Thermodynamic modelling assessment of the ternary system Cs-Mo-O
Résumé
This work reports the thermodynamic modelling assessment of the rather complex Cs-Mo-O system, which is key for the understanding of fission products chemistry in oxide fuelled Light Water Reactors (LWRs) and next generation Sodium-cooled and Lead-cooled Fast Reactors (SFRs and LFRs). The model accounts for the existence of the ternary molybdates Cs$_2$MoO$_4$ ($\alpha$ and $\beta$ ), Cs$_2$Mo$_2$O$_7$ ($\alpha$ and $\beta$ ), Cs$_2$Mo$_3$O$_{10}$, Cs$_2$Mo$_4$O$_{13}$, Cs$_2$Mo$_5$O$_{16}$, and Cs$_2$Mo$_7$O$_{22}$, for which sufficient structural and thermodynamic information are available in the literature. These phases are treated as stoichiometric in the model. The liquid phase is described with an ionic two-sublattice model, and the gas phase as an ideal mixture. The optimized Gibbs energies are assessed with respect to the known thermodynamic and phase equilibrium data in the Cs$_2$MoO$_4$-MoO$_3$ pseudo-binary section. A good agreement is generally obtained within experimental uncertainties. The calculated vapour pressures above Cs$_2$MoO$_ 4$ (solid and liquid) are also compared to the available experimental data. Finally, isotherms of the Cs-Mo-O ternary phase diagram are calculated at relevant temperatures for the assessment of the fuel pin behaviour in LWRs, SFRs and LFRs.
Origine : Publication financée par une institution
licence : CC BY - Paternité
licence : CC BY - Paternité
