Development of uranium reference particles to support nuclear safeguards

Controlled hydrolysis of certified uranium hexafluoride, carried out in a specifically constructed aerosol chamber, leads to the production of uranyl fluoride particulates which – deposited on a graphite planchet support may be used as a quality control reference material. The particle size and surface distribution depends on several parameters, such as the relative humidity inside the aerosol chamber and the concentration of gaseous uranium hexafluoride, determined by the distillation conditions. The best quality samples were obtained at RH ranging from 55 to 70% and low gas amount. These improvements for a single deposition were used to prepare a reference sample with two different uranium enrichments. Preliminary SIMS measurements proved good results with respect to both types of particles. It was also revealed that – in some cases – the micrometer size uranium particles are accompanied by a large uranium background.