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: The invention relates to the use of a compound of formula KMgF3 to trap metals present in the form of fluorides and/or of oxyfluorides in a gaseous or liquid phase. It also relates to a compound of formula KMgF3 which has a surface specific 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: A method for recovering nitrate ions as nitric acid from nuclear industry effluents by thermally decomposing the nitrate ions in solution, and recovering the NOx vapors generated by the heat treatment in an aqueous medium. The resulting nitric acid may be recycled in the nuclear industry.

Abstract: A thermal decomposition method useful in the nuclear industry for preparing a powdered mixture of metal oxides having suitable reactivity from nitrates thereof in the form of an aqueous solution or a mixture of solids. According to the method, the solution or the mixture of solids is thermomechanically contacted with a gaseous fluid in the contact area of a reaction chamber, said gaseous fluid being fed into the reaction chamber at the same time as the solution or mixture at a temperature no lower than the decomposition temperature of the nitrates, and having a mechanical energy high enough to generate a fine spray of the solution or a fine dispersion of the solid mixture, and instantly decompose the nitrates. The resulting oxide mixtures may be used to prepare nuclear fuels.

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 of treating a gas based on fluorine and containing hydrofluoric acid, and which may optionally contain condensable gaseous compounds, especially uranium compounds, and non-condensable gases. The gas is refrigerated to obtain a gaseous component containing fluorine and any non-condensable gases present, and a liquid phase containing liquid HF and condensable compounds in solution and/or suspension. The liquid phase is filtered to recover the compounds in suspension.

Abstract: A method for removing ruthenium from a uranium-containing solution comprising adding a nitrite to the solution and passing the solution over a quaternary ammonium or tertiary amine resin to selectively fix the ruthenium.

Abstract: An X-ray tube anticathode, intended to be used, for example, in medical iruments, such as scanners, includes a support made of a ceramic/ceramic composite material and a refractory metal film directly in contact with this support. The use of a ceramic/ceramic composite makes it possible to rotate the anticathode at an extremely high speed. In addition, this composite is selected 1) so that its coefficient of expansion is as compatible as possible with that of the refractory metal, which favors adhesion between the support and the active film, and 2) so that the phenomenon of the diffusion of carbon atoms is suppressed or minimized at the active film under the effect of the rise of temperature by not using a graphite material, which renders it ineffective in using an anticarbonizing film, such as rhenium, indium, SiC, etc.

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 for producing a strong, adherent protective layer on copper parts, with a high rate of covering of the substrate, by passivating anodization, characterized in that the copper parts are immersed in a liquid KF, 2HF bath and subjected to anodic current of low surface-related density which is less than 0.1 A/dm.sup.2, which current may be continuous or intermittent.

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.

Abstract: Process for the preparation of pulverulent metallic oxides with predetermined reactivity which is adjusted by the specific surface area, which are intended to be subjected to subsequent conversions, by thermal treatment of corresponding nitrates in the form of an aqueous solution or of a solids material, consisting of hydrated uranyl nitrate, on its own or in admixture with at least one of thorium nitrate, cerium nitrate and plutonium nitrate, which process is characterized in that it consists of two treatment stages:(a) the first stage essentially consisting of incompletely dehydrating the hydrated uranyl nitrate.(b) the second stage essentially consisting of decomposing the product resulting from the first stage by calcination under controlled steam pressure.The process is used for obtaining uranium oxide on its own or in admixture with thorium oxide, cerium oxide and plutonium oxide, with a view to subsequent chemical conversions and/or sintering.

Abstract: A process for the production of uranium trioxide having a large specific surface by the thermal denitration of hydrated uranyl nitrate corresponding to the formula UO.sub.2 (NO.sub.3).sub.2 .multidot.xH.sub.2 O, in which 2.ltoreq.x.ltoreq.6, characterized in that, in a first stage, the said nitrate is treated in the form of a liquid at room temperature in the range from 160.degree. C. to 260.degree. C. until a solid phase containing at least 55% by weight of uranium is obtained and, in a second stage, the said solid phase is progressively heated to a temperature of at most 600.degree. C. at a heating rate of at most 1000.degree. C. per hour, and is kept at this temperature of at most 600.degree. C. until a second solid phase of UO.sub.3 having a large specific surface is obtained. The UO.sub.3 product produced has a specific surface of at least 10 m..sup.2 g.sup.-1.