.salley@nrc.gov 301.415.2474

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PurposeofPresentation

  • ProvideHighLevelOverviewofCurrentNRC OfficeofNuclearRegulatoryResearch(RES)

MajorProjectsandtheirPartinImprovingFire PRARealism

  • HighEnergyArcFault(HEAF)GenericIssuewill bediscussedinaseparatepresentation

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC FireResearchPlan TheOfficeofNuclearRegulatoryResearch(RES)iscurrentlydevelopinga 5yearFireResearchPlan Theplandescribesasetofprojectsthatfocusonfiresafetyresearchto ensurerealisminregulatoryguidanceandmethods Theprojectsmainfocusareasare:

fireandelectricalcircuitanalysis,firehazardanalysis,highenergyarcfaults(HEAFs),fire probabilisticriskassessment(PRA)&humanreliabilityanalysis(HRA),trainingandFAQ support NRCiscollaboratingwithEPRIunderaMOUonanumberofprojects Aimtomaximizestakeholderinputonprojectsthroughpublicmeetings andcomments Foradditionalinformationcontact:

TammieRivera,tammie.rivera@nrc.gov U.S.NRC,OfficeofNuclearRegulatoryResearch

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC CircuitAnalysisJACQUEFIREIII

- Harmonizationofrecommendations fromVolume1&2

- Recommendationsontreatmentof

  • Clarificationofterminologyandfigures
  • Justificationforclassificationchanges
  • Multiplespuriousoperations(MSOs)
  • Shortingswitch
  • SpuriousOperationDuration
  • CurrentTransformers

- CurrentlywithNRCpublications

- PresentationwithNEIat2017RIC

  • InformationformsmuchoftheTechnicalBasisforNEI0001Rev.4

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC CurrentTransformerTesting Issue

- Fireinducedopencircuitcausesasecondaryfireinaseparatelocation

[NEI0001,Rev.2,Section3.5.2.1]

Resolution

- Basedonavailableliterature,engineeringprinciples,andexpert judgement,NUREG/CR7150Vol.1recommendednotconsidering failuremodeforCTswithturnsratio1200:5orless

- NRCsponsoredtestingtounderstandiflargerCTratioswereconcern.

[EPRIparticipationandobservation]

- NEIrecommendeddiscontinuingtesting[Item27,ML15279A048]

Results

- NUREG/CR7228,PublishedMay2017

- Nosecondaryfireorpotentialforsecondary firesobserved

- JACQUEFIREusedresultstosupportrecommendation

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC InstrumentationCircuitTesting Issue

- Limitedunderstandingoffireinducedfailuremodesfor instrumentationcircuits[seeNUREG/CR6776]

- PIRTrankedastopresearchpriorityandrecommendedadditional testing Resolution

- LimitedscoperadianttestingatSNLtoadvancestateofknowledge[81 FR80688]

Results

- Signaldecayrangedfrom0tomorethan21minutes

  • QuestionstheassumptionsusedforInstrumentCircuitsFireDamage

- Draftreportunderreview HowdotheseresultsimpactMCRFireHumanReliability Analysis?

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ElectricalCableFireRetardantCoatings

  • Issue

- Unclearguidanceondelayaddedbycoatingforignition andfunctionality(i.e.,damage)[NUREG/CR6850/EPRI 1011989]

  • Resolution

- 1)Literaturesurvey,2)scopingtests,3)fullscaletesting

  • Results

- InformationtosupportCableTrayIgnitionFAQ

- Analysisofdataunderway

- Reportestimatedlate2017

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ContactInformation GabrielTaylor,PE T:301.415.0781 E:gabriel.taylor@nrc.gov

  • JACQUEFIRE
  • CurrentTransformer
  • Instrumentation FelixGonzalez,PE T:301.415.2413 E:felix.gonzalez@nrc.gov
  • CableCoating

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC RESTechnicalSupporttoNRR

  • Issue

- IndustrysubmitsFrequentlyAskedQuestions(FAQs)andother fireanalysismethodstoNRRforreview

  • Resolution

- OngoingFAQReviews

  • 1)CableTrayFires,2)VEWFDS,3)TransientWeightingFactors, 4)HEAFNonSuppression,5)MaintainingFrequencyBinsApportioning

- VettingPanelSupport

  • 1)FireLocationFactor,2)TransientsFires,3)LiquidSpillHRR
  • Results

- SupportdevelopmentofFAQclosureguidance

- Supportreviewandassessmentofindustryreportssubmittedto vettingpanel

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ImprovedHeatReleaseRate(HRR)

Guidance

  • Issue

- NUREG/CR6850(EPRI1011989)HRRguidance,developedfrom limitedexperimentaldata,canleadtosomeoverlyconservative firePRAresults

  • Resolution

- JointworkwithEPRI

  • ElectricalEnclosureHRR,
  • ObstructedPlumeMethodology,
  • PumpsandMotorsHRR,
  • CabinettoCabinetPropagation,
  • Results

