A comparative study on dissolution rate of sintered (Th–U)O2 pellets in nitric acid by microwave and conventional heating

[摘要] ThO2withapproximately3%233UO2istheproposedfuelfortheAdvancedHeavyWaterReactor(AHWR)andcharacterizedasamixedoxide(MOX)fuel.Duetotheexistenceofasingleoxidationstate,quantitativedissolutionofMOXsampleslike(Th–U)O2and(Th–Pu)O2isachallengingtaskforanyanalyticalchemist.However,dissolutionisapre-requisiteforcompletecharacterizationofthefuel.Thepresentpaperdescribesadetailedstudycarriedoutonthecomparisonofdissolutionofsintered(Th–U)O2mixedoxidepellets,in16MHNO3usingmicrowaveandconventionalheatingtechniques,underrefluxconditions.ThestudywascarriedoutwithvariationofparameterssuchasconcentrationofHFandUO2substitutionintheMOXsolidsolution.TheconcentrationofdissolvedUandThwasdeterminedbymodifiedDaviesandGraypotentiometrictitrationandTh-EDTAcomplexometrictitrationusingxylenolorangeasthetitrationendpointindicatorrespectively.Experimentalresultsclearlyindicatethatthemicrowaveheatingassisteddissolutionrateis2to3timeshigherthantheconventionalinfraredheatingassisteddissolutionrate,forsinteredpellets.TheconcentrationofHFisacriticalparameter,anexcessleadstoprecipitationofinsolubleThF4.TheconcentrationofHFwasoptimizedto0.025M.ExperimentalresultsalsoclearlyshowthatatthisconcentrationofHFin16MHNO3,ahighersubstitutionofUO2inMOXsolidsolutionalsofacilitatesthedissolutionprocess.DifferenttracemetalimpuritiesweredeterminedintheMOXsamplesafterdissolvingbymicrowaveandinfraredheatingtechniquesanditwasobservedthattheresultsarecomparable...

[学科分类] 分析化学