Improved ionic model of liquid uranium dioxide

The paper presents a model for liquid uranium dioxide, obtained by improvin g a simplified ionic model, previously adopted to describe the equation of state of this substance [1]. A "chemical picture" is used for liquid UO2 of stoichiometric and non-stoichiometric composition. Several ionic species a re considered here: U(+5), U(+4), U(+3), O(-2) and O(-1). The ions are desc ribed as charged hard-spheres of different diameters. Coulomb interaction o f ions is taken into account according to the modified Mean Sphere Approxim ation The main result of the new model is the appearance of natural "plasma " equivalent, which, from the theory, is directly related to the definition of oxygen potential in liquid UO2+x. The features of the model make it pos sible to describe non-congruent phase equilibrium (and evaporation) in uran ium dioxide, as well as other relevant phenomena characterising the phase e quilibrium in chemically active matter. First calculation results are discu ssed.