JPH0631760B

Method for manufacturing sintered oxidic nuclear fuel bodies by molding uranium oxide starting powder, a mixture of uranium oxide and plutonium oxide starting powder or of uranium-plutonium oxide mixed-crystal starting powder to form blanks and by a heat treatment of these blanks with a U4O9 or (U, Pu)4O9 crystal phase developed in them to a degree which can be crystallographically detected at a sintering temperature in the range of 1000 DEG to 1400 DEG C. in an oxidizing and subsequently in a reducing gas atmosphere. The starting powder and/or the blanks are preroasted at a roasting temperature below the sintering temperature in a roasting gas atmosphere with oxidizing action and with an oxygen potential in which the U4O9 (U, Pu)4O9 crystal phase is developed and cooled down subsequently to a starting temperature below the roasting temperature in an inert or oxidizing cooling-down gas atmosphere. Starting from this starting temperature, the blanks are heated to the sintering temperature in an inert or oxidizing heating gas atmosphere while maintaining the U4O9 or the (U, Pu)4O9 crystal phase.