Designation:C1832−16StandardTestMethodforDeterminationofUraniumIsotopicCompositionbytheModifiedTotalEvaporation(MTE)MethodUsingaThermalIonizationMassSpectrometer1ThisstandardisissuedunderthefixeddesignationC1832;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethoddescribesthedeterminationoftheisotopeamountratiosofuraniummaterialasnitratesolutionsbythemodifiedtotalevaporation(MTE)methodusingathermalionizationmassspectrometer(TIMS)instrument.1.2Theanalyticalperformanceinthedeterminationofthe235U/238UmajorisotopeamountratiobyMTEissimilartothe(“classical”)totalevaporation(TE)methodasdescribedinTestMethodC1672.However,intheMTEmethod,theevaporationprocessisinterruptedonaregularbasistoallowmeasurementsandsubsequentcorrectionsforbackgroundformpeaktailing,performinternalcalibrationofasecondaryelectronmultiplier(SEM)detectorversustheFaradaycups,peakcentering,andionsourcerefocusing.Performingthesecalibrationsandcor-rectionsonaregularbasisduringthemeasurement,improvesprecision,andsignificantlyreducesuncertaintiesfortheminorisotopeamountratios234U/238Uand236U/238UascomparedtotheTEmethod.1.3Inprinciple,theMTEmethodyieldsmajorisotopeamountratioswithouttheneedformassfractionationcorrec-tion.However,dependingonthemeasurementconditions,smallvariationsareseenamongsampleturrets;therefore,asmallcorrectionbasedonmeasurementsofacertifiedrefer-encematerialisrecommendedtoimproveconsistency.Theuncertaintyaroundthemassfractionationcorrectionfactorusuallyincludesunity.1.4Units—ThevaluesstatedinSIunitsaretoberegardedasthestandard.Whennon-SIunitsareprovided,theyareforinformationonly.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesandde...
