Designation:C1493−09StandardTestMethodforNon-DestructiveAssayofNuclearMaterialinWastebyPassiveandActiveNeutronCountingUsingaDifferentialDie-AwaySystem1ThisstandardisissuedunderthefixeddesignationC1493;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversasystemthatperformsnonde-structiveassay(NDA)ofuraniumorplutonium,orboth,usingtheactive,differentialdie-awaytechnique(DDT),andpassiveneutroncoincidencecounting.Resultsfromtheactiveandpassivemeasurementsarecombinedtodeterminethetotalamountoffissileandspontaneously-fissioningmaterialindrumsofscraporwaste.Correctionsaremadetothemeasure-mentsfortheeffectsofneutronmoderationandabsorption,assumingthattheeffectsareaveragedoverthevolumeofthedrumandthatnosignificantlumpsofnuclearmaterialarepresent.Thesesystemsaremostwidelyusedtoassaylow-levelandtransuranicwaste,butmayalsobeusedforthemeasure-mentofscrapmaterials.Theexamplesgivenwithinthistestmethodarespecifictothesecond-generationLosAlamosNationalLaboratory(LANL)passive-activeneutronassaysystem.1.1.1Intheactivemode,thesystemmeasuresfissileiso-topessuchas235Uand239Pu.Theneutronsfromapulsed,14-MeVneutrongeneratorarethermalizedtoinducefissionintheassayitem.Betweengeneratorpulses,thesystemdetectsprompt-fissionneutronsemittedfromthefissilematerial.Thenumberofdetectedneutronsbetweenpulsesisproportionaltothemassoffissilematerial.Thismethodiscalledthediffer-entialdie-awaytechnique.1.1.2Inthepassivemode,thesystemdetectstime-coincidentneutronsemittedfromspontaneouslyfissioningisotopes.Theprimaryisotopesmeasuredare238Pu,240Pu,and242Pu;however,thesystemmaybeadaptedforuseonotherspontaneously-fissioningisotopesaswell,suchaskilo-gramquantitiesof238U.Thenumberofcoincidentneutronsdetectedisproportionaltothemassofspontaneously-fissioningmaterial.1.2Theactivemode...
