Process for producing uranium dioxide

This patent describes a process for the production of uranium dioxide powder by calcining a uranium compound, whereby an off-gas stream is produced by an ammonium diuranate calciner which contains ammonium fluoride vapor and uranium-containing particulate matter. The improvement comprises: maintaining the off-gas stream after discharge from the calciner at an elevated temperature in excess of about 3400C; passing the off-gas stream while at the elevated temperature into a separate vessel, also maintained at a temperature in excess of about 3400C; passing the off-gas in the separate vessel through a filter within the separate vessel, so that the uranium-containing particulate matter is retained within the separate vessel while the ammonium fluoride vapor passes through the filter while at the elevated temperature; and contacting the ammonium fluoride vapor from the off-gas after it passes through the filter with water to form an aqueous solution of ammonium fluoride