ML21138A781

PRA and RIDM NCSU

ML21138A781
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Issue date:	10/22/2020
From:	Nathan Siu NRC/RES/DRA, North Carolina State University
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PRAandRiskInformedDecisionMakingattheNRC:

SomeTrendsandChallenges*

NathanSiu SeniorTechnicalAdvisorforPRA OfficeofNuclearRegulatoryResearch NuclearEngineeringResearchSeminar(Virtual)

NorthCarolinaStateUniversity,Raleigh,NC October22,2020

• TheviewsexpressedinthispresentationarenotnecessarilythoseoftheU.S.NuclearRegulatoryCommission ML20293A370(pdf)

2 Thatsso cool Arewe thereyet?

Outline

• Adecisionmakingchallenge

• UseofriskinformationatNRC

• SomePRAtechnology challenges(audience participation)

• Closingthoughts

• Additionalmaterial

3 Acknowledgments Iwouldliketothankmanycolleagues(especiallyJingXing,JamesChang, SusanCooper,KeithCompton,TinaGhosh,ChrisHunter,ShivaniMehta, StaceyRosenberg,TomWellock,SunilWeerakkody,JohnGarrick,and AndreasBye)fortheirassistanceanddiscussionsindevelopingmaterial forthispresentation.IwouldalsoliketothankJorgeLuisHernandezand ShahenPoghosyan(IAEA)fororganizingarecentinternationalworkshop thatprovidedcurrentperspectivesonanumberofkeytopics.Anyerrors orchangesinemphasisinmaterialaremyown.

4 DAEDALUS,ICARUS,ANDRISKINFORMED REGULATORYDECISIONMAKING Justforfun

5 3000+Years Ago Greetings Daedalus!

Y200:Earthquake,conquest Y5:DevelopercomplaintstoKingMinos(impedimentstoinnovation)

Y450:Theraexplosion,earthquake,giantwaves Today Y100:MinoanTransportationDevelopmentAgency(MinTDA)

Y75:MinTDA =>

MinoanMinistryofTransportation(MinMoT)

MinoanTransportationRegulatoryCommission(MinTRC)

MinTRC Chronology

DaedalusProposal

• Designconcept:humanpoweredwings(imitatebirds)

• Construction:feathersattachedbywaxandthread/twine, assemblybentintoslightcurve

• Procedures:oral

- Dontflytoohigh(scorching)ortoolow(dampfeathers)

- Sticktogether;dontnavigatebystarsorconstellations

• Testing:

- Demonstrationofprinciple

- Twopersonflightnorth

ARiskInformedDecisionMakingProblem Current regulations Defensein depth Safetymargins Risk Monitoring Integrated Decision Making AdaptedfromRG1.174

• Currentregulations:noneapplicable

• Defenseindepth:none

• Safetymargins:unknown,heavy relianceonDaedalusskill

• Riskassessment:possiblescenarios recognizedbutincomplete(seenext)

• Performancemonitoring:possible

Known Unknowns Unknown Unknowns Conceivability (Daedalus)

Scenarios AltitudeEffects?

ExternalEvents DeityAction MidAirCollision DesignError ClearAirTurbulence MechanicalFailure PilotInexperience LongFlightLogistics Modernhanggliders,scenarionotidentified Modernhanggliders,scenarioidentifiedbyDaedalus Possible,scenarionotidentified RiskAssessmentConcerns

• Completenessofriskmetrics

• Correctnessofmodelsfor identifiedscenarios

• Otherpossiblescenarios

• Peerreview

• Structuralfailure Scorching

? Waxfailure(heat,cold)

? Thread/twinefailure

• Liftfailure Dampness

? Fatigue

• Piloterror Flightparameters Navigation 1000 1100 1200 1300 1400 0

5000 10000 Irradiance(W/m2)

Altitude(m)

IrradiancevsAltitude MtIda Models CALL1800HELPRES CALL1800HELPRES

• Additionalimpacts Publichealthandsafety Environment

Construction

Postaccident Culture

• Unsanctionedusesoftechnology andpotentialconsequences RiskMetrics

10 NRCUSEOFRISKINFORMATION Itisofthehighestimportanceintheartofdetection decisionmaking tobeabletorecognize,outofanumberoffacts,whichareincidental andwhichvital.Otherwiseyourenergyandattentionmustbe dissipatedinsteadofconcentrated.

WithapologiestoSherlockHolmes (TheHoundoftheBaskervilles)

11 BuildingConfidence NRCUseofRiskInformation FullPRAdesired butnotfeasible*

Technology available Regulatoryguidance established Regulatorypolicy established 1940 1950 1960 1970 1980 1990 2000 2010 2020 HanfordtoWASH1400 Early PRAs ExpansionAcross Industry ModernApplications

• SeeT.R.Wellock,Afigureofmerit:quantifyingtheprobabilityofanuclearreactoraccident,TechnologyandCulture,58,No.3, 678721,July2017.

Indian Indian Point

12 TripletDefinitionofRisk(KaplanandGarrick,1981)*

Risk{ i, i,

i }

Features

• Vector,notscalar

• Qualitativeand quantitative

• Differencesacross accidentspectrum

• Whatcangowrong?

• Whataretheconsequences?

• Howlikelyisit?

• AdoptedbyNRC.See:

WhitePaperonRiskInformedandPerformanceBasedRegulation(Revised),SRMtoSECY98144,March1,1999 GlossaryofRiskRelatedTermsinSupportofRiskInformedDecisionmaking,NUREG2122,May2013 ProbabilisticRiskAssessmentandRegulatoryDecisionmaking:SomeFrequentlyAskedQuestions,NUREG2201,September2016 NRCUseofRiskInformation

13 NRCUsesofRiskInformation PRAPolicyStatement(1995)

• IncreaseuseofPRAtechnologyinall regulatorymatters

- ConsistentwithPRAstateoftheart

- Complementdeterministicapproach, supportdefenseindepthphilosophy

• Benefits:

(1) Considersbroadersetofpotentialchallenges (2) Helpsprioritizechallenges (3) Considersbroadersetofdefenses U.S.NuclearRegulatoryCommission,UseofProbabilistic RiskAssessmentMethodsinNuclearActivities;Final PolicyStatement,FederalRegister,60,p.42622(60FR 42622),August16,1995.

Regulations and Guidance Licensing and Certification Oversight Operational Experience Decision Support NRCUseofRiskInformation Notjustdesign approval

14 RecentApplication(2019)

Inanylicensingrevieworother regulatorydecision,thestaffshould applyriskinformedprincipleswhen strict,prescriptiveapplicationof deterministiccriteriasuchasthe singlefailurecriterionisunnecessary toprovideforreasonableassurance ofadequateprotectionofpublic healthandsafety.

StaffRequirements-SECY190036-Applicationofthe SingleFailureCriteriontoNuScale PowerLLCsInadvertent ActuationBlockValves,SRMSECY190036,July2,2019.

RiskInformedRegulatory DecisionMaking(RIDM) aphilosophy wherebyrisk insightsareconsidered togetherwithotherfactors toestablishrequirements thatbetterfocuslicensee andregulatoryattentionon designandoperationalissues commensuratewiththeir importancetopublichealth andsafety.[Emphases added]

WhitePaperonRiskInformedand PerformanceBasedRegulation,SECY98144, January22,1998.

Currentregulations Defenseindepth Safetymargins Risk Monitoring Integrated DecisionMaking AdaptedfromRG1.174 Adaptedfrom:U.S.NuclearRegulatoryCommission,AnApproachforUsingProbabilisticRiskAssessmentinRiskInformed DecisionsonPlantSpecificChangestotheLicensingBasis,RegulatoryGuide1.174,Revision 3,January2018.

NRCUseofRiskInformation Notjustrisk information

15 MultipleProducts andUses RiskInformation

• Results

• Insights

• Explanations

• Uncertainties

• Qualifications AdaptedfromNUREG2150 NRCUseofRiskInformation Notjustimmediate decisionsupport

16 PhotocourtesyofNEAHalden ReactorProject SomeTrends

• Marketforces

- Increasednumberofapplications

- Increasedcreditforcapabilities(e.g.,FLEX)

- Greaterroleindesign(e.g.,LMP)

• Noveldesigns,technologies,and operationalconcepts

• Improvinganalysiscapabilities

- Computationalresources

- Smarttechnologies(e.g.,contentanalytics)

• Changingworkforce(KSAs,preferences)

ChallengetoNRC:

BeReady!

NRCUseofRiskInformation

17 SOMEPRATECHNOLOGYCHALLENGES*

AudienceParticipation

• InthispresentationTechnology={methods,models,tools,data}

itisincumbentuponthenewindustryandtheGovernmenttomakeeveryefforttorecognize everypossibleeventorseriesofeventswhichcouldresultinthereleaseofunsafeamountsof radioactivematerialtothesurroundingsandtotakeallstepsnecessarytoreducetoareasonable minimumtheprobabilitythatsucheventswilloccurinamannercausingseriousoverexposureto thepublic.

W.F.Libby(ActingChairman,AEC)- March14,1956responsetoSenatorHickenlooper

[fromD.Okrent,ReactorSafety,U.WisconsinPress,1981]

18 IdentifyingChallenges:ManyPerspectives FukushimaReview*

PRAscope (2)

Feedbackloops (1)

Gameovermodelingand intentionalconservatisms (4)

Longdurationscenarios (3)

Externalhazardsanalysis (12)

Humanreliabilityanalysis(HRA) (5)

Representationofuncertaintyin phenomenologicalcodes (1)

Searching(vs.screening) (5)

IAEATechnicalMeeting**

DynamicPSA (7)

Combinationsofhazards (3)

Portableequipment (4)

UseofPSAindevelopmentof SAMGs(6)

Level3PSA (4)

Softwarereliabilityand modelling(4)

Incorporationofageing aspects(5)

• N.Siu,etal.,PSAtechnologychallengesrevealedbytheGreatEastJapanEarthquake,PSAMTopicalConferenceinLightoftheFukushimaDaiIchiAccident,Tokyo,Japan,April1517,2013.

[ML13038A203 (paper),ML13099A347 (presentation)]

• • IAEATechnicalMeetingontheEnhancementofMethods,ApproachesandToolsforDevelopmentandApplicationofProbabilisticSafetyAssessments, September29October2,2020.

• • • M.Drouin,etal.,GuidanceontheTreatmentofUncertaintiesAssociatedwithPRAsinRiskInformedDecisionmaking,NUREG1855,Rev.1,2017.

UncertaintyTypology***

Parameteruncertainty (3)

Modeluncertainty (6)

Completenessuncertainty (8)

PRATechnologyChallenges

+Internalriskcommunication (9)

Picka topic

19 PRATECHNOLOGYINSIGHTSFROM3/11 QualitativelessonsfromaPRAorientedreview PRATechnologyChallenges

[FukushimaReview]

Topics PRAscope Feedbackloops Gameovermodeling Longdurationscenarios Externalhazardsanalysis Humanreliabilityanalysis(HRA)

Representationofuncertaintyin phenomenologicalmodels Searching(vs.screening)

20 PRATechnologyInsightsfrom3/11*

• Review:2013,updated2016

Purpose:

supportongoingactivities(Level3PRA, R&Dplanning,internationaldiscussions)

• Scope:allaffectedplants

• Approach

- Literaturereview

- Eventreview

• Timelinebased

• PSAtopicbased

• Results:PRAtechnologyReminders, Challenges,anddiscussionsofselectedtopics PRATechnologyChallenges

[FukushimaReview]

• See:

1)

N.Siu,etal.,PSAtechnologychallengesrevealedbytheGreatEastJapanEarthquake,PSAMTopicalConferenceinLightoftheFukushimaDaiIchiAccident, Tokyo,Japan,April1517,2013.[ML13038A203 (paper),ML13099A347 (presentation)](usedforthispresentation) 2)

N.Siu,etal.,PSAtechnologyremindersandchallengesrevealedbytheGreatEastJapanEarthquake:2016update,13thInternationalConferenceon ProbabilisticSafetyAssessmentandManagement(PSAM13),Seoul,Korea,October27,2016.[ML16245A871 (paper),ML16270A522 (presentation)]

21 PRAScope(1/2)

Dimension TypicalU.S.(c.2011)

Observations(3/11/2011)

Space

Singleunit(reactor)

Frontlinemitigatingsystems+support

Multiplereactors,SFP;multiplesites

Additionalsystems(e.g.,securityaccess)

Time

Atpoweroperation

Accident

Shutdownoperations(incl.testing)

Postaccidentsusceptibility Organization

Onsitestaff

Offsiteinvolvement(directions,requests forinformation)

PRATechnologyChallenges Recovery Preparedness Preparedness Reconstitution

+ Analysis

Response

time Warning Event Stabilize site Permanently restore site Identify and promulgate lessons Improve posture Damage control Reduce vulnerabilities, plan, prepare for effective response Reduce vulnerabilities, plan, prepare for effective response

[FukushimaReview]

22 PRAScope(2/2):MultiSiteEvents March11,2011 August14,2003 PRATechnologyChallenges

[FukushimaReview]

23 FeedbackLoops(1/1)

PRATechnologyChallenges GeneralAnalysisFlow GeneralAnalysisFlow Analysis Refinements Onsiteactions inhibitedbyradiation, explosioneffects Containmentventing delayeduntillocal evacuationconfirmed

[FukushimaReview]

24 GameOverModeling(1/4)

• PlantLevel:LossofACandDC

- ConventionalPRAanalysis:core damage(ifACpowerisnot recovered)

- Deterministicanalysis:rapid onsetoffueldamage

• SystemLevel:LossofDC

- Isolationcondenser,RCIC,and HPCIfail(unabletocontrol)**

PRATechnologyChallenges

• Unmitigatedshorttermstationblackout(STSBO).SeeN.Bixler,etal.,

StateoftheArtReactorConsequenceAnalysesProjectVolume1:

PeachBottomIntegratedAnalysis,NUREG/CR7110,Rev.1,2013.

