Band 107, Heft 2

In this study, UCl 4 was prepared by the reaction of HCl gas with UO 2 in the LiCl-KCl eutectic. Then, the electrochemical behavior of U 4+ and U 3+ on a Mo cathode was investigated by various electrochemical techniques. The reduction process of U 4+ was regarded as two steps: U 4+ +e=U 3+ ; U 3+ +3e=U. Diffusion coefficients of U 4+ and U 3+ , the apparent standard potential of U 4+ /U 3+ , U 3+ /U as well as U 4+ /U in the LiCl-KCl molten salt on the Mo electrode was determined by numerous electrochemical methods. The thermodynamic functions of formation of Gibbs free energy of UCl 4 and UCl 3 are calculated as well.

Technetium carbonates complexes produced by chemical, electrochemical and radiolytic methods have been studied by UV-Visible, X-ray Absorption Fine Structure (XAFS) and Density Functional Theory methods. The (NH 4 ) 2 TcCl 6 salt was dissolved in 2 M KHCO 3 . The resulting purple solution was analyzed by XAFS and UV-Visible spectroscopy. The UV-Visible spectra exhibits a band centered at 515 nm. The XAFS results were consistent with the presence of polymeric species containing the [Tc 2 (μ−O) 2 ] 4+ core coordinated to carbonate ligand. Concerning the electrochemical methods, the pertechnetate anion was electrochemically reduced in concentrated carbonate solution [(CO 3 2− )=5 M and (HCO 3 − )=0.5 M]. For the radiolytic reduction, the speciation of Tc under Helium ions particle beam and γ radiation was examined by UV-Visible and XAFS spectroscopy in high concentrated carbonate media. In concentrated carbonate solutions, pertechnetate as Tc(VII), was not reduced under irradiation due to the formation of carbonate radical which is a strong oxidant. Then, the solution proposed was the addition of formate to the solution which can scavenge hydroxyl radical 10 times faster than carbonate and prevent re-oxidation of reduced technetium. The XANES and EXAFS spectroscopies, approved by theoretical methods, revealed that the final product of the radiolytic reduction of pertechnetate is in the +IV oxidation state. The final structure of the reduced product by He 2+ radiolysis was the same as electrochemical reduction. From this complex determination and evolution vs. the dose, this study is reporting the solubility of the Tc(IV) complex.

Smectite-rich natural clay is being evaluated as the backfill and buffer material in the Indian repository program for the nuclear high level waste disposal. In the natural clay, montmorillonite is one of the major mineral component governing the sorption behavior of various radionuclides. In the present work, influence of sulfate anion on sorption of Eu(III) by Na-montmorillonite has been investigated. The effect of pH and sulfate concentration on Eu(III) sorption by Na-montmorillonite was used to understand the mechanism of sorption process. The Eu(III) sorption by clay at varying pH was virtually pH independent at lower pH (<4), with ion exchange as the dominant mode for Eu(III) sorption. In the pH region of 4–6.5, sharp increase in sorption indicates surface complexation as predominant mechanism. At pH>6.5, the sorption attained a constant value. To deduce the mechanism of sorption of Eu(III) on Na-montmorillonite surface in presence of sulfate, ATR-FTIR spectroscopic investigations has been carried out which indicate the presence of sulfate bearing species on Na-montmorillonite surface. Using spectroscopic findings as a guide, the surface complexation modeling, in absence and presence of sulfate, was successfully carried out.

It is important to study the behavior of recoiling radon atoms 222 Rn after decay of parent 226 Ra and the effect of parameters on their access to the surrounding medium. The present study was carried out using CR-39 detector to study the effect of grain size on the correlation between surface and mass exhalation rates and the correlation between emanation coefficient and exhalation rate at different masses of soil and phosphate fertilizer. In addition, the relationship between emanation coefficient and the sample mass was studied for different grain sizes (0.1, 0.3, 0.5 and 1 mm). The results showed that there is no effect of grain sizes on the correlation coefficient between surface and mass exhalation rates in soil and fertilizer. The correlation coefficient between emanation coefficient and exhalation rate in different masses of soil was slightly influenced by the grain sizes. While the correlation coefficient between emanation coefficient and exhalation rate in different masses of phosphate fertilizer samples was not affected by the grain sizes (0.1, 0.3 and 0.5 mm). However, it was found that the emanation coefficient decreases exponentially with the mass for soil and phosphate fertilizer. This relationship was not significantly affected by grain size in soil except grain size 1 mm. While this relationship was affected by grain size >0.3 mm in phosphate fertilizer.

