Volume 108, Issue 2

A radiochemical method for producing 82 Se sources with an ultra-low level of contamination of natural radionuclides ( 40 K, decay products of 232 Th and 238 U) has been developed based on cation-exchange chromatographic purification with reverse removal of impurities. It includes chromatographic separation (purification), reduction, conditioning (which includes decantation, centrifugation, washing, grinding, and drying), and 82 Se foil production. The conditioning stage, during which highly dispersed elemental selenium is obtained by the reduction of purified selenious acid (H 2 SeO 3 ) with sulfur dioxide (SO 2 ) represents the crucial step in the preparation of radiopure 82 Se samples. The natural selenium (600 g) was first produced in this procedure in order to refine the method. The technique developed was then used to produce 2.5 kg of radiopure enriched selenium ( 82 Se). The produced 82 Se samples were wrapped in polyethylene (12 μm thick) and radionuclides present in the sample were analyzed with the BiPo-3 detector. The radiopurity of the plastic materials (chromatographic column material and polypropylene chemical vessels), which were used at all stages, was determined by instrumental neutron activation analysis. The radiopurity of the 82 Se foils was checked by measurements with the BiPo-3 spectrometer, which confirmed the high purity of the final product. The measured contamination level for 208 Tl was 8–54 μBq/kg, and for 214 Bi the detection limit of 600 μBq/kg has been reached.

Certified reference materials (CRM) are being widely used for quality control assurance in environmental analysis. For certain CRM, the analytes and/or the range of concentrations are not be available or certified at all. The Joint Research Centre – Institute for Reference Materials and Measurements (JRC-IRMM) of the European Commission has issued a CRM of Wild Berries (IRMM-426) in order to validate radionuclide measurement methods for activity concentrations of the natural radionuclide 40 K and the anthropogenic nuclides 90 Sr and 137 Cs, but not for 210 Po. The aim of the work was to determine low-level activity concentration of 210 Po in these wild berries. The activity concentration of 210 Po was assessed by α-particle spectroscopy after dissolution of the sample by wet digestion and chemical isolation of Po by extraction chromatography. According to the time elapsed since sample collection, the results here shown can be useful not only for ultra low-level analysis of 210 Po but also for 210 Pb in the reference material.

Quinazoline derivatives are well known to have a diverse array of therapeutic activities. Unfortunately, “classic” chemical synthesis does not provide an opportunity for the formation of N -phenyl quaternary 1,3-diazinium compounds. A devised nuclear-chemical method of synthesis based on chemical effects of nuclear transformations enables a new way of the direct nitrogen atom phenylation by the nucleogenic (generated by tritium β-decay) phenyl cations in 1,3-diazines, furnishing, based on our prediction, formation of previously unknown derivatives with N -phenyl quaternary quinazolinium scaffold.

Because of high mobility, the immobilization of long-lived fission product 79 Se (often existed as 79 Se(IV) and 79 Se(VI) anions) is a critical consideration in the repository of high-level radioactive waste. In this work, a Fe-OOH modified bentonite (Fe-OOH-bent) was synthesized as a potential filling material in the repository site for effective adsorption and present the migration of different species of 79 Se. The adsorbent was characterized using FT-IR, XRD, XFS, zeta potential and BET to clarify its physical properties, compositions and structures. A good thermal and radiation stabilities of Fe-OOH-bent was confirmed by its stable uptake ratio for Se(IV) and Se(VI) compared to original samples. The batch experimental results show that Se(IV) and Se(VI) can be efficiently removed from aqueous by Fe-OOH-bent within 60 min with maximum adsorption capacities of 68.45 mg/g for Se(IV) and 40.47 mg/g for Se(VI) in the optimal conditions, indicating its high potential application in consideration of its simple synthesis process, low cost and high adsorption capacity in view of immobilization of 79 Se. The surface species and variation of oxide state of Fe as well as Se(IV) and Se(VI) onto Fe-OOH-bent were investigated by XPS analysis. The values of relative area of Se(IV)–O and Se(VI)–O in XPS spectra followed the same tendency as their adsorption ratio with the variation of system pH, suggesting that the formation of complexes between selenium species and Fe-OOH-bent surface.