Plant Core Damage Onset(hr)

PeachBottom(NUREG/CR7110)*

1.0 FukushimaDaiichiUnit1 19 FukushimaDaiichiUnit2 89 FukushimaDaiichiUnit3 52

• • DCpowerisusedtooperateanumberofcontrolvalves.UncontrolledRCICand/orHPCIcouldleadtoRPVoverfill,waterinthe RCIC/HPCIsteamline,and potentialfailureoftheRCIC/HPCIturbine(s).Duringtheaccident,operatorsbypassedsomeflowthroughaminiflowtestline(whichreturnswatertothe CondensateStorageTank)toreducethepossibilityofRPVoverfill.

[FukushimaReview]

25 PRATechnologyChallenges GameOverModeling(2/4):LossofDC

[FukushimaReview]

26 GameOverModeling(3/4):RIDMImplications

• Usefulsimplificationforapplicationsfocusedon totalresults

• Concerns

- Potentialoveremphasisonscenariosthatare actuallynotasimportantasothers(masking effect)

• Trainingresources

• Establishingexpectations(bias)

- Strongconstraintsonmitigationactionsconsidered asviable,worthemphasizing(e.g.,through proceduresandtraining)

- LossofPRAmodelcredibilitytokeystakeholders PRATechnologyChallenges

[FukushimaReview]

Fire InternalEvents InternalFlooding Seismic HighWinds ExternalFlooding Fire InternalEvents InternalFlooding Seismic HighWinds ExternalFlooding

?

27 GameOverModeling(4/4):OtherNotes

• Assumingimmediatefailuresisnotnecessarilyconservative

- inreality,lackingomniscience,operatorsmightspendtime tryingtoimplementanonfeasiblepath

• Othercommongameovermodelingassumptions

- Lackofcreditforrecoveryorrepair

- Assumedlossofstructurecontentsonfailureofstructure PRATechnologyChallenges

[FukushimaReview]

28 LongDurationScenarios(1/3):FukushimaEarly PRATechnologyChallenges Datafrommultiplesources,including:

1)

InternationalAtomicEnergyAgency,TheFukushimaDaiichiAccident:ReportbytheIAEADirectorGeneral,STI/PUB1710,Vienna,Austria,2015.

2)

GovernmentofJapan,InvestigationCommitteeontheAccidentattheFukushimaNuclearPowerStationsofTokyoElectricPowerCompany,InterimReport.

December26,2011.

[FukushimaReview]

29 LongDurationScenarios(2/3):FukushimaLate PRATechnologyChallenges Datafrommultiplesources,including:

1)

InternationalAtomicEnergyAgency,TheFukushimaDaiichiAccident:ReportbytheIAEADirectorGeneral,STI/PUB1710,Vienna,Austria,2015.

2)

GovernmentofJapan,InvestigationCommitteeontheAccidentattheFukushimaNuclearPowerStationsofTokyoElectricPowerCompany,InterimReport.

December26,2011.

[FukushimaReview]

30 LongDurationScenarios(3/3):ModelingChallenges

• Recoveryandrepair

- Humanreliabilityanalysis(HRA)

- Siteandequipmentconditions(debris,roads, tools,spares,housing,)

• Nonbinarybehavior(e.g.,intermittent and/ordegradedperformance)

• Offsite

- Conditions(siteaccess,demandson emergencyservices,)

- Organizationalresponse PRATechnologyChallenges Yuriage - BeforeandAfter3/11Tsunami

[FukushimaReview]

31 ExternalHazardsAnalysis(1/12) 3/11/2011:Seismicallyinducedlossofoffsite power,tsunamiinducedlossofallpowerand multiplesevereaccidents Longstandinggeneralapproach,e.g.,

- Zion/IndianPointPRAs(1982)*

- PRAProceduresGuide(1983)*

Typicalpractice

- Generalemphasisoninternalevents, earthquakes,internalfiresandfloods

- Otherexternalhazards(includingexternal floods)sometimesdismissed(pre3/11)

Typicalresults

- Importantorevendominantcontributortorisk

- Uncertaintydriver:hazardsanalysis PRATechnologyChallenges

• See:

1)

B.J.Garrick,Lessonslearnedfrom21nuclearplantprobabilisticriskassessments,NuclearTechnology,84,No.3,319-339(1989) 2)

AmericanNuclearSocietyandtheInstituteofElectricalandElectronicsEngineers,PRAProceduresGuide,NUREG/CR2300,1983.

[FukushimaReview]

32 ExternalHazardsAnalysis(2/12):PastPRAResults PRATechnologyChallenges

[FukushimaReview]

Anearlystudy(c.1980)

NUREG1150(1990)

Note:Ordersofmagnitudeuncertainties

33 ExternalHazardsAnalysis(3/12):PastPRAResults PRATechnologyChallenges

[FukushimaReview]

1.E07 1.E06 1.E05 1.E04 1.E03 1.E07 1.E06 1.E05 1.E04 1.E03 IPEEECDF IPECDF IPEEEvsIPECDF 1.E07 1.E06 1.E05 1.E04 1.E03 1.E07 1.E06 1.E05 1.E04 1.E03 External Internal Externalvs.InternalCDF(SAMA)

Note:Externalincludesinternalfires

34 ExternalHazardsAnalysis(4/12):AFukushimaPrecursor

• Winddrivenwaves+majorstormsurge

- Overtopandsweeparounddike,damagedike, floodsite

- Floodwaterspassthroughpenetrations,burstan internalfiredoor,andfloodkeyareas

• Systemimpacts

- Lossofoffsitepower(LOOP)atUnits2and4

- Unit1servicewaterdegraded

- Units1and2lowheadsafetyinjectionand containmentspraypumpslost

- Siteaccesslost E.deFraguier,Lessonslearnedfrom1999Blayais flood:overviewofEDFfloodriskmanagement plan,NRCRegulatoryInformationConference, Rockville,MD,March911,2010.

PRATechnologyChallenges LeBlayais (December27,1999)

[FukushimaReview]

35 0.00 0.05 0.10 0.15 0.20 0.25 0.30 probabilitydensity MajorFloodFrequency(/yr)

ExternalHazardsAnalysis(5/12):PFHA*Background Parameterofinterest:frequencyofmajorflooding()

Priorstateofknowledge:minimal Evidence:12majorfloodsover19322019(87years)

BayesTheorem:

Posteriorstateofknowledge:

Date FloodHeight(ft) 5/14/1932 15.25 2/27/1936 14.69 3/19/1936 28.10 4/28/1937 23.30 10/30/1937 15.62 10/17/1942 26.88 4/29/1952 14.17 8/20/1955 17.60 6/24/1972 22.03 11/7/1985 17.99 1/21/1996 19.29 9/8/1996 17.84 05 =0.079/yr 50 =0.13/yr 95 =0.21/yr mean=0.14/yr prior posterior PRATechnologyChallenges

Poisson Noninformative

• Notes:

1)

PFHA=probabilisticfloodinghazardsanalysis 2)

Datafrom:https://water.weather.gov/ahps2/crests.php?wfo=lwx&gage=brkm2&crest_type=historic 3)

MajorFlood:height>14ft PotomacRiver(LittleFalls,VA)*

[FukushimaReview]

36 ExternalHazardsAnalysis(6/12):PFHABackground 10 12 14 16 18 20 22 24 26 28 30 FloodHeight(ft)

PotomacRiverFlooding(LittleFalls,VA)

MajorFlood ModerateFlood 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 0

10 20 30 40 50 60 70 9

12 15 18 21 24 27 30 More Count FloodHeight(ft)

PRATechnologyChallenges

[FukushimaReview]

Notes:

1)

Datafrom:https://water.weather.gov/ahps2/crests.php?wfo=lwx&gage=brkm2&crest_type=historic 2)

MajorFlood:height>14ft;ModerateFlood:12ft<height<14ft

37 ExternalHazardsAnalysis(7/12):PFHAChallenge 0.00 0.20 0.40 0.60 0.80 1.00 5

10 15 20 25 30 P{X>x}

FloodHeight(ft)

PotomacRiverFloods(LittleFalls):19322019 WeibullCCDF Weibullpdf(scaled)

GumbelCCDF Gumbelpdf(scaled)

EmpiricalCCDF MajorFlood ModerateFlood PRATechnologyChallenges Beyondhistorical experience:

howtoestimate forRIDM?

[FukushimaReview]

38 ExternalHazards(8/12):PFHAChallenge PRATechnologyChallenges

[FukushimaReview]

39 ExternalHazardsAnalysis(9/12):PFHAChallenge PRATechnologyChallenges

[FukushimaReview]

40 ExternalHazardsAnalysis(10/12):Lessonsfrom SomeOtherFloodRelatedOperationalEvents*

• Qualitativereviewof5floodsand5storms

• Observations:

• See:N.Siu,etal.,QualitativePRAinsightsfromoperationalevents,14thInternationalConferenceonProbabilisticSafetyAssessment andManagement(PSAM14),LosAngeles,CA,September1621,2018.[paper(ML18135A109),presentation(ML18249A340)]

Confirmatory Multiplehazards Asymmetricalmultiunitimpacts Lessthanextremehazards Hazardpersistence FailureofmitigationSSCs FailureofimplicitlyconsideredSSCs Warningtimesandprecautionarymeasures HRAandemergencyresponsecomplexities Lessdiscussed Multipleshocks Scenariodynamics Geographicalextentand potentialformultisiteimpacts PRATechnologyChallenges

[FukushimaReview]

41 ExternalHazardsAnalysis(11/12):Lessonsfrom SomeSeismicallyInitiatedOperationalEvents*

• Qualitativereviewof50events

• Observations:

- ReportedPGAs<<maxvaluesconsideredinrecentPRAs

- Otherthanoffsitepower,nodirectdamagetomajormitigatingsystemsduetoground motion;majoreffectsduetoinducedhazards(fire,externalflood)

- Somereactortrips/safetysystemactuationsforeventswithverylowonsitePGAs

- Ifoneunitaffected,typicallyallunitsonsitealsoaffected

- Someeventsaffectedmultiplesites:

- Reactivityeffects:

• Fluxinducedtrips(Onagawa,1993;NorthAnna,2011)

• Stuckcontrolrod(KashiwazakiKariwa,2007)

• See:N.Siu,etal.,QualitativePRAinsightsfromseismicevents,25thConferenceonStructuralMechanicsinReactorTechnology (SMiRT25),Charlotte,NC,August49,2019.[paper(ML19162A422),presentation(ML19210D835)]

ImpactsatMultipleSites

1. Events Minimalresponse**orgreater 10 Reactortrip 3

Seriouschallenge 1

PRATechnologyChallenges

[FukushimaReview]

42 ExternalHazardsAnalysis(12/12):Challenges Hazardsanalysis

- Relevanceofhistoricaldata Naturaltrends Manmadetrends

- Needforknowledgeableexperts

- Roleofsimulation

- Combinationofhazards

- Technicalcultures Whatisthehazard(varyingpointsofview)

Buyinforriskassessment(especiallyrareevents)

Fragilityanalysis

- Fullrangeofhazards(dynamicloads,clogging,)

Plantresponseanalysis

- Humanreliabilityanalysis(HRA)

- Dynamics PRATechnologyChallenges

[FukushimaReview]

https://commons.wikimedia.org/wiki/File:Storms_Lothar_and_Martin_december_1999.png Treatmentofconsecutiveevents (andpreconditioning)?

HurricanetracksadaptedfromUniversityofWisconsinMilwaukee (https://web.uwm.edu/hurricanemodels/models/archive/)

EmergencyresponsebasedondatafromNationalHurricaneCenter:

(https://www.nhc.noaa.gov/1992andrew.html)

Roleofstochasticsimulation?

