Fluidised bed coating of nuclear fuel particles - e.g. with graphite or silicon carbide, using a curtain of inert gas to prevent secondary deposition

摘要

Formation of coatings on articles, esp. spherical nuclear fuel cores, involves injecting a coating gas e.g. a hydrocarbon and/or silane, into the base of a fluidised bed furnace and also injecting an inert gas into the base of the furnace in such a way as to form an envelope of inert gas round the coating gas, the ratio of the gas velocities being regulated so as to prevent mixing of the gases and to establish an inner zone in the furnace rich in coating gas in which the coating is deposited on the articles and which is surrounded by an external zone rich in inert gas. This prevents the establishment of a secondary coating deposition zone where the deposit tends to be non-uniform due to a deficiency of coating gas and a higher concn. of articles to be coated which prevents their free rotation and the uniform exposure of their whole surface.