Isotopic analysis of uranium particles by large-geometry SIMS for nuclear safeguards: a comparison of carbon planchets and silicon wafer substrates

Isotopic analysis of uranium particles collected from nuclear facilities provides important safeguards-relevant information on material origin and uranium enrichment status. In this study, uranium particle isotope ratios were measured using a large geometry- secondary ion mass spectrometry (LG-SIMS) installed at Korea Basic Science Institute (KBSI). The accuracy and precision of the analytical protocol were evaluated using the uranium certified reference materials (CRM). In addition, the effect of sample substrates on analytical performance was assessed by comparing conventional carbon planchets with silicon wafer substrates for particle fixation. The results confirm that LG-SIMS provides reliable uranium isotope ratio measurements at the single-particle level. As in the case of ²³⁵U with a relatively strong signal, the analytical results demonstrated accuracy within ~ 1% bias, independent of the CRM and substrate type. In addition, a decrease in uranium hydride formation was observed on silicon wafers compared to carbon planchets. These findings confirm the suitability of silicon wafers as a cost-effective alternative substrate for uranium particle analysis.