conversion of uranium hexafluoride in the structures of uranium dioxide with density and size of grain controlled

摘要

1372760 Uranium dioxide structures GENERAL ELECTRIC CO 2 June 1972 [16 June 1971] 25774/72 Heading C1A Ceramic structures of uranium dioxide are produced by (a) preparing a uranium dioxide rich powder from uranium hexafluoride by introducing into a reactor a first gaseous reactant, a second gaseous reactant and a shielding gas, said first reactant comprising a mixture of uranium hexafluoride with a carrier gas which is oxygen or a mixture of oxygen with another gas or gases, said second reactant comprising a reducing gas and said shielding gas being introduced into the reaction zone between said first and second reactants and to allow cross diffusion of said reactants as they pass through the reactor and eventually to allow formation of a flame by reaction of said uranium hexafluoride, oxygen and reducing gas; (b) separating the uranium dioxide rich powder from the gaseous reaction by-products produced in the conversion of the uranium hexafluoride; (c) prepressing the uranium dioxide rich powder (d) granulating the structure of step (c) to produce a full flowing granular powder (e) defluorinating the granulated uranium oxide rich powder in a non-oxidizing atmosphere (f) pressing the uranium dioxide rich powder of step (e) to a structure of predetermined shape and dimensions and (g) sintering the structure of step (f) in a non- oxidizing atmosphere to give a uranium dioxide structure of controlled density and grain size. The reaction products of step (a) may be oxidized to convert uranium dioxide rich powder to a higher oxide of uranium and the gaseous reaction by-products of step (a) may be treated to recover hydrogen fluoride and water vapour as hydrofluoric acid. The controlled atmosphere in the difluorinating and/or sintering step may comprise wet hydrogen, vaporized alcohol carrier gas, carbon dioxide, hydrogen or dissociated ammonia. The product of step (d) may be screened prior to defluorination and a lubricant may be added to the defluorinated powder of step (e) prior to pressing.