A fundamental study on cesium migration to sodium at low temperature

Our experiment study aims to understand the behavior of cesium in severe accident of sodium cooled fast breeder reactor, especially cesium migration rate to sodium. In past study, exact migration rate of cesium to sodium has not been reported because of difficulty of the cesium-sodium interfacial area evaluations of gas bubble. In this study, we developed a pool-type experimental apparatus which can simplify the shape of interfacial area, and measured cesium migration rate in a low temperature range of 200degC to 300degC. The cesium migration rates obtained under the condition that the cesium mixed argon gas flow is the same temperature with sodium vary in the range of 10^-3 - 10^-1 mol/m²min and increase with increasing the system temperature. The difference of cesium migration rates between non-oxidized sodium surface and oxidized sodium surface is also clearly observed. (author)