Abstract: A process for the selective electrofluorination of metallic alloy based on U characterized by effecting a selective anodic reaction on at least one of the components of the alloy by means of a controlled anodic voltage applied to the alloy in a bath of molten fluorides.

Abstract: An agent for trapping the radioactivity of the fission products which appear in a nuclear fuel based on sintered uraniferous oxides in the course of irradiation characterized in that it comprises a stable oxygenated compound, a combination of at least two metallic oxides and at least one oxide of a non-radioactive isotope of the radioactive fission product or products whose radioactivity is to be trapped.

Abstract: A nuclear fuel element comprising sintered pellets based on uraniferous oxide which are surrounded by a metallic sheath and permitting trapping of the fission products which appear in the course of irradiation characterized in that the pellets contain or are coated with or that the sheath is internally coated with an agent for trapping said fission products based on mixed metallic oxide comprising SiO.sub.2 and one at least of the oxides ZrO.sub.2 or CeO.sub.2.

Abstract: Process for obtaining nuclear fuel pellets, which produces no liquid effluent, for which the starting product is metallic uranium, which is oxidized to U.sub.3 O .sub.8, then crushed and either reduced to UO.sub.2 and activated (or vice versa) with the aid of at least one fine milling operation, or reduced to UO.sub.2 and activated using at least one oxidation-reduction cycle, the UO.sub.2 obtained then being shaped by pressing and fritting and the intermediate powders obtained are dense and pourable, no intermediate conditioning operation being required.

Abstract: A method of obtaining pellets of MxOy oxide, where M represents one or more elements used to make nuclear fuel pellets, as a means of obtaining very high density fritted pellets directly, i.e. without the intermediate powders being conditioned, comprising starting with a solution of soluble salts of the M elements, and treating them with hydrogen peroxide with the pH kept at from 2 to 2.5, in a continuous fluidized bed reactor comprising at least 3 superposed cylindrical sections of different diameters, the solutions in the central section being agitated vigorously, to obtain a precipitate which is subsequently calcined reduced, pressed then fritted.

Abstract: Process for the purification of reprocessing uranium from which have previously been separated the fission products generated in a nuclear reactor and consisting of eliminating the U232 daughter products appearing during storage, by passing said uranium in its hexafluoride form through a chemically inert porous material.

Abstract: The invention concerns a thermal transfer layer with high transfer coefficient between two materials which can have different expansion coefficients. The thermal transfer layer comprises expanded graphite inserted between the materials which are selected from among carbonaceous materials, ceramics and metals or metal alloys. The expanded graphite is either inserted in the form of a rolled or compressed sheet, or is compressed in situ. The invention also concerns a device for the cooling of a structure subjected to intense, continuous, intermittent or pulsating heat flux, by means of fluid circulation tubes placed in the passages in the structure. A flexible material which is a good heat conductor in a compressed state, such as expanded graphite, is placed between the structure to be cooled and each tube.

Abstract: A process for the recovery of uranium which has been extracted from phosphate-bearing solutions by means of an organic solvent and which is re-extracted from said solvent by means of hydrofluoric acid is disclosed.The process is characterized in that sodium ions are introduced into the solution of hydrofluoric acid, while aluminum and magnesium ions may also be added to the sodium ions. That solution may be produced by recycling of a fraction of the suspension of fluoride from the re-extraction step, after having separated the solvent, and to which a make-up of sodium, aluminum and magnesium ions and hydrofluoric acid was added.

Abstract: The present invention relates to a proces for separating rare earths and uranium from a UF.sub.4 concentrate and for placing them into useful form, comprising attacking the UF.sub.4 concentrate with potassium hydroxide, followed by nitric acid dissolution of the resulting precipitate, and extraction of the solution using an organic solvent. The extraction results in an organic solution containing purified uranyl nitrate, and an aqueous solution from which rare earths are precipitated by means of a base.

Abstract: Uranium is recovered as UF.sub.4 from phosphate solutions. The uranium is reduced to the tetravalent state and extracted with an organic extractant. The uranium is recovered as UF.sub.4 by reextracting with an aqueous HF solution which includes UF.sub.4 in suspension for improved reextraction.