- RACHELLEFireIIReportestimatedlate2017

- TransientsHRRReportestimatedmid2018

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC FIREPRARealism

  • Issue

- FirePRAscanbemademorerealistic

  • Resolution

- Identifycontributorstopotentialoverconservatism

- Explorenew/improvedmethodsforcouplingfire frequencies,HRRdistributions,firegrowthprofiles, andfiredetectionandsuppressioneffectiveness

- Develop/Improvetheassociatedtools,methods,and data

  • Result

- UpdatetoEPRI1011989,NUREG/CR6850

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC UpdatetoNUREG/CR6850 NUREG/CR6850FirePRAMethodologywaspublishedin2005 Multiplesourcesneedtobeconsolidationinordertoupdatethe guidancedocumenttoreflectthemostrecentmethods,tools,anddata

- Supplement1toNUREG/CR6850(17FAQspublishedin2010)

- MultipleRecentFrequentlyAskedQuestions(FAQs)

FAQ130005 CableFiresSpecialCases:SelfIgnitedandCausedbyWeldingandCutting FAQ130004 ClarificationsonTreatmentofSensitiveElectronics FAQ130006 ModelingJunctionBoxScenariosinaFirePRA FAQ140009 TreatmentofWellSealedMCCElectricalPanelsGreaterthan440V Etc...

- MultipleNew NUREGs NUREG2169 UpdatedFireEventsDatabase NUREG2180 DeterminingtheEffectiveness,Limitations,andOperatorResponsefor VeryEarly WarningFireDetectionSystems NUREG2178RefiningAndCharacterizingHeatReleaseRatesFromElectricalEnclosuresDuringFire NUREG/CR7150JointAssessmentofCableDamageandQuantificationofEffectsfromFire Etc...

StartPlanningUpdate/RevisionEPRI1011989NUREG/CR6850

- ThiswouldbeaMajorSteponImprovingFirePRARealism

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ContactInformation DavidW.Stroup,PE T:301.415.1649 E:david.stroup@nrc.gov

  • TechnicalSupporttoNRR
  • HRRGuidance NicholasMelly T:301.415.2392 E:nicholas.melly@nrc.gov FirePRARealism NUREG/CR6850

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC RealisminFireHRA NUREG/CR6850didnotprovideguidanceforperformingdetailedHRA NUREG1921,EPRI/NRCRESFireHRAGuidelinesfilledthisgap Guidanceaddressesfirespecific impactsonoperators(i.e.,morerepresentative&realisticforfire events)

NUREG1921didnotprovideguidanceforperformingdetailedHRAformain controlroomabandonment(MCRA)scenarios FirePRAsresultscouldbeconservativewithoutajustifiablewaytocreditoperatoractionsin MCRAscenarios,especiallylossofcontrol(LOC)scenarios FireHRAcouldbeinconsistentwithasoperatedplantifinfluencingfactorsonoperator reliabilityinMCRAscenariosarenotappropriatelyunderstood EffectivefixesonhowtobettersupportoperatorsrespondingtoMCRAscenarioscannotbe developedwithoutaqualitativeHRAthataddressestherealimpactsoftheremote shutdowndesign,MCRAprocedures,communicationstrategies,etc.

NUREG1921,asstateoftheartinHRA&withdevelopmentofguidancefor operatoractionsoutsidetheMCR,alsohasbeenusedasthebasisforother advancesinHRA,suchas:

EPRIsApproachtoHRAforExternalEventsWithaFocusonSeismic,(EPRI3002008093, 2016)

NRC/RESsLevel2HRAapproachforL3PRAproject

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC CurrentFireHRAResearch:MCRA

  • NRC/RESisworkingcollaborativelywithEPRIunderMOU toaddressfireHRAforMCRAscenarios
  • Thisworkisbeingdeveloped

- usingthecombinationofNRCs&industrys experienceinHRA&fireHRA/PRA

- withanunderstandingoflatestavailablepsychological research&literature

- Withinputfrompeerreviews,NRR,NRCsAdvisory CommitteeonReactorSafeguards(ACRS)PRA Subcommittee

- TestingatNPPsitesisbeingplanned(whichis importantforrealism!)

