Simulation of Cs behavior during the high temperature voloxidation process using the HSC chemistry code

The HSC chemistry code was employed to calculate the chemical and physical changes of Cs during the oxidative decladding and high temperature voloxidation processes. Five systems, Cs–O, Cs–I, Cs–Te, Cs–U, and Cs–Mo, were investigated to determine the stable phases at the oxidative decladding process, and to simulate a release of Cs from the stable phases. Theoretical calculation results revealed that metallic Cs and Cs oxides might react with other oxides to form stable compounds including CsI. At 500 °C under an air atmosphere, CsI, Cs2TeO4, Cs2UO4, and Cs2MoO4 were determined as stable phases for each system. The effect of operation temperature on these compounds during the high temperature voloxidation process was investigated for a temperature range of 500–1500 °C. In addition, the effect of heating atmosphere was studied by employing four different conditions of oxygen, air, argon, and 4% H2/Ar atmospheres.