Extraction of Actinide Salts and Oxides by β-Diketones in Supercritical or Liquid Carbon Dioxide as Applied to Decontamination

This work presents results of studying the extraction of dry actinide salts and oxides by complexone solutions in carbon dioxide. The conditions for efficient removal of actinide salts and oxides from solid surfaces were determined and the solubilities of different actinide complexes were compared. It was shown that the “solubility” of actinide complexes, as a rule, increases in the following order: acetylacetone ≈ divivaloylmethane ≈ thenoyltrifluoroacetone < trifluoroacetylacetone ≈ hexafluoroacetylacetone; as to additional ligands, this order is as follows: water < pyridine < tributylphosphate. The exception is provided by hydrated actinide complexes with hexafluoroacetylacetone (HFA) and trifluoroacetylacetone (TFA). The “solubilities” of similar complexes of uranium(VI), plutonium(IV), europium(III) and americium(III) differ insignificantly from each other. The “solubility” of corresponding neptunium(VI) complexes is much lower..