Advancedtreatmentofzircaloycladdinghigh-temperatureoxidationinsevereaccidentcodecalculations:PartI.ExperimentaldatabaseandbasicmodelingOriginalResearchArticle

Progressinthetreatmentofzirconiumoxidationkineticsindifferentsevereaccident(SA)codesandconvergencetowardsanagreeddatabasearerequiredforthereliableverificationofsophisticatedLWRcoredegradationmodels. Focusedonthecomprehensiveexperimentalstudiestheavailableinformationonthehigh-temperatureoxidationkineticsofzircaloy(Zry)isevaluated.Importantdiscrepanciesbetweenresultsforthehigh-temperaturerangeareinterpretedintermsofdifferentexperimentalandevaluationprocedures.Thecriticalassessmentidentifiesthefollowingitems,whichrequireseparateconsiderationinthesimplifiedconventionofusingfixedreactionratecorrelationsforthehighandlowtemperatureranges:theco-existenceoftwooxidephasesub-layersgivesrisetoatransitionalkineticresponseinanintermediatetemperaturerange.Towardshighertemperaturesthevalidityofthecorrelationsapproach(assumingreactionratecontrolasinasemi-infinitesolid-statediffusionsystem)isrestrictedfurther,ontheonehandbykineticcontrolwithinthegasphase(initialoxidationrange),ontheotherhandbymetalmatrixconsumption(finaloxidationrange).Theanalyticaltreatmentofthetwolast-mentionedconcomitantphenomenaisgiven,andtheconsiderationallowstoreconcileapparentdiscrepanciesbetweenexperimentalresults.Areasonablebaseofcombineddataisthusidentified,foramomentwithcertainuncertainty,whichisnotsuitablefordirectapplication. InPartII,thekineticbasewillbefurtherverifiedandrefinedbystatisticalevaluationofcomplementaryexperimentaldataandtransferredtotheform,allowingimplementationincodes.InPartIII,thesatisfactoryapplicationinICARE2codecalculationsofseparate-effectandbundleexperimentswillbepresented.