Band 104, Heft 3

Chemical studies of superheavy elements require fast and efficient techniques, due to short half-lives and low production rates of the investigated nuclides. Here, we advocate for using a tubular flow reactor for assessing the thermal stability of the Sg carbonyl complex – Sg(CO) 6 . The experimental setup was tested with Mo and W carbonyl complexes, as their properties are established and supported by theoretical predictions. The suggested approach proved to be effective in discriminating between the thermal stabilities of Mo(CO) 6 and W(CO) 6 . Therefore, an experimental verification of the predicted Sg–CO bond dissociation energy seems to be feasible by applying this technique. By investigating the effect of 104,105 Mo beta-decay on the formation of 104,105 Tc carbonyl complex, we estimated the lower reaction time limit for the metal carbonyl synthesis in the gas phase to be more than 100 ms. We examined further the influence of the wall material of the recoil chamber, the carrier gas composition, the gas flow rate, and the pressure on the production yield of 104 Mo(CO) 6 , so that the future stability tests with Sg(CO) 6 can be optimized accordingly.

With an aim to understand the nature of species, cyclic voltammetry (CV) of Pu(IV) in dilute HBr and in a room temperature ionic liquid (RTIL), 1-octyl-3-methylimidazolium bromide (C 8 mimBr) was carried out. Shifts of cathodic and anodic peak potentials of Pu(IV) cyclic voltammograms were observed towards negative potentials in the extended electrochemical window for ionic liquid medium compared to 2 M HBr. The diffusion coefficient of the most likely species of Pu(IV) in aqueous medium was found to be greater than that of the corresponding species in ionic liquid while the activation energy showed reverse trend. The Pu(IV)/Pu(III) redox reaction was found to be exothermic in aqueous medium while it was endothermic in C 8 mimBr. The redox reaction was found to be quasi reversible for both the media while the extent of irreversibility was more in ionic liquid. UV-Vis spectroscopy of Pu in these media showed significant differences in the peak positions and their relative intensities, indicating the possible differences in the interactions of Pu(IV) with the solvent molecules resulting in speciation differences. A new prominent peak was observed in RTIL which could be for a new species of Pu(IV). Computational studies were also carried out to understand the solvation of Pu and the possibility of thermodynamic conversion from Pu(IV) to Pu(III).

Piperidinium nitrate (Pip − NO 3 ) and pyrrolidinium nitrate (Pyr − NO 3 ) functional groups were anchored on a poly(styrene-divinylbenzene) matrix and evaluated the resultant anion exchange resin for the extraction of plutonium from nitric acid medium. The distribution coefficient ( K d , mL/g) of Pu(IV) in these resins increased with the concentration of nitric acid, reaching a maximum K d at 7 M nitric acid, followed by decrease. The extraction of Pu(IV) increased with the duration of equilibration followed by the establishment of equilibrium, occurred within four hours of equilibration. The kinetic data were fitted with pseudo-first order and pseudo-second order rate equations. The apparent plutonium exchange capacity was determined to be ∼256 mg/g for Pip − NO 3 resin and 285 mg/g for Pyr − NO 3 resin at 7 M nitric acid. The radiolytic degradation of Pip − NO 3 and Pyr − NO 3 in presence of nitric acid (7 M) was studied upto a dose of 200 KGy and the results are reported in this paper.

The alkyl derivatives of N , N ,-dialkyl-2-hydroxyacetamide (DAHyA), namely, N , N ,-dihexyl-2-hydroxyacetamide (DHHyA), N , N ,-dioctyl-2-hydroxyacetamide (DOHyA), N , N ,-didecyl-2-hydroxyacetamide (DDHyA), were synthesized and characterized by FT-IR, and NMR spectroscopy. The extraction behaviour of Am(III) in a solution of DAHyA in n -dodecane was studied as a function of various parameters to evaluate the feasibility of using DAHyA for partitioning of trivalent actinides from high-level liquid waste (HLLW). The distribution ratio of Am(III) ( D Am(III) ) in 0.1 M DAHyA/ n -DD increased from 10 −4 to > 200 with increase in nitric acid concentration from 1 M to 6 M. A D Am(III) value 10–70 was obtained in a nitric acid concentration range from 3–4 M. The extraction of Am(III) in 0.1 M DAHyA/ n -dodecane decreased in the order DHHyA > DOHyA > DDHyA. The third-phase formation behaviour of nitric acid and neodymium (III) in 0.2 M DAHyA/ n -dodecane was studied. Near stoichiometric amount of neodymium (III) can be loaded in octyl and decyl derivatives without any third-phase formation from 3–4 M nitric acid medium. Unlike other extractants, the loaded trivalent metal ion in DAHyA can be recovered even with 1 M nitric acid. Therefore, the study revealed that N , N ,-dialkyl-2-hydroxyacetamides are promising candidates for partitioning the trivalent actinides from HLLW.

