The Effect of Deposition Parameters on the Properties of Pyrolytic Carbon and SiC Layer In TRISO-Coated Particles Deposited by Fluidized-Bed Chemical Vapor Deposition

TRISO coatings on ZrO2 (or UO2) kernels were conducted by a fluidized-bed chemical vapor deposition (FBCVD) method. Effects of the reaction gas mixture, gas flow rate and deposition temperature on the properties of PyC and SiC layer were investigated in the TRISO-coated particles. The deposition parameters on the properties of PyC density could be varied from 1.0 g/cm3 to 2.0 g/cm3 by controlling the deposition parameters. The density decreased and the deposition rate increased as the deposition temperature and reactant concentration increased. Deposition rate of the SiC layer changed as the deposition temperature increased in the temperature range of 1400-1550oC. At 1550°C, the SiC layer contained excess carbon, whereas the SiC layers had stoichiometric compositions at 1500oC. The microstructure of the SiC layer deposited on the gas flow rate of 4000 sccm showed high porosity and large pores more than 1um.