| 摘要 |
Nuclear fuel particles are coated with pyrolytic graphite produced by the thermal decomposition of a hydrocarbon gas in the presence of the particles to be coated. The fuel is preferably uranium monocarbide, uranium dicarbide or a uranium oxide while methane, ethane, propane and benzene are suitable hydrocarbons. The process is carried out at a temperature between 1700 DEG C. and 3000 DEG C. and a pressure of between 1 mm. and 200 mm. of mercury, in a hollow graphite cylinder rotatable about its longitudinal axis. For example, 30 gm. of uranium dicarbide in the shape of spherical particles of diameters between 177 and 250 microns are charged into the graphite cylinder which is filled with argon at a pressure of 20 mm. of mercury and rotated at a speed of 30 r.p.m. while its temperature is raised to 1700 DEG C. by means of a surrounding induction coil, methane being introduced into the cylinder at a rate of 0.2 litre/min. After 4 hours of processing, the methane supply is shut off and the cylinder allowed to cool to room temperature, the particles then having a graphite coating of average thickness about 80 microns. |
