New approaches in the characterization of uranium dioxide

Uranium dioxide has been characterized for several years by the well-known BET, Fisher, and other methods. However, it has now been possible to draw new conclusions by combining the common characteristics to arrive at new characteristics. For example, in the preparation of the powder precursor ammonium diuranate (ADU), the increase in particle size with increase in precipitation temperature (as shown by sieve analysis) could be either due to crystal growth or clustering of smaller crystals. A corresponding increase in specific surface area (SSA) and the decrease in tap density would indicate clustering while the opposite would indicate crystal growth. The product of the SSA and the average particle size (APS) characterizes the compactability of the uranium dioxide powder while the ratio characterizes its sinterability. In addition, new characterization methods have also been evolved. Compaction maps have been drawn to characterize the compaction process in relation to pressing defects, such as cracks, end caps, and low density. The coarsening–densification transition temperature (CDTT) has been suggested to characterize the sintering process in relation to pretreatment.