ML20318A172
| ML20318A172 | |
| Person / Time | |
|---|---|
| Issue date: | 11/12/2020 |
| From: | Alex Garmoe NRC/NRR/DRO/IRAB |
| To: | |
| Alex Garmoe, NRR/DRO/IRAB, 415-3814 | |
| References | |
| Download: ML20318A172 (10) | |
Text
Treatment of Long Term Exposure Times
ReflectingonStakeholderFeedback
- Itisalwayshealthytoreflectonprograms,processes,and communications
- ThequantitativecalculationsofCDFandLERFarewellfounded andconsistentwithawiderangeofriskapplications
- TheSDPincludesamaximumlimitofoneyearwhenconsideringthe lengthoftimeaconditionexistedbecausethethresholdsaresetup asaperyearfrequencyofcoredamageorlargeearlyrelease
- Annualizingexposuretimetoaperyearfrequencyworkswellfor conditionsthatexistforuptooneyearbuttheapproachdoeshave somelimitationsforconditionslastinggreaterthanoneyear 2
ReflectingonStakeholderFeedback
- TheexistingquantificationisaccuratefromaCDF/yr or LERF/yr standpoint;however,theriskduetoexposuretime beyondoneyearisnotaccountedforintheriskcalculation
- Aquantitativesolutionwouldbechallengingtoidentifyand wouldresultinadeparturefromconsistencywithotherrisk applications
- Includingextendedexposuretimeasaqualitative considerationmaybeareasonableapproach 3
ExistingRegulatoryTools
- ActionMatrixDeviations
- TheagencycanimplementdifferentfollowupactionsthantheActionMatrixwould ordinarilyprescribebasedonplantperformance
- Supplementalinspectionguidanceincludesreviewofprioropportunitiesfor discovery
- Longtermdegradedconditionsmayhaveincludedsomeprioropportunityfordiscoveryand, ifso,thiscouldbereviewedbyasupplementalinspection
- OlddesignissuecriteriainIMC0305forcertainsituations
- SupplementalinspectionstillperformedforgreaterthanGreenolddesignissues
- IMC2515AppendixCinspections
- Includestraditionalenforcementfollowupandsafetyconsciousworkenvironment
- LIC504processtocoversituationswithoutaspecificappropriateprocess
- ROPfeedbackprocess 4
ApplicationsofRiskInformation
- Usedinmanyagencyprocesses
- Inspectionplanning
- SignificanceDeterminationProcess(SDP)
- AccidentSequencePrecursor(ASP)Program
- Licensing
- Decisionsaremadeusingablendofquantitative mathematical methodsandqualitative assessments CoreDamage Frequency CDF CoreDamage Probability CDP ConditionalCore DamageProbability CCDP RG1.174 AppendixM 5
QuantitativeCalculations
- Wellestablishedtoolsandmethodsfor quantitativecalculations
- SPARmodels
- SAPHIRE
- RASPHandbook
- Guidancedocuments
- Resultsshouldnotbetreatedasaprecisenumber
- Riskinformeddecisionmakingaccountsforuncertaintieswithassumptions andmodelinginputs
- Quantitativethresholdsarebasedonsubsidiaryobjectivesderived fromthesafetygoalsandtheirQuantitativeHealthObjectives.
6
QualitativeConsiderations
- Properuseofappropriatequantitativetoolsisthepreferred methodforassessingtheriskincreaseofadegradedcondition
- However,quantitativetoolshavelimitationsandnotevery situationorfactorcanbemathematicallyquantified
- Qualitativeassessmentscanfurtherinformquantitativeresults andcanbeusedwhenquantitativetoolsdontapply
- RegulatoryGuide(RG)1.174
- InspectionManualChapter(IMC)0609,AppendixM
- Appliedinconcertwithquantitativeresultstoberiskinformed 7
SignificanceDeterminationProcess
- Riskinformedprocessthatusesbestavailableinformationtomakedecisions inatimelymanner,blendingquantitativeandqualitativeinformation
- Resourceandinspectionplanningtool
- Amaximumofoneyearexposureisusedsincetheresultisannualized
- Byannualizingtheresult,riskoutputsfromvariousagencyprogramscanbe comparedandevaluatedagainstquantitativehealthobjectives Green
<1E6CDF White 1E61E5CDF Yellow 1E51E4CDF Red
>1E4CDF 8
ASPProgram
- Usesthechangeincoredamageprobability(CDP)forconditionassessments orconditionalcoredamageprobabilities(CCDP)forinitiatingevents
- Usingthemaximumexposuretimeof1yearforindividualASPanalyses continuestosupportprogram'sobjectiveswithintheexistingframeworkfor riskassessmentandensuresconsistencywithotherNRCprogramsand historicalASPresults
- Greaterthanoneyeardegradedconditionsareaccountedforinthe integratedASPindex
- Unlikeotherprecursortrendsthatfocusonoccurrenceratesofaprecursor,theASP indexevaluatesthetotalriskduetoprecursorsonanannualbasis
- TheASPindexsummarizestheCDP/CCDPofprecursorsintheyeartheevent occurredorthatdegradedconditionexisted
Questions