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC FireHRAResearchfor MCRAScenarios Results

  • Twoproductsareplanned:

- Supplement1toNUREG1921:Qualitative HRA GuidanceforMCRAScenarios

- Supplement2toNUREG1921:HRAQuantification GuidanceforMCRAScenarios

  • Inaddition,updatedguidancetoNUREG/CR6850 onmodelingMCRAscenariosisprovidedin Supplement1
  • Foradditionalinformation,pleasecontact:

- Dr.SusanE.Cooper,Sr.Reliability&RiskEngineer, NRC/RES/DRA/HFRB,Susan.Cooper@nrc.gov,

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC FirePRATraining NRCRESandEPRIcontinuetoprovidespecializedtrainingsince2005 FiveModules: IFirePRAII ElectricalAnalysisIII FireAnalysisIV FireHRA V AdvancedFireModeling Modulesofferedtoallowparticipantstotake4modulesperyear NRCHostatWhiteFlintHeadquarters ElectricalAnalysis,FireAnalysis,&AdvancedFireModeling EPRIHostatEPRICharlotteNC FirePRA&FireHRA Approximately65participantsregisteredfor2017 For2017workshopinformationvisit https://www.nrc.gov/publicinvolve/conferencesymposia/eprifirepracourse/eprifirepracourse info.html Futureconsiderations:

AnnuallypublishaNUREG/CPwithupdatedtrainingmaterialssoindividualswhotookthetraining inpreviousyearswillhaveaccesstothelatestinformation Offerwebinarsformodules Foradditionalinformationcontact:

TammieRivera,tammie.rivera@nrc.gov U.S.NRC,OfficeofNuclearRegulatoryResearch

Pre-decisional Information - for internal use only Seismic PRAs -

10CFR50.54(f) Responses Brett Titus Nuclear Regulatory Commission June 28, 2017

Objectives

  • Provide a brief history of NTTF Recommendation 2.1: Seismic and the 50.54(f) request for information
  • Describe the purpose and scope of the project
  • Explain the process and level of effort associated with the task 2

=

Background===

  • March 11, 2011 - Earthquake and subsequent tsunami impact Fukushima Daiichi nuclear power plant
  • July 12, 2011 - Near Term Task Force report recommendations (ML111861807)
  • March 12, 2012 - NRC issues 50.54(f) letter requesting licensees to reevaluate seismic hazards using latest methods and guidance (ML12053A340) 3

Rec 2.1-Background NTTF 2.1 - Focused Eval or Integrated Assessment/Seismic PRA If the design basis does not bound reevaluated hazard: Licensees determine the effectiveness of the existing DB and any other planned or installed features for protection and mitigation against the reevaluated hazard.

NTTF 2.1 - Hazard Reevaluations Licensees reevaluate hazard based on present day guidance/methods used to define the design basis for new reactors.

Regulatory Actions NRC staff determines whether additional regulatory actions are necessary to provide additional protection against the updated hazards NTTF 2.1 - Interim Actions/Expedited Approach If the design basis does not bound reevaluated hazard: Licensees evaluate the need for interim actions while the longer-term integrated assessment is performed.

PHASE 1: Information Gathering PHASE 2:

Regulatory Decision Making 4

Screening, Prioritization and Implementation Guidance (SPID)

Endorsed February 2013

  • Guidance for licensees to address the 50.54(f) letter in a uniform, technically sound, optimized way
  • Provides guidance on hazard evaluation, screening, and elements of seismic PRA 5

Contents of SPID

1. Purpose and Approach
2. Seismic Hazard Development
3. GMRS Comparisons and Screening of Plants
4. Seismic Hazard and Screening Report
5. Prioritization (Schedule)
6. Seismic Risk Evaluation
7. Spent Fuel Pool Evaluation Four appendices to SPID with detailed guidance on special topics 6

Seismic - High Exceedance 7

Seismic Evaluations

  • GMRS SSE for frequencies 1-10 Hz and > 10 Hz &

GMRS > SSE by 2x or more = Seismic PRA needed for 18* plants

  • Seismic PRA final determinations and schedule

- Letter dated Oct. 27, 2015 (ML15194A015)

- Elements: reevaluated hazard, fragility, plant response

- Review: Verify completeness and suitability; assess SCDF/SLERF and importance measures; and, if necessary, screen potential safety improvements 8

Seismic PRA Dates January 2017 Jan 2018 Jan 2019 January 2020 Mar 2017 Vogtle Sept 2017 Beaver Valley Diablo Canyon Mar 2018 Peach Bottom North Anna Sep 2018 VC Summer Mar 2019 Columbia Robinson Sep 2019 Palisades Jun 2017 Watts Bar Indian Point 2 Dec 2017 Callaway Pilgrim Jun 2018 DC Cook Indian Point 3 Dec 2018 Oconee Jun 2019 Dresden Dec 2019 Browns Ferry Sequoyah 9

Seismic PRA Submittals

  • Licensees prepare their Seismic PRA

- Seismic Hazard

- Seismic Fragility

- Systems/Accident Sequences

- Risk Quantification

  • Seismic PRA is Peer Reviewed using ASME/ANS PRA Standard (RA-Sa-2009)
  • Deltas between the SPID approach and the ASME/ANS Standard (SPID Section 6.6.2)
  • Peer Review assesses the adequacy of methodologies and their implementation (SPID Section 6.7 )

10

Seismic PRA Reviewer Checklist

  • Provides specific staff guidance on 16 topics

- SPID contains specific guidance which is either prescriptive or different than the Standard

  • Staff guidance for each Seismic PRA Supporting Requirement

- Clarifies governing requirement when there are differences between the Standard and the SPID

