Abstract: Process for the batch purification of uranium recovered in a reprocessing process, after a first separation of impurities, in which for each batch an aqueous, nitric acid uranyl-nitrate solution (UNH original solution), which still contains residual amounts of impurities, is cooled to crystallize out purified UO.sub.2 (NO.sub.3).sub.2 .multidot.6H.sub.2 O (UNH) from the solution and the resulting crystals are separated out of their mother liquor and washed. The original solution is adjusted to a specified uranium concentration and the adjusted solution is cooled to below 0.degree. C. to bring about the crystallization. The duration between starting and ending the crystallization is held between 0.1 and 10 hours. The amount of the UNH crystals which is crystallized out corresponds to at least about 80 weight % of the uranium content introduced. The ratio of the volume of the crystals formed to the volume of the remaining mother liquor is not larger than 0.5.