Irradiation and isolation of fission products from uranium metal–organic frameworks

Journal of Radioanalytical and Nuclear Chemistry - A customized single-stage cylindrical combined air lift mixer-settler (C-CALMIX) device has been developed and its performance was evaluated by...     

Studies on the separation of cesium-137 from the acidic fission product waste solutions on a new complex inorganic exchanger (Zr−P-APW)

A new inorganic exchanger zirconiumphosphate-ammonium phosphotungstate (Zr–P-APW) has been synthesized in granular form suitable for column work. TheK _d values for different metal ions were determined and the affinity order was found to be CsRb>Zr>Ce> rare earths. Sodium exchange capacity, pH-titration curve, breakthrough capacities for cesium (both in pure HNO₃ and in different types of simulated nuclear wastes) and elution of cesium from the Zr–P-APW column have been studied. A selective method for the removal of cesium from other radioactive fission products has been developed. The exchanger was found to be stable to a -radiation dose of 10⁸ rads in presence and absence of 2M nitric acid.     

The preparation of β-substituted amines from mixtures of epoxide opening products via a common aziridinium ion intermediate

Here we describe a one-pot synthesis of a series of β-substituted amines as single enantiomers from an initial regioisomeric mixture of styrene oxide ring-opening products. We also report the isolation and characterization of a key β-chloro intermediate and provide additional insight into the mechanism of the reported alkylations. These results require that the reaction proceeds through a common aziridinium ion intermediate on two separate occasions in order to account for the observed overall net retention of configuration in proceeding from (S)-styrene oxide to the desired β-substituted amine products.     

Separation of metallic impurities from uranium by anion exchange on Dowex 1×8 resin

The separation of metallic impurities from uranium by anion exchange with a Dowex 1×8 resin has been investigated. The following elements can be quantitatively separated from 400 mg uranium using a 1 cm diameter 15 or 30 cm long column. The elements Ag, Al, Ba, Ca, Cr, Cs, K, Mg, Mn, Na, Ni, Rb, REE, Sc, Th, Ti and Y can be separated by eluting the elements with conc. HCl. Uranium is retained by the resin. Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, REE and V can be separated by eluting with 0.01 N H₂SO₄. Uranium is retained by the resin. Cd and Zn can be separated by first eluting uranium with 0.5 N HCl and then eluting Cd and Zn with 1 N NH₃. Hf, Zr and V can be separated by eluting with 5 N HCl but some uranium contamination is unavoidable.     

Mass–yield distributions of fission products from photo-fission of natPb induced by 50–70 MeV bremsstrahlung

The mass–yield distributions of various fission products have been determined in the 50-, 60- and 70-MeV end point bremsstrahlung induced fission of ^natPb using off-line γ-ray spectrometric technique in the electron linac at Pohang Accelerator Laboratory, Korea. The mass–yield distributions are symmetric with average mass of 102.34, 102.25 and 102.03 and FWHM of 21, 22 and 23 mass unit, respectively. From the present data and literature data in the 50–85 MeV bremsstrahlung induced fission of ²⁰⁹Bi the following observations were obtained: (i) The average masses of the yield distributions in the 50–85 MeV bremsstrahlung induced fission of ^natPb and ²⁰⁹Bi are around 102.25 ± 0.25 and 103 ± 0.5, respectively. (ii) The FWHM of the mass–yield distributions increases from about 21 mass units at 50 MeV to 23 mass units at 70–85 MeV, which is explained from the point of increase in multi-chance fission probability with increasing excitation energy. (iii) Within the bremsstrahlung energy range of 50–85 MeV, the role of nuclear structure effect in the mass–yield distribution was observed in the photo-fission of ²⁰⁹Bi, whereas it was not seen in case of ^natPb. This may be due to the presence of so many isotopes in ^natPb unlike mono-isotopic ²⁰⁹Bi.     

Selective extraction of uranium from uranium–beryllium ore by acid leaching

Journal of Radioanalytical and Nuclear Chemistry - Both uranium and beryllium are very important strategic metals and have been applied to many fields, such as nuclear industries, atomic energy,...     

Separation of acetone/water mixtures by a modified γ-alumina membrane via a new method

A new surface deposition method was researched to decrease pore size of ceramic membranes. CaCO₃ was chosen to modify the top layer of γ-alumina membranes prepared by sol–gel processes. Separation of gaseous acetone/water mixtures by vapor permeation was carried out to characterize the membranes. Improvement of membrane separation property after modifications and SEM photographs proved that this new method was effective to reduce the membrane pore size.     

