First principles calculation of the Al3U–Si3U pseudobinary fcc phase equilibrium diagram

In the frame of RERTR Program (Reduced Enrichment for Research and Test Reactors) it is being developed a high density uranium based fuel that could remain stable in the body cubic centered (bcc) phase during fabrication and irradiation in the reactor. Research is focused in a U–Mo alloy dispersed fuel in aluminum matrix. The main problem focuses in an undesirable growth of the interface between fuel and Al matrix. This problem could be reduced with the addition of Si to the matrix and the subsequent stabilization of UAl3 in the interface. We investigated this possibility in this work using first principles theory and methods. We demonstrated that U(Al,Si)3 phase is stable in the UAl3–USi3 pseudobinary system. Moreover, calculations were able to justify the existence of an experimentally reported phase with U4Al9Si3 stoichiometry and a wide composition range.

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► Solubility of Si in U(Al,Si)3 phase is predicted in the whole range of composition within the pseudobinary UAl3–USi3.
► A first principles study for the pseudo-binary system UAl3–USi3 is reported.
► The existence of the experimentally reported U4Al9Si3 phase is confirmed with a wide solubility range.