Chemical state of strontium in irradiated oxide fuel

The oxygen potential and Ellingham diagram of strontium-uranium-oxygen system have been calculated using FactSage code. The partial pressure of oxygen over the equilibrium phase fields were computed by minimization of Gibbs energy of the system. The calculated oxygen potential and Ellingham diagrams for Sr-U-O system showed SrUO3(s) to coexist with UO2(s) at Δμ(O2) ≅ -400 kJ.mol-1 and SrUO4(s) with UO2(s) at Δμ(O2) ≅ -100 kJ.mol-1. Combining the results of present calculations with experimental finding of post irradiation studies, present study predicts that strontium in an oxide fuel will present in grey phase as (Ba1-x-ySrxCsy) (U, Pu, Ln, Zr, Mo)O3 at Δμ(O2) ≥ -400 kJmol-1 and as (Rb, Cs, Sr, Ba) (Mo,U)O4 at Δμ(O2) ≥ -100 kJ mol-1. (author)