Reduction behaviour of the U O3 GeL microspheres

U O3 gel microspheres prepared using internal gelation process (H-process) has been calcined in air under different calcination conditions. It has been found that the calcined density of spheres increases with both calcination temperature and time particularly above 1000 degree C due to the initiation of sintering of U3 O8. The calcined spheres were reduced in hydrogen or ammonia atmosphere at temperatures ranging from 600 to 1100 degree C. It has been found that the reduced spheres density depends on the ignition temperatures of U O3 and increases with both reduction temperature and calcining time. The density of spheres reduced in hydrogen was higher than that reduced by ammonia