43 HRA(1/5):Observationsfrom3/11

• Errorofcommission(isolationof1F1IsolationCondenser)

• Psychologicalimpacts

• Externalinterventionsindecisionmaking

- Seawaterinjection

- Containmentventing

• Uncertaintyinplantconditions

- Lossofinstrumentation

- Lossofaccess

- Lossofcommunicationsystems=>messengers(withassociateddelaysfortransit, reporting)

• Evolvingconditions(radiation,explosions,evacuatingstaffandcontractors) affectingrecoveryactions PRATechnologyChallenges

[FukushimaReview]

Seenextslides

44 PRATechnologyChallenges ISOXHEEOCTERM OPERATORTERMINATES ISOLATIONCONDENSER OPERATION BUT WHY?

HRA(2/5):CurrentPRAandEOCs

[FukushimaReview]

45 HRA(3/5):AddingEOCs Detection ActionExecution Decisionmaking Understanding InterteamCoordination (1)CognitiveBasis (2)DynamicContext*

PRATechnologyChallenges

[FukushimaReview]

• Approachestoaddresscontextinaclassicaleventtree/faulttreePRAframeworkinclude:

1)

L.Podofillini,V.N.Dang,O.Nusbaumer,andD.Dres,ApilotstudyforerrorsofcommissionforaboilingwaterreactorusingtheCESAmethod, ReliabilityEngineeringandSystemSafety,109,8698(January2013).

2)

C.Picoco andV.Rychkov,AdvancedthermalhydraulicsimulationsforHRA,IAEATechnicalMeetingonEnhancementofApproachesandToolsfor theDevelopmentandApplicationofProbabilisticSafetyAssessments(Virtual),September29October2,2020.

46 HRA(4/5):TheHumanDimension(3/11)

• Decisionmakerfrustrations

- Limitationsofavailableaccidentmanagement guidance

- Offsiteorganizationalinterventions

• Staffstressors

- Progressivelossofsituationawarenessandcontrol

- Onsiteconditions(aftershocks,tsunamiwarnings, radiation,dark,debris,openmanholes,)

- ERCconditions(food,sleep,sanitation,)

- Offsiteconditions PRATechnologyChallenges

[FukushimaReview]

Yoshidawasaskedifheopenedupthe accidentmanagementmanualandusedit asareference.Hesaidheneverreferred toitorevenopeneditup.

Heexplainedhowineffectivemeasures thoughtupbypeoplebeforehandcanbe.

Yoshidaalsoexplainedthatnuclearplants inJapanweredesignedwithpriority placedoninternalfactorsleadingto malfunctions.Hewentontoexplainthat nothoughtwasgiventomalfunctions occurringsimultaneouslyatanumberof plantsduetoexternalfactors,suchas tsunami,tornado,aplanecrashoranact ofterrorism.

TheYoshidaTestimony (2014)

TheYoshidaTestimony:TheFukushimanuclearaccidentastoldbyplantmanagerMasaoYoshida,AsahiShimbun,2014.

(Availablefrom:http://www.asahi.com/special/yoshida_report/en/)

47 HRA(5/5):BeyondFukushima Otheranalysisconcerns

- Needforimprovedqualitativeanalysis(littlestories)

• Basisforanalysisassumptions

• Qualitativedimensionofrisk:whatcangowrong

- Treatmentofnewsituations

• ExMCR(particularlyportableequipment)

• Level2

• Eventandconditionsassessment

- Collectionanduseofempiricaldata ARIDMconcern:recognitionandtreatmentofmodel uncertainty-morebenchmarks?

Samemethod,differentteams Sameteam,differentmethods NRI,CREAM NRI,DT+ASEP NRC,SPARH INL,SPARH PRATechnologyChallenges

[FukushimaReview]

IntegratedHumanEventAnalysisSystem(IDHEAS)

ScenarioAuthoring,Characterization,andDebriefing Application(SACADA)

SomeIDHEASandSACADAreferences:

1)

Y.J.ChangandJ.Xing,ThegeneralmethodologyofanIntegratedHumanEventAnalysisSystem(IDHEAS)forhumanreliabilityanalysismethoddevelopment, 13thInternationalConferenceonProbabilisticSafetyAssessmentandManagement(PSAM13),Seoul,Korea,October27,2016.(ML16298A411) 2)

Y.J.Chang,etal.,TheSACADAdatabaseforhumanreliabilityandhumanperformance,ReliabilityEngineering&SystemSafety,125,117133(2014).

ABye,etal.,InternationalHRAEmpiricalStudy,NUREG/IA0216,2011.

48 RepresentationofUncertainties(1/1)

Post3/11FukushimaForensicstudy(SNL,ORNL):*

- ReconstructsaccidentprogressionatUnits13andUnit4SFP

- Keychallenge:accidentdatagapsanduncertainties

- Demonstratesthatcurrenttools(MELCOR,TRACE)and modelingapproachescanreproducegeneraltrends,with goodquantitativeagreementinportionsoftheresults Questions

- HowtoincorporatefindingsintoaPRA?IntoRIDM?

- Howtorepresentandcommunicateanalysisuncertainties?

Challenges

- Subjectcomplexity

- Multiplepurposes

- Personalanddisciplineviewpoints,sometimesstronglyheld PRATechnologyChallenges

[FukushimaReview]

• R.Gauntt,etal.,FukushimaDaiichiAccidentStuy (StatusasofApril2012),SAND20126173,SandiaNational Laboratories,July2012.

UncertaintyFrameworksand Typologies Subjective(Bayesian)vs.

Objective(frequentist)

Aleatory/Epistemic Parameter/Model/Completeness Probabilisticvs.NonProbabilistic Additionaldiscussiononparameter,model,andcompletenessuncertainty

49 Searching(1/5):ActiveSupplement?

TypicalPRAapproachforidentifyingexternalhazards:

systematicallygeneratepossibilities,thenscreen Post3/11observations

- IPEEEguidance*allowedscreeningofexternalfloods basedondeterministic,designbasisconsiderations

- ASME/ANSPRAstandardaddenda(2009and2013) allowedsimilarscreening

- TheBlayais flood(1999)canbeviewedasanon seismicallyinducedprecursortotheFukushimaDaiichi reactoraccidents Activesearchesforhazardsandhazardcombinations (redteaming)mightsupportefficientidentification

- Logicbasedapproaches(e.g.,MasterLogicDiagram, HeatBalanceFaultTree,STAMP/STPA,)

- Functionalclassifications

- Operationalexperience PRATechnologyChallenges

[FukushimaReview]

• U.S.NuclearRegulatoryCommission,ProceduralandSubmittalGuidancefortheIndividualPlantExaminationofExternalEvents(IPEEE) forSevereAccidentVulnerabilities,FinalReport,NUREG1407,1991.

Whatisneededto causeareactivity excursion?

Howcanan earthquakecausea reactivityexcursion?

50 Searching(2/5):ExampleDeductiveApproach PRATechnologyChallenges

[FukushimaReview]

HeatBalanceFaultTree

51 Searching(3/5):

ExternalHazards ScenarioBased Classification Example PRATechnologyChallenges

[FukushimaReview]

52 Searching(4/5):EmpiricalExperience Accidents Year Plant(s)

Precursor?

1979 TMI DavisBesse (1977) 1986 Chernobyl Leningrad(1975) 2011 Fukushima Blayais (1999)

SomeSignificant*U.S.Precursors Year Plant(s)

Notes 1975 BrownsFerry Worstprecursor Fire=>lossofU1ECCS 1978 RanchoSeco Nextworstprecursor Humanerror(maintenance)=>loss ofNNI,LOFW 2002 DavisBesse Mostrecentsignificantprecursor Multiplehuman/organizationalfaults

=>RPVheadcorrosion

• PerAccidentSequencePrecursor(ASP)program PRATechnologyChallenges

[FukushimaReview]

53 Searching(5/5):OtherInterestingEvents Year Plant(s)

ScenarioType Notes 1957 Windscale1(UK)

Fire Graphitefireincore,releasetoenvironment.

1975 Greifswald1(EastGermany)

Fire Powercablefire,lossofmainfeedwater,pressurizersafety valvesfailtoreseat.

1977 Gundremmingen A(EastGermany)

LOOP/LOCA Partiallossofoffsitepower(LOOP)andsubsequentlossof coolingaccident(LOCA)withinternalflooding.

1978 Beloyarsk 2(SovietUnion)

Fire TurbineBuildingfirespreadsintoMainControlRoom,collapses TurbineBuildingroof.

1981 HinkleyPointA1,A2(UK)

ExternalFlood;LOOP(weather)

SevereweatherLOOPandlossofultimateheatsink(LOUHS).

1982 Armenia1(SovietUnion)

Fire Fireinducedstationblackout(SBO).

1989 Vandellos 1(Spain)

Fire Fireinducedinternalflood.

1991 Chernobyl2(SovietUnion)

Fire FireinducedTurbineBuildingroofcollapse.

1993 Narora 1(India)

Fire FireinducedSBO.

1993 Onagawa 1(Japan)

ReactivityExcursion Seismicallyinducedreactivityexcursion.

1999 Blayais 1,2(France)

ExternalFlood SevereweatherLOOPandpartialLOUHS.

2001 Maanshan 1(Taiwan)

LOOP(Weather);Fire(HEAF)

SevereweatherLOOPandsubsequentSBO.

2003 Pickering 48;Darlington 1,2,and4;Bruce 3,4,and6(Canada);

Fermi2,Fitzpatrick,Ginna,IndianPoint 2and 3,NineMile Point 1and 2,OysterCreek,Perry(U.S.)

LOOP(weather)

NortheastBlackout.

2004 Madras2(India)

ExternalFlood TsunamiinducedLOUHS.

2009 Cruas 24(France)

ExternalFlood LOUHSduetoflooddebris.

2011 FukushimaDaiichi 56,FukushimaDaini 14,Onagawa 13, TokaiDaini,Higashidori 12(Japan)

ExternalFlood Earthquake andtsunamiinducedincidents(inadditionto accidentsatFukushimaDaiichi 13).

PRATechnologyChallenges

[FukushimaReview]

54 IAEATECHNICALMEETING(TM)ONPSA TECHNOLOGYENHANCEMENT:TOPICS PerspectivesonselectedadvancedPRAtopics

[IAEATM]

PRATechnologyChallenges Topics DynamicPSA Combinationsofhazards Portableequipment UseofPSAindevelopmentofSAMGs Level3PSA Softwarereliabilityandmodelling Incorporationofageingaspects

55 IAEATMonPSATechnologyEnhancement*

TechnicalMeetingontheEnhancementofMethods,ApproachesandToolsforDevelopmentand ApplicationofProbabilisticSafetyAssessments(virtual),September29October2,2020 Objectives:

- DiscusscurrentstatusofandMemberStateexperiencewithadvancedPSAmethods,approachesand applications

- UpdateinformationonrelevanttopicsinadrafttechnicalreportonadvancedPSAapproachesand applications.

Highlightedtopics(candidateareasforenhancements):

- DynamicPSA

- Combinationsofhazards

- Portableequipment

- DevelopmentofSAMGs

- Level3PSA

- Softwarereliabilityandmodelling

- Incorporationofageingaspects

[IAEATM]

PRATechnologyChallenges T:Technology K:Knowledge A:

Analyses Analyses(forapplication)

Technology(providescapability)

Knowledge(providescontext)

Why?

• Includingstateofpracticeaswellastechnology

56 DynamicPRA(1/7):Reality Adaptedfrom:R.Gauntt,FukushimaDaiichiAccidentStudy:MELCORAnalysesandResults,OECD/NEAFukushimaAccidentAnalysisWorkshop,IssylesMoulineaux,France,June1820,2012.

SeealsoR.Gauntt,etal.,MELCORSimulationsoftheSevereAccidentattheFukushima1F1Reactor,ANSWinterMeetingandNuclearTechnologyExpo,SanDiego,CA,November1115,2012.

ContainmentVenting:

Preventscatastrophic failure Causesreleaseto environment PRATechnologyChallenges

[IAEATM]

Pressure(MPa) 1.0 0.5 0.0 0

5 10 15 30 25 20 Time(hr) steamdome drywell wetwell RPVTEPCO DWTEPCO WWTEPCO manual ventingof wetwell lowerheadfailure steamlinerupture pressurizationfromcore relocationtolowerhead Startprep forventing Govt orders venting Localevacuationconfirmed,1st teamdispatched 2nd teamdispatched,turnedback(radiation)

UnsuccessfulattemptstoopenAO90 OpenAO72 3/11/2011 14:46

57 DynamicPRA(2/7):ClassicalRepresentation PRATechnologyChallenges

[IAEATM]

58 DynamicPRA(3/7):Basics

• Risk{scenarios,consequences,likelihoods}

• PRA:likelihoodexpressedusingprobabilities

• DynamicPRA:

- Asimpleview:PRAthatexplicitlymodels systemdynamics(whatnothow)

- Typicallyenvisionedasaformofdirect simulationbutdoesnthavetobe

- Notintendedtoaddressdynamicallychanging PRAs(e.g.,riskmonitors)

PRATechnologyChallenges

[IAEATM]

Dy*nam*ics,n. abranchofmechanics thatdealswithforcesandtheirrelation primarilytothemotionbutsometimes alsototheequilibriumofbodies TypicalModelingApproaches Statetransition(celltocell)

Dynamiceventtrees Directsimulation RelatedNames/Concepts IntegratedDeterministicProbabilistic SafetyAssessment(IDPSA)

IntegratedSafetyAssessment(ISA)

Computationalriskassessment(CRA)

IntegratedPRA(IPRA)

Simulationmodeling(e.g.,discrete eventsimulation)

59 DynamicPSA(4/7):BenefitsofEnhancement

• Analyses(anticipated,potential)

- Advancedreactordesignapprovals

- Operatingreactorriskinformedapplications(e.g.,

FLEX,security)

- Externalhazardsscenarios(e.g.,flooding)

- Severeaccidents

• Technology

- Improvedrealism(fewermodellingapproximations)

- Reducedcompletenessuncertainties(e.g.,EOCs, passivesystems)

- Improvedsynergy(otherfields,educationaltrends)

• Knowledge

- Improvedriskinsights(margins,contributors)

PRATechnologyChallenges

[IAEATM]

Longhistory(startingwithfastrx)

J.M.Lanore,etal,ProgressinMethodologyfor ProbabilisticAssessmentofAccidents:Timingof AccidentSequences,"ANS/ENSIntlMtgProbabilistic RiskAssessment,PortChester,NY,1981.

