Nuclear fuel pellet manufacturing method

Handling for UO2 powder and molding operation before molding are performed in an inactive atmosphere in a first step so that the O/U ratio of the molding product does not exceeds 2.25 times, to maintain the crystal structure of the molding product to a UO2 phase and not to change into U4O9. In a second step, it is sintered in a reducing atmosphere, at a high temperature of 1200 to 1800degC to densify the molding product having the UO2 phase in a state as it is, and to control the O/U ratio of the pellet to 2.00. It is preferred that the molding is conducted after adding, to a starting UO2 powder, a pore-forming agent having an average grain size of 5 to 300μm, decomposing and evaporating at a temperature not higher than 600degC in order to control the sintering density. With such procedures, UO2 pellets having a large grain size and having a predetermined sintering density neither cracking nor chipping are manufactured and can be utilized effectively as fuels of high burnup performance. (T.M.)