- Relies on peer review findings (internal events and seismic) to balance the need for a detailed review of the Seismic PRA model by the staff

  • NEI Comments received and dispositioned (ML17041A329) 11

SPRA Reviewer Checklist

  • Intended to ensure appropriate scope, consistency, and focus during NRCs Seismic PRA quality review
  • Maintains fidelity of review with endorsed SPID guidance
  • Aids in documenting the staffs review findings, including any deviations, deficiencies, and resolutions
  • Does not represent additional guidance or interpretation for the licensee 12

Rec 2.1-Background NTTF 2.1 - Focused Eval or Integrated Assessment/Seismic PRA If the design basis does not bound reevaluated hazard: Licensees determine the effectiveness of the existing DB and any other planned or installed features for protection and mitigation against the reevaluated hazard.

NTTF 2.1 - Hazard Reevaluations Licensees reevaluate hazard based on present day guidance/methods used to define the design basis for new reactors.

Regulatory Actions NRC staff determines whether additional regulatory actions are necessary to provide additional protection against the updated hazards NTTF 2.1 - Interim Actions/Expedited Approach If the design basis does not bound reevaluated hazard: Licensees evaluate the need for interim actions while the longer-term integrated assessment is performed.

PHASE 1: Information Gathering PHASE 2:

Regulatory Decision Making 13

Depth of Review

  • Review depth is commensurate with safety implications of a beyond design basis event and associated risk
  • Review time dependent on:

- Quality of submittal

- Number and significance of peer review findings

- Uniqueness/departure from guidance and accepted methods

- Plant-specific relationship to actionable threshold 14

Phase 2 Decision-making SPRA Review Flowchart Senior Management Review Panel No further regulatory actions Backfit consideration is warranted SPRA Tech Review Board Recommend Plant as Group 1, 2, or 3 Group 1: Regulatory action not warranted Group 2: Regulatory action should be considered under backfit provisions Group 3: Regulatory action may be needed, but more thorough consideration is needed first Draft Recommendation for TRB Consideration Provide Status Updates: Prior to Issuing RAIs, Completion of Review Stage 2, and Completion of Review Stage 3 SPRA Tech Review Team (typ)

Additional Information Needed from Staff or Licensee 15

Senior Management Review Panel

  • Phase 2 Decision-making Guidance Memorandum (ML16237A103)
  • NRR Division Directors

- Division of Japan Lessons-Learned (JLD or responsible division)

- Division of Risk Assessment (DRA)

- Division of Operating Reactor Licensing (DORL) 16

SPRA Technical Review Board

  • Three management/senior-level staff experts with diverse backgrounds and specialties
  • Provide consistency across the review teams

- Questions/RAIs

- Application of guidance and thresholds

- Responsible for recommendation to Senior Management Review Panel (SMRP) 17

Seismic PRA Technical Review Team

  • Diverse team with specialized skillsets and areas of responsibility

- Technical Team Lead (Project Manager)

- Seismic Hazard Reviewer (Hazard)

- Civil/Structural/Mechanical Reviewer (Fragility)

- Plant Response Reviewer (Risk) 18

Planned Flow of Review

  • Stage 1 (approx. 1 month)

- Submittal is received and distributed to team

- Team kickoff meeting

- Read through submittal and evaluate completeness

- Provide feedback to Tech Team Lead 19

Planned Flow of Review

  • Stage 2 (approx. 5 months)

- Work to complete SPRA Checklist

- Team discussion including potential questions

- Meet with Seismic PRA TRB (if questions are needed)

- Review responses to questions (as necessary)

- Provide completed Seismic PRA Checklist (and other input as necessary) to Tech Team Lead

- Meet with Seismic PRA TRB 20

Planned Flow of Review

  • Stage 3 (as directed by Seismic PRA TRB)

- More detailed investigation

- More dialogue (questions/answers) with licensee

- Provide additional input to Tech Team Lead

- Meet with Seismic PRA TRB 21

Planned Flow of Review

  • NRC will prepare a response letter to licensee informing them of the SMRPs decision and next steps, if any 22

Ongoing Review Effort

  • Peer Review Observations
  • Vogtle Electric Generating Plant Submittal (ML17088A130)

- Low SCDF/SLERF

- 128 Pages

- 10 Not Met or CC-I Supporting Requirements

  • April submittal - roughly halfway through review
  • Very useful Checklist Crosswalk summary (Best Practice) 23

Questions?

