Americium isotopes are crucial in various nuclear-related fields such as nuclear fuel cycle, nuclear forensics and nuclear safeguards. This study introduces enhanced methodologies for precise determination of 242Am/241Am and 243Am/241Am in trace americium by employing Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) and Total Evaporation-Thermal Ionization Mass Spectrometry (TE-TIMS). We established a standard-sample bracketing (SSB) method with uranium-certified reference material (U CRM) to correct the mass fractionation and ion counter gain yield among different isotopes in MC-ICP-MS. The new methods were successfully applied to an aliquot of an 241Am progeny sample, an 241Am activity standard solution and an in-house Am isotopic working standard, achieving detection limits of 10−7 for 242Am and 243Am. Analysis requires an aliquot containing about 1 ng of 241Am for MC-ICP-MS with a desolvation device for sample introduction and about 5 ng for TE-TIMS to determine 242Am/241Am ratios close to 10−5 and 243Am/241Am ratios close to 10−4, with observed relative standard deviations of 0.2 %. Comparative analysis of 242Am/241Am and 243Am/241Am using classical TE-TIMS and the newly developed MC-ICP-MS confirms their consistency within uncertainties, validating the precision of MC-ICP-MS in americium isotope ratio determination. These findings indicate that the 241Am activity standard sample was directly sourced from irradiated material rather than from a 241Pu solution, highlighting the methodology's applicability to nuclear forensics and nuclear fuel cycles.
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