[en] Uranium tetrafluoride (UF₄), is the key intermediate compound in the production of uranium hexafluoride or uranium metal. In order to produce uranium metal by a metallo thermic process it was necessary to developed a method to prepare UF₄ with UO₃, as raw material. The method consist in the reduction of UO₃ to UO₂ using H₂, follow by the hydro fluorination of uranium dioxide with HF. All this chemical reactions were performed in an unique fluidized bed reactor. At the beginning the conversion percentages were low on account of the low chemical reactivity of the starting compound (UO₃). The low reactivity persists even when UO₃ is reduced to UO₂ becoming it unreactive to the action of HF in a wide range of temperatures and HF concentrations. So that, in this conditions is technically impossible to obtain a compound with the he necessary purity for calcium or magnesium metallo thermic reaction. The uranium dioxide was submitted to several oxidation to U₃O₈ and reduction to UO₂ cycles in order to improve it reactivity. With two reactivation cycles this compound was treated with HF, conversion percentages near 99% were achieved, fundamental requirement for this compound can be used successfully in uranium metallo thermic. All the process, i.e., the UO₃ reduction, the UO₂ oxidation to U₃O₈, the second reduction to UO₂ and finally the hydro fluorination to UF₄ was carry out in an unique fluidized bed reactor. By means of an adequate prototype, preliminary assays were performed. The information obtained was used to outline and build the fluidized bed reactor and the furnace employed. The tests contributed too, to the determination of the working parameters used with this technique