PURPOSE: To manufacture a UO2 powder with a very high activity from an uranyl solution including separate acids, and to manufacture a UO2 sintered pellet suitable for a high burnup of a nuclear fuel whose sintered density is close to the logic density and the crystal grain diameter is large, from the UO2 powder in a simple method.

CONSTITUTION: As to the method to manufacture a UO2 sintered pellet from a uranyi solution including separate acids, either UO2 or U3O8, or both of them, of sufficient amount to expend the separate acids are added to the uranyl solution and reacted, and then, a uranyl solution including no separate acid is produced in a solid-liquid separation. By adding H2O2 to the uranyl solution, an uranium peroxide (UPO) hydrate is produced and precipitated, and then, the UPO hrdrate is solid-liquid separated to collect the precipitation. After the collected precipitation is dried, the UPO hydrate is roasted-and-reduced in a reducing atmosphere, and converted into UO2, and after the resultant UO2 is formed into the powder, it is sintered to process into a UO2 sintered pellet.