Separation of γ-linolenic and other polyunsaturated fatty acids from Boraginaceae via supercritical CO2

Essential fatty acids were extracted from Echium amoenum (Boraginaceae) seed oil via supercritical carbon dioxide and the results were compared with conventional Soxhlet method as the base case of 100% recovery. The response surface methodology was used to optimize the effective extraction parameters. The chemical composition of recovered oil was analyzed by polar and non-polar gas chromatograph-flame ionization detector columns. The experimental results indicated that echium seed contained 25 wt% oil and the maximum extraction oil recovery of 92% was obtained via supercritical CO(2) at optimal operating conditions (43°C, 280 bar, 1.5 mL/min, 25 min static time and 130 min dynamic time). At similar operating conditions, applying 2.5 and 5 mol% ethanol as a modifier enhanced the recovery to 96 and 112%, respectively. The results showed that supercritical fluid extraction is a viable technique for separation of constituents such as γ-linolenic acid (7-8%), palmitic acid (6-7%), stearic acid (3-4%), oleic acid (12-13%), linoleic acid (19-20%), α-linolenic acid (40-41%) and stearidonic acid (8-9%) from Boraginaceae.     

Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP–MS with multiple ion counters

This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC–ICP–MS)—a Nu Plasma HR—equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the ²³⁵U/²³⁸U, ²³⁶U/²³⁸U, ¹⁴⁵Nd/¹⁴³Nd, ¹⁴⁶Nd/¹⁴³Nd, ¹⁰¹Ru/(⁹⁹Ru+⁹⁹Tc) and ¹⁰²Ru/(⁹⁹Ru+⁹⁹Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred μm to about 1 mm and with surface alpha activities of 3–38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA–MC–ICP–MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15–20 min (excluding MC–ICP–MS optimization and calibration). The ¹⁰¹Ru/(⁹⁹Ru+⁹⁹Tc) and ¹⁰²Ru/(⁹⁹Ru+⁹⁹Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in ¹⁴⁶Nd of about 3–5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The ²³⁵U/²³⁸U and ²³⁶U/²³⁸U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the ²³⁵U/²³⁸U ratios measured in ten microsamples varied in the range from 0.0073 (corresponding to the natural uranium isotopic composition) to 0.023 (corresponding to initial ²³⁵U enrichment in reactor fuel). An inverse correlation was observed between the ²³⁶U/²³⁸U and ²³⁵U/²³⁸U isotope ratios, except in the case of one sample with natural uranium. The heterogeneity of the uranium isotope composition is attributed to the different burn-up grades of uranium in the fuel rods from which the microsamples originated. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Separation and identification of a new saponin from the flowers of Guaiacum officinale L

A triterpenoid saponin, guaianin O (1), oleanolic acid 3-O-{α-L-rhamnopyranosyl-(1 → 2)-[β-D-glucopyranosyl-(1 → 3)]-α-L-arabinopyranoside}-28- O-[β-D-glucopyranosyl]-ester, was isolated from the n-butanol extract of flowers of Guaiacum officinale L. The structural elucidation of 1 was accomplished by extensive studies of both one and two dimensional 1H, 13C-NMR spectra, the FAB mass spectrum, and alkaline and acid hydrolyses.     

Identification of several Tonalide® transformation products in the environment

This work reports on the survey carried out to determine the presence of microcystins (MCs) by using ELISA tests and HPLC-UV for such determination in different sample sites along the Spanish course of the Guadiana River. The most important cyanobacteria species identified were, Microcystis aeruginosa and Oscillatoria spp. The highest total microcystin content recorded was 6.40?µg?L^?1 in 2002. The main toxins found were microcystins RR and LR, with microcystin YR present at trace levels. Improvements in sample clean up were carried out by using Immunoaffinity solid phase extraction (SPE) and its advantages regarding to conventional SPE were clearly demonstrated. The confirmation of MCs presence in the evaluated water reservoirs, underlines the necessity of monitoring programs as well as the improvement of analytical methodologies to efficiently prevent the human health risks as a consequence of MCs contamination.     

Liquid–liquid extraction of actinides,lanthanides, and fission products by use of ionic liquids: from discovery to understanding

Liquid–liquid extraction of actinides and lanthanides by use of ionic liquids is reviewed, considering, first, phenomenological aspects, then looking more deeply at the various mechanisms. Future trends in this developing field are presented.     

