Study of SiC Layer with Fine Grains in HTGR Coated Fuel Particles

High temperature gas-cooled reactor (HTGR) with inherent safety characteristics is considered as one of the attractive and competitive generation Ⅳ nuclear reactors in the future energy markets. Tristructural-isotropic (TRISO) coated particle fuel is the most significant safety aspect in this nuclear reactor, since it relies on the properties of the four coating layers surrounding the kernel fuel to hinder the release of harmful radioactive material. Among these layers, the silicon carbide (SiC) coating is considered the most important as it not only provides the TRISO particle with structural integrity but also retains fission products at elevated temperatures. The preparation of high quality SiC layers is one of significant issues and key technologies in nuclear fuel fabrication. The basic structure of the TRISO-coated fuel particles and the fluidized bed chemical vapor deposition (FBCVD) method to prepare SiC layers were introduced. The advantages of decreasing grain size of SiC layers were analyzed and the idea to prepare SiC layers with fine grain size was proposed. In the preparation strategies, recent research developments of fine grain SiC materials in the forms of powders, ceramics, thin films and coatings were reviewed. Based on the progresses achieved by our group, basic synthesis routes for the preparation fine grain SiC coatings were proposed.