Evaluationofductile–brittletransitiontemperaturebeforeandafterneutronirradiationforRPVsteelsusingsmallpunchtestsOriginalResearchArticle

Smallpunch(SP)testswereperformedtoevaluatetheductile–brittletransitiontemperaturebeforeandafteraneutronirradiationofreactorpressurevessel(RPV)steelsproducedbydifferentmanufacturing(refining)processes.TheresultswerecomparedtothestandardtransitiontemperatureshiftsfromtheconventionalCharpytestsandtheMasterCurvefracturetoughnesstestsinaccordancewiththeAmericanSocietyforTestingandMaterials(ASTM)standardE1921.Smallpunchspecimensweretakenfroma1/4tlocationofthevesselthicknessandmachinedintoa10mm×10mm×0.5mmdimension.ThespecimenswereirradiatedintheresearchreactorsatKoreaAtomicEnergyResearchInstituteNuclearResearchInstituteintheCzechRepublicatthedifferentfluencelevelsofabout290°C.SmallpunchtestswereperformedinthetemperaturerangeofRTto−196°Cusinga2.4mmdiameterball.Forthematerialsbeforeandafterirradiation,thesmallpunchtransitiontemperatures(TSP),whicharedeterminedatthemiddleoftheuppersmallpunchenergies,showedalinearcorrelationwiththeCharpyindextemperature,T41J.TSPfromtheirradiatedsampleswasincreasedwiththefluencelevelsandwaswellwithinthedeviationrangeoftheunirradiateddata.However,thetransitiontemperatureshiftfromtheCharpytest(ΔT41J)showsabettercorrelationwiththetransitiontemperatureshift(ΔTSP(E))whenaspecificsmallpunchenergylevelratherthanthemiddleenergylevelofthesmallpunchcurveisusedtodeterminethetransitiontemperature.TSPalsohadacorrelationwiththereferencetemperature(T0)fromtheMasterCurvemethodusingapre-crackedCharpyV-notched(PCVN)specimen.