Abstract: Process for pretreatment at atmospheric pressure or a pressure close to atmospheric pressure by alkaline wetting and holding at temperature of natural materials whose gangue comprises argillaceous compounds capable of forming a stable plastic suspension in the presence of water and containing at least one combustible element which can be put into useful form wherein, in order to permit subsequent easy operations for separation of the liquid aqueous and solid phases of the gangue:(a) the natural material which was possibly been subjected to a preliminary drying operation is brought into intimate contact with at least 4 kg expressed in terms of OH.sup.- of at least one alkaline agent per ton of clay contained in said material, the total volume of liquid present in the natural material after the contacting operation being such that the ratio L/S of said volume expressed in terms of cubic meters to the weight of solid expressed in tons of dry ore is at most equal to 0.

Abstract: Process for the selective separation of uranium in carbonated aqueous solution from soluble impurities including in particular at least one of the elements zirconium and/or hafnium and/or molybdenum, thereby making it possible to produce a uraniferous liquor in a greatly improved state of purity, comprising precipitation of the zirconium and/or hafnium by introducing an alkali metal hydroxide, then separation of the zirconiferous precipitate which possibly contains hafnium and/or molybdenum from the resulting uraniferous solution with its reduced impurities content, which still possibly contains molybdenum, which is characterized in that in order to increase the removal of zirconium and/or hafnium and/or molybdenum, the uraniferous carbonated aqueous solution is treated by means of a dilute alkaline aqueous solution containing at most 17 g/l of at least one alkali metal hydroxide expressed in respect of OH.sup.

Abstract: A process for the purification by selective separation of uranium and/or molybdenum from zirconium and/or hafnium among other impurities contained in an amino organic phase by bringing them together with an aqueous sulphuric re-extraction solution, characterized in that, with a view to increasing the separation factor of the zirconium and/or hafnium on the one hand and the uranium and/or molbydenum on the other hand, the aqueous sulphuric re-extraction solution contains at least one alkali or equivalent sulphate.

Abstract: A process for the recovery of the uranium present in phosphoric acid produced by a wet process in (A) by means of a suitable solvent (L.sub.9), which is carried out after separation of the gypsum in (B) formed in the attack operation, and elimination of the solid materials which are still in suspension, characterized in that, in order to avoid the formation of dross in the course of the operation of extracting the uranium which is previously reduced in (D), the step of eliminating the solid materials which are still in suspension is effected by a final solid-liquid separation operation in (C) and/or in (E), prior to extraction of the uranium in (F), in the presence of an added fraction of gypsum (S.sub.22) and/or (S.sub.23) resulting from the production of H.sub.3 PO.sub.4.

Abstract: A process for the removal of cadmium contained in wet-process phosphoric acid by flotation by means of a cadmium-collector anionic surface active agent and an injected gas in the presence of other impurities including iron and possibly uranium which is characterized in that, in order to improve the removal of cadmium, the iron contained in the phosphoric acid in the trivalent state is reduced to the divalent state before the cadmium collector is introduced into the medium to be purified by flotation.The collector agent is selected from the group of dithiophosphoric acid esters and the alkali metal salts thereof.

Abstract: A process for pretreatment at high temperature by means of an aqueous pretreatment solution, of crushed ores containing at least one usable metal element, whose gangue contains argillaceous compounds which, in the attack operation for making use of the ore, are capable of forming a stable plastic suspension in the presence of water, which makes it virtually impossible subsequently to separate the liquid and solid phases by virtue of its character being such that it cannot be subjected to filtration and/or settlement, which is characterized in that, to cause stabilization of the argillaceous gangue before the operation of subjecting the ore to attack and to produce easy separation of the liquid and solid phases after the attack operation, the ore, the granulometry of which is at most equal to the liberation sieve mesh size of the metal or metals to be put to use, and before being subjected to the attack operation for making use of the ore, is brought into contact with an aqueous pretreatment solution containin

Abstract: A method of purifying uraniferous aqueous solutions containing impurities, particularly at least one of the elements zirconium and/or hafnium, and also containing at least one of the anions SO.sub.4.sup.=, NO.sub.3.sup.-, Cl.sup.- or F.sup.- acting as complexing agents for the uranium and impurities, by precipitation of said impurities by means of an alkaline agent, characterized in that the following stages are carried out for the purpose of selectively and quantitatively separating the impurities from the uranium:(a) said uraniferous solution is brought to a temperature of at least 40.degree. C.,(b) the content of complexing agent is adjusted to bring the molar ratio: [complexing agent]/[soluble U+Zr and/or Hf] to at least 3,(c) the pH of said solution is adjusted between 2.2 and 4.3 by introducing an alkaline agent.