In a previous work, we showed that the oxidation of Cr(III) to Cr(VI) by OH˙ present in the atmospheric water droplets has the potential to threaten the people’s health since non-toxic species is transformed into environmental carcinogens. The same oxidation might be initiated by the SO 4 − ˙ free radicals. Here, we shed some light on the detailed mechanisms of this oxidation reaction occurring in ambient atmosphere. Steady state irradiation and pulse radiolysis technique were used to generate SO 4 − ˙. The advanced oxidation process mechanism was investigated at pH 4 and 6 selected as typical values of cloud water acidity. Our findings showed that the oxidation is pseudo-first order with respect to Cr(III) and is pH dependent. In the suggested reaction mechanism, the electron transfer proceeds via an inner sphere mechanism, with formation of the [Cr(III)–SO 4 − ˙] precursor adduct, followed by an electron transfer inside the adduct, from Cr(III) to SO 4 − ˙, to form Cr(IV): Cr(III)+SO4−·⇌[Cr(III)–SO4−·]→Cr(IV)+SO42−.$${\rm{Cr(III)}} + {\rm{S}}{{\rm{O}}_4}^{ - \cdot}[Cr({\rm{III}})-{\rm{S}}{{\rm{O}}_4}^{ -\cdot }] \to {\rm{Cr(IV)}} + {\rm{S}}{{\rm{O}}_4}^{2 - }.$$ At pH 4, the equilibrium constant and the rate constant are 7.52 × 10 4 M −1 and 2.47 × 10 4 s −1 , respectively. At pH 6 these values become 1.90 × 10 5 M −1 and 1.41 × 10 4 s −1 , respectively.

The aim of this work is directed to prepare nanoparticles of egg shell hydroxyapatite-humic acid (ESHAP-HA) as a novel composite material. FTIR, EDX, TEM, XRD, and SEM identified it. Sorption characteristic studies on ESHAP-HA at different pH of solutions, shaking time, initial ion concentration and complexing agent were performed at 152,154 Eu, 99 Mo and 63 Ni. The results were demonstrated that selectivity removal of 152,154 Eu (~96 %) rather than 99 Mo (8.5 %) and 63 Ni (26.7 %). The sorption capacity of 152,154 Eu(III), 63 Ni(II) and 99 Mo(VI) are 80.1, 12.5 and 2.3 mg/g, respectively, onto the ESHAP-HA nanoparticles. Application on the eclectic removal of 152,154 Eu from mixed radionuclides ( 152,154 Eu, 60 Co, and 137 Cs) solution has been evaluated. It concluded that the prepared ESHAP-HA composite material is a promising and recommended for separation of radio lanthanides and/or actinides (such as Am) from nuclear liquid waste and/or contaminated aquatic environmental.

Biocomposites of waste polypropylene (wPP) with 20 phr (part per 100 parts of [wPP]) corn husk fibers (CHF) as bio-filler were prepared for environmental aspect. Maleic anhydride (MAH) was used, with 5, 10 phr concentration as compatabilizer was carried out. The obtained biocomposites were irradiated by γ radiation ranging from 5 to 25 kGy. Mechanical, physical and thermal properties of the biocomposites were studied to evaluate the effect of CHF addition on the properties of obtained composites. It has been found that there is deterioration in all properties. However, by the addition of MAH, the former properties were improved. The obtained results were confirmed by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM).

The ability to precisely predict the volume fraction percentage of the different phases flowing in a pipe plays an important role in the oil, petroleum and other industries. In this research, the volume fraction percentage was measured precisely in water-gasoil-air three-phase flows by using a single pencil beam gamma ray attenuation technique and multilayer perceptron (MLP) neural network. The volume fraction percentage determination in three-phase flows requires least two gamma radioactive sources with different energies while in this study, we used just a 137 Cs source (with the single energy of 662 keV) and a NaI detector. Also, in this work, the MLP neural network in MATLAB software was implemented to predict the volume fraction percentage. The experimental setup provides the required data for training and testing the network. Using this proposed method, the volume fraction was predicted in water-gasoil-air three-phase flows with mean relative error percentage less than 6.95 %. Also, the root mean square error was calculated 2.60. The set-up used is simpler than other proposed methods and cost, radiation safety and shielding requirements are minimized.