A NEXT GENERATION SODIUM-COOLED FAST REACTOR CONCE

ANEXTGENERATIONSODIUM-COOLEDFASTREACTORCONCEPTANDITSR&DPROGRAMMASAKAZUICHIMIYA*,TOMOYASUMIZUNOandSHOJIKOTAKEJapanAtomicEnergyAgency4002,Naritacho,Oarai-machi,IBARAKI,Japan*Correspondingauthor.E-mail:[e-mail]14,20071.INTRODUCTIONCriticalissuesinthedevelopmenttargetsforthefutureFastReactor(FR)cyclesystem,includingSodium-cooledFastReactor(SFR)weretoensuresafetyassurance,efficientutilizationofresources,reductionofenvironmentalburden,assuranceofnuclearnon-proliferation,andeconomiccompetitiveness.SeveralconceptualdesignsfornextgenerationSFRhavebeendevelopedaimingatfullysatisfactionofthedevelopmenttargets.Amongthem,JapanAtomicEnergyAgency(JAEA)SodiumFastReactor(JSFR)isasodium-cooled,MOXfueled,advancedloop-typeevolvedfromJapanesefastreactortechnologies.ThreekeyissuesareincorporatedfortheJSFRplantsystemdesigntomeetthedevelopmenttargets.(1)Reductionofconstructionandoperationcostsbyinnovativetechnologies;FRplantconstructioncostisthelargestfactorintheelectricitygenerationcostamongthefuelcyclesystem.ToreducetheconstructioncostinJSFRplantsystem,variousinnovativetechnologieswererequiredforthesystemconceptandmaincomponentsinJSFR.(2)Strategyforsafetydesignimprovements;Passivesafetyfunctionsandre-criticalityfreecoreshouldbeintroducedtoenhancethesafetyforDesignBasisEvents(DBEs)andDesignExtensionConditions(DECs).(3)Conqueringthedrawbacksofsodiumsystem;Possibilityofsodium-waterreactioninasteamgenerator(SG)shouldbeminimizedalongwiththehigheravailabilityandloweroperationcost.In-serviceinspectionandrepair(ISI&R)capabilityandsodium-leaktightmethodologyshouldalsobetakenintoaccounttoensurethereliabilityofthesystemforcommercialoperation.ThispaperprovidesdevelopmenttargetsforthenextgenerationFR,adetaileddescriptionofJSFRandevalu-ationontheJSFRperformancesforsafetyandeconomiccompetitiveness.Furthermore,aroadmaptowardJSFRcommercializationisdescribed,tobefollowedupinanewframeworkoftheFastreactorCycleTechnologydevelopment(FaCT)Projectlaunchedin2006.2.DEVELOPMENTTARGETSANDDESIGNREQUIREMENTFORNEXTGENERATIONFR2.1DevelopmentTargetsThedevelopmenttargetsforthenextgenerationSFRaresummarizedasfollows[1]:(1)SafetyassuranceThesafetydesignapproachfortheSFRplacesthehighestpriorityonpreventingtheoccurrenceandevolutionofabnormalconditionsbasedontheconceptofDefenseinDepth.Asafetylevelequivalenttoorbetterthanconte-mporarylight-waterreactorcyclesystemsshouldbeachieved.Additionally,inlightofthefacilitycharacteristics,amorereliableandclearersafetyapproachisrequired.Passivesafetyfunctionsshouldpossiblybeaddedorenhanced,andregardingthereactor,measuresshouldbetakenforthepreventionofre-criticalityinthecaseofanyhypotheticalcoredisruption,inordertoensurethatCriticalissuesinthedevelopmenttargetsforthefuturefastreactor(FR)cyclesystem,includingsodium-cooledFRweretoensuresafetyassurance,efficientutilizationofresources,reductionofenvironmentalburden,assuranceofnuclearnon-proliferation,andeconomiccompetitiveness.Apromisingdesignconceptofsodium-cooledfastreactorJSFRisproposedaimingatfullysatisfactionofthedevelopmenttargetsforthenextgenerationnuclearenergysystem.AroadmaptowardJSFRcommercializationisdescribed,tobefollowedupinanewframeworkoftheFastreactorCycleTechnologydevelopment(FaCT)Projectlaunchedin2006.KEYWORDS:Sodium-cooledFastReactor,InnovativeTechnology,ConstructionCost,MABurning,ISI&R,JSFR,FastReactorCycleTechnologyDevelopment(FaCT)Project171NUCLEARENGINEERINGANDTECHNOLOGY,VOL.39NO.3JUNE2007theimpactofsuchahypotheticalaccidentisconfinedwithintheboundaryofthereactorvesselorthecontainmentvessel.ThegoaloftheimplementationofthesemeasuresistorendertheriskofinstallingtheSFRcyclesystemsufficientlysmallcomparedwithotherrisksalreadyexistinginsociety.(2)EconomiccompetitivenessForthecommercializationofSFRsystem,itisimpo-rtanttoachievealevelofeconomiccompetitivenessthatenablesthesysteminstallationinaccordancewithmarketprinciples.Forthispurpose,animportantgoalshouldbetoensureenoughcompetitivenessintermsofenergycost(unitcostofpowergeneration)comparedwiththecompetingenergysourcesinthefuture.(3)ReductionofenvironmentalburdenFortheeffectivecommercializationofSFRsystems,itisnecessarytobringintofullplaytheadvantagesofafastspectrumreactorwithfullrecycleastheenergygenerationsystemthatcanminimizetheimpactontheglobalenvironment,withfeaturessuchasitsexcellentthermalefficiency,thegreaterutilizationoffuelresources,andthe172NUCLEARENGINEERINGANDTECHNOLOGY,VOL.39NO.3JUNE2007ICHIMIYAetal.,ANextGenerationSodium-CooledFastReactorConceptanditsR&DProgramTable1.MajorDesignRequirementsoftheSFRSystemandGenerationIVGoalsBreedingCapabilityBreedingratio:ca.1.2,Systemdoublingtime:ca.30yearsSustainability-1:Resourceutilization-2:Wasteminimizationandmanagement-1:Minimizediversionorundeclaredproduction-2:Reactorshavepassivefeaturesthatresistsabotage-1:Operationswillexcelinsafetyandreliability-2:Verylowlikelihoodanddegreeofreactorcoredamage-3:Eliminatetheneedforoffsiteemergencyresponse-1:Life-cyclecostadvantageoverotherenergysources(Lowovernightconstructioncost,Lowproductioncos