Production of uranium tetrafluoride from the effluent generated in the reconversion via ammonium uranyl carbonate

Uranium tetrafluoride (UF4) is the most used nuclear material for producing metallic uranium by reduction with Ca or Mg. Metallic uranium is a raw material for the manufacture of uranium silicide, U3Si2, which is the most suitable uranium compound for use as nuclear fuel for research reactors. By contrast, ammonium uranyl carbonate is a traditional uranium compound used for manufacturing uranium dioxide UO2 fuel for nuclear power reactors or U3O8-Al dispersion fuel for nuclear research reactors. This work describes a procedure for recovering uranium and ammonium fluoride (NH4F) from a liquid residue generated during the production routine of ammonium uranyl carbonate, ending with UF4 as a final product. The residue, consisting of a solution containing high concentrations of ammonium (NH4+), fluoride (F−), and carbonate (CO32−), has significant concentrations of uranium as UO22+. From this residue, the proposed procedure consists of precipitating ammonium peroxide fluorouranate (APOFU) and NH4F, while recovering the major part of uranium. Further, the remaining solution is concentrated by heating, and ammonium bifluoride (NH4HF2) is precipitated. As a final step, NH4HF2 is added to UO2, inducing fluoridation and decomposition, resulting in UF4 with adequate properties for metallic uranium manufacture.