Isotope ratio analysis of individual uranium particles for safeguards

Japan Atomic Energy Research Institute (JAERI) was qualified, in January 2003, as a member of the IAEA network analytical laboratories (NWALs) for particle and bulk analyses of safeguards environmental samples. The particle analysis gives more detailed information on nuclear facility operation than the bulk analysis because the isotope ratios of nuclear materials in the samples collected inside nuclear facilities (swipe samples) can be determined for individual particles. We applied secondary ion mass spectrometry (SIMS) to the uranium isotope ratio measurement for particle analysis. Prior to the SIMS analysis, the particles in a swipe sample are recovered onto a carrier by impaction. The carriers with the recovered particles are then screened by total reflection X-ray fluorescence spectrometry. We integrated these techniques into a standard procedure, which is applied to domestic and IAEA swipe samples routinely. For the analysis of the particles with the diameter smaller than 1 μm, with which the SIMS has insufficient sensitivity, we are developing a more sensitive method, the combination of fission track detection and thermal ionization mass spectrometry. (author)