Abstract: A method for converting UO3 and/or U3O8 into hydrated UO4 of formula UO4.nH2O wherein n is 2 or 4, comprising the following successive steps: a) preparing an aqueous suspension of a UO3 powder and/or a U3O8 powder; b) adding hydrogen peroxide H2O2 to the aqueous suspension of a UO3 and/or U3O8 powder, converting the UO3 and/or U3O8 into hydrated UO4 and precipitating, crystallizing the hydrated UO4 in the suspension; c) recovering the precipitate, crystals of UO4 hydrate; d) optionally, washing the recovered UO4 hydrate precipitate, crystal(s); e) optionally, repeating step d); f) optionally, drying the precipitate, the crystals; wherein the addition of H2O2 to the aqueous suspension is carried out so that the suspension contains a stoichiometric excess of H2O2 relatively to the stoichiometry of the reaction from UO3: UO3+nH2O+H2O2?UO4.nH2O+H2O??(1) or of the reaction from U3O8 UO2.67+1.33H2O2+nH2O?UO4.nH2O+1.

Abstract: The invention relates to the use of a compound of the formula KmgF3 to trap metals in the form of fluorides and/or of oxyfluorides in a gaseous or liquid phase. It also relates to a compound of the formula KMgF3 which has a surface area at least equal to 30 m2/g and at most equal to 150 m2/g and also to its methods of preparation. The invention notably finds application in the nuclear industry, in which it can advantageously be used to purify uranium hexafluoride (UF6) present in a gaseous or liquid stream, with regard to metal impurities which are also present in this stream.

Abstract: A method for converting UO3 and/or U3O8 into hydrated UO4 of formula UO4.nH2O wherein n is 2 or 4, comprising the following successive steps: a) preparing an aqueous suspension of a UO3 powder and/or a U3O8 powder; b) adding hydrogen peroxide H2O2 to the aqueous suspension of a UO3 and/or U3O8 powder, converting the UO3 and/or U3O8 into hydrated UO4 and precipitating, crystallizing the hydrated UO4 in the suspension; g) recovering the precipitate, crystals of UO4 hydrate; h) optionally, washing the recovered UO4 hydrate precipitate, crystal(s); i) optionally, repeating step d); j) optionally, drying the precipitate, the crystals; wherein the addition of H2O2 to the aqueous suspension is carried out so that the suspension contains a stoichiometric excess of H2O2 relatively to the stoichiometry of the reaction from UO3: UO3+nH2O+H2O2?UO4.nH2O+H2O??(1) or of the reaction from U3O8 UO2.67+1.33H2O2+nH2O?UO4.

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: Process for repairing or restoring a part with a locallly damaged surface, articularly an anticathode or target consisting of depositing in preferred manner at damaged points of said surface, preferably by chemical vapor deposition, the material constituting said part and then machining said surface in such a way that it conceals its original state.

Abstract: A process is disclosed for producing sintered mixed metal oxide nuclear f pellets containing UO.sub.2 and the oxide of at least one other fissionable or rare earth element M, the pellets being directly soluble in nitric acid without nitric acid additive or prior treatment of the pellets. The process comprises the steps of mixing together nitrate solutions of the elements, concentrating the mixture of solutions, thermally denitrating the concentrated nitrate mixture without additives, to obtain an intermediate mixed oxide powder, calcining the intermediate mixed oxide powder, reducing the calcined mixture, stabilizing the uranium oxide UO.sub.2 in the reduced oxide mixture, shaping and pressing the resulting stabilized, reduced oxide mixture to obtain pellets of green material, sintering the pellets of green material and grinding the sintered pellets.

Abstract: An industrial process for the obtaining, preferably without casting, of its of high-purity master alloy based on at least one rare earth and at least one transition metal by metallothermic reduction of a compound of said rare earth by means of a reducing agent such as alkali or alkaline earth metals, characterized in that the transition metal is introduced into the starting reaction mixture, at least in part in the form of a compound which can be reduced by the reducing agent used.