The effect of various process variables on the powder properties of recycled U 3 O 8 from MnO-Al 2 O 3 doped large grain UO 2 pellets and the effect of those recycled U 3 O 8 powders on the sintered density and grain size of MnO-Al 2 O 3 doped large grain UO 2 pellets have been investigated. The evolution of morphology, size, and BET surface area of the recycled U 3 O 8 powders according to the respective variation of the thermo-mechanical treatment variables of oxidation temperature, powder milling, and sequential cyclic heat treatment of oxidation and then reduction was examined. The correlation between the BET surface area of recycled U 3 O 8 powder and the sintered pellet properties of MnO-Al 2 O 3 doped pellets showed that the pellet density and grain size of doped pellets were increased and then saturated by increasing the BET surface area of the recycled U3O8 powder. The density and grain size of the pellets were maximized when the BET surface area of the recycled U3O8 powder was in the vicinity of 3m 2 /g. Among the process variables applied in this study, the cyclic heat treatment followed by low temperature oxidation was a potential process combination to obtain the sinter-active U 3 O 8 powder.