CharacterizationofneutronfieldintheexperimentalfastreactorJOYOforfuelandstructuralmaterialirradiationtestOriginalResearchArticle

TheexperimentalfastreactorJOYOhasbeenoperatedasanirradiationtestfacilityforfastreactorfuelandstructuralmaterialsince1983withitsMK-IIcore.Duringthistime,anextensivestudywasconductedtocharacterizetheneutronfieldinordertoassuretheaccuracyandreliabilityofneutronfluence.Neutronfluxforagivenirradiationtestwascalculatedusingacoremanagementcodesystembasedonthree-dimensionaldiffusiontheory.Itwasthencorrectedwiththeadjustedneutronspectrumbymeansofthemultiplefoilactivationmethod.Theneutronfluencecalculationaccuracyinthefuelregionwasevaluatedwithina5%errorbycomparingtheburn-upofspentfuelwiththemeasuredvalues,whichhadbeenobtainedfromtheirpost-irradiationexamination.Atpositionsawayfromthefuelregion,theneutronfluxdistributionwascalculatedusingatwo-dimensionaltransportcode.AMonteCarlocodewasalsousedtoanalyzethedetailedneutronfluxdistributionwithinanirradiationtestsubassemblythathadaheterogeneousinternalstructure.Withtheneutronfluxresultsvariousirradiationparameters,suchasdisplacementperatom(dpa)andheliumproduction,couldbeevaluated.Aheliumaccumulationfluencemonitorhasbeendevelopedtomeasurenotonlyneutronfluencebutalsoheliumproduction.Neutronfluxandfluenceobtainedfromthecoremanagementcalculationswerecompiledasadatabaseforusers’conveniencetogetherwithrelatedirradiationinformationandfuelsubassemblymaterialcompositions.Thesedataareexpectedtobewidelyusedinthepost-irradiationanalysisoffuelandstructuralmaterial.