Reactive Spark Plasma Sintering of UAlx + Al Powder Mixtures, Prospects for Manufacturing Targets for 99mo Production

A U + 5 wt.% Al powder (written U-5Al), manufactured by centrifugal atomization, was used in this study to assess the feasibility of densifying UAlx + Al powder mixtures by Spark Plasma Sintering (SPS) and obtaining a final composition with a minimum content of UAl2 that meets specifications of targets for 99Mo production. The microstructure of the U-5Al powder was studied first and mainly consists of a mixture of UAl2 primary dendrites and α-U phase. Three SPS conditions differing in terms of UAlx/Al volume ratio and dwell time at 800 K were tested. The sintered discs were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. A very quick transformation of the U-5Al particles into a mixture of aluminides (UAl2 + UAl3 + UAl4, referred to UAlx) was evidenced: only a few minutes were sufficient to transform the U-based particles into a mixture of aluminides containing about 80 wt.% of UAl3. According to these first tests, this new highly versatile manufacturing process could advantageously replace the conventional method of producing targets, subject to technical adjustments and parametric studies.