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 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: 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 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.