Diffuse-interface modelling of multicomponent diffusion and phase separation in the U-O-Zr ternary system

M.A. Rasolofomanana (1) , C. Cardon (1) , M. Plapp (2) , Thomas Philippe (3) , H. Henry (3) , R. Le Tellier (1)

1 CEA Cadarache
2 LPMC - Laboratoire de Physique de la Matière Condensée
3 LPMC - Laboratoire de physique de la matière condensée

The ternary mixture of uranium, zirconium and oxygen is investigated as a minimal model for corium, the mixture that forms after the meltdown of a nuclear reactor. Like corium, U-Zr-O exhibits a liquidliquid phase separation between a metal-rich and an oxyde-rich phase at high temperatures. A CALPHAD database built on an associate model is used to set up a ternary Cahn-Hilliard model, which can describe two-phase patterns in U-Zr-O and may be coupled to the Navier-Stokes equations for hydrodynamic flows. The interface structure and properties, which depend on the choice on the gradient energy coefficients in the free-energy functional, are studied in detail. It is found that interface adsorption is generally present, but that its magnitude is small, such that the model remains a robust and useful tool for future simulations of corium pool stratification dynamics.

Mots clés: Cahn-Hilliard; CALPHAD; liquid phase segregation; multicomponent diffusion; U-O-Zr system; in-vessel corium

Domaines: Physique [physics]

M.A. Rasolofomanana, C. Cardon, M. Plapp, Thomas Philippe, H. Henry, et al.. Diffuse-interface modelling of multicomponent diffusion and phase separation in the U-O-Zr ternary system. Computational Materials Science, 2022, 214, pp.111650. ⟨10.1016/j.commatsci.2022.111650⟩. ⟨hal-03835047⟩