Abstract: A method for producing uranium oxide includes combining uranium oxyfluoride and silicon and heating the combination below the vapor point of the uranium oxyfluoride to sufficiently react the uranium oxyfluoride and silicon to produce uranium oxide and a non-radioactive fluorine compound; and removing the fluorine compound, e.g. silicon tetrafluoride.

Abstract: A process for controlling the oxidation reaction of oxides of uranium and fixing the ratio of oxygen to uranium in uranium oxide compounds by means of a passification process, and the stabilized uranium oxide compounds produced therefrom. The method is especially useful in the production of uranium oxide fuel for nuclear reactors.

Abstract: A method for producing uranium oxide includes combining uranium oxyfluoride and a solid oxidizing agent having a lower thermodynamic stability than the uranium oxide after "oxide"; heating the combination below the vapor point of the uranium oxyfluoride to sufficiently react the uranium oxyfluoride and the oxidizing agent to produce uranium oxide and a non-radioactive fluorine compound; and removing the fluorine compound after "compound".

Abstract: A method for producing uranium oxide includes combining uranium tetrafluoride and a solid oxidizing agent having a lower thermodynamic stability than the uranium oxide; heating the combination below the vapor point of the uranium tetrafluoride to sufficiently react the uranium tetrafluoride and the oxidizing agent to produce uranium oxide and a non-radioactive fluorine compound; and removing the fluorine compound.

Abstract: A method for producing uranium oxide includes combining uranium tetrafluoride, silicon and a gaseous anhydrous oxidizing agent having a lower thermodynamic stability than any oxide of uranium produced; heating the combination below the vapor point of the uranium tetrafluoride to sufficiently react the uranium tetrafluoride, silicon and the oxidizing agent to produce uranium oxide and a non-radioactive fluorine compound; and removing the fluorine compound.

Abstract: A method of preparing uranium (VI) peroxide hydrate from uranium tetrafluoride hydrate, comprising the steps of digesting uranium tetrafluoride hydrate in an aqueous acid in the presence of a fluoride complexing agent to produce an aqueous uranium solution, adjusting the aqueous uranium solution to a pH between about 1 to about 3, filtering the aqueous uranium solution to remove undissolved material, reacting the aqueous uranium solution with peroxide to precipitate uranium (VI) peroxide hydrate, and separating the precipitated uranium (VI) peroxide hydrate.

Abstract: A method of preparing uranium (VI) peroxide hydrate from uranium tetrafluoride hydrate, comprising the steps of digesting uranium tetrafluoride hydrate in an aqueous acid in the presence of a fluoride precipitating agent to produce an aqueous uranium solution, filtering the aqueous uranium solution to remove precipitated fluorides and undissolved material, adjusting the aqueous uranium solution to a pH between about 1 to about 3, reacting the aqueous uranium solution with peroxide to precipitate uranium (VI) peroxide hydrate, and separating the precipitated uranium (VI) peroxide hydrate.

Abstract: A method for producing uranium oxide includes combining uranium tetrafluoride and a phyllosilicate mineral containing a solid oxidizing agent within the mineral's structure having a lower thermodynamic stability than the uranium oxide; heating the combination below the vapor point of the uranium tetrafluoride to sufficiently react the uranium tetrafluoride and the oxidizing agent to produce uranium oxide and a non-radioactive fluorine compound; and removing the fluorine compound.

Abstract: Process for obtaining uranium trioxide from a uranyl nitrate solution, the trioxide obtained having to have a specific surface between 12 and 15 m.sup.2 /g, consisting of producing in a zone of the reaction chamber called the contact zone, a thermomechanical contact between the uranyl nitrate solution, atomized into fine droplets according to a given axis in the contact zone, and a gaseous fluid introduced into the contact zone, the gaseous fluid being at a sufficiently high temperature and having a sufficiently high mechanical energy to carry out, within the contact zone, the dehydration and calcination of the uranyl nitrate.

Abstract: A method for producing silicon tetrafluoride includes combining uranium oxyfluoride and silicon dioxide; heating the combination below the melting point of the uranium oxyfluoride to sufficiently react the uranium oxyfluoride and the silicon dioxide to produce non-radioactive silicon tetrafluoride and an oxide of uranium; and removing the silicon tetrafluoride.

Abstract: A method for producing silicon tetrafluoride includes combining uranium tetrafluoride and silicon dioxide; heating the combination below the melting point of the uranium tetrafluoride to sufficiently react the uranium tetrafluoride and the silicon dioxide to produce non-radioactive silicon tetrafluoride and an oxide of uranium; and removing the silicon tetrafluoride.

