and A. I. KomyakThe effects of several metal cations and anions on complexation of tetra-and pentavalent uranium in an acetone solution of UO 2 (ClO 4 ) 2 ·5H 2 O irradiated by an LED (420-440 nm) were studied using electronic absorption. It was shown that addition of background components to the solution had an insignifi cant effect on complexation of the lowest-valent uranium. The composition of the 2+ 2 UO coordination sphere could change at a certain irradiation time (>90 min) but the system as a whole was maintained.Introduction. Radioactive wastes are always formed during operation of nuclear power plants. Reprocessing of spent nuclear fuel requires its dissolution in acids and multiple operations with solutions including the purifi cation of liquid radioactive wastes (LRW). Such solutions contain not only radioactive elements (uranium and transuranium elements) but also several stable decay products. The processing solutions also contain large amounts of background metals, e.g., K, Na, Mg, Ca, Al, etc., and several anions, primarily