GB846861A - Process of recovering uranium - Google Patents

Abstract

In the separation of isotopes of uranium by means of a calutron, such as is described in Specification 816,772, by vaporization of a charge of uranium tetrachloride, the uranium values are recovered from parts of the calutron by washing them with a solvent for uranium whereby metal impurities including iron are introduced into the wash solution; the pH of the solution is then adjusted to 1:3, the solution refrigerated to produce ice crystals therein and then treated with hydrogen peroxide thereby precipitating uranium peroxide. The uranium peroxide may be calcined to the trioxide and the latter reacted with carbon tetrachloride to produce uranium pentachloride which on calcining <PICT:0846861/III/1> gives uranium tetrachloride for recycling to the calutron, or alternatively the uranium trioxide may first be reduced by methane to the dioxide and thereafter reacted with calcium tetrachloride to give uranium tetrachloride direct. As shown in Fig. 3, a solution derived from washing or acid treating parts of the calutron to take up the uranium values and generally contaminated with copper, iron, chromium and nickel, is first treated with carbonate-free ammonium hydroxide solution or excess ammonia gas thereby precipitating ammonium diuranate and the hydroxides of iron and chromium away from the copper and nickel which remain in solution as amine complexes. The precipitate after washing is taken up in nitric acid and depending on its ferric ion content is, or is not, treated with a complexing agent such as lactic acid, acetic acid or a fluoride ion thereby inhibiting the catalytic decomposing effects of the ferric ion on hydrogen peroxide. If the ferric ion content is below 3% this is not necessary. In either case the solution is then treated with ammonium hydroxide to adjust the pH between 1 and 3 and the solution thereafter cooled below its freezing point to form minute ice crystals. Pre-cooled hydrogen peroxide is added in excess and the solution is refrigerated to a solid mass at temperature for example of -45 DEG C. It is then thawed to the incipient freezing p range namely -2 to -10 DEG C. whereupon the solution may be filtered and the precipitate of uranium peroxide washed with an aqueous solution containing ammonium nitrate and hydrogen peroxide.