L. I. Guseva

A study of ion-exchange behavior of Pb in dilute HBr solutions, aimed to evaluate the possibility of on-line isolation of element 114. 228Ra-212Pb generator

Ion-exchange behavior of Pb (homolog of element 114), Ra, some actinides and Hf (homolog of Rf) in aqueous and aqueous-methanolic solutions of HBr was studied as influenced by the solution composition, acid concentration, type of ion exchanger, and other factors. The best conditions for Pb separation from other radionuclides with a high decontamination factor (≥105−106) on a cation exchanger and the conditions for its preconcentration from dilute solutions on an anion exchanger in the continuous (on-line) mode were determined. Based on the operation principle of a radioisotope generator containing a cation exchanger and HBr solutions, an efficient procedure for repeated separation of 212Pb (T1/2 = 10.6 h) from its parent radionuclides (228Ra, 228Ac, and 228Th) was developed. The possibility of on-line isolation of element 114 formed by the 242Pu(48Ca, 3n) nuclear reaction and its detection by long-lived decay product [267Rf (T1/2 ∼ 3.3 h)] was demonstrated.

Development of a tandem generator system 229Th/225Ac/213Bi for repeated production of short-lived α-emitting radionuclides

Abstract229Th was isolated from a long-stored 233U sample using an anion exchanger and 8 M HCl. Thorium was separated from macroamounts of inactive impurities on an anion exchanger in aqueous-methanol HNO3 solutions. A tandem generator system was developed for repeated isolation of 225Ac (α, 10 days) from the parent radionuclide 229Th (7.3 × 103 years) sorbed on an anion-exchange column, with the subsequent sorption of Ac on a cation-exchange column and repeated elution of 213Bi (α, 45.6 min) with dilute HCl and HBr solutions. The γ-ray spectra of the radionuclides at various steps of their isolation are presented. Alternative procedures for production and isolation of 225Ac and 213Bi are described. The application potential and advantages of the newly developed tandem generator system are discussed.

A tandem generator for produciton and isolation of short-lived α-emitting radionuclides of Ra, Pb, and Bi in EDTA solutions

A tandem generator (anion-exchange column series-connected with a cation-exchange column) was developed for repeated production and isolation of 223Ra and 211Pb/211Bi in EDTA solutions suitable for biomedical purposes. The optimum conditions for repeated on-line separation of 223Ra from its parent radionuclides 227Ac/227Th sorbed on an anion-exchange column (generator 1) with subsequent concentration on a cation-exchange column (generator 2) from HNO3/CH3OH solution were determined. The behavior of Ra and Pb on the cation exchanger in EDTA solutions was examined in relation to the composition, concentration, and pH of solution. The cation-exchange column can be used as the second generator both for continuous production and isolation of short-lived isotopes 21lPb/211Bi and for isolation of 223Ra in complexing agent solutions. The curves of radionuclide accumulation and operation conditions of the generator were calculated. The advantages of the tandem generator for preparing short-lived α-emitting radionuclides were demonstrated.

Ion-Exchange Procedure Developed for Isolation of Element 106 (Seaborgium) and Study of Its Chemistry in H2SO4 and H2SO4/HF Solutions, with W as Imitator

Ion-exchange behavior of W, Hf, Sr (homologs of elements 106, 104, and 102, respectively), U (pseudohomolog of element 106), Cm, and Eu in H2SO4 and H2SO4/HF solutions was studied. The static and dynamic ion-exchange properties of these elements were determined as influenced by the solution composition and the nature of the ion exchanger. The best conditions were found for separating element 106 (seaborgium) from daughter elements (Rf, No, and Fm) and its pseudohomolog, U, on a single cation-exchange column with the purification coefficients of ≥105-106. A possibility of using the anion exchanger for concentrating element 106 and separating it from the long-lived decay products was demonstrated. The speciation of these elements in dilute sulfuric acid solutions and in solution containing strong complexing agents was discussed.

A 211Pb Generator as a Methodical Approach to Studying the Chemistry of Element 114 in Solutions

A simple and efficient procedure was developed for continuous preparation of short-lived 211Pb (T1/2 = 36.1 min) by elution from a cation-exchange column containing its parent radionuclides 227Ac and 223Ra with aqueous-alcoholic solutions of HCl. The possibility of studying ion-exchange properties of element 114 in solutions under on-line conditions was demonstrated by the example of its homologue, 211Pb. The advantages of the 211Pb generator in simulation experiments on isolation and investigation of chemical properties of element 114 in different systems were discussed.

