JPH0458417B

PURPOSE:To obtain UO2 powder capable of pelletizing as it is by adding aqueous ammonia into an uranyl nitrate soln. of prescribed concn. controlling the addition velocity. CONSTITUTION:The precipitate of ammonium biuranate is produced by adding aqueous ammonia of 20-35% concn. to an uranyl nitrate soln. of 50-100g/l uranium concn. and 0-2.5N concn. of free nitric acid while controlling the addition velocity at 0.01-0.025gNH3/min per 1g uranium in the case of 3.5-4.5 pH of the uranyl nitrate soln. and at 0.1-0.5g/min per 1b uranium in the case of >=4.5 pH thereof and holding the mixture. Then after separating and drying this precipitate, it is calcined at 660-760 deg.C for 2-4hr in an air current of 0.3-0.3M /h.kgU flow rate and then reduced for 20-1hr in the reducing atmosphere of 2-5M /h.kgU flow rate of H2 to obtain UO2 powder.