The solubilities of zirconium hydroxide and oxide after aging at 278, 313, and 333 K were measured at 278, 298, 313, and 333 K in the pH c range of 0.3–7 in a 0.5 M ionic strength solution of NaClO 4 and HClO 4 . Size distributions of the colloidal species were investigated by ultrafiltration using membranes with different pore sizes, and the solid phases were examined by X-ray diffraction. The apparent solubility of zirconium amorphous hydroxide (Zr(OH) 4 (am)), prepared by the oversaturation method, decreased with increasing aging temperature ( T a ), and the size distributions obtained after aging at elevated temperatures indicated the growth of the colloidal species. We, therefore, suggested that agglomeration of the colloidal species and dehydration and crystallization of Zr(OH) 4 (am) as the solubility-limiting solid phase occurred over the course of aging at elevated temperatures. For sample solutions of the crystalline oxide (ZrO 2 (cr)), the aging temperature had no significant effect on the solubility, but the solubility data at lower temperatures were found to be slightly higher than those at higher temperatures, implying a small fraction of the amorphous components. In the analysis of different solid phases (Zr(OH) 4 (s, T a ), T a  = 278, 313, and 333 K) depending on the aging temperatures, the solubility products ( K sp , T a ) were determined at different measurement temperatures, and the enthalpy change ( Δ r H ○ ) for Zr 4+ + 4OH –  ↔ Zr(OH) 4 (s, T a ) was calculated using the van't Hoff equation. The solid-phase-transformation process at elevated temperatures was also analyzed based on the obtained K sp , T a and Δ r H ○ values.

The radioisotope 89 Sr as 89 SrCl 2 is medically useful for bone pain palliation and is produced in fast reactors using the 89 Y(n, p) 89 Sr reaction. A procedure for isolation of the radionuclide 89 Sr by chemical processing of the irradiated Y 2 O 3 target has been standardised and trial runs have been carried out at the Fast Breeder Test Reactor (FBTR), Kalpakkam. The chemical processing of the irradiated Y 2 O 3 target involves i) the removal of target Y(III) by TBP extraction and ii) further purification of the separated 89 Sr fraction by cationic exchange chromatography. However a selective isolation of 89 Sr by the Sr-specific crown ether makes the above chemical processing faster and relatively simple. This work presents a study on the selective removal of Sr from the irradiated target dissolver solution using the Sr-specific crown ether 4,4′(5′) di-tert-butyl-cyclohexano-18-crown-6 (DtBuCH18C6) in octanol medium. The separation behaviour of the other impurities such as Ce(IV), Y(III), Tb(III), Eu(III), Zn(II), Mn(II) and Rb(I) present along with Sr(II) in the irradiated sample was also investigated. The method of separation by using the crown ether DtBuCH18C6 is proved to be a potential tool for the purification of 89 Sr(II) source produced from yttria target in fast reactors.

The preparation and characterization of (K 1− x Rb x ) 2 U 4 O 13 solid solutions has been studied for the x values in the range of 0 − 1. The solid solutions were prepared by heating K 2 U 4 O 13 and Rb 2 U 4 O 13 in required stoichiometry at about 600–700 ℃ for about 50 h in air atmosphere. The XRD patterns of the products suggest formation of the solid solutions in full composition range of Rb 2 U 4 O 13 and K 2 U 4 O 13 . The cell volume of the crystal unit cell of solid solutions changes linearly with Rb atom % in (Rb + K) present in the solid solutions and follows Vegard's law. The solid solutions when heated in Ar/He atmospheres at 900 ℃ produce corresponding low valent uranate solid solutions (K 1− x Rb x ) 2 U 4 O 12 or their mixtures.

Instrumental neutron activation analysis technique (INAA) was applied for nondestructive multi-element analysis of seed samples of the plant Dodonaea viscosa hopseed. This plant is distributed all over Egypt, because of its suitable properties. The samples were collected from some bushes grown at different sites in some governorates, in July of each year during the period from 2004 to 2011. The determined elements are: Co, Cs, Eu, Fe, Hg, Ni, Rb, Sc, Se, Sr and Zn, under the chosen irradiation and cooling times. The content of some elements has been compared with data obtained from previous work on analysis of various kinds of seeds. The influence of some parameters on the determined elemental content is discussed. Standard reference materials IAEA-155 and IAEA-V-10 were used to assure quality control, accuracy and precision of the technique.