PRODUCTION METHOD FOR URANIUM DIOXIDE SINTERED BODY WITH LARGE GRAIN

摘要

PROBLEM TO BE SOLVED: To obtain a production method of UO2 sintered body with large grain by sintering without adding foreign material sintering additive and in reducing gas atmosphere. SOLUTION: A method is constituted of a first process producing U3O8 monocrystal and a second process producing UO2 sintered body with large grain by using mixed powder of U3O8 monocrystal and UO2 powder. In the first process, U3O8 powder is annealed for more than 1 hour at the temperature of 1000 to 1500 deg.C in non-reducing gas atmosphere to produce U3O8 polycrystal agglomerate and the U3O8 polycrystal agglomerate is finely separated to produce U3O8 monocrystal. In the second process, UO2 powder and U3O8 monocrystal are mixed to produce stuff powder and the stuff powder with U3O8 monocrystal of 1 to 15 wt.% is granulated and molded to produce green pellets, which is sintered in reducing gas atmosphere for more than 1 hour at the temperature of 1600 deg.C or higher.