SiC coating on UO2 pellet by a combustion synthesis

Multi-layer coating of silicon carbide and graphite on UO2 nuclear pellet was carried out with a fluidized bed type chemical vapor deposition unit to enhance the inherent safety of the nuclear pellet and to develop a renovative coating process. Silane, propane and argon gases were used as the source and carrier gases to deposit silicon and pyrolytic carbon. Combustion reaction was performed in an inert argon atmosphere, which conditions were pre-determined by numerical evaluation of the combustion reaction between silicon and carbon to synthesize silicon carbide. Microstructural observation of the combustion products by scanning electron microscopy showed that the inner and outer pyrolytic carbon layers were equiaxed structure. Chemical analysis by Auger electron spectroscopy and X-ray diffractometry revealed that the middle layer formed by a combustion reaction was fine crystalline beta-silicon carbide. (author)