Volume 97, Issue 1

Liquid scintillation counting according to the CIEMAT/NIST method was used for the activity standardization of 41 Ca. The counting efficiencies were computed with two different atomic rearrangement models KLM and KL 1 L 2 L 3 M ) applying an improved model for the interaction of low-energy X-rays with the scintillation cocktail. This report comprises a detailed description of the determination of nuclear and atomic input data, sample preparation as well as a comprehensive uncertainty analysis.

UTEVA and TRU extraction chromatographic resins, the products of Eichrom Technologies Inc. have been systematically studied with the objective to develop a procedure for the simultaneous determination of Th, U, Np, Pu and Am nuclides. Elution chromatograms of the spiked model solutions and environmental samples were determined under different conditions (in nitric and hydrochloric acids, in oxidative and reducing media) using inductively coupled plasma mass spectrometry (ICP-MS). Resin capacity factors ( k ′) for the actinides in different oxidation states were obtained and the interaction of the analytes with each other and the resin matrices were revealed. Data obtained contribute to the better understanding of the mechanism of the extraction chromatography of the actinides and provide additional information about the properties of UTEVA and TRU described by Horwitz et al.

Samples of murataite-based ceramics with chemical composition (wt.%): 5 Al 2 O 3 , 10 CaO, 55 TiO 2 , 10 MnO, 5 Fe 2 O 3 , 5 ZrO 2 , 10 AnO 2 (An=Th, U) were produced by melting in both glassy carbon crucibles in a resistive furnace and a cold crucible followed by crystallization during slow cooling. All the ceramics were composed of predominant murataite polytypeswith 5-, 8-, and 3-fold elementary fluorite unit cell, minor crichtonite and pyrophanite/ilmenite, and rare grains of perovskite and pyrochlore. More than 95% of total Th and U enter the murataite polytypes. The murataite grains have zoned structure where the 5C, 8C and 8C polytypes form their core, middle zone and rim respectively. Leach rates of Th and U were determined using a single-pass-flow-through (SPFT) procedure at pH=2 and pH=6.5 at a temperature of 90±2 °C. Average Th leach rates from the ceramics produced in the resistive furnace and cold crucible were found to be 1.00×10 -5  g/(m 2 ×d) and 1.97×10 -5  g/(m 2 ×d). Uranium was found to be higher leachable element than thorium: its average leach rate was 1.42×10 -3  g/(m 2 ×d). Higher leachability of U as compared to Th may be due to either occurrence of U in minor crichtonite phase with lower chemical durability or hydrolytic processes resulting in formation of higher leachable U(VI).

The adsorption parameters of local yellow sand and clay towards cobalt and cesium were investigated by batch equilibration technique. The influences of equilibration time, initial metal concentration, solution pH, volume of aqueous solution to weight of adsorbent ratio and temperature have been studied and discussed. Cobalt and cesium removal from 0.1 M sodium chloride solution were quantitatively evaluated using Langmuir and Freundlich isotherm models. The two tested models fit the data reasonably well. The maximum removal capacity of clay was found to be greater than that of yellow sand for both ions and the mean free energy in all cases in the range corresponding to ion exchange mechanism. The values of the first order rate constants, the rate constants of intraparticle transport and the particle diffusion coefficients for cobalt and cesium ions were determined from the graphical representation of the proposed models. The removal studies were also performed at different temperatures to obtain the thermodynamic parameters of the process.

The potential interference from competing inorganic anions, chelating agents, and low molecular weight organic acids (LMWOAs), and the potential surface effects of selected minerals on the TcO 4 - -sulfide immobilization reaction (to form Tc 2 S 7 ) were investigated. The presence of the common inorganic anions, such as nitrate, studied did not affect the TcO 4 - -sulfide immobilization process even though their concentrations were 20 times higher than that of sulfide. The chelating agents relevant to nuclear waste sites ( e.g. , ethylenediaminetetraacetic acid) did not compete with the TcO 4 - -sulfide reaction even in high excess. Of the ten selected LMWOAs investigated, only maleic acid and fumaric acid were able to inhibit the immobilization process by forming anionic water-soluble complexes with pertechnetate at concentrations significantly higher than found in the environment. None of the non-reducing minerals ( e.g. , goethite) investigated interfered with the immobilization reaction. X-ray absorption spectroscopy showed that the product obtained in the presence of the selected co-existing species was predominantly Tc 2 S 7 .

The sorption behavior of cadmium ions from aqueous media was investigated on styrene-divinylbenzene copolymer beads (StDVB) as an adsorbent. Various physico-chemical parameters were optimized to simulate the best conditions which can be used to decontaminate cadmium ions from aqueous media using StDVB beads as an adsorbent. Maximum adsorption was observed at 0.001 mol L -1 acid solutions (HNO 3 , HCl, H 2 SO 4 and HClO 4 ) using 0.2 g of adsorbent for 8.89×10 -5  mol L -1 of cadmium ions within three minutes equilibration time. The adsorption data followed the Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherms over the cadmium concentration range of 8.89×10 -4  to 8.01×10 -3  molL -1 . The characteristic Freundlich constants, i.e. 1/ n =0.243±0.007 and A =1.783×10 -3 ±2.069×10 -5  mol g -1 have been computed for the sorption system. Langmuir isotherm gave a saturated capacity of 0.334±0.0123 mmol g -1 . The sorption mean free energy from D–R isotherm was found to be 16.31±0.31 kJ mol -1 indicating chemisorption involving chemical bonding for the adsorption process. The uptake of cadmium increased with the rise in temperature. Thermodynamic parameters, i.e. Δ G , Δ H and Δ S have also been calculated for the system. The sorption process was found to be endothermic. The proposed procedure was applied to remove cadmium from tap water and industrial effluent.

Gallium-67 labeled superparamagnetic iron oxide nanoparticles ([ 67 Ga]-SPION were prepared and evaluated for their altered biodistribution in normal rats. Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution were synthesized by a co-precipitation technique using ferrous salts at Fe 3+ /Fe 2+ =2 molar ratio followed by structure identification using XRD, TGA, DSC, VSM, HRSEM, TEM and FT-IR techniques (≈5 nm diameter). In order to trace SPION bio-distribution, the radiolabeled iron oxide nanoparticles were prepared using 67 Ga with a high labeling efficiency (over 96%, RTLC method) and they also showed an excellent stability at room temperature for at least 4 d. The biodistribution of the radiolabeled SPION was checked in normal male rats up to 24 h compared to free Ga 3+ cation biodistribution. The data strongly support the alteration of the tracer accumulation in reticuluendothelial system while the stability of the complex is highly retained.

Ceragenins (CSAs) are a new class of antimicrobial agents that display broad spectrum antibacterial activity and may find use in the treatment of various infections. A member of this class CSA-13 was labelled with 99m Tc using SnCl 2 ·H 2 O as a reducing agent. The labelling efficiency depended on the ligand/reductant ratio, pH and volume of the reaction mixture. The radiochemical purity and stability of 99m Tc-CSA was determined by thin layer chromatography. Biodistribution studies of 99m Tc-CSA were performed in Sprague Dawley rats. Liver and spleen uptake was quite high. A significantly higher accumulation of 99m Tc-CSA was seen at sites of S. aureus infected rats. The results were compared with 99m Tc-Ciprofloxacin.