Chernobyl fuel microparticles: uranium oxidation state and isotope ratio by HERFD-XANES and SIMS

Fuel “hot” particles are the most unpredictable dose-forming components in the soils of uranium contaminated regions, such as Chernobyl Exclusion Zone. Over time in the environment, “hot” particles undergo gradual dissolution with the release of uranium as well as fission and neutron-activation products trapped inside the uranium-oxide fuel matrix. The environmental fate of fuel particles depends not only on the environmental conditions but mainly on the conditions of their formation in the reactor and during the accident. In the present work micromorphology, fuel burnup and uranium oxidation state of several fuel “hot” particles, collected on the Western trace of Chernobyl fallout, were studied using a combination of non-destructive or semi-non-destructive techniques: gamma-spectrometry, secondary-ion mass-spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, the X-ray absorption near-edge structure and the high-energy resolution fluorescence-detected X-ray absorption near-edge structure spectroscopy. An attempt has been made to assess the contribution of the conditions of particle formation and the conditions of being in the environment to the current state of particles after more than a quarter of a century of history in the environment.