Thermodynamic modelling assessment of the ternary system Cs-Mo-O

This work reports the thermodynamic modelling assessment of rather complex Cs-Mo-O system, which is key for understanding fission products chemistry in oxide fuelled Light Water Reactors (LWRs) and next generation Sodium-cooled Lead-cooled Fast (SFRs LFRs). The model accounts existence ternary molybdates Cs 2 MoO 4 ( α β ), Mo O 7 3 10 , 13 5 16 22 sufficient structural information are available literature. These phases treated as stoichiometric model. liquid phase described with an ionic two-sublattice model, gas ideal mixture. optimized Gibbs energies assessed respect to known equilibrium data -MoO pseudo-binary section. A good agreement generally obtained within experimental uncertainties. calculated vapour pressures above (solid liquid) also compared data. Finally, isotherms diagram at relevant temperatures fuel pin behaviour LWRs, SFRs LFRs. • system modelled using CALPHAD method. formalisms used compatible those TAF-ID database. Calculations performed assess nuclear behaviour. Remaining discrepancies or missing on identified.