Abstract: A matrix material for safe temporary and/or ultimate disposal of radioactive wastes suitable for the embedment of radioactive wastes, contains graphite and at least inorganic binder which can be glass, aluminosilicate, silicate, borate and lead sulfide.

Abstract: A package for storing radioactive waste, which is suitable for safe, ultra-long ultimate disposal having a moisture-impermeable, corrosion-resistant graphite matrix and metal-encased waste products, which are embedded into the matrix. A method for producing such packages is also part of the invention.

Abstract: The invention relates to a novel design and production of fuel element pebbles which satisfy the requirements of high temperature pebble bed nuclear reactors of the next generation. The invention uses a shell of the fuel element pebbles that is devoid of fuel and consists of silicon carbide (SiC) and/or zircon carbide (ZrC), in addition to natural graphite and graphitized petroleum coke, said shell having a maximum average nominal thickness of 5 mm and preferably only 3 mm.

Abstract: Disclosed is reflector graphic which is characterized in that the main component of the graphite is nuclear-purity natural graphite in addition to silicon carbide and/or zirconium carbide, the pressed pieces are shaped by a combined cold-hot pressing process, and the thermal treatment of the pressed pieces is limited to temperatures of less than 2000° C.

Abstract: A matrix material for safe temporary and/or ultimate disposal of radioactive wastes suitable for the embedment of radioactive wastes, contains graphite and at least inorganic binder which can be glass, aluminosilicate, silicate, borate and lead sulfide.

Abstract: The invention relates to a novel design and production of fuel element pebbles which satisfy the requirements of high temperature pebble bed nuclear reactors of the next generation. The invention uses a shell of the fuel element pebbles that is devoid of fuel and consists of silicon carbide (SiC) and/or zircon carbide (ZrC), in addition to natural graphite and graphitized petroleum coke, said shell having a maximum average nominal thickness of 5 mm and preferably only 3 mm.

Abstract: In order to have carbon fiber reinforced carbon resistant to oxidation, the proposal is for a process by means of which a bonding layer of amorphous SiNx is applied to the carbon fiber reinforced carbon to which in turn is applied a protective layer which is oxidation resistant at a temperature T, where T>400.degree. C. consisting preferably of Si.sub.3 N.sub.4.

Abstract: A method and a device for sintering ceramic shaped articles in a furnace which saves costs and energy but provides high throughput. To this end, the shaped articles are guided vertically through the furnace on the helical rib of a stationary, vertically positioned helix by the inner longitudinal ribs of a rotating, vertically standing tube which concentrically surrounds the helix.

Abstract: There is described a process for the production of high temperature resistant, high density ceramic molded articles at a temperature above 1300.degree. C. and at high pressure in a mold. For this purpose, the blank is heated outside the mold, transferred with a die at 1 to 10 m/sec into the cold mold, compressed there and ejected in the pressing direction. Thereby, the residence time in the mold must be less than 3 msec and the sum of the transport time of the blank from heating up to the mold and the residence time in the mold so regulated that the temperature drop between the nucleus of the blank and the surface of the blank does not exceed 150.degree. C.

Abstract: There are known molded bodies for the safe, long time fixation of radioactive and toxic wastes which have a matrix of graphite and inorganic binding agent, preferably nickel sulfide. An increased resistance to leaching is obtained with molded bodies that have a waste containing nucleus and a waste free shell made of the same graphite matrix.

Abstract: There is described a process for the production of ceramic fuel pellets which contain fission and/or fertile material in oxidized form, by heating porous green fuel pellets in a reducing atmosphere to a temperature below 2500.degree. C., molding in a die, ejecting from the die and cooling the finished pellets. Thereby the heating and cooling is carried out stepwise whereby the heating and cooling speed below 1200.degree. C. is less than 30.degree. C./second and above 1200.degree. C. is greater than 30.degree. C./second.

Abstract: For the longtime fixation of radioactive and toxic waste there are used molded bodies made of graphite with nickel sulfide as a binding agent. The molded bodies show especially good properties if the nickel sulfide is in the form of Ni.sub.3 S.sub.2.

Abstract: For the production of plate shaped fuel elements for material testing and research reactors with highly enriched uranium recently there has been needed U.sub.3 O.sub.8 fuels which have a high density, high strength and a small open porosity. Such fuels are obtained if U.sub.3 O.sub.8 powder produced in known manner is first compressed mechanically to molded bodies of any shape, then processed to a granulate having a size of fuel grains below 200.mu. and subsequently sintered to high density particles, preferably at 1370.degree..+-.50.degree. C.

Abstract: Previously the conditioning of radioactive wastes took place through binding the waste in a matrix of glass, silicon carbide, cement, bitumen, synthetic resin or vitreous carbon. These processes have many disadvantages, particularly the matrix has poor heat conductivity, insufficient resistant to extraction or poor heat resistance and radiolysis effects. A remedy is provided through a carbon matrix in which there is employed as the starting material graphite which is molded with a binder at a temperature above 100.degree. C. There have particularly proven good as the binder sulfur in admixture with nickel powder from which nickel sulfide forms.

Abstract: A process for producing ceramic fuel pellets for nuclear reactors containing the fissionable material and/or fertile material in the form of the oxide or carbide by heating to a temperature above 1300.degree. C. the crude molded fuel articles compacted to 30 to 60% of theoretical density at room temperature, molding in a die and ejection from the die wherein the heating, molding and ejection take place in a vacuum and the molding and ejection take place within 3 to 300 milliseconds.

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: 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.