Volume 107, Issue 8

The solubility and hydrolysis of U(VI) were investigated in 0.10–5.6 m NaCl solutions with 4 ≤ pH m  ≤ 14.3 (pH m  = −log [H + ]) at T  = 25, 55 and 80 °C. Batch experiments were conducted under Ar atmosphere in the absence of carbonate. Solubility was studied from undersaturation conditions using UO 3  · 2H 2 O(cr) and Na 2 U 2 O 7  · H 2 O(cr) solid phases, equilibrated in acidic (4 ≤ pH m  ≤ 6) and alkaline (8.2 ≤ pH m  ≤ 14.3) NaCl solutions, respectively. Solid phases were previously tempered in solution at T  = 80 °C to avoid changes in the crystallinity of the solid phase in the course of the solubility experiments. Starting materials and solid phases isolated at the end of the solubility experiments were characterized by powder XRD, SEM-EDS, TRLFS and quantitative chemical analysis. The enthalpy of dissolution of Na 2 U 2 O 7  · H 2 O(cr) at 25–80 °C was measured independently by means of solution-drop calorimetry. Solid phase characterization indicates the transformation of UO 3  · 2H 2 O(cr) into a sodium uranate-like phase with a molar ratio Na:U ≈ 0.4–0.5 in acidic solutions with [NaCl] ≥ 0.51 m at T  = 80 °C. In contrast, Na 2 U 2 O 7  · H 2 O(cr) equilibrated in alkaline NaCl solutions remains unaltered within the investigated pH m , NaCl concentration and temperature range. The solubility of Na 2 U 2 O 7  · H 2 O(cr) in the alkaline pH m -range is noticeably enhanced at T  = 55 and 80 °C relative to T  = 25 °C. Combined results from solubility and calorimetric experiments indicate that this effect results from the increased acidity of water at elevated temperature, together with an enhanced hydrolysis of U(VI) and a minor contribution due to a decreased stability of Na 2 U 2 O 7  · H 2 O(cr) under these experimental conditions. A thermodynamic model describing the solubility and hydrolysis equilibria of U(VI) in alkaline solutions at T  = 25–80 °C is developed, including log *Ks,0°{Na2U2O7⋅H2O(cr)}, log *β1,4∘$\log^* {\rm K}_{\rm s,0}^{\circ} \ \{{\rm Na}_{2}{\rm U}_{2}{\rm O}_{7} \cdot {\rm H}_{2}{\rm O}({\rm cr})\}, \log^{*} \beta _{1,4}^{\circ} $ and related reaction enthalpies. The standard free energy and enthalpy of formation of Na 2 U 2 O 7  · H 2 O(cr) calculated from these data are also provided. These data can be implemented in thermodynamic databases and allow accurate solubility and speciation calculations for U(VI) in dilute to concentrated alkaline NaCl solutions in the temperature range T  = 25–80 °C.

Polonium ( 210 Po) concentrations in different honey samples from Lower Silesian Voivodeship and Lesser Poland Voivodeship (southern Poland) were determined. Significantly higher 210 Po concentrations were observed near mining heaps and former excavations versus background areas. Differences in 210 Po concentrations were also observed for honeydew versus nectar honey and between the two voivodeships.

A rapid high performance liquid chromatography (HPLC) and thermal ionisation mass spectrometric (TIMS) methods have been developed for the separation and estimation of fission product elements molybdenum and lanthanum for the burn-up measurements on the dissolver solution of Indian pressurised heavy water reactor (PHWR) spent fuel. Reverse phase chromatography method was developed to separate molybdenum from dissolver solution using mandelic acid as mobile phase and a dynamic ion exchange chromatography technique was used for the separation of lanthanum as well as neodymium from a dissolver solution. Sample loading methods which resulted in enhanced ionisation efficiency have been developed for the TIMS analysis of HPLC separated molybdenum and lanthanum fractions. Ascorbic acid mixed with silicic acid in HCl medium was used for loading the molybdenum on to a rhenium filament to obtain stable and intense ion beam. A novel sample loading method for lanthanum in which a mixture of graphite + boric acid (H 3 BO 3 ) + silica gel was employed to achieve enhanced and steady ion beam formation of LaO + . Concentrations of species of interest were determined employing suitable spikes by isotope dilution mass spectrometry (IDMS) method. The developed methods were adopted for PHWR dissolver solution to establish molybdenum and lanthanum as alternate burn-up monitors. The burn-up data obtained were compared with the well established method of neodymium as fission product monitor. This is a first study of its kind where the data obtained by using molybdenum and lanthanum as fission product monitors were compared with that obtained by Nd-148 method.