A.AmendolaandG.Reina,EventSequencesand ConsequenceSpectrum:AMethodologyforProbabilistic TransientAnalysis,"NuclearTechnology,77,297315(1981).

Seealsodraftwhitepaper(ML19066A390)andpresentationfrom2019IAEAworkshop (ML19248C656)

60 DynamicPSA(5/7):StatusandTechnicalChallenges

• Currentstatus

- U.S.:technologydevelopment,multipledemonstrations

- International:someapplications

• TechnicalChallenges

- Phenomenologicalmodels(particularlyoperatingcrews)

- Data

- Computationalrequirements(forcomplexscenarios)

- Treatmentofuncertainties

- Postprocessingforinsights PRATechnologyChallenges

[IAEATM]

61 DynamicPSA(6/7):ModelingOperatingCrews PRATechnologyChallenges

[IAEATM]

BasedondatafromABye,etal.,

InternationalHRAEmpirical Study,NUREG/IA0216,2011.

62 DynamicPSA(7/7):ImplementationChallenge

• Challenge:transitionfromR&Dto RIDMsupport

- Conflictinggoals:technology advancementvs.problemsolving

- Communicationandperception

- Investmentrequirements, cost/benefit

- Culturalresistance PRATechnologyChallenges

[IAEATM]

Notalwayscomplicated T.J.McIntyreandN.Siu,"ElectricPowerRecoveryatTMI1,ASimulation Model,"ANS/ENSIntlTopicalMtgThermalReactorSafety,SanDiego, California,February26,1986.

TAF Computationalcapabilities+investments(e.g.,

DOE,TSOs,universities)=>timetoreapbenefits?

63 CombinationofHazards(1/3):Background

• Historicaltreatment

- Hazards(earthquakes,fires,floods, highwinds,aircraftcrashes,offsite industrialaccidents,)typicallytreated oneatatime

- Specificcombinations(seismically inducedfiresandfloods)recognized andaddressedinPRAguidance

• Increasedinterestinbroader considerationfollowingthe FukushimaDaiichireactoraccidents (3/11/2011)

PRATechnologyChallenges

[IAEATM]

AmericanNuclearSocietyandtheInstituteofElectricalandElectronicsEngineers,PRAProceduresGuide,NUREG/CR2300,1983.

J.A.Lambrightetal.,"FireRiskScopingStudy:InvestigationofNuclearPowerPlantFireRisk,IncludingPreviouslyUnaddressedIssues,"NUREG/CR5088,1989.

TheGreatLisbonEarthquake(November1,1755) https://commons.wikimedia.org/wiki/File:Lissabon2.jpg

64 CombinationofHazards(2/3):BenefitsofEnhancement

• Analyses(ongoing)

- Currentriskinformedapplications(specificcombinations)

• Technology

- Improvedrealism(correlationofhazards)

- Reducedcompletenessuncertainties

- Improvedsynergywithnaturalhazardscommunity

• Knowledge

- Additional/improvedinsights PRATechnologyChallenges

[IAEATM]

65 CombinationofHazards(3/3):StatusandChallenges

• Currentstatus

- U.S.:somemethodsdevelopedand used,includedinPRAstandardsand guidance

- International:activedevelopment(focus onsystematic,exhaustiveapproaches)

• Challenges

- Efficientidentificationandprioritization

- Dataaugmentation(simulation?)

- Communication(disciplinespecific frameworks-whatisahazard?Area ofresponsibilitywhenperforming analyses https://commons.wikimedia.org/wiki/File:Storms_Lothar_and_Martin_december_1999.png Treatmentofconsecutiveevents (andpreconditioning)?

HurricanetracksadaptedfromUniversityofWisconsinMilwaukee (https://web.uwm.edu/hurricanemodels/models/archive/)

EmergencyresponsebasedondatafromNationalHurricaneCenter:

(https://www.nhc.noaa.gov/1992andrew.html)

Roleofstochasticsimulation?

PRATechnologyChallenges

[IAEATM]

66 PortableEquipment(1/4):EarlyPerspectives

• McCullough,Mills,andTeller(1955):nuclearfire fighters

• IndianPoint3PRA(1983):alternativestofixed measures(e.g.,corecatcher,filtered/vented containment)

• IPE/IPEEE(19882002)plantimprovements:

- Portablepumps(e.g.,isolationcondensermakeup)

- Portablegenerators(batterychargers)

- Portablefans(roomcooling,smokeremoval)

• Severeaccidentmanagementalternatives(SAMAs, 20022018)includesimilarideas

• ReluctancetocreditinPRAwithoutincorporationin proceduresandtraining PRATechnologyChallenges

[IAEATM]

Seealsopresentationfrom2019IAEAworkshop(ML19248C655)

67 PortableEquipment(2/4):SomePre3/11Events

• MajorExternalEvents

- HurricaneAndrew/TurkeyPoint3&4(1992)

- WinterStormMartin/Blayais 1&2(1999)

• MajorInternalFires

- Greifswald1(1975)

- Armenia1&2(1982)

• Lesserevents

- SanOnofre1(1982):submersiblepumpforintakestructure

- DiabloCanyon(2000):generatorforswitchyardbatterycharger

• NonNuclearEvents

- NorthridgeEarthquake,M6.7(1994)

- KobeEarthquake,M6.9(1995)

Onsitedamage, lossofsiteaccess, offsitedamage; portablefire pumps,debris removal Lossofpowerandcontrol, smoke,explosions(A);

temporarycables Facilityandinfrastructuredamage, fires,emergencyservicedemands; portablegenerators,preplanning, workarounds PRATechnologyChallenges

[IAEATM]

TurkeyPointTurbineDeck EffectofHurricaneAndrewontheTurkeyPointNuclear GeneratingStationfromAugust2030,1992,NUREG 1474,March1993(ML063550235)

68 PortableEquipment(3/4):BenefitsofEnhancement Analyses(ongoing)

- U.S.:RIDMapplications(FLEX,othernon safetyrelatedequipment)

- International:PSAupdates(PSR),

EOP/SAMGimprovement,margins assessments Technology

- ImprovedHRAforexMCRactivities (possiblyincludingtaskbased simulation)

- Improvements(practice,methods?)in constructinginformedpriors(potential)

Knowledge

- Improvedinsights PRATechnologyChallenges

[IAEATM]

M.T.Lawless,K.R.Laughery,andJ.J.Persensky,UsingMicroSainttoPredictPerformanceina NuclearPowerPlantControlRoom:ATestofValidityandFeasibility,NUREG/CR6159,1995.

S.Fogarty,ApproachesandToolstoQuantifyingFacilitySecurityRisk,INMMWorkshoponRisk InformedSecurity,StoneMountain,GA,February1112,2014.

TaskBasedSimulation:OldIdea,RecentApplications

69 PortableEquipment(4/4):StatusandChallenges

• Currentstatus

- StronginterestU.S.andabroad

- Manyapplications(e.g.,NOED,CRM, SDP,licensingactions,NTTF2.1seismic PRA)

- Furtherapplicationsbeingdeveloped

- ImprovedHRAdemonstration(IDHEAS)

• Challenges

- Reliabilitydata(higherfailurerates)

- HRA(e.g.,granularity/aggregation, quantification,creditfornon proceduralized actions)

PRATechnologyChallenges

[IAEATM]

MobilePumps DieselFuelSupply ToSG ToCore AdaptedfromT.Hong,ApplicationofPortableEquipmentinPSAModelfor WHtypeNuclearPowerPlant,IAEATechnicalMeetingontheEnhancementof Methods,ApproachesandToolsforDevelopmentandApplicationof ProbabilisticSafetyAssessments,September29October2,2020.

70 UseofPSAinDevelopmentofSAMGs(1/6):Background

• SAMG/SAMGs=SevereAccident ManagementGuidance/Guidelines

• SevereAccidentPolicyStatement*

- [T]hecommitmentofutilitymanagementto thepursuitofexcellenceinriskmanagementis ofcriticalimportance.

- 1983draftcriticizedforperceivedoverreliance onPRA

• SECY88147:NRCplanforclosingsevere accidentissues**

• NEI9104,Rev.1(1994):industry commitmenttoimplementSAMGs;noNRC regulation***

PRATechnologyChallenges

[IAEATM]

• U.S.NuclearRegulatoryCommission,PolicyStatementonSevereReactorAccidentsRegardingFutureDesignsandExistingPlants,50FR3218,August8,1985.

• • U.S.NuclearRegulatoryCommission,"IntegrationPlanforClosureofSevereAccidentIssues,"SECY88147,May25,1988.

• • • NuclearEnergyInstitute,SevereAccidentIssueClosureGuidelines,NEI9104,Rev.1,(formerlyNUMARC9104),December1994.(ML072850981)

SevereAccident Anaccidentmoreseverethandesignbasis accidents;involvessubstantialdamagetoreactor coreregardlessofoffsiteconsequences.*

71 DevelopmentofSAMGs(2/6):Respondinginextremis PRATechnologyChallenges

[IAEATM]

[BeforeTMI]coredamagewasnevernever land R.Bari1 TheNPSERC[EmergencyResponseCenter]receivedreports thatthenuclearreactorsweresuccessivelylosingtheir powersuppliesandUnits1,2and4inparticularhadlostall oftheirpowersources.EveryoneattheNPSERCwaslostfor wordsattheongoingunpredictedanddevastatedstate.

InvestigationCommitteeInterimReport2

[SiteSuperintendent]Yoshidawasaskedifheopenedupthe accidentmanagementmanualanduseditasareference.Hesaid heneverreferredtoitorevenopeneditup.Heexplainedhow ineffectivemeasuresthoughtupbypeoplebeforehandcanbe.

TheYoshidaTestimony3 1)

PlenaryPanel:PerspectivesonNuclearSafetySincetheThreeMileIslandEvent,ANSIntlMtgProbabilisticSafetyAssessment(PSA2019),Charleston,SC,2019.

2)

GovernmentofJapan,InterimReport(MainText),GovernmentofJapanInvestigationCommitteeontheAccidentatFukushimaNuclearPowerStationsofTokyo ElectricPowerCompany),Tokyo,Japan,2011.

3)

TheYoshidaTestimony:TheFukushimanuclearaccidentastoldbyplantmanagerMasaoYoshida,AsahiShimbun,2014.(Availablefrom:

http://www.asahi.com/special/yoshida_report/en/)

72 DevelopmentofSAMGs(3/6):Respondinginextremis PRATechnologyChallenges

[IAEATM]

TheFukushimaDaiichiaccidentextendedovermultipledays andimposedseverementalandphysicalfatigueoncontrolroom operators,fieldstaff,andpersonnelintheplantsemergency responsecenter.Controlroomoperatorsandfieldpersonnel werealsoexposedtophysicalstressors(e.g.,lossoflightingand highradiation)aswellaspsychologicalstressorsassociatedwith risktotheirlivesandthoseoftheircoworkersandfamilies.

NationalResearchCouncil1 weneverhadenoughtime,sothepumpthefireengineranoutof fuel,anditcouldnolongerpumpwaterinwhenitwastimetodoso whenreactorpressurehadfallen.Thatgaveusanotherletdown,and wetalkedaboutsending(workers)topumpin(water).Thatwaswhen Ithoughtwewerecomingtotheend.

M.Yoshida,TheYoshidaTestimony2 1)

NationalResearchCouncil,LessonsLearnedfromtheFukushimaNuclearAccidentforImprovingSafetyofU.S.NuclearPlants,NationalAcademiesPress, Washington,DC,2014.

