Abstract: A method for converting uranium hexafluoride to uranium dioxide includes steps of hydrolysis of UF6 to uranium oxyfluoride (UO2F2) in a hydrolysis reactor (4) by reaction between gaseous UF6 and dry water vapour injected into the reactor (4), and pyrohydrolysis of UO2F2 to UO2 in a pyrohydrolysis furnace (6) by reaction of UO2F2 with dry water vapour and hydrogen gas (H2) injected into the furnace (6). The hourly mass flowrate of gaseous UF6 supplied to the reactor (4) is between 75 and 130 kg/h, the hourly mass flowrate of dry water vapour supplied to the reactor (4) for hydrolysis is between 15 and 30 kg/h, and the temperature inside the reactor (4) is between 150 and 250° C.

Abstract: A conversion process for converting uranium hexafluoride into uranium dioxide includes the steps of hydrolysis of UF6 to uranium oxyfluoride (UO2F2) in a hydrolysis reactor (4) by reaction between gaseous UF6 and dry water vapour injected into the reactor (4), pyrohydrolysis of UO2F2 to UO2 in a pyrohydrolysis furnace (6) by reacting UO2F2 with dry steam and gaseous hydrogen (H2) injected into the furnace (6), extracting excess gas in the reactor (4) via a collecting device (50) comprising several filters (52), periodically cleaning the filters (52) by injecting a neutral gas into the filters (52) from the outside to the inside of the reactor (4) to remove powder stuck on the filters (52), and measuring the relative pressure in the reactor (4). The conversion method further includes carrying out point cleaning of the filters (52) when the relative pressure in the reactor (4) exceeds a predetermined point cleaning threshold.

Abstract: A method of declogging at least one filter of a plant for manufacturing uranium oxide from uranium hexafluoride, including separating, from the wall of the filter, uranium oxyfluoride particles deposited, by a stream of inert gas such as nitrogen, injected into the filter, in a counter-currentwise direction to the flow of hydrofluoric acid.

Abstract: A substance in a condensed state, for example a powdered solid, is in continuous movement in the longitudinal direction (6) of a furnace (4, 5). A reactive gas mixture is brought into contact with the substance in the condensed state. A plurality of samples of the gaseous mixture are removed at a plurality of reference points (14) spaced apart from one another along the longitudinal direction (6) of the furnace (4, 5); each of the gas samples is analyzed outside the furnace to determine the composition of the gas mixture and for each point (14), the extent of a chemical reaction between the condensed substance and the reactive gas mixture is deduced from the composition of the gas mixture at each of the reference points (14). In particular, the apparatus comprises a sampling and injection rod (10) introduced into the furnace (4, 5) and disposed in its longitudinal direction (6).

Abstract: A process for manufacturing nuclear fuel pellets through sintering of a material containing uranium dioxide obtained from a powder from a power originating from a process for a conversion of uranium hexafluoride.

Abstract: A method of declogging at least one filter of a plant for manufacturing uranium oxide from uranium hexafluoride, including separating, from the wall of the filter, uranium oxyfluoride particles deposited, by a stream of inert gas such as nitrogen, injected into the filter, in a counter-currentwise direction to the flow of hydrofluoric acid.

Abstract: The conversion apparatus comprises in succession: a reactor provided with injectors of UF.sub.6, steam, and nitrogen so as to cause UO.sub.2 F.sub.2 to be formed by hydrolysis; a rotary tubular pyrohydrolysis furnace for transforming UO.sub.2 F.sub.2 into uranium oxide, and provided with heaters distributed in at least five zones; and a tail end for conditioning the oxide powder. The injectors comprise three concentric nozzles connected respectively to inlets for UF.sub.6, nitrogen, and steam, UF.sub.6 being fed to the central nozzle and nitrogen being injected between UF.sub.6 and steam.

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.