Investigation of direct simultaneous uranium isotopic determination and age dating of micrometer-sized uranium particles by laser ablation – multi-collector ICPMS†

In this study, we demonstrate that it is possible to simultaneously determine accurate uranium ²³⁴U and ²³⁵U abundances and the date of purification (or “age”) of uranium oxide materials at the particle scale using laser ablation – multi-collector ICPMS coupling. The method was successfully applied to microparticles of uranium materials enriched at 5%, 85% and 90% and purified 70 years ago. The deviations from the reference age are, at most, respectively 6 years, 2 years and 1 month which is comparable to what can be obtained using the reference technique LG-SIMS. The precision of ²³⁵U abundances and ²³⁴U abundances, at the particle scale, was respectively between 0.11% and 1.95% and between 0.4% and 5% which is equivalent to or better than what was previously published for the analyses of depleted to moderately enriched materials by LA-ICPMS, showing that adding ²³⁰Th determination doesn't degrade the determination of ²³⁴U and ²³⁵U abundances. Due to the small amount of material introduced into the ICPMS, μm-sized particle analysis by LA-ICPMS has the advantage of being less subject to laser-induced fractionation than bulk material analyses by LA-ICPMS. In contrast to the latter, a correction for uranium versus thorium fractionation can be applied based on the measurement of their relative sensitivities in standard solutions.