ModellingtheCABRIhigh-burnupRIAtestCIP0-1usinganextendedversionoftheFALCONcodeOriginalResearchArticle

AnimprovedversionoftheFALCONfuelperformancecodeisusedtomodelthethermal–mechanicalbehaviourofthetestrodintheCABRIhigh-burnupRIAtestCIP0-1.First,theoriginalFALCONcode(versionMOD01)ismodifiedbyintroducingnewroutinesyieldingabetterdescriptionoftheinitialfuelandcladgeometry,whichallowsthemodellingofhighlyoxidizedcladdingswithnon-uniformaxialoxidethicknesses.BycalculatingtheHoopstrainexertedbytheoxidelayeronthecladding,thecorrectinitialrelativepositionbetweeninnerandfuelcladoutersurfacesisobtained.ApplicationofthenewalgorithmtotheREP-NA4experimentandcomparisonwiththepreviouscoderesultsshowsthatthenewversionyieldsbetterpredictionsofthefinalcladouterdiameterprofile.Thenewcodeversionisthenemployedtopredictthethermal–mechanicalbehaviouroftheCIP0-1testrod.Themeasuredcladdiametraldeformation,cladelongationandcoolanttemperaturearetakenasfiguresofmerit,thecodecalculationsbeingcomparedagainstthese.Theagreementbetweencodecalculationsandmeasurementsisremarkable:(a)thefinalcladdiameterprofileiscorrectlypredicted,providedthatthetransientoxidespallingistakenintoaccount;(b)thecladelongationissatisfactorilyreproducedifabondedcladdingandlargeaxialfrictionfactorsareassumed;and(c)thecoolanttemperaturesatdifferentaxiallocationsaregenerallyoverpredicted,butcanbesatisfactorilyreproducedifthethermalinertiaofthethermocoupleisconsidered.