Radiochemistry

The developed process for producing 90Y is based on semicountercurrent extraction separation with phase inversion on two series-connected blocks of centrifugal extractors. The main advantage of the suggested process over the known procedures is the practically unlimited output capacity of the installation: from trace amounts to several tens of curie in cycle; the possible limitations are only imposed by the chemical or radiation resistance of the materials and chemicals used. Production of 90Y takes from 30 to 60 min. The warranted degree of 90Y separation from the parent 90Sr (with respect to activity) is 10- 9% by the day of calibration.

The electronic structure and energetics were calculated for molecules of binary compounds of element 120 and its homologs with common elements strongly differing in chemical properties. The calculations were performed within the framework of the relativistic density functional theory using the model of precision two-component atomic core pseudopotentials. The results obtained show that all the examined compounds of element 120 should differ from the corresponding compounds of the known heavy metals of the second group (Sr-Ra) in lower strengths and larger lengths of chemical bonds. Therefore, one can suppose that element 120 will be, on the whole, more inert chemically than its nearest homologs.

Technetium carbonyl complexes [TcBr(CO)5], [TcI(CO)5], [TcX(CO)3]4 (X = Cl, Br, I), [TcBr(CO)3en] (en = ethylenediamine), [Tc(RCOCHCOR′)(CO)3(Et2NH)] [R = CH3 or C(CH3)3, R′ = CF3], Tc2(CO)10, and [Tc(C5H5)(CO)3] were tested as starting compounds for chemical vapor deposition of technetium coatings. The conditions of deposition of technetium coatings were determined, and the deposition yields were evaluated.

Extraction of trace quantities of Am(III) from aqueous HNO3 solutions with solutions of bis(diphenylphosphinylmethyl)phosphinic acid (I), bis[2-(diphenylphosphinyl)phenoxymethyl]phosphinic acid (II), and bis[2-(diphenylphosphinylmethyl)phenoxymethyl]phosphinic acid (III) in dichloroethane was studied. The stoichiometry of the extractable complexes was determined; the effect of organic diluent on the extraction was considered. The extractive power of the reagents toward Am(III) grows in the order III < II < I. Acid I surpasses in the extractive power a neutral bidentate extractant, tetraphenylmethylenediphosphine dioxide (TPMDPD), by three orders of magnitude. A synergistic effect in extraction of Am with mixtures of TPMDPD and acid I was revealed.

Radium-224 isolated from a generator having the form of a solution of thorium and Trilon B with pH 6.5–7.0 (molar ratio 4 : 1) was used to examine the sorption of radium from tap water by inorganic sorbents of T-3A, T5(400), and T5 (MnO2) brands under dynamic and static conditions.

A model study is made of the sorption-barrier properties of intact monolithic samples of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV). In sorption from simulated groundwater (pH 8.3), the surface distribution coefficient in surface sorption K a was determined to be 8–37 and 4–80 cm for Am and Pu, respectively. The mineral components of the rocks responsible for the radionuclide sorption were identified by autoradiography. The rocks tested are characterized by high retention capacity for Am and Pu.

Radiation-induced and hydrolytic decomposition of HDBP and its zirconium salt in organic solutions and two-phase aqueous-organic systems in the presence of TBP and nitric acid is studied. The yields of radiation-induced decomposition of HDBP and temperature dependences of its hydrolysis rate constants are determined. Kinetic equations for radiation-induced decomposition of HDBP are derived.

Coprecipitation of microamounts of Cs with ferrocyanides of various metals, exhibiting a high sorption activity with respect to Cs ions, was studied. The distribution coefficients of 117Cs were determined in coprecipitation with the ferrocyanides in 0.1 M NaNO3. The precipitated ferrocyanide was separated from solution by filtration through a Trumem metal-ceramic membrane. Cesium is recovered most efficiently with ferrocyanides of bivalent transition metals (Ni, Co, Cu, Fe, Cd).

The results of thermodynamic studies of alkali metal uranoniobates are summarized. The thermodynamic functions of formation of alkali metal uranoniobates, reactions of their synthesis, and ionic equilibria involving these compounds are analyzed.