ML22153A343
| ML22153A343 | |
| Person / Time | |
|---|---|
| Issue date: | 03/08/2022 |
| From: | Mark Thaggard NRC/RES/DRA |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML22153A343 (13) | |
Text
PerspectiveonSafetyImprovements forCommercialNuclearPowerPlants MarkThaggard,Director DivisionofRiskAnalysis OfficeofNuclearRegulatoryResearch,U.S.NRC
2 Overview
3 RESConsiderationsinLookingatDifferentMeasuresofPerformance
- Whattimeframeshouldweconsider?
- 20years(2000+)
- 30years(1990+)
- Advancementsmakeitdifficulttocompareperformance measuresovertime
- Measuresofperformancemayneedtobeinterpretedusing engineeringjudgment
4 1988-2000PlantSafetyImprovements Theperiodofinterest impactsoverall conclusions Manysafetysignificant actions/changes weremade
5 1988-2000PlantSafetyImprovements SignificantEvents
2000-Present:PlantSafetyImprovements 6
Improvementsmade duringthisperiodare notassignificantas thoseinthe1990s Notallchangeshave beenfullyrealized
7 RESCategoriesofPerformanceMeasures Operationaltrends Plantriskduetointernalevents/internalfloods Plantriskduetootherhazards NRCstudies,orders,models,etc.
Industrystudies,standards,models,etc.
Other
SafetyMeasureTrends 8
51measures NegativeTrends Lossofoffsitepower(LOOP)recoverytime PositiveTrends Annualscrams NRCreactiveinspections Accidentsequenceprecursor(ASP)results Radiationexposure Performanceindicators Internaleventscoredamagefrequency(CDF)
Reactorcoolantpump(RCP)sealperformance Lossofoffsitepower(LOOP)frequency 1
measure 8
measures
RemainingSafetyRelatedMeasures 9
Apparentfavorabletrends Lowerconditionalprobabilitythataradiologicalreleasewouldleadto promptorlatenthealtheffects Improvementsrelatedtofloodingandseismichazardreevaluations Mitigatingstrategiesimprovements(FLEX)
RiskinsightsfromtheStateoftheArtReactorConsequenceAnalyses (SOARCA)
GenericIssuesProgramimprovements B.5.bimprovements Improvementsinconsensusstandardsandregulatoryguidance Pressurizedwaterreactorsteamgeneratorperformanceimprovements ImprovementsinPRAdevelopmenttools 32neitherfavorableornegativetrend 9
SomeObservations 10
- Largereductioninaveragecoredamagefrequency(CDF)(sincetheIPEresults)
- Limitedtocontributionsfrominternalevents
- Externaleventhazardscanaddsignificantlytoplantrisk,soitisimportant toincludeindiscussionofsafetytrending
- Reductioninperformanceissues
- RiskbelowNRCsafetygoals
- Boththeuncertaintiesandexternalhazardsneedtobeconsideredwhen lookingatthesafetygoalimpacts
Conclusions 11
- Performancemeasuresappeartoshowimprovementsinnuclearpowerplants Couldbeattributedtoinitiativesandrulesaddressingkeysafetyissues (e.g.,stationblackout(SBO)rule,greateruseofriskinformeddecisionmaking)
- Plantsafetyimprovementsimplementedsincetheyear2000haveshownagradual increaseinsafety,buttoasmallerextentthanduringtheprevious10years
- Notallsafetymeasuresmovedinthesamepositivedirection
- Externaleventimpactsareimportant,andsignificantuncertaintiesstillexist
Questions 12
13 PointsofContact Mehdi.Reisifard@nrc.gov BranchChief, DivisionofRiskAnalysis,RES Matthew.Humberstone@nrc.gov SeniorReliabilityandRiskAnalyst DivisionofRiskAnalysis,RES