The monograph deals with the thermodynamic properties of fluid uranium dioxide, one of the most investigated materials of the last century, up to its critical point. It presents an exhaustive theoretical introduction to "quasi-chemical" models of liquids, as well as their behaviour under non-congruent vaporisation conditions. Particular emphasis is given to the properties of pure Coulombic systems and to the pseudoparticle approach, which enables the partition function to be expressed in a simple, but physically rigorous formulation. The construction of the equation of state of stoichiometric and non-stoichiometric uranium dioxide is described in distinct steps, from a critical assessment of the theoretical fundamentals to a thorough review of the pertinent thermochemical and thermophysical data. Calculations of the thermodynamic properties of UO2+x are performed for temperatures up to 10,000 K both for the condensed and gas phase. More than one hundred tables are collected in the Appendix, containing all relevant thermodynamic data.

Introduction.- Governing Equations and Fundamental Formulae.- Ionic Models for Liquid Urania.- Gas-Liquid Coexistence in Uranium Dioxide.- Application of the Chemical Model within the van der Waals Approximation.- New Equation of State for Fluid Uranium Dioxide Based on Thermodynamic Perturbation Theory.- Thermodynamic Properties of UO2, as Predicted by the New Equation of State.- Appendix.