RECYCLING PROCESS OF U3O8 POWDER IN MnO-Al2O3 DOPED LARGE GRAIN UO2 PELLETS

The effect of various process variables on the powder properties of recycled U₃O 8 from MnO-Al₂O₃ doped large grain UO₂ pellets and the effect of those recycled U₃O 8 powders on the sintered density and grain size of MnO-Al₂O₃ doped large grain UO2 pellets have been investigated. The evolution of morphology, size, and BET surface area of the recycled U₃O 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 U₃O 8 powder and the sintered pellet properties of MnO-Al₂O₃ 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 U₃O 8 powder. The density and grain size of the pellets were maximized when the BET surface area of the recycled U₃O 8 powder was in the vicinity of 3㎡/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 U₃O 8 powder.

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