To compare and evaluate various fuel cycle options for a 500-MW(electric) fast breeder reactor, the electrorefining process has been examined for reprocessing spent fuel. Making use of an improved thermochemical model, optimum process conditions for electrorefining have been worked out. These conditions are the following: capacity of the electrorefining cell, number of cells, batch size, feed adjustments, sequential operations for recovery of uranium and co-recovery of uranium and plutonium, number of cycles, and timeframe to meet the refueling schedule. The spent fuel is envisaged to undergo reprocessing in three campaigns: (a) the inner core campaign, (b) the outer core campaign, and (c) the blanket and the leftover campaign. Feed adjustments are done by mixing either the spent inner core or the outer core fuels with the blankets. Three product streams with required fuel composition for direct refabrication of the inner core, the outer core, and the blanket fuel subassemblies, respectively, are obtained by certain sequential electrorefining operations. These calculations made for a mixed-oxide fuel core can be easily extended to the metallic core.