Brett Titus Sr. Project Manager NRC/NRR/JLD Brett.Titus@nrc.gov 301-415-3075 24

Acronym List PRAs - Probabilistic Risk Assessments CFR - Code of Federal Regulations NTTF - Near Term Task Force EPRI - Electric Power Research Institute GMRS - Ground Motion Response Spectrum SSE - Safe Shutdown Earthquake SCDF - Seismic Core Damage Frequency SLERF - Seismic Early Release Frequency NEI - Nuclear Energy Institute ASME - American Society of Mechanical Engineers ANS - American Nuclear Society RAI - Request for Additional Information 25

1 Crediting Mitigating Strategies in Risk-Informed Decision Making Matt Humberstone Ph.D.

Reliability and Risk Analyst PRA Operations and Human Factors Branch Division of Risk Assessment Office of Nuclear Reactor Regulation June 28, 2017

2 OBJECTIVE

  • Project History

- Interactions

  • Areas of Credit

- Recent Activities

- Agency Interactions (Regions, RES, NRR)

  • Communications
  • Path Forward

3 Project History

  • Fukushima orders required strategies to maintain/restore core cooling, containment, and spent fuel pool cooling
  • Licensees installed equipment can be utilized for multitude of uses beyond the orders (outages, defense-in-depth)
  • Mitigating Strategies (MS) could provide added safety enhancements The NRC wants to encourage safety enhancements Need to provide proper regulatory footprint

4 Overall Approach

  • Industry

- Developed tiered approach to crediting portable equipment

- Guidance in NEI 16-06

- NRC has engaged

  • NRC

- Identified areas of application

- Following submittals

- Engage with Industry

5 Interactions with NEI NEI 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making (ML16286A297) (August, 2016)

- Tier 1: Qualitative assessment

- Tier 2: Semi-quantitative streamlined assessment

- Tier 3: Full PRA (RG 1.200 compliant) (new section when submitted)

Letter from NRR Office Director (ML16167A034) (August, 2016)

- Tier 1 and Tier 2

- Listed areas of additional staff focus NRR staff has reviewed Tier 3 of NEI 16-06

- Developed a publicly available internal memo (ML17031A269)

- Highlighted some possible concerns

6 Areas of Potential Credit Incident Response (Management Directive 8.3)

Significance Determination Process (SDP)

Accident Sequence Precursor (ASP) Program Maintenance Rule 10 CFR 50.65 Notices of Enforcement Discretion (NOEDs)

License Amendment Requests Qualitative/Quantitative Credit Mitigating Systems Performance Indicator (MSPI)

Security Target Sets / Force on Force / EALs Regulatory Analysis - Rulemaking Issue Resolution Generic Issue Resolution

7 SRA Counterpart meeting - October 2016 and May 2017 Inspector Newsletter article - October2016 and April 2017 Deputy EDO and RA briefing - April 2017 NRC Reporter article - April 2017 RIC Session -March 2016 and March 2017 Internal RISC update - February 2017 Public RISC - February 2017 Division Director counterpart meeting - November 2016 JNRA Bilateral meeting - November 2016 ET Significant Topic briefing - November 2016 IAEA Technical meeting - November 2016 ACRS-Reliability and PRA Subcommittee - September 2016 Recent Communications

8 Path Forward Communication plan Communications with JLD SharePoint site Risk analyst / SRA engagement SPAR Model Updates Monitor RIDM program areas for additional application specific guidance changes Continue work on draft guidance documents RASP Handbook update NOED technical guideline/SRA Engagement Engage stakeholders Memo on NRRs review of NEI 16-06 Guidance Updates

9 Questions?

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC HighEnergyArcFault(HEAF)

GenericIssue MarkHenrySalleyP.E.

Chief,FireandExternalHazardsAnalysisBranch U.S.NuclearRegulatoryCommission June2628,LeMeridien Charlotte,NC markhenry.salley@nrc.gov 301.415.2474

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC 2

ElectricalEnclosures FailureModes September 21-24, 2014, Milwaukee, WI 3

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC WhatisaHEAF?

  • HighEnergyArcFaults(HEAFs)areenergeticorexplosive electricalequipmentfaultscharacterizedbyrapidreleaseof energyintheformofheat,light,vaporizedmetaland pressureincreasesduetohighcurrentarcsbetween energizedelectricalconductorsorbetweenenergized electricalcomponentsandneutralorground.

- Firstphase:short,rapidreleaseofelectricalenergywhichmay resultinprojectiles(fromdamagedelectricalcomponentsor housing)and/orfire(s)involvingtheelectricaldeviceitself,as wellasanyexternalexposedcombustibles,suchasoverhead exposedcabletraysornearbypanels,thatmaybeignited duringtheenergeticphase

  • ArcTemperaturesintherangeof35,000F(19,426C)

- Secondphase,i.e.,theensuingfire(s):istreatedsimilartoother postulatedfireswithinthezoneofinfluence

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC SafetySignificance GDC3 Structures,systems,and componentsimportanttosafety shallbedesignedandlocatedto minimize,consistentwithother safetyrequirements,theprobability andeffectoffiresandexplosions.

GDC17 Theonsiteelectricpowersupplies, includingthebatteries,andthe onsiteelectricdistributionsystem, shallhavesufficientindependence, redundancy,andtestabilityto performtheirsafetyfunctions assumingasinglefailure.