2)

TheYoshidaTestimony:TheFukushimanuclearaccidentastoldbyplantmanagerMasaoYoshida,AsahiShimbun,2014.(Availablefrom:

http://www.asahi.com/special/yoshida_report/en/)

73 DevelopmentofSAMGs(4/6):FormsandImplications

• Forms

- Tacticaldirection(procedurelike)

- Strategicguidance

• PRAconsiderations

- Scenariodevelopment(e.g.,RCS conditions,siteconditions)

- Instrumentationsurvivability, trustworthiness

- Crewfactors

• PSFs/PIFsandeffectonperformance

- Cognition,decisionmaking

- Execution,coordination

• Crewtocrewvariability PRATechnologyChallenges

[IAEATM]

Strategic Identifyavailablemeanstoperformfunction (e.g.,reducingcontainmentrelease)

Identifypreferredstrategytoperformfunction

Systemsandlineups

Detectionmeansfornegativeimpacts

Limitationsonusesofmeans

Specialparameterstomonitor DirectControlRoomtoimplementstrategy Verifystrategyimplementation Determineifchallengeisbeingmitigated Tactical IF[condition(s)]

THEN[specificaction(s)]

74 DevelopmentofSAMGs(5/6):BenefitsofEnhancement Analyses

- ImprovedSAMGsandimplementation(e.g.,

newscenarios,prioritizationfortraining)

Technology

- ImprovedHRAforpostcoredamage, guidanceorientedresponses

- Improvedphenomenologicalmodels(e.g.,for severeaccidentinducedcascadingfailures)

Knowledge

- Additional/improvedinsights(e.g.,safety margins,prioritiesforsevereaccidentR&D)

- Improvedrealism=>improvedacceptanceand appreciationofLevel2PRA PRATechnologyChallenges

[IAEATM]

75 DevelopmentofSAMGs(6/6):StatusandChallenges Currentstatus(useofPRA)

- U.S.

• SOARCAanalysesofbenefit

• SomechangesidentifiedduringFLEXimplementation

- International:widespread Challenges

- Level2PRAuncertainties

• HRA

• Severeaccidentphenomenology

- Scope:whichscenarios/possibilities

- Appropriaterealism

• Dependencies(e.g.,multisource)

• UseofGameOvermodeling

- Lowlikelihoodofevent,incentivesforfullLevel2PRA PRATechnologyChallenges

[IAEATM]

D.Collins,etal.,ModelingPotentialReactorAccidentConsequences,NUREG/BR0359Rev.1,2012.(ML12347A049)

SOARCAAssessmentofB.5.bMeasures

76 Level3PSA(1/4):Background

• Includesanalysisofoffsiteconsequences; someterminologyambiguity

- Initiatingeventtooffsiteconsequences

- Releasecategorytooffsiteconsequences

• ScopeofearlyPRAs

- NRC:WASH1400(1975),NUREG1150(1990)

- Industry:OysterCreek(1979),Zion(1981),Indian Point(1982),Limerick(1982),Millstone(1983),

Seabrook(1983),Oconee(1984)

• Vulnerabilityanalyses(IPE,IPEEE)andlater:

focusoncoredamageandlargeearlyrelease PRATechnologyChallenges

[IAEATM]

77 Level3PSA(2/4):ProbabilisticConsequenceAssessment Keyelements

- Weatheranddispersion(atmospheric)

- Response(sheltering,evacuation, interdiction)

- Consequences

• Dose(individual,societal)

• Healtheffects(LNT,other)

• Economic Tools

- MACCS(U.S.)

- COSYMA(EU)

- PACE(UK)

- OSCAR(Japan)

PRATechnologyChallenges

[IAEATM]

78 Level3PSA(3/4):BenefitsofEnhancement Analyses

- DemonstrationofLicensingModernizationProgram(LMP) foroperatingplants(pilot)

- Regulatoryanalysisguidancerevisions(potential)

- ApplicationstoEmergencyPlanningZone(EPZ)sizing (potential)

Technology

- Developmentsinselectedareas(e.g.,multisourcePRA)

- Assessmentofimpactofmoredetailedmodels(e.g.,

dispersion)

Knowledge

- Improvedinsightsregardingsafetymargins

- Improvedinsightsforperforminganalyses(risk,feasibility ofandbenefitsfromfutureLevel3studies)

- Improvedstaffcapabilitiesforperformingandreviewing PRAs PRATechnologyChallenges

[IAEATM]

"RiskInformedPerformanceBasedTechnologyInclusiveGuidancefor NonLightWaterReactors,"NEI1804,Rev.1,August29,2019.

79 Level3PSA(4/4):StatusandChallenges

• Status

- U.S.:referenceplantstateofpractice studyongoing

- International:someRIDMapplications, e.g.,

• Genericdesignassessments(UK)

• Safetymargins(Korea)

• Challenges

- Technical

• Currentelements(dispersion,etc.)

• Unaddressedelements(e.g.,aquatic pathways,nonradiologicalconsequences)

• Uncertainties

- Programmatic(scopeandresources)

PRATechnologyChallenges

[IAEATM]

Level3PRAProjectScope

80 SoftwareReliabilityandModeling(1/4):I&CExample Passiveisolationcondenser:flow(and cooling)controlledbyopening/closing DCmotoroperatedisolationvalve Possiblecontrolapproaches

- Analog(relays)

- Digital

- Manual(operators)

- Combination PossibleI&Cfailuremodesinclude

- Lossofsignal(s)

- Incorrectsignal(s)

- Incorrect(forsituation)criteria

- Incorrectdecision(signal/criteria processing)

- Incorrectcommand(decision implementation)

PRATechnologyChallenges

[IAEATM]

Hardware Software Wetware Signals Criteria

ACpower, dTRCS/dt,

LIC,

C DC Command Power

81 SoftwareReliability(2/4):DiversityandCommonality Diverseviews

- Softwaredoesntfailrandomlylikehardware; importantsoftwarefailuresaredueto erroneous/inadequaterequirements=>improperto modelinclassicalPRAframework

- SoftwareispartofanoverallXwaresystem (hardware,software,wetware)wheresimilar argumentscanbemadeaboutothersystem components=>OKtomodelasacomponentat conventionalPRAlevelofabstraction Diverseproblems

- CertificationofI&Csystems

- Riskinformedplantdesign,operation,andoversight Commoncurrentview:Toomanyitemstoaddress deterministically=>riskinformedapproachesare needed PRATechnologyChallenges

[IAEATM]

P{XlC,H}

subjective proposition conditions knowledge

[A]ll modelsarewrong,butsome areuseful.

G.E.P.Box G.E.P.BoxandN.R.Draper,EmpiricalModel BuildingandResponseSurfaces,JohnWileyand Sons,1987.

82 SoftwareReliability(3/4):BenefitsofEnhancement

• Analyses

- Licensingdigitalupgrades

- Approvingnewdesigns

- Generalriskinformedapplications

• Technology

- Improvedhazardidentification

- Reducedcompletenessuncertainties

- ImprovedsynergywithI&Ccommunity

• Knowledge

- Improvedinsights PRATechnologyChallenges

[IAEATM]

83 SoftwareReliability(4/4):StatusandChallenges Currentstatus

- Conventionalfaulttreeanalyses(AP600,SizewellB,

)

- U.S.:Technologydevelopment(e.g.,integrationof STAMP/STPAwithconventionalPRA)

- International:multipleactivities Individualcountries(e.g.,Finland,France,Korea)

WGRISKbenchmarkingstudy(DIGMAP)

IAEAreview Challenges*

- Technical SoftwareCCF Data

- Implementation:standardsandguidance

- Cultural M.Porthin,etal.,ComparativeapplicationofdigitalI&CmodelingapproachesforPSA, InternationalTopicalMeetingonProbabilisticSafetyAssessment(PSA2019),Charleston,SC,April28 May3,2019.

WGRISKBenchmarkingStudy PRATechnologyChallenges

[IAEATM]

• SeealsoS.Arndt,E.Thornsbury,andN.Siu,WhatPRAneedsfromadigitalsystemsanalysis,6th InternationalConferenceon ProbabilisticSafetyAssessmentandManagement(PSAM6),SanJuan,PuertoRico,June2328,2002.

84 IncorporationofAgeingEffects(1/5):Background

• ConventionalPRAmodels

- Failuresarememoryless

• Failondemand:Bernoulliprocess(binomialdistribution)

• Failureduringoperation:Poissonprocess(Poissonand exponentialdistributions)

- Failureratescanbeadjustedtoreflectageing

• Moregeneralmodel:timedependentfailurerates

- Burnin,steadystate,ageing(degradation)=>bathtub curve

- Differentagingandrepair/replacementfordifferentSSCs

=>morecomplexmodel(RenewalTheory)

PRATechnologyChallenges

[IAEATM]

Asgoodasnew 1

85 AgeingEffects(2/5):Experiences

• Activecomponents

- Subjecttotestingandrenewal

- Largeuncertaintybands

• Passivecomponents

- Moredifficulttoinspectandrenew

- Subjecttophenomenapotentially amenabletomechanisticmodelingand analysis

- Famousexample:DavisBesse (2002)

DavisBesse ReactorPressureVesselHead Degradation AdaptedfromNUREG/BR0353,Rev.1 PRATechnologyChallenges

[IAEATM]

86 AgeingEffects(3/5):ModelingApproaches

• Statistical

- Parametricmodelsforfailurerate(e.g.,linear)

- Quantificationviaoperationalexperiencedata

- Challenges

• Datacollection(currentsystemsareinsufficient)

• Datacharacterization(failure?rectifiability?)

• Mechanistic

- FirstprinciplescausalmodelsforSSCs

- Challenges

• Completeness(e.g.,unexpectedmechanisms,combinationsand synergies;detectionandresponse)

• Treatmentofuncertainties

• CompatibilitywithconventionalPRAframework PRATechnologyChallenges

[IAEATM]

M(ModeloftheWorld):

Scope,structure i:

Parameters Universe KnownUnknowns UnknownUnknowns

87 AgeingEffects(4/5):BenefitsofEnhancement Analyses

- Riskinformedtreatmentofotherdegradation mechanisms(potential)

Technology

- Capabilitiesshouldregulatoryneedarise(e.g.,

subsequentlicenserenewal)

- Improvedperspectivesandapproachestomechanistic modeling(includingthetreatmentofuncertainties)

- ImprovedsynergywithnonPRAtechnicalcommunities Knowledge

- Improvedinsightssupportingawarenessand prioritizationofmechanisms/scenarios/mitigation measures(ascomparedwithotherriskcontributors)

- Improvedunderstandingofmodeledmechanisms PRATechnologyChallenges

[IAEATM]

88 AgeingEffects(5/5):StatusandChallenges Currentstatus(U.S.)

- U.S.:longhistoryofR&D,PTSapplication*

- International:researchwithdemonstration applications(EuropeanUnionAgingPSANetwork)

Challenges

- Data

- Physicsoffailuremodeling

- Recognitionandtreatmentofothertrends,e.g.,

• Technology(NDE,prognostics,)

• Workforce

• Fleet(uniquereactors)

- Implementation

• SeparatingadvocacywantsfromRIDMneeds

• IncorporationinRIDMstandardsandguidance)

PRATechnologyChallenges

[IAEATM]

D.RudlandandC.Harrington,xLPR PilotStudyReport,NUREG2110,2012.(ML12145A470)

Blendingmechanisticandstatisticalperspectives changesPRAapproach?

M.EricksonKirk,etal.,TechnicalBasisforRevisionOfthePressurizedThermalShock(PTS)ScreeningLimitinthe PTSRule(10CFR50.61):SummaryReport,NUREG1806,2006.

89 TREATMENTOFPARAMETER,MODEL,AND COMPLETENESSUNCERTAINTY PerspectivesontheanalysisandcommunicationofuncertaintiesforRIDM PRATechnologyChallenges

[UncertaintyTypology]

Topics ParameterUncertainty ModelUncertainty CompletenessUncertainty InternalRiskCommunication

90 Parameter,Model,andCompletenessUncertainty M(ModeloftheWorld):

Scope,structure i: Parameters

Universe KnownUnknowns UnknownUnknowns mod*el,n. a representationofreality createdwithaspecific objectiveinmind.

A.Mosleh,N.Siu,C.Smidts,andC.Lui,Model Uncertainty:ItsCharacterizationand Quantification,CenterforReliability Engineering,UniversityofMaryland,College Park,MD,1995.(AlsoNUREG/CP0138,1994)

PRAmodelsforNPPs Distinctionsarenot necessarilycrisp Regardlessofallocationto categories,needtoconsider incharacterizationof uncertainties PRATechnologyChallenges

[UncertaintyTypology]

See:

M.Drouin,etal.,GuidanceontheTreatmentofUncertaintiesAssociatedwithPRAsinRiskInformedDecisionmaking,NUREG1855,Rev.1,2017.

U.S.NuclearRegulatoryCommission,AnApproachforUsingProbabilisticRiskAssessmentinRiskInformedDecisionsonPlantSpecificChangestotheLicensingBasis,Regulatory Guide1.174,Revision 3,January2018.

