Method of manufacturing nuclear fuel ceramic

At first, a double-layered pellet molding product having UO2 pellet incorporated with Gd2O3 at the outer side and a UO2 molding product at the inner side is manufactured. In this case, it is not necessary to apply any treatment for UO2 obtained by the ADU method as starting materials, but it is important to admix 25 to 45% of U3O8 upon manufacturing the inner UO2 molding product for UO2 obtained by the ADU method. Subsequently, thus manufactured co-compact molding products are sintered at 1000 to 1400degC, in a gas containing 10-3 to 500 ppm of oxygen. Thereafter, reducing treatment under heating is applied at 1650 to 1800degC in a reducing atmosphere containing hydrogen applied with a slight amount of water. The characteristic of the resultant fuel pellet are improved, FP gas retainability is improved for the entire pellet and PCMI characteristics are also made advantageous. (T.M.)