I. G. Tananaev

Production of actinium, thorium and radium isotopes from natural thorium irradiated with protons up to 141 MeV

Abstract Cross sections of 225Ac, 227Ac, 227Th and 228Th in thorium-232 targets irradiated with protons in the energy range 21–141 MeV have been measured. Based on these data, production yields of 225Ac and 223Ra in thick thorium targets have been calculated. It is possible to produce in proton energy range 60–140 MeV about 96 GBq (2.6 Ci) 225Ac per 10-d irradiation with 100 μA proton beam current and 10-d decay, and much higher amount of 223Ra. The impurities of 227Ac and 224Ra are important and need to be assessed for further medical applications.

Amine-templated uranyl selenates with chiral [(UO2)2(SeO4)3(H2O)]2– layers: topology, isomerism, structural relationships

Abstract Eleven new amine-templated uranyl selenate hydrates have been prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amines. The structures of the compounds have been solved by direct methods and refined using least-squares techniques. Each structure is based upon [(UO2)2(SeO4)3(H2O)]2– layers of corner-sharing UO7 pentagonal bipyramids and SeO4 tetrahedra. The layers are based upon 4- and 6-membered rings arranged in different fashion. In topology I, 6-membered rings form edge-sharing chains, whereas, in topology II, they form corner-sharing chains. Layers with the topology II exist in two geometrical isomers that differ in the system of ‘up’ and ‘down’ orientations of tetrahedra relative to the plane of the layer. There are two isomers, one of which is chiral and the other is achiral. The layers with the topology II are chiral. Chirality is induced by the combination of orientations of tetrahedra and direction of the U → H2O bond. The analysis of the relationships between composition and shape of amine molecules and layer topology reveals two important regularities. 1. Aliphatic components of amine molecules tend to associate with 6-MRs of the inorganic layers. 2. Molecules with longer and spacious aliphatic components favor formation of the layers with topology II, whereas those with shorter aliphatic components prefer layers with the topology I.

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.

Uranyl selenates with organic templates: Principles of structure and characteristics of self-organization

Basic structural principles of uranyl selenates with organic templates are outlined as follows. In compounds with short chain amine molecules (C:N < 8) the primary role plays the correspondence between topology of inorganic complex (isomerism) and structure and shape of a template. In the structures with long chain molecules (C:N ≤ 8), the molecules are associated to form 2- or 1-dimensional supramolecular templates that are connected with inorganic structure according to the charge density matching principle. Compounds with electro neutral molecules (crown ethers) have composite structure, where bonding between organic and inorganic parts is achieved through hydrogen bonding via intermediate oxonium clusters.

Acetyl-containing phosphine oxides as extractants for actinides and lanthanides

Extraction capability and selectivity of acetyl-containing phosphine oxides R2P(O)CMe2CH2C(O)Me (R = Pr, Bu, n-C5H11, n-C6H13, n-C8H17, Ph) toward actinides (UVI, ThIV) and trivalent lanthanides (LaIII, NdIII, HoIII, YbIII) were studied. The new ligands were shown to be more efficient and selective in the extraction of uranium, thorium, and heavy lanthanides from nitric acid solutions into chloroform as compared to the known extractants such as carbamoylphosphine oxide Ph2P(O)CH2C(O)NBu2, trioctylphosphine oxide (n-C8H17)3P(O), and tributyl phosphate (n-BuO)3P(O).

Macrocyclic receptor for pertechnetate and perrhenate anions

The design and synthesis of a neutral macrocyclic host that is capable of perrhenate and pertechnetate recognition is described. The anion affinities and underlying coordination modes were estimated by several experimental and theoretical methods including a new technique--reverse (99)Tc NMR titration.

Plutonium volatility in ozonization of alkaline solutions of Pu(VI) hydroxo complexes

69 Processes involving the transition of chemical compounds into the gas phase are of both theoretical and practical significance. Such processes are impor� tant for actinides because their concentration, isola� tion, and purification and also isotope separation are known to present serious difficulties. Such processes are also important for plutonium. Assuming that the properties of the previously described plutonium tetroxide [1, 2] can be analogous to those of easily sub� limable osmium and ruthenium tetroxides and taking into account that both RuO 4 and OsO 4 can sublime even on weak heating from alkaline media, we tested the hypothesis of PuO4 volatility from alkaline solu� tions containing Pu(VIII). The existence of Pu(VIII) complexes (although of unknown composition) in a mixture with Pu(VII) complexes was postulated for the first time in [3–6], where it was assumed that Pu(VIII) derivatives can form under the action of an ozone–oxygen mixture on alkaline solutions of Pu(VI) complexes. This is also indicated by the corresponding spectral characteristics of Pu(VIII) and Pu(VII) complexes [7]. The extrac� tion of presumably PuO4 [1] from ozonated solutions suggests that they are characterized by a complex sys� tem of equilibria and contain both Pu(VII) and Pu(VIII) complexes and the said binary oxide. Thus, in an alkaline solution, there is likely a complex–tet� raoxide dynamic equilibrium, which can shift under the action of suitable extractants [1] and, furthermore, on heating. A similar equilibrium can also be assumed

Synthesis and crystal structure of a new uranyl selenite(IV)-selenate(VI), [C5H14N]4[(UO2)3(SeO4)4(HSeO3)(H2O)](H2SeO3)(HSeO4)

AbstractCrystals of a new uranyl selenite(IV)-selenate(VI), [C5H14N]4[(UO2)3(SeO4)4(HSeO3)(H2O)]·(H2SeO3)(HSeO4) were obtained by evaporation from aqueous solutions. The compound crystallizes in the triclinic system, space group

Sorption of Tc(VII) and Am(III) by carbon materials: effect of oxidation

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