New method for coating microspheres with zirconium carbide and zirconium carbide--carbon graded coats

A new method for the chemical vapor deposition of ZrC and C--ZrC alloys has been developed. This process has been applied to the fabrication of coated particle nuclear fuels of the type used in the large High-Temperature Gas-Cooled Reactor. A powder feeder is used to supply ZrCl$sub 4$ to the fluidized bed coating furnace where it undergoes reaction with a hydrocarbon to form ZrC. Quantitative metering of the ZrCl$sub 4$ makes it possible to control the deposition of the ZrC and the codeposition of the C--ZrC alloys on the fuel particles. Examples of both types of coats made using the described technique are discussed and illustrated. (auth