Thermodynamic re-assessment of the Pu–U system and its application to the ternary Pu–U–Ga system

[Display omitted] •The ab initio aided CALPHAD assessment of the Pu–U system has been realized.•The Pu–U–Ga thermodynamic database has been developed.•The δ-phase (fcc) of the Pu–U–Ga system is stabilized by Ga.•The stability of the complex η and ζ phases is promoted by U in the Pu–U–Ga system. Phase diagram and thermodynamic properties of the Plutonium–Uranium (Pu–U) system have been successfully re-assessed using the CALPHAD method with input from ab initio electronic-structure calculations for the bcc phase (γ-U, ∊-Pu). Results and methodology are discussed and compared with previous assessments. In addition, the already assessed Pu–Ga (Gallium) and U–Ga data are combined to build the Pu–U–Ga thermodynamic database. The predictions made using this database indicate that a small amount of U impacts the (δ-Pu) Pu–Ga phase stability by precipitating the complicated η and ζ phases that exist in the Pu–U system. Finally, the present investigation provides guidelines for further experimental studies.