Thermodynamic modeling and phase equilibrium calculations in nuclear materials

Abstract: Thermodynamic systems of interest in nuclear engineering generally consist of many components and many phases. To perform thermodynamic calculations involving equilibria among solid, liquid and gaseous phases, large evaluated databases of the thermodynamic properties of compounds and multicomponent solutions are required, as well as software for performing the equilibrium computations. The development of general Gibbs energy minimization software is well advanced, and a number of software packages are available commercially. The development of thermodynamic databases for multicomponent systems proceeds by the critical evaluation of sub-systems in which all available thermodynamic and phase equilibrium data are optimized simultaneously to obtain one self-consistent set of model equations for the Gibbs energies of all phases as fbnctions of temperature and composition. The parameters of these equations are stored in the databases, and the models are used to estimate the properties of the multicomponent solutions. It is very important to choose a model which correctly reflects the structure of the solution. Examples of databases and of equilibrium calculations in nuclear materials applications are presented