Synthesis and Spark Plasma Sintering of Microcrystalline Thorium Dioxide for Nuclear Fuel Products

Thorium dioxide represents a future of the world market of nuclear fuel for fourth generation nuclear reactors. In this regard, the problems of technologies for thorium separation from irradiated fuel, its conversion into fuel raw materials, and fabrication of required quality fuel products need effective solutions. In this work the synthesis of microcrystalline mesoporous ThO 2 powders through the deposition of the oxalate complex from nitrate solutions, and its consolidation by spark plasma sintering (SPS) technology has been studied. The influence of the SPS temperature ranging within 1000–1600°С on the ThO 2 powder shrinkage dynamics, phase composition, microstructure, and density of pelletized ceramic products has been studied. Vickers microhardness parameters of samples have been determined. The results show that high-speed (minutes-taking) SPS consolidation of powders at 1600°C and 80 MPa can provide ThO 2 ceramics with 92.5% theoretical density. Microcrystalline powders with particle sizes averaging 3-4 µm can be used as raw materials instead of less accessible nanoscale materials. The study shows the expediency and prospects of further studies with the view of SPS technology adaptation for the needs of the nuclear industry.