Key words: supercritical and liquid carbon dioxide, actinides, fission products, actinide oxides, organic ligands, radionuclide extraction, spent nuclear fuel reprocessing, countercurrent chromatography
The main regularities of actinide recovery from oxide mixtures by supercritical carbon dioxide CO2 (SC-CO2) containing adduct of tri-n-butylphosphate (TBP) and other organic ligands with HNO3 are studied. It was found that effective actinide extraction by such adducts can be achieved even in the absence of SC-CO2. The extraction of Uranium and main fission products (FP) from model spent nuclear fuel (MSNF) was investigated. It was shown that at >99 % of U extraction the principal fractions of 95Zr и 95Nb (up to 90 %) transferred into adduct phase, as well as 131I and partially 103Ru (~30 %), 99Tc (20 %) and lanthanides (Ln) (up to 10 %). A complete separation of U from 137Cs, 85Sr, 140Ba, as well as from the main part of 140La, 141-144Ce and 147Nd can be achieved. Uranium separation from the remaining part of FP is completed by the adduct dissolution in liquid CO2, transfer of the obtained solution to the separation column of planetary centrifuge, and its further processing by countercurrent chromatography (CCC) in dynamic mode.