AB Initio Study of Advanced Metallic Nuclear Fuels for Fast Breeder Reactors

Density-functional formalism is applied to study the ground state properties of γ-U-Zr and γ-U-Mo solid solutions. Calculated heats of formation are compared with CALPHAD assessments. We discuss how the heat of formation in both alloys correlates with the charge transfer between the alloy components. The decomposition curves for γ-based U-Zr and U-Mo solid solutions are derived from Ising-type Monte Carlo simulations. We explore the idea of stabilization of the (delta)-UZr2 compound against the α-Zr (hcp) structure due to increase of Zr d-band occupancy by the addition of U to Zr. We discuss how the specific behavior of the electronic density of states in the vicinity of the Fermi level promotes the stabilization of the U2Mo compound. The mechanism of possible Am redistribution in the U-Zr and U-Mo fuels is also discussed.