Fundamental Study on the Vaporization of Cesium and Iodine Dissolved in LiF-NaF-KF Molten Salt

As a basic study related to a severe accident of molten salt reactor, the vapor pressures and chemical activities of Cs and I dissolved in molten LiF-NaF-KF eutectic salt (46.5-11.5-42.0 mol%, FLiNaK) were measured by a transpiration method under pure Ar gas flow at the temperature ranging between 900 and 1100K. As the result, the vapor pressure and the chemical activity of I in molten FLiNaK were evaluated to be higher than that expected from ideal solution assumption. Additionally, the elemental composition of the evaporated content indicated that Cs had a tendency to combine with I and evaporate as CsI.