Development of various elemental technologies related to decommissioning

This study investigated the following three items for elucidating the unique wetting mechanism on the surface of UO₂ polycrystalline solids reported in liquid CsI, which can have a significant effect on the release behavior of volatile fission products Cs and I. First, to confirm the reproducibility, the authors verified the wettability of liquid CsI on the (111) and (100) planes of Yttria-stabilized zirconia (YSZ) and the surface of YSZ polycrystal, which have the same crystal structure as UO₂. Second, to evaluate the effect of the surface energy of a liquid on the wetting on the solid surface, they evaluated the wetting behavior of B₂O₃, which has the melting point and surface energy almost the same as CsI. Third, to expand the knowledge about the wetting behavior of liquid CsI on the oxide solid surface, they examined the wettability of CsI, CsCl and CsBr on the solid single crystal (100) plane of TiO₂ and MgO, which have different crystal structures from UO₂ and YSZ. As a result, it was clarified that the extremely good wettability of liquid CsI confirmed on the UO₂ polycrystalline solid surface is a phenomenon due to the chemical properties of liquid cesium halide, and that the peculiar wetting is a phenomenon that occurs on the solid surface of a specific oxide. (A.O.)