Using first principles DFT (density functional theory), we have examined the thermochemical mechanism of electrorefining spent uranium (U) from a LiCl–KCl molten salt on a tungsten (W) surface. We calculated 197 different U/W(110) surfaces to identify the most thermodynamically and electrochemically stable structures as a function of U and Cl coverages. The results indicate that local structures of the double-layer interface between the W(110) surface and the LiCl–KCl salt are the key factors governing the electrorefining performance. The results also provide important thermodynamic properties for the design of efficient recycling systems for spent nuclear fuels, such as pyroprocessing technologies, and may be applicable as well to general electrochemical applications involving strong redox reactions of transition metals exposed to non-aqueous solutions.