On the use of CALPHAD-based enthalpy-temperature relations in suboxidized corium plane front solidification modelling

The present study demonstrates the feasibility of using CALPHAD-based enthalpy-temperature relations in the modelling of plane front solidification of suboxidized in-vessel corium. Along with theoretical considerations on the equations formulation, this paper discusses the use of associate models with species as its constituents for obtaining U-O-Zr thermodynamic description, owing to the sub-stoichiometric nature of (U,Zr)O2-x phase. As a result of incorporating such associate models, there is a need for modification of species conservation equations in order to evaluate interface quantities. The numerical results based on a model developed in the PROpagation of CORium (PROCOR) platform interfaced with the Open-Calphad thermodynamic software show the linearity of these EOS for solid and liquid phases with changing temperature and composition. The 'almost'linear trends in the EOS confirm their usefulness in predicting system behaviour at macroscopic scales.