Primary reference measurement procedure for Cr determination in biological samples by radiochemical neutron activation analysis (RNAA) has been elaborated. The procedure is based on quantitative and selective separation of chromium from neutron irradiated sample by column chromatography using MnO 2 -Resin and determination of 51 Cr by γ-ray spectrometry. Quality components have been incorporated into the RNAA method which makes it possible to meet the requirements of the definition of ratio primary reference measurement procedure. The usefulness of the elaborated procedure to assign the certified values for Cr in new certified reference material (CRMs) based on animal tissues is demonstrated. The tentative certified values for Cr have been proposed for: MODAS M-4 Cormorant Tissue and M-5 Cod Tissue CRMs.

The purpose of this study is to demonstrate the feasibility of elemental analysis of sand samples by photon activation induced by high energy bremsstrahlung photons at an end point energy of 18 MeV from a clinical electron linear accelerator. The γ-ray spectra of the activated samples were collected using a high resolution spectrometer. Qualitative analysis of major and trace components of the samples (12 in total) was carried out whilst the spectra of eight of the samples were evaluated quantitatively. The contents of elements obtained by photon activation analysis were compared with values obtained by X-ray fluorescence.

Silica nanoparticles (SNPs) are known as intrinsic radiolabeling agents and offer a fast and reliable approach to deliver theranostic agents into targeted organs. Radiolabeled amorphous silica nanoparticles are of great interest to radiation oncology communities. In order to improve the performance of these nano materials in cancer diagnosis and treatment, their inherent properties, such as surface area and the ability to accumulate in cancer cells, should be enhanced. Pyridine functionalized mesoporous silica MCM-41 is known as a potential anticancer-drug delivery system with high suface area. In thiswork, in order to produce an image-guided drug delivery system for diagnostic applications, [ 68 Ga] radionuclide was grafted on pyridine functionalized MCM-41. The nanoparticles were assessed with atomic force microscopy (AFM), paper chromatography, X-ray diffraction, FTIR spectroscopy, CHN and TGA/DTA analyses. The pharmacokinetic profile evaluation of the radiolabeled nano silica, [ 68 Ga]-Py-Butyl@MCM-41, was done in Fibrosarcoma tumor-bearing mice. This labeled nanocomposite with appropriate blood circulation in body, high structural stability, high tumor/blood ID/g% ratio and fast excretion from the body can be proposed as an efficient nano engineered composite for upcoming tumor targeting/imaging nanotechnology-based applications.

Kinetics of dehydration of unirradiated and γ-ray irradiated neodymium (III) acetate hydrate with 10 3 kGy total γ-ray dose absorbed in air atmosphere were studied by isoconversional nonisothermal method. The dehydration proceeds in two steps with the elimination of 0.8 and 0.4 mol of H 2 O, respectively. This result indicates that the investigated neodymium (III) acetate hydrate contains 1.2 mol of crystalline water in its structure. The dehydration reactions are best described by nucleation ( A 2 model) and gas diffusion ( D 4 model) for unirradiated and γ-ray irradiated samples, respectively. Analysis of the kinetic data using linear and nonlinear isoconversional methods showed that the apparent activation energy, E a (kJ/mol) is dependent on the conversion degree, α , of the dehydration process. The E a −α plots for both unirradiated and γ-ray irradiated neodymium (III) acetate hydrate showed that the dehydration is a complex process and contains multistep reactions. The results showed that γ-ray irradiation has a significant effect on the kinetics and thermodynamic parameters of the dehydration reaction. Powder X-ray diffraction showed that neodymium (III) acetate hydrate has a monoclinic system ( SG P 2 /m ) and no phase transformation was detected by γ-ray irradiation up to 10 3 kGy absorbed dose. The system maintains the same crystal structure before and after dehydration.

In this work, the radiation shielding parameters like mass and linear attenuation coefficient, half value layer, tenth value layer, mean free path, effective atomic number, effective electron density, exposure buildup factor and fast neutron removal cross section were examined for the peridot, aluminum nitride, ruby, yttrium oxide, magnesium silicate, and silicon nitride ceramic samples. Furthermore, the dependence of the effective conductivity on the energy was investigated. The experimental studies were carried out in the photon energy range of 81 keV–1333 keV using a high resolution HPGe detector and six different radioactive sources. The experimental results were validated with the theoretical results and a good agreement was observed for all samples. The yttrium oxide has more shielding effectiveness for γ radiation, while magnesium silicate, aluminum nitride and silicon nitride possess least γ-ray shielding. However, the optimum neutron shielding material is ruby.