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC BackgroundoftheHEAFProgram

  • OECDFireIncidentRecords ExchangeProject(FIRE)

- AnalysisofHighEnergyArcing Fault(HEAF)FireEvents, NEA/CSNI/R(2013)6

- 48of415fireeventscollected representHEAFinducedfire events(over10%)

https://www.oecd nea.org/nsd/docs/2013/csnir2013 6.pdf

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC CSNIWGIAGETaskonHighEnergyArcing Faults(2009-2013)

  • TaskReportAReviewofCurrent CalculationMethodsUsedto PredictDamagefromHighEnergy ArcingFault(HEAF)Events, NEA/CSNI/R(2015)10

- Insightsfromoperating experiencewithpartly significantHEAFevents

- Literaturestudyonmethodsfor predictingHEAFconsequences BackgroundoftheHEAFProgram http://www.oecd nea.org/nsd/docs/2013/csni r201510.pdf

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC RealisticQuantificationofHazard

  • NRCtestinghasbeen,andwillcontinuetobe, informedbyOperatingExperienceandNPP configurations:

- LERsdescribenumerousthreephasearcfaults withfailureofanupstreambreaker

- Realplantequipmentusedintesting

- Voltage,current,arcdurationwithinthebounds observedinLERs

- DamageobservedcomportswithLERs

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ExampleofRecentUSElectrical EnclosureHEAFExperience SONGS,2001 Brunswick,Feb2016 Robinson,2010

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ExampleofRecentUS BusDuctHEAFExperience ZionBusDuct(testing)

February9th2016 ColumbiaBusDuct(OpE) 2009 DiabloCanyonBusDuct(OpE) 2000

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC U.S.OperatingEventHistory(OpE) Duration

  • OperatingEventhistoryshowsthatbreakersdonotalways workasexpected(designvs.realworld)
  • HEAFeventstypicallypersistfortimeframesmuchlongerthan designfaultclearancetimesthroughthemechanismof breakerfailuresorothercomplicatingfactors 10 Event Hold Time Cause Waterford; 06/10/1995 Unknown BreakerFailure; restrictedmovementofthetrip latchrollerbearing PrairieIsland; 08/03/2001 Unknown>2 seconds Breaker Failure;Ionizinggasfromthebreakerwas theinitiator Songs; 02/032001 Unknown; >2Seconds BreakerFailure;Ionizinggasfromthebreakerwas theinitiator Robinson; 03/27/2010 812seconds BreakerFailure; LossofDC ControlPower DiabloCanyon05/15/2000 11seconds Location; VoltageDecay Columbia 10/20/2009 Unknown Aging

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC U.S.OpE-ThreePhaseFaults

  • MostHEAFeventthatweareawareofquicklyprogressto threephasefaults.ThisisevidentfromanumberofLERs:

- TheKewauneeHEAFevent(LER8700900)involvedaphaseto groundfault,whichprogressedtoaphasetophasefaultwhich accountedfortheextensivebusdamage.

- ThePrairieIslandHEAFevent(LER010500)involvedaC phasegroundarcingevent,whichquicklyinvolvedallphases.

- TheZionHEAFevent(LER9400501)statesthatthefailure startedasasinglephasetogroundfaultwhichrapidlyevolved intoathreephasetogroundfault.

11

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC U.S.OperatingEventHistory(OpE)- Overpressurization

  • HEAFeventscanleadtooverpressurizationofcompartments andchallengefireratedbarriersevenwhenbreaker protectionworksasexpected

- TurkeyPointHEAFEventMarch18,2017

  • FaultClearedin35.8cycles(or~0.6seconds)
  • Theprotectiverelaysoperatedasexpected
  • FireDoorD0703,located4.4m(14.5ft.)awayfromtheoriginof thefaultwasdamagedandthelatchmechanismwasdeformed
  • Damagewascausedbytheoverpressurizationoftheroom correspondingtotheincreaseinpressureattheonsetofthearc event
  • Thedamageddoordefeatedthe3hourratedbarrierbetweenthe 3Aand3B4kVswitchgearrooms

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITesting

  • 26fullscaleexperimentscarriedoutatKEMAhighenergy testfacilitybetween20142016.

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITesting Test#3:480V,35kA,8seconds CopperBusBars

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITesting Test#15:10kV,15kA,3seconds Oilfilledbreaker(oilremoved),copperbusbars

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITesting Test#23:480V,40kA,7seconds Aluminumbusbars

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITesting Test#26:4.16kV,26kA,3.5seconds BusDuct,copperbusbars,aluminumhousing

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITestingResults

- Potentiallymuch largerZOI

- Potentiallygreater likelihoodof maintaininganarc atlowvoltages

- Higherriskoffire propagation

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITestingResults

  • NewFailureMode:

ConductiveProductsof Combustion

- ConductiveAL byproductscoated facility

- Shortedoutequipment anddamagedelectrical circuits

  • FortCalhounHEAF event June7,2011

- Adjacentcabinets affectedbyconductive smokeandsoot Test 23 Test 26

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PhaseITestingReport

  • ReportontheTesting Phase(20142016)ofthe HighEnergyArcingFault Events(HEAF)Project:

ExperimentalResultsfrom theInternationalEnergy ArcingFaultResearch

Program, NEA/CSNI/R(2017)7 https://www.oecd nea.org/nsd/docs/2017/csni r20177.pdf

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PostulatedHEAFMitigation HEAFShields

  • Proposedlightweightshieldingtolimittheextent ofdamagefromaHEAFevents

- objectiveistominimizedamagetorisksignificant targetsbeyondthefaultedswitchgearandtoprevent damageandignitionoverheadcabletrays:

- InorderforHEAFShieldstobeSuccessful:

  • WhatistheDesignBasis?
  • WhatistheAcceptance/Rating/QualificationTestMethod?
  • HowdoestheInstalledHEAFShieldmatchwhatwasTested?
  • WhyshouldthisEngineeredFeaturebetreatedanydifferent than:FireBarriers(Walls/Floors),FireDoors/Dampers ElectricalRacewayFireBarrierSystems,PenetrationSeals, etc?

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PostulatedHEAFMitigation Louvers/SolidTops Misconceptions:

  • TheforceoftheHEAFenergywill bedirectedbyventlouver

- Energywillonlytravelindirectionof theventsandwillpreventsignificant energy/mechanicaldamagetargets locatedaboveorawayfromthevent path

  • Solidtopsonswitchgearsalways containtheHEAFandprevent damagetotargetsabove

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC AluminumHEAFGenericIssue

  • GenericIssuesProgramPreGI018

- TheNRChasperformedascreeningreviewaspartof theGIprocessrelatedtoHEAFeventsinvolving aluminumcomponents

- Thegenericissuereviewpanel(GIRP)determinedthat thesevenscreeningcriteriaweremetinaccordance withmanagementdirective6.4(ML14245A048)andis intheprocessoffinalizationandreleaseofthe screeningphasedocument

- Thestaffhasrecommendedatwophaseapproachto addressthegenericissueandidentifiedbothshort termandlongtermactions

- GIRPmemocurrentlyinconcurrence

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC InformationNotice(IN)2017XX

  • HighEnergyArcFaultsinElectricalEquipmentContaining AluminumComponents

- OECD/NEAinternationaltestprograminsights

- 6U.S.operatingexperienceeventsinvolvingaluminum components

- ExpecttobeIssuedSummer2017 Plant Date FortCalhoun June7,2011 Columbia August5,2009 DiabloCanyon May15,2000 Zion April3,1994 ShearonHarris October9,1989 Kewaunee July10,1987

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC NRCRegulatoryActions

  • ShortTermActions

- Industrysurveyon extentofAluminum

- Estimatetheriskfrom potentialZOI increasesidentified bytestingandOpE

- Determineif additionalactionsare necessary

  • LongTermActions

- Performadditional focusedHEAFtesting designedtoquantify theZOIwithAluminum

- Updateandrevise currentHEAFguidance inNUREG/CR6850 AppendixMand FAQ070035

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC PIRT&PhaseIITesting

  • PhaseIItestingtobeconductedasanNEA/OECD InternationalProjectwithmorefocusedobjectives
  • InternationalPhenomenaIdentificationandRanking Table(PIRT)exerciseheldinFebruary2017
  • EarlyInsights:

- Aluminumoxidationandbyproducts

- Pressureeffects

- Targetcharacterizationandsensitivity

- Mitigatingfactors(HEAFshields)

  • PIRTNUREGtobeissuedSummer2017
  • OECD/NEAPhaseIITestingcurrentlyunder development

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC DevelopLongTermDefenseinDepth Solution SafeShutdown Protect&PreserveSafeShutdown RapidDetection&Mitigation Fuse/Breaker/RelayProtectionHEAF

Shields, Prevention SafeWorkPractices,Maintenance,ArcProofCabinets

NEIRiskInformedRegulationandFireProtectionForumJune26-28,2017,LeMeridien Charlotte,NC ContactInformation NicholasMelly T:301.415.2392 E:Nicholas.melly@nrc.gov GabrielTaylor,PE T:301.415.0781 E:gabriel.taylor@nrc.gov KennethHamburger T:301.415.2022 E:Kenneth.hamburger@nrc.gov DavidW.Stroup,PE T:301.415.1649 E:david.stroup@nrc.gov

Guidance on Treatment of Uncertainty in Risk-Informed Decisionmaking (NUREG-1855)

NEI Risk Informed Regulation Forum June 28, 2017 Mary Drouin Senior Program Manager Division of Risk Analysis Office of Nuclear Regulatory Research

=

Background===

Originally published in March 2009 Developed in collaboration with EPRI EPRI 1016737, Treatment of Parameter and Model Uncertainty for PRAs EPRI 1026511, Practical Guidance on the Use of PRA in Risk-Informed Applications with a Focus on the treatment of Uncertainty Revision 1 better structures the guidance to licensees and further clarifies the NRC staff decisionmaking process in addressing uncertainties Web-Based course developed and is available on our public website https://www.nrc.gov/reading-rm/training/nureg-1855/

2

Why is the Guidance Needed?