A new biosorbent containing vinylsulphonic acid and 2-acryloamido-2-methyl-1-propanesulphonic acid in the presence of magnetic nanoparticles, iron (III) oxide, grafted to carboxymethylcellulose sodium salt P(VSA/AMPSO 3 H/MNPs)-g-CMC bionanocomposite material (BNC) has been synthesized by γ radiation induced grafting copolymerization technique. The effect of comonomer, crosslinker, CMC concentration and the absorbed dose (kGy) on the grafting efficiency and swelling degree was studied. The BNC has been successfully synthesized and the structure of the prepared BNC was confirmed by Fourier transform infrared (FTIR), thermal analysis (TGA and DTA), X-ray powder diffraction (XRD), high-resolution 1 H NMR spectroscopy and scanning electron microscopy (SEM) micrograph. Batch studies relevant to adsorption of Cs-137 and Sr-90 from the reactor actual liquid waste samples by the BNC were performed as a function of contact time, solution pH, metal ion concentration, and temperature in simulation studies using the γ emitting isotopes Cs-134 and Sr-85 as representatives of Cs-137 and Sr-90, respectively. Those studies were used to find out the best conditions for isolation of Cs-137 and Sr-90 from reactor actual liquid waste. The isotherms and kinetics were analyzed using different models at 25 °C. The maximum capacity of BNC was found to be 297 and 330 mg g −1 for Cs(I) and Sr(II) metal ions, respectively.

The radiation stability of three phosphine oxide functionalized pillar[5]arenes (POP5A) was studied by an electron accelerator with dose up to 5 MGy in air at room temperature. The structures of both irradiated and unirradiated pillar[5]arenes samples were comparatively characterized by Micro-FTIR, NMR, UV-vis, ESI-HRMS and HPLC techniques. The results revealed different degrees of radiation damage at different doses for POP5A, and the degradation products are mainly composed of organic species containing hydroxyl groups and carbonyl groups. The possible radiolytic degradation pathway was proposed. In addition, extraction of uranyl ion with irradiated POP5A samples was examined. The distribution ratio of uranyl ion was found to increase at low radiation dose and decrease until 3000 kGy. This is the first time that the irradiation stability of pillar[5]arenes derivative extractants has been studied in detail and it provides reliable data support for further application of pillar[5]arenes extractants in practical applications.

Polyaniline (PANI) nanoparticles and PANI/poly vinyl alcohol (PVA) nanocomposite films were synthesized by the oxidative polymerization of aniline and ammonium peroxodisulfate (APS), as an oxidizing agent in aqueous medium. The PANI/PVA nanocomposite films were exposed to γ-irradiation after oxidative polymerization. Synthesized polyaniline (PANI) nanoparticles and PANI/PVA nanocomposite films were characterized by attenuated total reflectance infrared spectroscopy (FTIR-ATR), X-ray diffraction, high resolution scanning electron microscopy, (HRSEM) high resolution transmission electron microscopy, (HRTEM) and UV-VIS absorption spectroscopy. Energy band gap of PANI nanofibers was determined from Tauc’s plots which equal 4.2 eV. Scanning electron microscopy images show that chemically synthesized of polyaniline has nanofibers structure and irradiated PANI/PVA nanocomposite have a mixture of nanorod and nanosphere structures. The transmission electron microscopy show that chemically synthesized of polyaniline has average length in the range 34 ± 10 nm with less wide distribution, where as the irradiated PANI/PVA nanocomposite has coreshell structure.

In this work, nanosilica and micro carbon black (CB) as a fillers were used to improve the properties of styrene butadiene rubber/natural rubber blends (SBR/NR) crosslinked by γ radiation. Nanosilica was prepared from silica sand and used as eco-friendly material. These composites were characterized by field emission scanning electron microscopy (FESEM) and the measurements of the physic-mechanical and thermal properties were measured. Field emission scanning electron microscopy showed that the composites reinforced by nanosilica and the measurements of the CB are uniformly dispersed in the blends matrix. The results showed that the physico-mechanical and thermal properties were improved indicating a good interaction between the fillers and rubber matrix. The volume fraction measurements confirmed the formation of crosslinking network structure. Meanwhile, the reinforcement of SBR/NR blend loaded with nanosilica showed improved mechanical than blend loaded with both the nanosilica/carbon black and the CB alone. The highest enhancement was obtained for the three fillers by using a concentration of 35 phr at a dose of 150 kGy of γ-irradiation. Thermogravimetric analysis (TGA) indicated that the thermal stability of SBR/NR blend reinforced by nanosilica is higher than those blends reinforced with combined filler the silica. It was also found that the irradiated SBR/NR nanocomposites were more stable than the un-irradiated ones.

Designing new shielding materials and calculating their shielding parameters are important task to keep living in safe from hazardous effects of radiation. In this study, the lithium borate glasses with chemical formula (Li 2 B 4 O 7 ) (100−x) Y x (x = 0, 10, 20, 30 and 40 wt % and Y = magnetite, siderite and zinc-borate) were fabricated via melt quenching technique. X-ray diffraction method was employed to confirm amorphous structure of fabricated glass samples. The glass sample’s shielding parameters such as mass attenuation coefficient, effective atomic number, and half value layer were measured experimentally by the narrow beam transmission method for 81, 276, 302, 356, and 383 keV of incident photon energies. Also, WinXCom software was used to calculate theoretical shielding parameters from 1 keV to 10 5 MeV photon energy. Moreover, Geometric Progression (G–P) method was used to calculate exposure buildup factor (EBF) values for incident photon energy 0.015 MeV–15 MeV up to penetration depths of 40 mfp (mean free path). Among the obtained results, while Li 2 B 4 O 7 glass with magnetite 40 % has the highest mass attenuation and effective atomic number, it has the lowest half value layer and exposure buildup factor. The results show that the fabricated glass systems could be considered as a good candidate for radiation safety.