Uranium oxide microparticle suspensions for the production of reference materials for micro-analytical methods

Research progress on the analysis and application of radioactive hot particle

Radioactive hot particle is the particulate form of nuclear material that exists in the environment. The U, Pu, Am, Cs, and other radionuclides isotope in the hot particle contain abundant and accurate fingerprint information, such as the origin and age of the nuclear material. The acquisition and analysis of the key information in the hot particle can be equivalent to the analysis of bulk nuclear material, which could directly reflect the real situation of nuclear activities. Therefore, the single particle analysis of hot particles has become an irreplaceable key technology in nuclear safeguards inspection. The rapid identification, screening, locating, and accurate isotope analysis of hot particles from a large number of particles dispersed in environmental media or on the surface of other materials are one of the most important research field in nuclear emergency. In this review, the research process of the analytical methods for hot particles in the last decade was summarized, including the physical character of hot particles, and the techniques of localization, screening, and extraction of hot particles. Furthermore, we also focused on the mass spectrometry technology for the analysis of hot particle. The advantages and disadvantages of the most used mass spectrometry were summarized. Finally, the research trend for hot particle analysis methods was proposed.

Production of mixed element actinide reference particulates to support nuclear safeguards using THESEUS, an aerosol-based particulate synthetic methodology

The THermally Evaporated Spray for Engineered Uniform particulateS (THESEUS) production platform was developed to generate highly uniform mixed actinide oxide particles. The particulate synthesis platform builds on previous efforts and utilizes an aerosol-based technology to generate, calcine, characterize, and aggregate a monodisperse oxide phase particle product. In this study, particles comprised of uranium oxide, incorporated with varying compositions of thorium, were produced. Th/U test materials with ²³²Th concentrations between 1 ppm and 10%, ratioed to ²³⁸U, were successfully generated with in situ calcination at 600 °C and characterized by in situ aerodynamic particle size spectrometry and ex situ microanalytical methods. Populations of monodisperse particulates (geometric standard deviation - GSD < 1.15) with an average diameter near 1 μm were generatated and micro-Raman spectroscopy of individual particles identified U₃O₈ as the primary material phase for the range of Th/U samples analyzed. Single particle measurements and automated particle analyses by secondary ion mass spectrometry (SIMS) were performed. Uniform inter-particle elemental and isotopic homogeneity for uranium and thorium isotopes was characterized by SIMS, and a ²³²Th/²³⁸U relative sensitivity factor of 0.53 was determined. SIMS results demonstrated differences in the ²³²Th/²³⁸U profiling behavior for Th/U particulates with increased Th content (>1%). Despite the observed profiling behavior, single particle measurements of the 10% Th sample indicate inter-particle homogeneity. This work represents the first systematic study of Th/U microparticulate reference materials generated and intended for nuclear safeguards applications and serves as a demonstration of THESEUS to support a sustained capability for the production mixed-element particulate reference materials.