Abstract: A process for chemical stabilization of a uranium carbide composite material: UCx+yC with x?1 and y>0, placed in a stabilization chamber, comprises: a rise in chamber internal temperature for oxidation of the compound based on uranium carbide between approximately 380° C. and 550° C., the chamber being fed with a neutral gas; isothermal oxidative treatment at the oxidation temperature, the chamber being placed under O2 partial pressure; controlling completion of stabilization of the compound, comprising monitoring the amount of molecular oxygen consumed and/or carbon dioxide or carbon dioxide and carbon monoxide given off, until achievement of an input set-point value for the amount of molecular oxygen, of a minimum threshold value for the amount of carbon dioxide or minimum threshold values for the carbon dioxide and carbon monoxide. A device implements the process.

Abstract: The present invention relates to a method for preparation of a powder comprising at least one carbide of at least one metal, comprising the steps consisting of: (a) preparing a solution comprising at least one organic gelling agent and at least one inorganic salt of at least one metal in a solvent; (b) modifying the pH of the solution prepared in step (a) in such a way as to precipitate said at least one metal and to obtain a colloidal suspension comprising nanoparticles of oxyhydroxides of said at least one metal; (c) removing the solvent from the colloidal suspension obtained in step (b) by which means a precursor of at least one carbide of at least one metal is obtained; and (d) subjecting the precursor obtained in step (c) to a thermal treatment in order to transform same into a powder comprising at least one carbide of at least one metal. The present invention also relates to the powder thus prepared and the various uses thereof.

Abstract: A process for chemical stabilization of a uranium carbide compound having formula: UCx+yC with x?1 or 2 and y>0, x and y being true numbers, placed in a stabilization chamber, comprises: a rise in chamber internal temperature for “oxidation” of the compound based on uranium carbide between approximately 380° C. and 550° C., the chamber being fed with a neutral gas; isothermal oxidative treatment at the oxidation temperature, the chamber being placed under O2 partial pressure; controlling completion of stabilization of the compound, comprising monitoring the amount of molecular oxygen consumed and/or carbon dioxide or carbon dioxide and carbon monoxide given off, until achievement of an input set-point value for the amount of molecular oxygen, of a minimum threshold value for the amount of carbon dioxide or minimum threshold values for the carbon dioxide and carbon monoxide. A device implements the process.

Abstract: Method for removing the epoxy and/or phenolic polymer encapsulating a nuclear fuel pellet comprising uranium dioxide UO2, the method comprising the following successive steps: a) the polymer is pyrolysed in a reducing atmosphere; and b) the carbon residues obtained after the pyrolysis step (a) are selectively oxidized, the oxidation being carried out at temperature above 1000° C. in an atmosphere comprising carbon dioxide CO2. Such a method makes it possible to remove the epoxy and/or phenolic polymer encapsulating the pellet while avoiding or limiting the risk of radiological contamination by the formation of U3O8.

Abstract: This invention relates to a method for conditioning a waste constituted of an aqueous solution of sodium hydroxide NaOH of 3 to 10 M, possibly radioactive. The method is as follows: a) a metakaolin powder is added to the aqueous solution such that a suspension is obtained capable of solidifying and forming a crystalline phase of the zeolite A type; b) the suspension is introduced into a mould; c) the suspension is left to solidify in the mould in order to obtain a moulded solid product based on zeolite A; d) the moulded product is dried; and e) the zeolite A phase is converted into a nepheline type phase by heat treatment at a temperature of 1000° C. to 1500° C.

Abstract: This invention relates to a method for conditioning a waste constituted of an aqueous solution of sodium hydroxide NaOH of 3 to 10 M, possibly radioactive.

Abstract: The invention relates to a method of manufacturing compounds of the Monazite type, doped or not doped with actinides, to a method of packaging radioactive waste, high in actinides and in lanthanides by incorporating this waste in a confining matrix based on Monazite, and to a block for the packaging of radioactive waste that includes a Monazite matrix containing the radioactive elements. This method includes mixing, in the solid phase, reactants comprising an inactive compound of the lanthanide metaphosphate type Ln (PO.sub.3).sub.3 and one or more lanthanide oxides and/or one or more compounds capable of reacting with this oxide or these oxides during a thermal sintering process; the shaping of the mixture thus obtained, and the reaction sintering of said formed mixture, as a result of which a Monazite or a compound of the Monazite type is obtained.