Abstract: The present invention contemplates the conversion of uranium hexafluoride with superheated steam to produce a fine, submicron, uranyl fluoride powder which is agglomerated and densified in a fluidized bed of a uranium oxide material. Thereafter, the agglomerated and densified uranyl fluoride is defluorinated and reduced in the fluidized bed to yield a fluoride containing uranium oxide material having a uranium to oxygen ratio of from about 1:2.0 to about 1:2.67. The so-produced fluoride contains uranium oxide material treated with steam and hydrogen to produce ceramic grade uranium dioxide.

Abstract: Uranium trioxide Is reduced to uranium dioxide using microwave radiation or radiofrequency radiation directed in such a way that the radiation encounters an Interface between uranium trioxide and the uranium-containing reduction product without first having passed through that product. By this method, and also using a reducing gas, it is possible to obtain UO2 with an O:U ratio less than 2.04:1.

Abstract: This invention relates to the integration of ammonium carbonate leach processes with established acid and alkaline uranium leach processes as multifunctional industrial processes for the extraction, high degree purification and conversion of processed or semi-processed uranium as U3O8, UO2, or most tetra or hexa-valent forms of uranium, and where applicable, for the recovery of uranium from uranium ores, using advanced multiple stage membrane based technologies for the separation and concentration of uranium in solution from heavy metals and lighter elements that may be present in the solution, and the selective leach and precipitation properties of an ammonium carbonate leach.

Abstract: A uranium oxide product is formed in a gaseous reaction medium from uranium hexafluoride by interaction with a fuel gas such as hydrogen and oxygen. Oxide content and particle properties of the uranium oxide product are governed by the improved method and the apparatus for carrying out the method. An improvement is provided by applying a quenching gas to quench the conversion reaction of uranium hexafluoride to uranium oxide, and a combustion reactor apparatus which enables the application of the quenching gas is also provided.

Abstract: A process for converting uranium hexafluoride (UF.sub.6) to uranium dioxide (UO.sub.2) of a relatively large particle size in a fluidized bed reactor by mixing uranium hexafluoride with a mixture of steam and hydrogen and by preliminary reacting in an ejector gaseous uranium hexafluoride with steam and hydrogen to form a mixture of uranium and oxide and uranium oxyfluoride seed particles of varying sizes, separating the larger particles from the smaller particles in a cyclone separator, recycling the smaller seed particles through the ejector to increase their size, and introducing the larger seed particles from the cyclone separator into a fluidized bed reactor where the seed particles serve as nuclei on which coarser particles of uranium dioxide are formed.

Abstract: A method of passivating the surface of particulate uranium oxides is disclosed comprising a process of continuously contacting uranium oxide particles with an oxygen containing and cooling counter flowing gas stream. The treatment produces a protective surface which inhibits subsequent oxygen chemisorption of the particulate uranium oxides.

Abstract: A process for the recovery of uranium by precipitation from a rich eluate by contacting the eluate with hydrogen peroxide to produce uranium peroxide yellowcake and reacting the yellowcake with a reducing agent to produce uranium trioxide. The reaction between the yellowcake and the reducing agent may be carried out at a temperature less than 100.degree. C. Subsequent to the reducing step, the uranium trioxide may be washed with water in order to remove water soluble salts present as impurities. Thereafter, the uranium trioxide is dried at a temperature less than 200.degree. C.

Abstract: The invention relates to a process for reprocessing a spent nuclear fuel and for preparing a mixed uranium-plutonium oxide, which process comprises: a) the separation of the uranium and plutonium from the fission products, the americium and the curium that are present in an aqueous nitric solution resulting from the dissolution of the fuel in nitric acid, this step including at least one operation of coextracting the uranium and plutonium from said solution by a solvent phase; b) the partition of the coextracted uranium and plutonium to a first aqueous phase containing plutonium and uranium, and a second aqueous phase containing uranium but no plutonium; c) the purification of the plutonium and uranium that are present in the first aqueous phase; and d) a step of coconverting the plutonium and uranium to a mixed uranium/plutonium oxide. Applications: reprocessing of nuclear fuels based on uranium oxide or on mixed uranium-plutonium oxide.

Abstract: In a process for the conversion of uranium hexafluoride to an uranium oxide by injecting uranium hexafluoride and dry steam into a first region of a vessel so as to form a plume of particles of uranyl fluoride and reacting the uranyl fluoride in a second region of the vessel with a countercurrent flow of steam and/or hydrogen the operation of the process is such that a major proportion of the uranyl fluoride is caused to circulate within the first region so that the original uranyl fluoride particles are able to grow and agglomerate in a dendritic manner.