91 ParameterUncertainty(1/3):CurrentPractice Routinelyestimated(Bayesianinference)andpropagated(e.g.,

directMonteCarlo,LatinHypercube)

PRATechnologyChallenges

[UncertaintyTypology]

92 ParameterUncertainty(2/3):BayesianExample Parameterofinterest:frequencyofmajorflooding()

Priorstateofknowledge:minimal Evidence:10eventsover18772017(140years)

BayesTheorem:

Posteriorstateofknowledge:

Date FloodHeight(ft) 3/19/1936 36.5 6/1/1889 34.8 10/16/1942 33.8 10/1/1896 33.0 11/6/1985 30.1 9/8/1996 29.8 1/21/1996 29.4 11/25/1877 29.2 4/27/1937 29.0 6/23/1972 27.7 0.00 0.05 0.10 0.15 0.20 0.25 0.30 ProbabilityDensity

MajorFloodFrequency(/yr) 05 =0.040/yr 50 =0.069/yr 95 =0.11/yr mean=0.071/yr prior posterior returnperiod=12yr 1880 1900 1920 1940 1960 1980 2000 PRATechnologyChallenges

Poisson Noninformative PotomacRiver(HarpersFerry,VA)*

• Notes:

1)

Datafrom:https://water.weather.gov/ahps2/crests.php?wfo=lwx&gage=hfew2&crest_type=historic 2)

MajorFlood:height>24ft

[UncertaintyTypology]

93 ParameterUncertainty(3/3):Challenges

• Datapreprocessing

- Selection

- Interpretation

• Effectofanalysisshortcuts

- Standard(e.g.,noninformative) priordistributions

- Simplifiedexpertelicitation

- Independenceassumption

• Ensuringcorrespondencewith stateofknowledge

- Basicevents(microview)

- Overallresults(macroview)

PRATechnologyChallenges 0.00 0.20 0.40 0.60 0.80 1.00 1.00E09 1.00E08 1.00E07 1.00E06 1.00E05 1.00E04 1.00E03 ProbabilityDensityFunction (Normalized)

FailureRate(/hr)

RuntimeFailures(MotorDrivenPumps)

ServiceWater NormallyRunning Standby 2015Industrywideestimatesfrom:https://nrcoe.inl.gov/resultsdb/AvgPerf/

ServiceWaterPumps:2failuresin16,292,670hours NormallyRunningPumps:225failuresin59,582,350hours StandbyPumps(1st houroperation):48failuresin437,647hours

[UncertaintyTypology]

94 HurricaneAndrew:8/22/1992,1200UTC (about2daysbeforeFLlandfall)

Model Uncertainty(1/6):

Hurricane Example PRATechnologyChallenges HurricanetracksadaptedfromUniversityofWisconsinMilwaukee:(https://web.uwm.edu/hurricanemodels/models/archive/)

EmergencyresponsebasedondatafromNationalHurricaneCenter:(https://www.nhc.noaa.gov/1992andrew.html)

[UncertaintyTypology]

95 Model Uncertainty(2/6):

Hurricane Example HurricaneIrma:9/8/2017,0000UTC (about2daysbeforeFLlandfall)

PRATechnologyChallenges HurricanetracksadaptedfromUniversityofWisconsinMilwaukee:(https://web.uwm.edu/hurricanemodels/models/archive/)

EmergencyresponsebasedondatafromNationalHurricaneCenter:(https://www.nhc.noaa.gov/1992andrew.html)

[UncertaintyTypology]

96 ModelUncertainty(3/6):HRAExample Samemethod,differentteams Sameteam,differentmethods Allteams,allmethods NRI,CREAM NRI,DT+ASEP NRC,SPARH INL,SPARH ABye,etal.,InternationalHRAEmpiricalStudy,NUREG/IA0216,August2011.

PRATechnologyChallenges

[UncertaintyTypology]

97 ModelUncertainty(4/6):HRAExample HFE2A HFE1C HFE1A HFE3A HFE1B HEPsbyHFE(AllMethods)

Decreasingdifficulty HumanErrorProbability(HEP) 1.0E+0 1.0E1 1.0E2 1.0E3 1.0E4 1.0E5 ASEPTeam1 ASEPTeam2 SPARHTeam1 SPARHTeam2 CBDT&HCR/ORETeam1 CBDT&HCR/ORETeam2 CBDT&HCR/ORETeam3 ATHEANATeam1 ATHEANATeam2 Empirical95th Percentile Empirical5th Percentile AdaptedfromNUREG2156 PRATechnologyChallenges

[UncertaintyTypology]

98 ModelUncertainty(5/6):CurrentApproaches

• Importanttoacknowledgeand treat(incontextofdecision)

• Standardsandguidance:

characterize

• Alternatives

- Consensusmodel

- Sensitivityanalysis

- Weightedalternatives(e.g.,SSHAC)

- Outputuncertainties AdaptedfromV.M.Andersen,SeismicProbabilisticRiskAssessment ImplementationGuide,EPRI3002000709,ElectricPowerResearch Institute,PaloAlto,CA,December2013 PRATechnologyChallenges

[UncertaintyTypology]

99 ModelUncertainty(6/6):Challenges

• Differenttechnicalpointsofviewon treatment:

- Competitionbetweenmodelsvs.multiple (correlated)sourcesofevidence

- Quantifyvs.characterize

- Includeorexcludeusereffects

• Methodstoquantifymodeloutput uncertaintyexist;*challengesinclude

- Uncertaintiesinunmeasuredparameters

- Submodellimitsofapplicability

- Representativenessofcomputedresults M.H.Salley andA.Lindeman,VerificationandValidationofSelected FireModelsforNuclearPowerPlantApplications,NUREG1824 Supplement1/EPRI3002002182,November2016.

• See,forexample,E.Droguett andAliMosleh,Bayesianmethodologyformodeluncertaintyusing modelperformancedata,RiskAnalysis,28,No.5,14571476,2008.

PRATechnologyChallenges

[UncertaintyTypology]

100 CompletenessUncertainty(1/8)

PRATechnologyChallenges

• Sources

- Knowngaps(missingscope)

- Unknowngaps

• Concerns

- Excessiveamplification(Fearofthedark)

- Excessivediscounting(availabilityheuristic:

Outofsight,outofmind)

Itwouldceasetobea dangerifwecoulddefineit.

SherlockHolmes (TheAdventureoftheCopperBeeches)

AdaptedfromB.Fischhoff,P.Slovic,S.Lichtenstein,Faulttrees:

Sensitivityofestimatedfailureprobabilitiestoproblemrepresentation, JournalofExperimentalPsychology:HumanPerceptionandPerformance, 4(2),May1978,330344.

CarWontStart BatteryCharge Insufficient StartingSystem Defective IgnitionSystem Defective MischievousActs OfVandalism AllOther Problems FuelSystem Defective OtherEngine Problems

[UncertaintyTypology]

101 CompletenessUncertainty(2/8):Terminology Model Known Gaps (Known Unknowns)

Unknown Gaps (Unknown Unknowns)

• Explicitorimplicit?

• Extentofcoverage?

• Knownbywhom?

• Knownwhen?

• Timefromideatotheory toPRAimplementation?

Viewpoint Preciseclassificationis importantonlyifitaffects:

• Understanding

• Communication

• Decisionmaking

[UncertaintyTypology]

PRATechnologyChallenges

102 CompletenessUncertainty(3/8):KnownGaps*

• Broadscenariocategories

• Contributorswithincategories Rationale CommonExample(s)

Outofscope security/sabotage,operationoutsideapprovedlimits Lowsignificance(preanalysisjudgment) externalfloods(manyplantspreFukushima)

AppropriatePRAtechnology*unavailable managementandorganizationalfactors PRAnotappropriate software,security Category Example(s)

Externalhazards multiplecoincidentorsequentialhazards Humanreliability errorsofcommission,nonproceduralized recovery Passivesystems thermalhydraulicreliability PRATechnologyChallenges

• akaKnownUnknowns

[UncertaintyTypology]

103 https://en.wikipedia.org/wiki/Hurricane_Irma#/media/File:Irma,_Jose_and_Katia_20170907.png MultipleHurricanes:AKnownUnknown PRATechnologyChallenges

[UncertaintyTypology]

104 CompletenessUncertainty(5/8):UnknownGaps*

Model Known Gaps Unknown Gaps Then(asurprise?)

Now(treatedincurrentPRAs?)

BrownsFerryfire(1975)- alongrecognizedhazard;notindraft WASH1400butroutinelytreatednow Chernobyl(1986)- precursoratLeningrad(1975);nonroutinetest duringshutdowninanyLPSDanalyses?

TMI(1979)- precursorsincludeDavisBesse (1977);operatorEOCs notinmodels;currentrecognitionandsomeexplorations Blayais flood(1999)- externalfloodsoftenscreenedattime; currentrecognition,multihazardunderdevelopment Maanshan HEAF/SBO(2001)- HEAFphenomenonknown,inanyPRAs attime?Nowincludedasaninitiator;smokeeffect?

DavisBesse RPVcorrosion(2002)- RPVfailureanalysesfocusedon crackpropagation;M&OfailurenotinPRAs FukushimaDaiichi(2011)- precursors:Blayais (1999),IndianOcean (2004),hazardunderreviewattime;PRAmodelsunderdevelopment PRATechnologyChallenges

• akaUnknownUnknowns

[UncertaintyTypology]

105 CompletenessUncertainty(6/8):CurrentApproaches

• Mindthegap

- Analysisguidance(NUREG1855)

• Progressiveanalysis(screening,bounding, conservative,detailed)

• Changescopeofriskinformedapplication

- Riskinformeddecisionmaking (RG1.174)

• Fill(oratleastreduce)thegap(R&D)

PRATechnologyChallenges

[UncertaintyTypology]

106 CompletenessUncertainty(7/8):RoleofR&D

• Continuetodeveloptechnologytoaddress knowngaps

- Riskinformedprioritization

- Fullyengageappropriatedisciplines

- Takeadvantageofgeneralcomputationaland methodologicaldevelopments

• Facilitatereemphasisonsearching

- Demonstrateefficiencyandeffectivenesswith currenttools(e.g.,MLD,HBFT)vs.

checklist/screening

- Developimprovedtools(includingOpE mining)

Event(NUREG/CR4839),1992 Aircraftimpact Avalanche Coastalerosion Drought Externalflooding Extremewindsandtornadoes Fire Fog Forestfire FrostHail Hightide,highlakelevel,orhigh riverstage

PRATechnologyChallenges

[UncertaintyTypology]

107 CompletenessUncertainty(8/8):

FromLamppoststoSearchBeacons Wheresthe goat???

PRATechnologyChallenges

[UncertaintyTypology]

108 InternalRiskCommunication(1/9):Context OtherConsiderations Currentregulations Safetymargins Defenseindepth Monitoring Quantitative Qualitative AdaptedfromNUREG2150 With To PRATechnologyChallenges

[UncertaintyTypology]

109 InternalRiskCommunication(2/9):Reminder Mean 7.6 x 10-5 /yr 95th 2.6 x 10-4 /yr 50th Median 3.9 x 10-5 /yr probabilitydensityfunction frequency(/yr)

Mean

• Mathematicallydefined Affectedbytail Doesnotcorrespondto aspecificpercentile PRATechnologyChallenges

[UncertaintyTypology]

110 InternalRiskCommunication(3/9):CurrentPractice

• Oftenimplicit(focusonmeanvalues)

• Variousgraphicdisplays

• Includesstoryaswellasnumbers Documentsand Presentations (Flatland)

Interactive Discussion (Storytelling)

LikelihoodClass 5 (10-5/yr) 4 (10-4/yr) 3 (10-3/yr) 2 (10-2/yr) 1 (10-1/yr)

SeverityClass A

Marginal Undesirable Undesirable Critical Critical B

Marginal Marginal Undesirable Undesirable Critical C

No Action Marginal Marginal Undesirable Undesirable D

No Action No Action Marginal Marginal Undesirable E

No Action No Action No Action Marginal Marginal PRATechnologyChallenges

[UncertaintyTypology]

111 InternalRiskCommunication(4/9):Breakdowns*

• Differencesinperceptionofinformation

- Relevance

- Consistencywithpriorbeliefs

• Lackofunderstandingofunderlying science

• Conflictingagendas

• Failuretolisten

• Trust

• Sourcesofbreakdownswithpublic,alsoatleastpartiallyrelevantforinternalriskcommunication.J.L.Marble,N.Siu,andK.Coyne, Riskcommunicationwithinariskinformedregulatorydecisionmakingenvironment,InternationalConferenceonProbabilisticSafety andAssessment(PSAM11/ESREL2012),Helsinki,Finland,June2529,2012.(ADAMSML120480139)

PRATechnologyChallenges

[UncertaintyTypology]

112 InternalRiskCommunication(5/9):InformationComplexity Hyperdimensional

- Scenarios

- Likelihood

- Multipleconsequencemeasures Heterogeneous

- Qualitativeandquantitative

- Multipletechnicaldisciplines Dynamic

- Systemchanges(e.g.,different operationalmodes,effectsofdecisions)

- Changinginformation(learning, adding/discountingdata)

- Newapplications(andcontexts)

Uncertain

- Sparseornonexistentdata

- Outsiderangeofpersonalexperience PRATechnologyChallenges Uhh,weseemtohave aTEPvulnerability, maybe,Ithink Thermal Exhaust Port

[UncertaintyTypology]

113 InternalRiskCommunication(6/9):MoreComplexities

• Individualuserdifferences,e.g.,

- Knowledge

- Preferences/heuristics

• Socialfactors,e.g.,

- Trust

- Decisionandgroupdynamics

• Situationalcontext,e.g.,

- Availabletime

- Decisionsupportvs.informational Willsomebodyfindmea onehandedscientist?!

