S. V. Ermolaev

Production of 225Ac and 223Ra by irradiation of Th with accelerated protons

The possibility of producing 225Ac and 223Ra by irradiation of natural 232Th with medium-energy protons was examined. Thorium foils were irradiated with 90-, 110-, and 135-MeV protons at the accelerator of the Institute for Nuclear Research, Russian Academy of Sciences, in Troitsk (Moscow oblast). The cumulative production cross sections for 225Ac were 6.7 ± 0.9, 9.8 ± 1.9, and 13.9 ± 1.5 mb, and for 227Th (223Ra precursor), 43 ± 5, 37 ± 6, and 35 ± 4 mb, respectively. Based on the experimental data and theoretical calculations, the possible yields of 225Ac and 223Ra in irradiation of thick thorium targets at various accelerators were determined. An efficient procedure was suggested for isolating the products from the irradiated targets: 225Ac, by liquid extraction and extraction chromatography, and 223Ra, by sublimation from a thorium-lanthanum melt followed by thermochromatographic separation in metallic titanium columns and extraction-chromatographic isolation of radium. The procedure allows production of large (units of curies) amounts of radiochemically pure 225Ac and 223Ra, which is promising for wide use of these radionuclides in nuclear medicine.

Isolation of Medicine-Applicable Actinium-225 from Thorium Targets Irradiated by Medium-Energy Protons

A method of isolation of actinium-225 for nuclear medical applications from thorium targets irradiated by protons is presented. It comprises liquid extraction and extraction chromatography separations. The method demonstrates high (> 85%) chemical yield and radionuclide purity of the final product. An impurity of 227Ac (0.1% at the end of bombardment) does not hinder 225Ac from being used for medical 225Ac/213Bi generators.

Extraction chromatographic behavior of actinium and REE on DGA, Ln and TRU resins in nitric acid solutions

The extraction-chromatographic behavior of actinium, rare earth elements and other radionuclides formed upon the irradiation of thorium by medium energy protons was studied. The k′ values for Ac(III), Ce(III) and La(III) in nitric acid solutions using Ln Resin, DGA Resin and TRU Resin (Triskem Int.) were determined. The optimal conditions for separation of Ac(III) and rare earth elements (REE(III)) were defined. The obtained results can be used to develop the multipurpose analytical procedure for actinium separation either for the needs of nuclear medicine or for radiochemical analysis of environmental samples.

Recovery of Ra-223 from natural thorium irradiated by protons

Abstract Irradiation of natural thorium with medium-energy protons is considered to be a prospective approach to large-scale production of 225Ac and 223Ra. In addition to the earlier-developed method of 225Ac isolation, the present work focuses on the simultaneous recovery of.223Ra from the same thorium target. Radiochemical procedure is based on liquid-liquid extraction, cation exchange and extraction chromatography. The procedure provides separation of radium from spallation and fission products generated in the thorium target. High chemical yield (85– 90%) and radionuclide purity of 223Ra (> 99.8% except 224Raand 225Ra isotopes) have been achieved.

Sorption of protactinium(V) on extraction chromatographic resins from nitric and hydrochloric solutions

Retention of Pa(V) on the extraction chromatographic resins (DGA, TRU, TEVA, UTEVA and octanol resin) produced by Triskem International Company has been studied. The capacity factor k′ values of Pa(V) were determined in static experiments (batch technique) for a wide concentration range of nitric and hydrochloric acid solutions. The obtained data are useful to devise chromatographic separation of Pa(V) from other actinides.

Characterization of a 82Rb generator for positron emission tomography

Characteristics of the developed 82Rb medical generator intended for the production of Rubidium Chloride, 82Rb from Generator radiopharmaceutical for positron emission tomography (PET) are examined. The results of laboratory tests and clinical trials are presented. The influence of thermal sterilization on the ionexchange characteristics of the sorbent based on hydrous tin(IV) oxide is studied. The possibility of radiation “self-sterilization” of the generator column and of the maintenance of aseptic conditions in it throughout the generator operation life is assessed. In the course of operation of one generator, it is possible to obtain up to 19 L of a sterile and apyrogenic solution of the radiopharmaceutical with permissible content of radioactive and stable impurities. The efficiency of the 82Rb elution from the sorbent at different eluent flow rates is determined. The efficiency of using the generator in PET investigations in cardiology and oncology is demonstrated.