Thoria-based cermet nuclear fuel : sintered microsphere fabrication by spray drying.

Cermet nuclear fuels have been demonstrated to have significant potential to enhance fuel performance because of low internal fuel temperatures and low stored energy. The combination of these benefits with the inherent proliferation resistance, high burnup capability, and favorable neutronic properties of the thorium fuel cycle produces intriguing options for advanced nuclear fuel cycles. This paper describes aspects of a Nuclear Energy Research Initiative (NERI) project with two primary goals: (1) Evaluate the feasibility of implementing the thorium fuel cycle in existing or advanced reactors using a zirconium-matrix cermet fuel, and (2) Develop enabling technologies required for the economic application of this new fuel form. Spray drying is a physical process of granulating fine powders that is used widely in the chemical, pharmaceutical, ceramic, and food industries. It is generally used to produce flowable fine powders. Occasionally it is used to fabricate sintered bodies like cemented carbides, but it has not, heretofore, been used to produce sintered microspheres. As a physical process, it can be adapted to many powder types and mixtures and thus, has appeal for nuclear fuels and waste forms of various compositions. It also permits easy recycling of process ''wastes'' and minimal chemical waste streams that can arise in chemical sol/gel processing. On the other hand, for radioactive powders, it presents safety challenges for processing these materials in powder form and in achieving microspheres of high density and perfection