Test samples containing four different types of uranium isotopic reference powder were used. From the results of test sample A (〇) obtained using the conventional method, distinguishing the four clusters of each reference powder was difficult. In contrast, from the results of test samples (B1: △, B2: ☐, and B3: ◇) obtained using a new method that uses micromanipulation, the four clusters of each reference powder were clearly observed.

Environmental samples (ES) for nuclear safeguards are used to detect trace levels of nuclear materials such as uranium and plutonium, and collected by IAEA inspectors from nuclear facilities around the world. IAEA uses the analytical results of ES to ensure compliance with treaty obligations. Consequently, high accuracy and precision are required for ES analysis.

Secondary ion mass spectrometry (SIMS) is one method to analyze isotopic abundance of uranium particles in ES. In the sample preparation process for SIMS analysis of ES, an aggregation of uranium particles is observed when uranium particles are collected onto a planchet. When this aggregation is detected as a single particle in SIMS analysis, the analytical results show the average isotopic abundances of uranium particles and indicate nonexistent isotopic abundances in the sample. This effect is called particle mixing and reduces accuracy of ES analysis using SIMS.

A new method, combining SIMS based screening and micromanipulation, was developed and could demonstrate complete removal of particle mixing from the screening results. Screening results of the new method clearly showed an accurate distribution of uranium isotopic abundances in the test samples. SIMS screening combined with micromanipulation was shown to be effective in removing particle mixing caused by adjacent uranium particles and as a result, accurate data could be obtained.

This study was conducted as part of the "Project for Environmental Sample Analysis and Analytical Method Development for Safeguards," supported by the Nuclear Regulation Authority of Japan.

Tomita, R. et al., Improvement in Automated Particle Measurement Using Micromanipulation and Large Geometry Secondary Ion Mass Spectrometry to Remove the Particle Mixing Effect of Uranium Particles, Journal of Nuclear Science and Technology, vol.62, issue 10, 2025, p.939–948.

Paper URL: https://doi.org/10.1080/00223131.2025.2512812

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