Process for the coating of particles for the production of fuel and/or absorbing elements for nuclear reactors and apparatus therefor

Fuel, fertile material and/or absorber material containing particles for fuel and/or absorber elements in nuclear reactors are coated by a process comprising introducing thermally cleavable gases into the reaction space heated to an operating temperature of a fluidized bed unit provided with a gas inlet nozzle cooled with a cooling medium and having an elongated inlet tube, decomposing the cleavable gases after leaving the nozzle, depositing the decomposition products on fuel, fertile material or absorber particles present in the fluidized bed and bringing these coated particles into fuel elements or absorber elements. The cooling medium is solely gaseous and only the portion of the inlet tube for the nozzle tips of the gas inlet nozzles within the axis are cooled and the heat flow penetrating from outside is reduced by heat insulation. An apparatus for carrying out the process is also described