Preparation of uranium oxide powder for nuclear fuel pellet fabrication with uranium peroxide recovered from uranium oxide scraps by using a carbonate–hydrogen peroxide solution

This work studied a way to reclaim uranium from contaminated UO₂ oxide scraps as a sinterable UO₂ powder for UO₂ fuel pellet fabrication, which included a dissolution of the uranium oxide scraps in a carbonate solution with hydrogen peroxide and a UO₄ precipitation step. Dissolution characteristics of reduced and oxidized uranium oxides were evaluated in a carbonate solution with hydrogen peroxide, and the UO₄ precipitation were confirmed by acidification of uranyl peroxo–carbonate complex solution. An agglomerated UO₄ powder obtained by the dissolution and precipitation of uranium in the carbonate solution could not be pulverized into fine UO₂ powder by the OREOX process, because of submicron-sized individual UO₄ particles forming the agglomerated UO₄ precipitate. The UO₂ powder prepared from the UO₄ precipitate could meet the UO₂ powder specifications for UO₂ fuel pellet fabrication by a series of steps such as dehydration of UO₄ precipitate, reduction, and milling. The sinterability of the reclaimed UO₂ powder for fuel pellet fabrication was improved by adding virgin UO₂ powder in the reclaimed UO₂ powder. A process to reclaim the contaminated uranium scraps as UO₂ fuel powder using a carbonate solution was finally suggested.     

Effective and rapid adsorption of uranium via synergy of complexation and cation-π interaction

Journal of Radioanalytical and Nuclear Chemistry - A novel indole-based aerogel (HTPRA) containing carboxyl groups was prepared for separation of uranium from aqueous solution. The adsorption was...     

Solvent extraction of uranium from aqueous solutions by α-benzoinoxime

Solvent extraction of uranium with α-benzoinoxime from aqueous solutions has been systematically investigated. The extraction equilibration was very fast and achieved at 60 s for uranium. The extraction of uranium was pH-dependent using α-benzoinoxime as extractant. The effect concentration of uranium and α-benzoinoxime was studied. The uranium loaded in the organic phase can be stripped efficiently with 93 % yield using 0.1 M HCl as the stripping agent in a single stripping step. A good selectivity for uranium was observed through α-benzoinoxime as extractant from aqueous solution with other interfering cation ions. Present study suggested that α-benzoinoxime can be used as a potential extractant for separation of uranium from aqueous solution using centrifugal extractor in industrial application.     

Preparation of a zeolite imidazole skeleton–silica hybrid monolithic column for amino acid analysis via capillary electrochromatography

We developed a novel, convenient and low-cost one-pot strategy for preparing a zeolitic imidazolate framework-8 (ZIF-8)–silica hybrid monolithic column by adding ZIF-8 directly to a polymer solution of the silica matrix. The simulated stationary phase and monolithic column prepared under optimal conditions were characterized using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis nitrogen physisorption and zeta potential. The results obtained confirmed the successful introduction of ZIF-8 into the silica monolithic column, and the prepared monolithic column exhibited good permeability and physicochemical stability. A capillary electrochromatography method was developed based on a ZIF-8–silica hybrid monolithic column through which 15 mixed amino acids, 4 neutral compounds, 4 nipagin esters and 2 chlorinated fungicides were separated in 14, 5, 7 and 6 min, respectively, under optimal conditions. The relative standard deviations retention times and column efficiencies in run-to-run, day-to-day and column-to-column varied in the ranges of 1.90%–2.21%, 2.13%–2.51% and 3.08%–6.65%, respectively, which demonstrated that ZIF-8–silica hybrid monolithic column exhibited satisfactory reproducibility and stability. The incorporation of ZIF-8 into a silica monolithic column is a promising method for preparing novel monolithic columns composed of a metal–organic framework.     

Analyses of radionuclides in soil,water, and agriculture products near the Urgeiriça uranium mine in Portugal

Analyses of soils, irrigation waters, agriculture products (lettuce), green pasture, and cheese were performed in samples collected in the area of the old Urgeiriça uranium mine and milling facilities, Centre-North of Portugal, in order to assess the transfer of uranium series radionuclides in the environment and to man. Soils close to milling tailings display an enhancement of radioactivity. In the drainage basin of the stream Ribeira da Pantanha, receiving drainage from the tailings piles and discharges from the acid mine water treatment plant, there was enhancement of uranium series radionuclide concentrations in water and suspended matter. Agriculture products from kitchen gardens irrigated with water from the Ribeira da Pantanha show an increase of radioactivity, mainly due to uranium isotopes. Agriculture products from other kitchen gardens in this area, irrigated with groundwater, as well pasture and cheese produced locally from sheep milk did not show enhanced radionuclide concentrations. In the Urgeiriça area, some soils display radionuclide concentrations higher than soils in reference areas and, in agriculture products grown there, ²²⁶Ra was the radionuclide more concentrated by vegetables. Through ingestion of these products ²²⁶Ra may be the main contributor to the increment of radiation dose received by local population.