Abstract <p>Crystallization affinage of uranium in spent nuclear fuel (SNF) reprocessing technology is described. Analysis of a linear crystallizer operation is conducted on the example of uranyl nitrate hexahydrate (UNH) crystallization. It is shown that the most effective operation regime (from the point of view of the yield of uranyl nitrate (UN) into the crystalline phase) is achieved by ensuring a lower temperature of uranyl nitrate solution in the washing zone of the apparatus, and thus, in the crystal discharge zone, which significantly complicates operation of the apparatus in pilot and industrial conditions. In this regard, a changed construction of the apparatus is suggested, to ensure effective crystallization without lowering the temperature in the working volume of the washing zone and the crystal discharge zone.</p>