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ReconsiderationofPRAFramework－AddressingLevel3PRACoverageand

Multi-UnitIssues－

KampanartSILVA(Ph.D.)*ThailandInstituteofNuclearTechnology

Shin-etsuSUGAWARA(Ph.D.)CentralResearchInstituteofElectricPowerIndustry

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ProbabilisticRiskAssessment(PRA)

Note

ThisstudyfocusesonPRAperformedasaseriesofPRAs from level 1 to level 3 PRA, and deliveraccident consequences represented by radiationexposureandlandcontaminationastheiroutputs.

Not those used to satisfy regulatory requirementsortojustifyfacilitymodification.

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ProbabilisticRiskAssessment(PRA)

Level3PRALevel2PRALevel1PRA

Initiatingevents

Coredamageaccidents

Coredamageaccidents

Accidentswithrelease

Coredamagefrequency

Releasefrequency

Amount/timeofrelease

Accidentswithrelease

Radiationexposure

Landcontamination

InputsOutpu

ts

Events

Probabilities

Consequences

ExpertiseThermalhydraulics

Physicalchemistry

Healthphysics

-Psychologicalburden?-Communitydisruption?-Politicalimpacts?-Societalimpacts?-Businesscontinuity?-Harmfulrumor?

Single-unitVS

Multi-unit

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Howhasthecommunitybeenaddressingtheissues?

“Quantificationoftotalriskofaccident”

•  Enlargethecoverageoflevel3PRA•  Accidentcostestimation•  Nonradiation-inducedhealtheffects

•  Multi-unitPRA•  Accidentsinitiatedbyexternaleventse.g.earthquake,tsunami,flood

•  Fromacademiatoindustryandregulatorbody

•  Justifiableandevidence-basedrisk-relateddiscussion

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Objective

“To identify foreseen issues arising from theenlargementofPRAcoverage,

and to propose an alternative approach totackle the issueonquantificationof the totalriskofaccident.”

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ForeseenIssuesfromtheEnlargementofPRACoverage

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1.DifficultyAttributedtoMultidisciplinaryApproachLevel3PRA

Notaffordable

!Level3PRA incompletelycoveringmorecategoriesofconsequences

Multi-unitPRA

•  Datamanagementskills•  Understandingofdownstreamassessments

Radiation-inducedhealtheffects

Psychologicaleffects

Economicimpacts/monetization

Environmentalimpacts

HealthPhysicist

Medicaldoctor

EconomistEcologist

Thermalhydraulics

Riskassessment

Physicalchemistry

Dataanalysis

Healthphysicists

…

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2.AcquisitionandManagementofExcessiveAmountofDataLevel3PRA

•  Quantificationofaccidentconsequencesmeans…•  Health,economic,

environment,society,…•  Meteorologicaldata,landuse

data,populationdata,economicdata,…

•  Howtointegratethedata?•  Monetization?•  Normalizedunit?•  Canpublic/decisionmakers

understand?

Multi-unitPRA

•  Single-unitPRAitselfneedsagreatdealofdata.

•  Multi-unitPRA•  Commoncausefailuresforall

possiblecombinations•  Several-foldofdata

•  Groupingofinputsfromupstreamresultsrequireefforts.

! Limitedscopemulti-unitPRAHardlycontributetoquantificationoftotalriskofaccident…

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3.DifficultyinDecisionMaking

LargeramountandhigherqualityofinformationmakesPRAevenmoredifficultfordecisionmakerstodealwith

RiskAssessor RiskManager

Results+

AssumptionsUncertainties

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4.DifficultyinCommunicatingwithStakeholders

•  Post-Fukushima:Riskinformationhastobesharedwithvariousstakeholders•  Likelihood,consequences•  Localcommunity,public,decisionmaker,regulatorybody,etc.

•  Challenge:Howtocommunicatecalculatedriskswithgreatuncertainties?•  Itdiffersfromconceptofso-called“safetymyth”.•  Itcanleadtonegativeand/orsensitivesocietalreactions.•  Enlargedscopeandincreaseduncertaintiesincreasecomplexity.

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ProposalofAlternativeFramework

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1.FollowingTraditionalPRAScope

•  Workwithinownterritory•  Solutiontodifficulty

attributedtomultidisciplinaryapproach

•  Limitedamountofdata•  Solutiontoacquisition

andmanagementofexcessiveamountofdata

•  Complexityisreduced•  SolutiontoDifficultyin

CommunicatingwithStakeholdersPerformsingleunitPRAseparately

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2.QualitativeorSemi-QuantitativeImpactAssessment•  Quantifyallquantifiableconsequencesusingsuitableunits.

•  Coverotherconsequencesbyqualitativeorsemi-quantitativeimpactassessment.

•  Showtrade-offsamongdifferentconsequences.

Solutiontoissuesfrom1Faccident(level3PRAcoverageandmulti-unitconsideration)

•  Qualitativeassessment•  Participatoryanalysis•  Questionnairesurvey•  Delphimethod•  Qualitativeimpactassessmentprotocol

•  Semi-quantitativeimpactassessment•  Likertscale•  Overallpercentagescore

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3.EstablishingaDeliberationPhase

PRA

Consequences

Consequences

Consequences

Deliberation

Analysis

Analysis

PRA

Techno-centrism IntegrationofdiverseprofessionsDiscussionb/wtechnicalandnon-technical

Discuss:-Differences-Trade-offs

Grasptotalriskquantitatively

Solutiontodifficultyindecisionmakingandalsodifficultyincommunicatingwithstakeholders

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Conclusions•  ForeseenissuesarisingfromtheenlargementofPRAcoverageinordertoquantifythetotalriskofaccidentwereidentified.•  Difficultyattributedtomultidisciplinaryapproach•  Acquisitionandmanagementofexcessiveamountofdata•  Difficultyindecision-making•  Difficultyincommunicatingwithstakeholders

•  Analternativeapproachwasproposedtotackleaforementionedissues.•  StickwithtraditionalPRAscope•  Covernon-quantifiableconsequencesbyqualitativeorsemi-quantitativeassessment

•  Gothroughdeliberationprocess

16“The essence of map consists in abstraction andhighlighting desiderata. The same is true for riskassessment. While overlooking necessary riskinsightsisneverallowed,ambitiontoreproduceallthe physical phenomenawill not serve its originalpurpose.PRAmay leadtoprudentdecisionswhenallocatinglimitedresourcestohighpriorityissues.”

KampanartSILVAkampanarts@tint.or.th

ThailandInstituteofNuclearTechnology

Shin-etsuSUGAWARAsugawara@criepi.denken.or.jp

CentralResearchInstituteofElectricPowerIndustry