A study of the ion-exchange behavior of Bi as a homolog of element 115 in dilute hydrohalic acid solutions

The ion-exchange behavior of Bi, a light homolog of element 115, in dilute HCl and HBr solutions was studied. The distribution coefficients of Bi, Pb, and other elements were determined in relation to the acid concentration and kind of the ion exchanger. From 0.25–0.5 M HCl and HBr, Bi is weakly sorbed by the cation exchanger with the distribution coefficients Kd ≤ 10, but is strongly sorbed (Kd ≥ 104) by the anion exchanger, which proves formation of negatively charged complexes in such solutions. High separation factors (≥105–106) of Bi from actinide and other elements were obtained. The distribution coefficients of Bi and Pb differ considerably, which was used for their separation. The optimum conditions were found for repeated isolation of the short-lived isotopes 211Bi (2.1 min), 212Bi (60.6 min), and 213Bi (45.6 min) and for their separation from the long-lived parent radionuclides (Th, Ac, Ra, Pb) used as the initial elements in various generator systems. The possibility of isolation of element 115 and its decay products in the continuous on-line mode was demonstrated.

Simulation Experiments on On-Line Isolation of Element 106 (Seaborgium, Sg) and Study of Its Chemistry in H2SO4 and H2SO4/HF Solutions

Model experiments with W and Mo were performed to simulate on-line ion-exchange isolation of element 106 (seaborgium, Sg) from H2SO4 and H2SO4/HF solutions. Short-lived isotopes of W and Mo were prepared by Sm(24xMg,xn)W nuclear reaction performed on a U-400 cyclotron. Molybdenum isotopes were prepared on an MT-25 microtron (Flerov Laboratory of Nuclear Reactions, JINR, Dubna) by fission of 235U with photoneutrons. The feasibility of isolation and chemical study of 265Sg in the course of its preparation and of identification of this radionuclide by long-lived daughter product, 253Fm, was demonstrated. The correlation of ion-exchange properties of W, Hf, Sr, and REE (TPE) under static and on-line conditions was revealed.

Radioisotope generators of short-lived α-emitting radionuclides promising for use in nuclear medicine

Abstractα-Emitting radionuclides open unique possibilities for nuclear medicine owing to short range of α-particles and high linear energy transfer values. The use of radioactive generators is the simplest and the most efficient method for production of short-lived α-emitting radionuclides. The designs of radioisotope generators and generator systems used for repeated production of short-lived α-emitting radionuclides 225Ac, 213Bi, 211Pb/211Bi, 212Pb/212Bi, 223Ra, and 224Ra, promising for targeted radiotherapy, are described in detail. Particular attention is paid to the methods for production and purification of short-lived α-emitting radionuclides and for their isolation in the form suitable for use in medicobiological studies. Other procedures for producing alternative α-emitting radionuclides (211At, 227Th, 230U, 253Es, 255Fm, 149Tb) and possibilities of their use are also considered. The objectives and prospects of radiochemical studies in the field of production and isolation of α-emitting radionuclides meeting the requirements of nuclear medicine are discussed.

Production of high-purity α-emitting 225Ac and 213Bi radionuclides for use in nuclear medicine

The ion-exchange behavior of Ac, Ra, Pb, Bi, and other elements in aqueous and aqueous-organic HNO3 solutions was studied in relation to the solution composition and kind of the solvent (H2O, CH3OH, C3H6O, CH3CN). Significant difference in the distribution coefficients of Bi and Pb, Ra, actinides, and other elements is revealed in the sorption by cation exchanger from aqueous-organic HNO3 solutions. Optimum conditions were found and a procedure was developed for on-line isolation and deep purification of 225Ac and 213Bi to remove both concomitant radionuclides and macroamounts of inactive impurities.

A comparative study of ion-exchange behavior of Hf and Pb as homologs of elements 104 (Rf) and 114, respectively, in solutions of hydrohalic acids. Relativistic effects

Ion-exchange behavior of Hf and Pb as homologs of elements 104 (Rf) and 114, respectively, and of some other actinides in solutions of hydrohalic acids was studied in relation to the kind and concentra tion of the acid, solution composition, and nature of the ion exchanger. The optimal conditions for isolation, separation, and preconcentration of ultrasmall amounts of transactinide elements from their solutions in HF, HCl, and HBr were found. A scheme for on-line isolation of element 114 and superheavy elements with Z = 108−116, followed by identification by “long-lived” decay products, was developed using as a model the repeated continuous isolation of 211Pb from its parent radionuclide 227Ac in dilute HBr. Based on comparative study of the ion-exchange behavior of Hf and Pb as typical d and p elements, respectively, in solutions containing various halide ligands, the possibility of estimating the contribution of the relativistic effects to the chemical behavior of Rf in dilute solutions of HBr was discussed.