InelasticanalysisofcylindricalsteelcontainmentvesselsunderinternalaccidentconditionsOriginalResearchArticle

Thepresentpaperisconcernedwiththestructuralsafetyassessmentofaproposednuclearsteelcontainmentshellduringapostulatedloss-of-coolantaccidentscenario.Thestructuralevaluationisperformedusingacomputationalsecond-orderrefinedplastic-hingemethod,whichiscapableofaccuratelypredictingallpossiblemodesoffailureinanefficientandcomputationallylessexpensivewaythanthegeneralFEMformulation.Atangentmodulusmodelandagradualreductionoftheinelasticresistancesurfaceareusedtotakeintoaccountdirectlythestructuralstrengthandstabilityperformancesintheelementformulation.Theimplementednumericalmethodprovidesmorereliablesafetymarginsandmaintainability,exhibitingamoreuniformstructuralsafetylevelthanthelinearelasticanalysis.Asimplifiednon-linearheattransfermodel,developedforsymmetricalcross-sections,isusedtodeterminethesteeltemperaturegradientandtoestablishalinkbetweenthethermoandthemechanicalanalysis.Theloadresultingfrompressureandtemperaturethermodynamiccalculations,obtainedfortheaccidentscenario,areconsideredinthestructuralquasi–staticanalysis,sothatthestructuralresponsecanbetrackedfortheentiredurationofthesimulatedaccident.