Abstract: 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 in the reaction space heated to above 1000.degree. C. of a fluidized bed unit with the help of a gas inlet nozzle cooled with a cooling medium and having an elongated inlet tube, decomposiing 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 glow penetrating from outside is reduced by heat insulation. An apparatus for carrying out the process is also described.

Abstract: Nearly isotropic spherical fuel elements of high strength and high heavy metal content for gas cooled high temperature reactors consisting of a fissile and fertile fuel material containing nucleus and a fuel free shell are prepared by preliminarily compressing a molding powder consisting of a mixture of natural graphite and binder resin, synthetic graphite and binder resin or a mixture of both types of graphite powder and binder resin together with coated fissile and/or fertile fuel material particles with addition of a lubricant in a rubber mold with an ellipsoidally shaped cavity at low molding pressure three dimensionally to preform the nucleus of the fuel element, shaping the preformed nucleus into the required molding powder for the shell in a second rubber mold with ellipsoidally shaped cavity, preliminarily compressing this fuel element compact and subsequently final pressing and heat treating at up to about 2000.degree. C.

Abstract: Coated nuclear fuel particles are produced by batchwise deposition of several pyrolytic carbon and/or silicon carbide layers on fuel particles wherein the first layer is a porous pyrolytic carbon layer and wherein the coated particles are subsequently sieved and/or sized. The process comprises fractionaling all of the coating batches according to the geometric density by the hydrostatic method of weighing by buoyancy after placing all batches in heavy liquids and selecting for further working up into fuel elements only the particle fraction which has a geometric density whose boundary value deviates from the average density by less than .+-.20%.

Abstract: There is provided a process for the production of block fuel elements for gas cooled high temperature reactors by multiple step molding of a granulated graphite material comprising a mixture of natural graphite powder, synthetic graphite powder and binder resin together with coated fissile and fertile fuel particles using a lubricant and a hydrocarbon, alcohol, phenol, amine, aldehyde, ketone or ether as an air displacing agent whereby the outer form and the cooling gas channels are produced by molding and the molding temperature in the last molding step is above the softening point of the binder resin and wherein the binder resin is so chosen that it has a softening point at least 15.degree. C above the melting point of the lubricant used and the block is ejected from the die in the temperature interval between the melting point of the lubricant and the softening point of the binder resin.

Abstract: There are provided pressed spherical fuel elements for high temperature reactors made of a graphite matrix with separate embedded coated fuel and fertile material particles wherein the fuel elements comprise 3 concentric layers including a graphite nucleus or core (1) which only contains fertile material particles (4), this graphite nucleus (1) is surrounded by a graphite zone (2) which only contains the fuel particles (5) and this is encased in a shell (3) of pure graphite, the same graphite material being present in all three layers.

Abstract: There is provided a process for the production of spherical fuel and/or fertile oxide or carbide particles for a nuclear reactor, especially a high temperature reactor, by casting an aqueous solution of a uranium and/or a thorium and/or plutonium salt, as well as in the case of the production of carbide particles finely dispersed carbon also, from a vibrating nozzle, passing the drops formed through an ammonia containing gas zone into an ammoniacal precipitation bath with subsequent washing, drying and sintering or melting. To the aqueous solution there is added individually or in admixture a water soluble or water miscible monomeric hydrocarbon having an aldehyde, keto, ether, amino, imino, phenol, carboxylic acid or carboxylic acid amide group, which substituted hydrocarbons form stable adducts with uranium, thorium and plutonium in aqueous alkaline solution, which adducts cannot be washed out with water and which does not impart to the solution a viscosity of over 15 cp at 20.degree. C.

Abstract: Block fuel element for high temperature reactors are produced by hot molding of a granulated graphite material consisting of natural graphite powder, synthetic graphite powder, phenolformaldehyde binder resin and stearic acid as a lubricant together with fissile and fertile coated fuel particles to a hexagonal block shape with cooling channels for helium gas and subsequent heat treatment of the molded block to a max. temperature of about 2000.degree. C. In order to displace the air from the die, an organic compound (air displacement agent) e.g., hydrocarbon, alcohol, phenol, aldehyde, ketone ether of amine is built into the granulated graphite material having a very low vapor pressure at room temperature which increases to about 760 Torr at molding temperature of about 180.degree. C and condensed into a liquid phase while the forming pressure is applied.

Abstract: Uniform spherical fuel and/or fertile particles are formed by conversion of an oscillating liquid stream of a uranium and/or thorium compound solution flowing from at least one nozzle in an amount of more than 3,000 drops per minute by allowing these drops to fall into an ammonia solution and subsequently drying and sintering the particles thus formed.

Abstract: Graphite or carbon molded articles of high isotropy and high heat conductivity, especially useful for high temperature reactor fuel elements are prepared by pressing a mixture of a binder and a powdery carbon filler which consists partially or wholly of pyrolytically produced isotropic carbon with subsequent heat treatment of the pressed article. There is used as the filler an isotropic pyrolytic carbon made by depositing a hydrocarbon on a carbon granulate and then grinding to a particle size of less than 100 .mu.m.

Abstract: There is provided a process for recovering block shaped graphite fuel elements made of a graphite block with a parallel cooling channel and which block contains the fuel arranged in separate zones. The process is especially useful for such fuel elements in which the cooling channels and the fuel zones are distributed in a screenlike manner adjacent to each other and wherein these fuel elements are first comminuted mechanically and then are reconditioned by burning and wet chemical separation into fissile material and waste material. For the mechanical comminution of the graphite block conical pins (or mandrels) are simultaneously pressed into several cooling channels until the block is broken apart along the entire length of these cooling channels.

Abstract: Graphite or carbon molded articles of high isotropy and high heat conductivity, especially useful for high temperature reactor fuel elements are prepared by pressing a mixture of a binder and a powdery carbon filler which consists partially or wholly of pyrolytically produced isotropic carbon with subsequent heat treatment of the pressed article. There is used as the filler an isotropic pyrolytic carbon made by depositing a hydrocarbon on a carbon granulate and then grinding to a particle size of less than 100 .mu.m.

Abstract: Graphite molding powders are prepared which contain phenol-formaledehyde as a binder and which are intended for use in the manufacture of graphite molded articles, especially fuel inserts, fuel elements and absorber elements for high temperature reactors by mixing a graphite powder with a phenol formaldehyde binder and subsequent heat treatment, in a given case in admixture of coated fuel, fertile or absorber particles. The invention resides in not adding to phenol-formaldehyde as such to the graphite powder but as the starting components namely phenol and formaldehyde or source of formaldehyde and heating the mixture to the resin condensation temperature.

Abstract: There is provided a process for the production of fuel compacts consisting of an isotropic, radiation resistant graphite matrix of good heat conductivity having embedded therein coated fuel and/or fertile particles for insertion into high temperature fuel elements by providing the coated fuel and/or fertile particles with an overcoat of molding mixture consisting of graphite powder and a thermoplastic resin binder. The particles after the overcoating are provided with hardener and lubricant only on the surface and subsequently are compressed in a die heated to a constant temperature of about 150.degree.C., hardened and discharged therefrom as finished compacts.

Abstract: A method for the production of spherical particles. The starting material for the particles and organic substances are used to form a liquid aqueous mix from which drops are formed. The starting material is introduced into an aqueous solution in the form of a fine powder. The solution contains condensable or curable organic substances. As the starting material a non-metal, metalloid or a compound of one of these is used.