液体セシウムハライドの酸化物単結晶表面に対する濡れ性

抄録

　The wettability of liquid-state volatile fission products （FPs） for solid-state fuels is important for the evaluation of FP release behavior during severe accidents. Previously, we have reported that liquid CsI exhibits extremely high wettability with a contact angle of virtually 0° on a polycrystalline UO₂ surface ［K. Kurosaki et al., Sci. Rep. 7, Article number: 11449 （2017）］ and a single-crystalline yttria-stabilized zirconia （YSZ） surface ［H. Ishii et al., J. Nucl. Sci. Technol. 55, No. 8, 838–842 （2018）］. Here, based on the previous studies, we investigate the wettability of liquid cesium halides （CsCl, CsBr） on single-crystalline YSZ, TiO₂, and MgO. We observe the high wettability of liquid cesium halides on single-crystalline YSZ and TiO₂ with contact angles of nearly 0° in all cases. However, liquid cesium halides exhibit completely different wettability on single-crystalline MgO, where the contact angles are measured to be 50°, 44°, and 25° for CsCl, CsBr, and CsI, respectively. Similarly to UO₂, YSZ and TiO₂ are non-stoichiometric compounds containing oxygen defects, while MgO is a stoichiometric line compound. Thus, it is assumed that the oxygen defects play a role in the high wettability of liquid CsI on solid UO₂.