Advancedtreatmentofzircaloycladdinghigh-temperatureoxidationinsevereaccidentcodecalculations:PARTII.Best-fittedparaboliccorrelationsOriginalResearchArticle

Progressinthetreatmentofzirconiumoxidationkineticsindifferentsevereaccident(SA)codesandconvergencetowardsanagreeddatabasearerequiredforthereliableverificationofsophisticatedLWRcoredegradationmodels. Thekineticdatabase,tobedefinedforrecommendedapplicationinsevereaccidentcodes,developedbycriticalassessmentoftheessentialexperimentalresultsinPartI,isfurtherverifiedandrefined.TheexperimentsofPraterandCourtright,themainhightemperaturedatasource,requirere-evaluationtoaccountforthetemperaturegradientsacrossthetestspecimens.ThistaskisperformedbyPawel’modelextensionfortreatmentoftemperaturegradientswithinscalesanddevelopmentofthesolutionalgorithm.Statisticalevaluationoftheoriginaldatawithinreasonableparameterlimitsallowstodeducecorrectedratecoefficientsforthecorrespondingisothermalcase.Moreover,theco-existenceoftwooxidephasesub-layers,givingrisetoatransitionalkineticresponseinanintermediatetemperaturerange,istreatedbymodelextensionanddescribedintermsofan“effective”diffusivity;asmoothtransitiontothehightemperaturerangeisobtained. Intotal,thededucedkineticswithcertainreductioninreactionrateathightemperatures,comparedtooriginalevaluationofPraterandCourtright,isabletoverifythecombinedoriginalexperimentalresults.Atthesametimecontradictorytrendsareexplainedandreconciledonbasisofthespecificexperimentalproceduresandconstraints. Theexaminationresultssupporttheconvictionthatthepresentedcorrelationsareadequatetransferfunctionsforthedirectapplicationincodes.Theirusecanberecommendedforeverycode,aptforthecorrelationsapproach.InPartIIItheverificationofobtainedcorrelationsinframesofICARE/CATHAREcodeagainstseparate-effectandbundleexperimentswillbepresented.