ИСТИНА

As a result of irradiation of natural thorium with high-energy protons various fission and activation products of 232Th are formed. Among them 225Ac is formed, which has characteristics that enable to use it in radiotherapy of cancer. There is a growing demand for this radionuclide, while current methods for producing actinium have significant limitations and can not satisfy it completely. Production of actinium from 233U is limited by its inaccessibility. In addition the formation of 223Ra should be noted, which is also a promising α-emitter for medicine. For fast effective isolation of actinium and radium from the thorium target the separation of macroscopic quantities of thorium is conducted. For this purpose method of solvent extraction is proposed. Irradiated thorium is dissolved in a mixture of concentrated hydrochloric and nitric acids, or in concentrated nitric acid with the addition of catalytic amounts of hydrofluoric acid. Tributylphosphate and trioktylphosphinoxide (TOPO) were used in extraction experiments. The behavior of radionuclides, depending on the composition of the aqueous phase is studied. By both extractants the principal amount (80%) of thorium was transferred in the organic phase. Disadvantage of TOPO is its low extraction capacity. 95Zr (70%), 223Ra (40%), 230Pa, and 233Pa (75%), 99Mo (22%), etc was transferred along with thorium in the organic phase. 103Ru, 126Sb, 132Te, 136Cs, 140Ba, 140La, 144Ce, 147Nd remain in the aqueous phase. Loss of actinium is 4%. The conditions of 223Ra back extraction from an organic solution after extraction of thorium macroamounts are obtained. Sorbents AG-1 (BioRad), Ln Resin (Eichrom), TRU Resin (Eichrom), TDi-2 (Karpov Institute) were taken for further chromatographic separations. The sorption capacity of AG-1 forwards thorium is investigated. The sorption behavior of radionuclides, depending on the parameters of the column is given. It is shown that 225Ac quantitatively adsorbed on Ln Resin and TDi-2 from dilute nitric acid (0.05 M HNO3). Desorption was carried out with acid of higher concentration (3 M). Significant difference in the sorption behavior of 225Ac for Ln Resin and TDi-2 was not observed. Actinium is eluted together with cerium and lanthanum. Therefore, for further separation the 3 M nitric acid was passed through the sorbent TRU Resin. The possibility of separation of the radionuclide 103Ru, which makes some difficulties for the production of final preparation 225Ac, by extraction with carbon tetrachloride in comparison with other methods of its isolation is observed.