Determination of Am full isotope compositions (241Am, 242Am, 243Am) at trace level by multiple-collector - ICP-MS with a desolvation device for sample introduction

Abstract

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.