Agglomerate-free fine UO2 powders

The final quality of a sintered ceramic depends on starting powder characteristics, forming and firing conditions. The powder characteristics are, in turn, dependent on the characteristics of the precursor from which the powder is obtained by thermal decomposition. The precursor precipitate ammonium diuranate is dried, calcined and reduced at specific temperatures and heating rates to yield UO2 powder. The final acceptance of sintered UO2 has been found to be high with a combination of a low precipitation temperature, intermediate precipitate aging, precipitate washing and controlled thermal decomposition that would not only preserve precursor morphology, but also develop sufficient porosity. These conditions yield agglomerate-free soft powders that do not require milling or binder addition before compaction. The powders, after granulation, pack well in compaction and yield homogeneous high density microstructures on sintering. (UK)