In dealing with uncertainties associated with PRAs, the decision maker needs to:

Understand to what extent the results are impacted by the uncertainties Understand whether there are uncertainties that are impacting the results that may challenge the acceptance guidelines Determine if the driver for the large uncertainties can be identified and remediated 3

There are Three Different Types of Uncertainties Associated with PRAs Completeness uncertainties Are risk-significant events included?

Parameter Uncertainties What is the confidence in our ability to predict PRA parameters?

Model Uncertainties What is the confidence in the models for the specific accident scenarios?

4

Overall Process

Part 1 - Guidance to Licensees and the NRC Staff Stage A - Determine the approach for the treatment of uncertainties

Part 2 - Guidance to Licensees Stage B -- Assess if the PRA has the needed scope and level of detail to support the risk-informed decision Stage C -- Assess completeness uncertainties Stage D -- Assess the parameter uncertainties Stage E -- Assess model uncertainties Stage F -- Develop the strategies to address key uncertainties in the application 5

Overall Process (contd)

Part 3 - NRC Process Stage G -- NRCs risk-informed review process

The guidance in Stages A through G are based on the NRC risk-informed decisionmaking process, and the treatment of uncertainties is consistent with the ASME/ANS PRA standard 6

7 Overall Process (contd)

How is Aggregation Treated?

Contributions from applicable hazards and plant operational states are combined to generate the risk results The level of detail - the uncertainties and the degree of conservatisms in the various hazards -

may differ The various levels of detail may bias the overall risk results The contributors to the risk need to be understood and their bases should be taken into account in the decisionmaking process 8

NRC Review Process NRC staff seeks to answer

Is the scope and level of detail of the PRA appropriate for the application?

Is the PRA model acceptable?

What is the proximity of the risk metric results to the acceptance guidelines?

How do parameter and model uncertainties each affect the risk metric results?

Is the acceptability of the application adequately justified?

9

Treatment of PRA Uncertainties in Risk-Informed Decisionmaking The staff review begins with determining the proximity of the application risk metric results to the acceptance guidelines and the licensees justification 10

Regime 1 - Risk Results Well Below the Acceptance Guidelines The staff would

Look for an assessment which shows that parameter uncertainties do not affect the risk results

Determine whether the key assumptions made in the PRA will be appropriately monitored

Determine whether degraded performance can be detected in a timely fashion

Likely place less importance on the use of compensatory measures, depending on the justification that is provided

Examine the peer review findings to identify any of particular relevance to the application

Generally not perform an audit on the application 11

Regime 2 - Risk Results do not Challenge the Acceptance Guidlines The staff would

Look for an assessment which shows that parameter uncertainties do not affect the risk results

Examine the application to determine that the proposed performance monitoring is appropriate and adequate

Determine whether degraded performance can be detected in a timely fashion

Consider if greater depth of review of the uncertainty aspects of the application should be performed

Examine the peer review findings with a higher degree of scrutiny than for applications that fall into Regime 1

Likely perform an audit on the application PRA 12

Regime 3 - Risk Results Challenge the Acceptance Guidelines The staff would

Expect that parameter uncertainties do not affect the risk results

Expect that the proposed performance monitoring is adequate

Expect that degraded performance can be detected in a timely fashion

Expect that compensatory measures be in place

Examine the peer review findings with an even higher degree of scrutiny

Consider if greater depth of review of the uncertainty aspects of the application should be performed

Likely perform an audit of the application PRA to determine the cause of the change in risk 13

Regime 4 - Risk Results Significantly Exceed the Acceptance Guidelines The staff would

Typically not accept such applications unless they represent an overall reduction in risk

Expect the licensee to identify areas of the PRA that are conservative and then perform a more realistic assessment to support the application

Expect that parameter uncertainties do not affect the risk results

Examine the application to ensure that the proposed performance monitoring is adequate

Expect that degraded performance can be detected in a timely fashion

Thoroughly review the peer review findings

Determine the appropriateness of compensatory measures

Review in greater detail the uncertainty aspects of the application

Perform a more in-depth audit of the application PRA to determine the cause of the change in risk 14

Risk-Informed Application When aggregating the results from different hazards, the staff evaluates whether the licensee demonstrates understanding of The individual risk contributions and the uncertainty associated with each hazard AND The sources and effects of conservatisms and model uncertainties that significantly impact the results For staff acceptance Licensee has demonstrated an acceptable treatment of uncertainties AND Demonstrated an acceptable risk effect to the plant 15

Retrieved from "https://kanterella.com/w/index.php?title=ML17174B290&oldid=5133282"