SenatorEdmundMuskie (Concordehearings,1976)

I.Flatow,Truth,Deception,andtheMythoftheOneHandedScientist, October18,2012.Availablefrom:

https://thehumanist.com/magazine/novemberdecember 2012/features/truthdeceptionandthemythoftheonehanded scientist PRATechnologyChallenges

[UncertaintyTypology]

114 InternalRiskCommunication(7/9):StakeholderTrends

• Experiences,knowledge

• Informationcontentand deliverypreferences

• Comfortwithanalytics, risk,probability

• Mobility Source:https://www.nrc.gov/readingrm/doccollections/commission/slides/2019/20190618/staff20190618.pdf Languageisnotmerelyatoolforhuman communication;languageisitselfameansby whichtherealitiesoftheworldaredivided andviewed.

P.S.Dull,1978 P.S.Dull,ABattleHistoryoftheImperialJapaneseNavy(19411945),NavalInstitutePress,Annapolis,MD,1978 PRATechnologyChallenges

[UncertaintyTypology]

115 InternalRiskCommunication(8/9):SolutionTrends

• Tufte model:escapeFlatlandusingrichdisplaysand reports,encourageusertoexplore

- Promotesactiveinvolvementofdecisionmaker

- Increasesgeneraltrust?

• Agraduatedtechnicalapproachtoassist?

Interface InteractionMode

Hyperlinkeddashboards,reports

Manual

Video

AIassist

Visualimmersion

Multisensoryimmersion Time

• Targetaudience(s)

- Heterogeneous

- Changing

- Constrainedresources

• Schema

- Nostandards:

currentlyanart

- Solutionsbeing developedintuitively; noscientifictesting ContinuingChallenges PRATechnologyChallenges

[UncertaintyTypology]

116 Graphicadaptedfrom https://www.flickr.com/photos/83823904@N00/64156219/

(permissionCCBY2.0)

InternalRiskCommunication(9/9):TheFuture?

M.Korsnick,RiskInformingtheCommercialNuclearEnterprise,PromiseofaDiscipline:Reliability andRiskinTheoryandinPractice,UniversityofMaryland,April2,2014.

PRATechnologyChallenges

[UncertaintyTypology]

117 CLOSINGTHOUGHTS Andwhatifthebirdwontsing?

Nobunaga:Makeitsing.

Hideyoshi:Makeitwanttosing.

Tokugawa:Wait.

Eiji Yoshikawa(Taik)

ClosingThoughts

118 IsWinterComing?

AnyonesubmittingaPRAfor useintheLWRregulatory processshouldfeelthathis longtermtechnicalreputation isontheline.

D.Okrent(1981) 100Reactors ClosingThoughts IncreasingrealismReducingconservatism

/

119 ChallengetoNRC/RESandOpportunities Toincreaseeffectivenessandefficiency

• [Enterprise]riskinformedprioritization

• Considernewtechnicalapproaches

• Bettertargetavailableresources(e.g.,university grantfunds)

• Leverageotherprograms

- Observe(learn,providefeedback)

- Cooperate

- Collaborate

• Goodideasarewelcome!

Dial1800CALLRES Dial1800CALLRES ClosingThoughts

120 ADDITIONALSLIDES

121 PRAHISTORY:TREATMENTOFUNCERTAINTIES AdditionalSlides

122 TMI2 FromHanfordtoWASH1400 SGHWR analysis WASH740 Formoreinformation:T.R.Wellock,AFigureofMerit:QuantifyingtheProbabilityofaNuclearReactorAccident, TechnologyandCulture,58,No.3,July2017,pp.678721.

CredibleAccident System reliability studies Recommend:

accident chain analysis Hanford AEC/NRC UKAEA TechnicalChallenges:1)Quantifyingaccidentprobability 2)Meanstocommunicaterisk notinthegeneration oftheACRSmembers present FarmerCurve WASH1400 Estimates:

OpE (pessimistic)

Decomposition (optimistic)

Windscale 1950 1960 1970 1980 Systemreliability studies Systemreliability studies AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

123 EarlyViewsonCompleteness W.F.Libby(ActingChairman,AEC)- March14,1956responsetoSenator Hickenlooper:itisincumbentuponthenewindustryandthe Governmenttomakeeveryefforttorecognizeeverypossibleeventor seriesofevents whichcouldresultinthereleaseofunsafeamountsof radioactivematerialtothesurroundingsandtotakeallstepsnecessaryto reducetoareasonableminimumtheprobabilitythatsucheventswill occurinamannercausingseriousoverexposuretothepublic.[Emphasis added]

• L.Silverman(Chairman,ACRS)- October22,1960lettertoAECChairman JohnA.McCone:Webelievethatasearchinganalysiswhichisnecessary atthisstage[reactorsitingapproval]shouldbedoneindependentlybythe ownerofthereactor[Emphasesadded]

AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

124 WASH1400Uncertainties(Level1)

WASH1400:itisreasonabletobelievethatthe coremeltprobabilityofabout5x105 perreactoryear predictedbythisstudyshouldnotbesignificantly largerandwouldalmostcertainlynotexceedthevalue of3x104 whichhasbeenestimatedastheupper boundforcoremeltprobability.

RiskAssessmentReviewGroup (NUREG/CR0400):

Weareunabletodefinewhethertheoverall probabilityofacoremeltgiveninWASH1400ishigh orlow,butwearecertainthattheerrorbandsare understated.Wecannotsaybyhowmuch.

1.E05 1.E04 1.E03 CDF(/ry)

WASH1400Uncertainties(Estimated*)

Surry PeachBottom 5th 50th 95th mean

• BasedondatafromTablesV314(PWR)and316(BWR)ofAppendixV, assumingdistributionsarelognormal;medianvaluesaresomewhathigher thanreportedinSection7.3.1oftheMainReport.

AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

125 ACRSConcernswithWASH1400Methodology*

ACRSConcern ExampleEvents[1]

PostWASH1400 Accidentinitiatorquantification (Presumablyexternalevents)

Fukushima Extensivetreatment:fires,earthquakes Inconsistenttreatment:floods Atypicalreactors Fermi1[2]

MultiplePRAsfornonLWRs Designerrors

[3]

Manydesignandoperationalimprovementsidentified byPRAs;databaseincludeseventsinvolvingdesign problems Operatorerrorquantification TMI2 Multiplemethodsemphasizingimportanceofcontext; stillanactiveareaofdevelopment Consequencemodeling Chernobyl,Fukushima Continuing,evolutionaryimprovements(MACCS)

Data Many Improvedhardwaredatabase;fitsandstartswith HRA;extremenaturalhazardsacontinuingchallenge

• ACRSlettertoCongressmanUdallre:adequacyforestimatinglikelihoodoflowprobability/highconsequenceevents(Dec.16, 1976)

TableNotes:

1.

Eventswhosekeycharacteristics(forthegiventopic)mightnothavebeencapturedbyaWASH1400vintageanalysis.

2.

Fermi1hadlimitedfuelmelting.However,withoutananalysis,itisntclearifaWASH1400vintageanalysiswouldhavecapturedthisscenario.

3.

Designweaknesseshaveplayedaroleinmultipleevents.Moredetailedreviewisneededtodetermineif:a)theseareerrors,andb)iftheywould havebeenmissedbyaWASH1400vintageanalysis.

AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

126 TMI2 Chernobyl SomeEarlyDevelopmentsandPRAs Challenges:1)Fillingknowngaps(completenessuncertainty) 2)Clarifyingmeaning:modelsandresults ClinchRiver (LMFBR)

Limerick Millstone Seabrook (fullscope)

Fleming (factor)

Zion (fullscope)

TMI1 (fullscope)

Oconee (fullscope) 1980 1985 1975 Apostolakis (subjective probability)

Forsmark Koeberg

(~WASH1400)

Super Phénix (FBRDHR)

AIPA (HTGR)

USDOE NRC USIndustry International OtherNotable Kaplan/

Garrick (risk)

EC/JRCBenchmarks (systems,CCF,HRA)

RSSMAP/IREP Sizewell

(+DI&C)

IndianPoint (fullscope)

OysterCreek

(+seismic)

Biblis

(+aircraft)

NUREG/CR2300 AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

127 SampleLevel1ResultsDisplay AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

128 SampleResults-SubModelUncertaintyEffect Effectsoffiremodel(COMPBRN) uncertaintyonfiregrowthtime N.Siu,"ModelingIssuesinNuclearPlant FireRiskAnalysis,"inEPRIWorkshopon FireProtectioninNuclearPowerPlants, EPRINP6476,J.P.Sursock,ed.,August 1989,pp.141through1416.

AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

129 SampleResults-ModelUncertainty(UserEffect)

DamageStateFrequency(/yr),Review DamageStateFrequency(/yr),Original 1010 108 106 104 1010 108 106 104 Earlycoremelt,containmentcooling Earlycoremelt,nocontainmentcooling Steamgeneratortuberupture Containmentbypass Directcontainmentfailure Latecoremelt,containmentcooling Latecoremelt,nocontainmentcooling 1.E11 1.E10 1.E09 1.E08 1.E07 1.E06 1.E05 1.E04 1.E03 1.E11 1.E10 1.E09 1.E08 1.E07 1.E06 1.E05 1.E04 1.E03 Original Review InternalEvents 1.E11 1.E10 1.E09 1.E08 1.E07 1.E06 1.E05 1.E04 1.E03 1.E11 1.E10 1.E09 1.E08 1.E07 1.E06 1.E05 1.E04 1.E03 Original Review ExternalEvents Datasource:G.J.Kolb,etal.,ReviewandEvaluationoftheIndianPointProbabilisticSafetyStudy, NUREG/CR2934,December1982.(ML091540534)

AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

130 Chernobyl 9/11 ExpansionAcrossIndustry(US)

Technicalchallenges:1)Characterizingthefleet(variability) 2)DevelopingconfidenceformainstreamingRIDM 1985 1990 2000 1995 GL8820 GL8820 Supplement4 NUREG1560 NUREG1742 NUREG1150 (final)

NUREG1150 (draft)

Severe AccidentPolicy Statement SafetyGoal Policy Statement PRAPolicy Statement ASPPlantClassModels 1982 SPARModels NRC USIndustry IPEs IPEEEs AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

131 NUREG1150Estimated*Uncertainties(Level1)

ModelUncertainty ModelUncertainty

• Notes:totalsshownareestimated.

1)

NUREG1150doesnotaggregatethehazardspecificresults.ThetotalsshownareroughestimatesassumingthattheNUREG1150distributionsarelognormal.

2)

TheWASH1400distributionsarebasedondatafromTablesV314(PWR)and316(BWR)ofAppendixV,assumingthatthedistributionsarelognormal.The medianvaluesaresomewhathigherthanreportedinSection7.3.1oftheMainReport AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

132 Parameter Uncertainties:

Industry Studies Industryresultsfrom:Garrick, B.J.,Lessonslearnedfrom21 nuclearplantprobabilisticrisk assessments,Nuclear Technology,84,No.3,319-339(1989).

AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

133 ParameterUncertainties:LogarithmicvsLinear AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

134 IPE/IPEEE-VariabilityAcrossFleet 0

10 20 30 40 Number BWR PWR CDF(/ry) 1x106 3x106 1x105 3x105 1x104 3x104 1x103 InternalEvents+InternalFloods 0

10 20 30 40 Number BWR PWR CDF(/ry) 1x106 3x106 1x105 3x105 1x104 3x104 1x103 Total AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

135 IPE/IPEEE-ContributionofExternalEvents 1.E07 1.E06 1.E05 1.E04 1.E03 1.E07 1.E06 1.E05 1.E04 1.E03 IPEEECDF IPECDF IPEEEvsIPECDF AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

136 9/11 TheModernEra(US)

Technicalchallenges:1)RIDMissues(e.g.,realism,heterogeneity,aggregation) 2)PostFukushimaissues(e.g.,externalhazards) 3)New/advancedreactors(e.g.,conductofoperations)

NUREG1855 Fukushima RG1.174 ASMEPRA Standard 10CFR50.48(c)

(FireProtection)

Risk Informed ROP NFPA805 NUREG2150 NTTFRequest forInformation (Reevaluations) 2000 2010 2020 2005 2015 NRC USIndustry SECY98144 RiskInformedLicenseAmendmentRequests(LARs)

SAMAs(LifeExtension)

SPARModels NFPA805LARs(FireProtection)

AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

137 SAMA-ContributionofExternalEvents 1.E07 1.E06 1.E05 1.E04 1.E03 1.E07 1.E06 1.E05 1.E04 1.E03 External Internal Externalvs.InternalCDF(SAMA)

Note:Externalincludesinternalfires AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

138 VariabilityinRecentResults(Level1) 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 6.0 5.5 5.0 4.5 4.0 3.5 3.0 1E6 1E5 1E4 1E3 CDF(perreactoryear)

FractionofPlants Highest Reported:

1.3x104 Lowest Reported:

3.5x106 PopulationMean:

4.7x105 AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

139 VariabilityinResults-ComparisonwithIPE/IPEEE 0.00 0.10 0.20 0.30 0.40 0.50 1

2 3

4 5

6 7

8 9

10 NFPA805 IPE/IPEEE 0.01 0.1 1

10 100 1000 FireCDF/InternalEventsCDF FractionofPRAs 0.00001 0.0001 0.001 1.00E05 1.00E04 1.00E03 TotalCDF(IPE+IPEEE)

TotalCDF(RecentLARs) 1E5 1E4 1E3 1E5 1E4 1E3 AdditionalSlides

[PRAHistory:TreatmentofUncertainties]

140 DRIVETORIDMANDTRENDS AdditionalSlides

141 RIDMandNRCsPrinciplesofGoodRegulation

• Independence

• Openness

• Efficiency

• Clarity

• Reliability U.S.NuclearRegulatory Commission,PrinciplesofGood Regulation(ADAMS ML14135A076)

Highest Standards Best Information Public Coherent Logical Practical Competence Acceptable Readily Understood Candid Independence Openness Efficiency Clarity Reliability Risk Safety Margins Defense-In-Depth Current Regulations Performance Monitoring Integrated Decision Making AdditionalSlides

[DrivetoRIDMandTrends]

142 DrivetoRIDM:BacktotheFuture

• Earlyyears:progressiveevolutionof protectionconsideringmaximumcredible accident

- Remotesiting

- Containment

- Engineeredsafeguards,singlefailurecriterion

• Current:engineeringsolutionsconsidered

- Singlefailure

- Containment?

SECY190036,April11,2019(ML19060A081):

thestaffisseekingCommissionaffirmationthat themostdamagingsingleactivefailureofsafety relatedequipmentisrequiredtobeconsideredin performingdesign,andtransientandaccident analyses,unlesssuchafailurecanbeshownwith highconfidencetonotbecredible.

SRMSECY190036,July19,2019 (ML19183A408):Inanylicensingrevieworother regulatorydecision,thestaffshouldapplyrisk informedprincipleswhenstrict,prescriptive applicationofdeterministiccriteriasuchasthe singlefailurecriterionisunnecessarytoprovide forreasonableassuranceofadequateprotection ofpublichealthandsafety.

AdditionalSlides

[DrivetoRIDMandTrends]

143 LookingAhead:PossibleFutures U.S.NuclearRegulatoryCommission,TheDynamicFuturesforNRCMissionAreas,2019.(ADAMSML19022A178)

AdditionalSlides

[DrivetoRIDMandTrends]

144 DrivetoRIDM:Transformation

• Evolvingsituation(marketforces,newnucleartechnologies,new analyticalmethodsanddata,newprofessionals)

ApplyingthePrinciplesofGoodRegulationasaRiskInformedRegulator, October15,2019(ADAMSML19260E683)

• Vision:makesafeuseofnuclear technologypossible

• Continuingstandard:reasonable assuranceofadequateprotection

• Attitude:recognizepotentiallydifferent waysofachievement-embracechange AdditionalSlides

[DrivetoRIDMandTrends]

145 0

10 20 30 40 50 FY17 FY18 FY19 FY20 Number FiscalYear RiskInformedLARSReceived*

Miscellaneous RiskInsights TMRE Fire Seismic GSI191 EPU 50.69 TSTFXXX RITSCompTime RIISI ILRT

• AsofJune8,2020 DrivetoRIDM:EffectofMarketForces "RiskInformedPerformanceBasedTechnologyInclusiveGuidancefor NonLightWaterReactors,"NEI1804,Rev.1,August29,2019.

OperatingRx-MoreuseofPRAmodels NewRx-EarlyuseofPRAindesign AdditionalSlides

[DrivetoRIDMandTrends]

146 DrivetoRIDM:NewTechnologies

• Newdesigns

• Newoperationalconcepts

• SmartReactorSystems

• ImprovedAnalysis Imworried aboutthe mission,Dave.

CmonHAL, openthepod baydoor PhotocourtesyofNEAHalden ReactorProject AdditionalSlides

[DrivetoRIDMandTrends]

147 DrivetoRIDM:NewProfessionals Changing

• Experiences,knowledge

• Informationcontentand deliverypreferences

• Comfortwithanalytics, risk,probability

• Mobility Source:https://www.nrc.gov/readingrm/doccollections/commission/slides/2019/20190618/staff20190618.pdf AdditionalSlides

[DrivetoRIDMandTrends]

148 TrendsandImpacts:ATwoWayStreet Trends Increasing#RIapplications Newlicensingapproaches Newdesigns Newoperationalconcepts Newtechnologies Newanalyticalmethods Newprofessionals

DecisionMaking IssueIdentification OptionIdentification Analysis Deliberation Implementation Monitoring PRATechnology Methods Models Tools Data ChallengetoNRC:

BeReady!

AdditionalSlides

[DrivetoRIDMandTrends]

149 Who?

What?

When?

Where?

How?

Why?

NRC/RES/DRA:TheCardinalQuestions DRA Users

Needs

Applications Suppliers

Contractors

Grantees

Collaborators NonNRC R&D Policy/Decision Makers NearTerm (UserNeed)

LongTerm (FutureFocused)

AdditionalSlides

[DrivetoRIDMandTrends]

150 PRA/RIDM:

TopicAreas forPotential R&D Technical Area Topic Area Reactors Level 1 internal events at power Level 2 Level 3 Low power and shutdown (LPSD)

Operational data Event analysis Generic safety issues (GSI)

Performance indicators and thresholds New reactors (evolutionary)

Advanced reactors Research and test reactors Non-Reactor Facilities and Activities Geologic repositories High-level waste (HLW)

Low-level waste/decommissioning Fuel cycle facilities Transportation Sources Implementation and Application PRA quality (e.g., guidance, standards)

Risk-informed regulation infrastructure Risk-informed regulation applications Risk perception and communication Technical Area Topic Area Special Topics HRA Ageing Passive components Passive systems Digital systems CCF Design and construction Fire Seismic Other external events Security-related events EP&R General Systems Analysis Methods and Tools PRA tools Uncertainty and sensitivity analysis methods and tools Advanced computational methods Advanced modeling methods (e.g., simulation)

Elicitation methods Ivegota littlelist AdditionalSlides

[DrivetoRIDMandTrends]

151 NeedforFocus 0

5 10 15 20 25 30 35 40 45 50 0

100 200 300 400 500 600 700 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

%NRCTotal ContractingBudget($M)

Year NRC Research Budget (FY 1976 - FY 2019)

Actual ($M)

Inflation Adjusted ($M)

% NRC Total BudgetdatafromNUREG1350(NRCInformationDigest)

AdditionalSlides

[DrivetoRIDMandTrends]

152 RIDMAPPLICATIONEXAMPLES AdditionalSlides

153 RiskInfoUses-RegulationsExample (RiskInformedFireProtection)

• BrownsFerryNuclearPowerPlantfire (3/22/75)

• Candleignitedfoampenetrationseal, initiatedcabletrayfire;watersuppression delayed;complicatedshutdown

• SecondmostchallengingeventinU.S.

nuclearpowerplantoperatinghistory

• Spurredchangesinrequirementsand analysis TVAFilePhoto 8.5m 8.5m 11.5m 11.5m 3m 3m Adapted from NUREG-0050 Adapted from NUREG-0050 8.5m 11.5m 3m Adapted from NUREG-0050 AdditionalSlides

[RIDMApplicationExamples]

154 RiskInfoUses-RegulationsExample (RiskInformedFireProtection)

PostBrownsFerrydeterministicfireprotection(10CFRPart 50,AppendixR)

- 3hourfirebarrier,OR

- 20feetseparationwithdetectorsandautosuppression,OR

- 1hourfirebarrierwithdetectorsandautosuppression Riskinformed,performancebasedfireprotection(10CFR 50.48(c),NFPA805)

- VoluntaryalternativetoAppendixR

- Deterministicandperformancebasedelements

- Changescanbemadewithoutpriorapproval;riskmustbe acceptable

- Morethan1/3U.S.fleethascompletedtransition Methodsadoptedbyinternationalorganizations FromCline,D.D.,etal.,InvestigationofTwentyFootSeparation DistanceasaFireProtectionMethodasSpecifiedin10CFR50, AppendixR,NUREG/CR3192,1983.

AdditionalSlides

[RIDMApplicationExamples]

155 RiskInfoUses-LicensingExample (Changesinplantlicensingbasis-RG1.174)

• Voluntarychanges:licenseerequests, NRCreviews

• Smallriskincreasesmaybeacceptable

• Changerequestsmaybecombined

• Decisionsareriskinformed AdditionalSlides

[RIDMApplicationExamples]

156 RiskInfoUses-OversightExample (ReactorOversightProgram)

• Inspectionplanning

• Determiningsignificanceoffindings

- Characterizeperformancedeficiency

- Usereviewpanel(ifrequired)

- Obtainlicenseeperspective

- Finalize

• Performanceindicators CDF < 1E-6 LERF < 1E-7 1E-6 < CDF < 1E-5 1E-7 < LERF < 1E-6 1E-5 < CDF < 1E-4 1E-6 < LERF < 1E-5 CDF > 1E-4 LERF > 1E-5 AdditionalSlides

[RIDMApplicationExamples]

157 RiskInfoUses-OpEExample (AccidentSequencePrecursorProgram)

• ProgramrecommendedbyWASH1400 reviewgroup(1978)

• Providesriskinformedviewofnuclear plantoperatingexperience

- Conditionalcoredamageprobability(events)

- Increaseincoredamageprobability (conditions)

• SupportedbyplantspecificStandardized PlantAnalysisRiskmodels LicenseeEventReports19692018 (Nosignificantprecursorssince2002) significant precursor precursor AdditionalSlides

[RIDMApplicationExamples]

158 RiskInfoUses-DecisionSupportExample (Research)

Typicalproducts(regulatoryresearch)

Waystolookatand/orapproachproblems(e.g.,

frameworks,methodologies)

Pointsofcomparison(e.g.,reference calculations,experimentalresults)

Jobaids(e.g.,computationaltools,databases, standards,guidance:bestpractices,procedures)

Problemspecificinformation(e.g.,results, insights,uncertainties)

Sidebenefits Education/trainingofworkforce Networkingwithtechnicalcommunity RegulatoryDecisionSupport Specific Analyses Methods,Models, Tools,Databases, Standards,

Guidance, FoundationalKnowledge Decision R&D re*search,n.diligentandsystematicinquiryorinvestigationin ordertodiscoverorrevisefacts,theories,applications,etc.

AdditionalSlides

[RIDMApplicationExamples]

159 RiskInfoUses-DecisionSupportExample (Research:Frameworks/Methodologies)

NRCsponsoredFirePRA R&D(universities)

StartedafterBrowns Ferryfire(1975)

DevelopedfirePRA approachfirstusedin industryZionand IndianPointPRAs (early80s),samebasic approachtoday Startedpathleadingto riskinformedfire protection(NFPA805)

TechnologyNeutral Framework Exploreduseofrisk metricstoidentify licensingbasisevents Inspirationandpart basisforcurrent Licensing Modernization Program AdditionalSlides

[RIDMApplicationExamples]

160 RiskInfoUses-DecisionSupportExample (Research:ReferencePoints)

NUREG1150 Continuingpointof comparisonfor Level1,2,3results Expectations (ballpark)

Basisforregulatory analysis (backfitting,generic issueresolution)

NUREG1150(Surry)

SOARCA Detailedanalysisof potentialsevere accidentsandoffsite consequences Updatedinsightson marginstoQHOs PeachBottom Surry Sequoyah AdditionalSlides

[RIDMApplicationExamples]

161 RiskInfoUses-DecisionSupportExample (Research:Methods/Models/Tools)

SPAR Independentplant specificmodels (genericdata)

Allhazards(many)

SupportSDP,MD8.3, ASP,GSI,SSCstudies Adaptableforspecific circumstances SAPHIRE Generalpurpose modelbuildingtool Multipleuser interfaces IDHEASG Improvedsupportfor qualitativeanalysis Explicittieswithcognitive science(models,data)

Generalframeworkfor developingfocused applications(e.g.,IDHEAS ECA)

BenefitsfromNPP simulatorstudies Consistentwithcurrent HRAgoodpractices guidance(NUREG1792)

Fromhttps://en.wikipedia.org/wiki/SAPHIRE IDHEASiscoming.

Resistanceisfutile!

AdditionalSlides

[RIDMApplicationExamples]