Uranyl Nitrate Research Articles

Mapping of uranium particles on J-type swipes with microextraction-ICP-MS.

A microextraction liquid sampling system coupled to a quadrupole inductively coupled plasma-mass spectrometer (ICP-MS) was utilized to spatially discern uranium particles, isotopically, on a cellulose-based swipe material (i.e., J-type swipe). These types of swipes are often used by the International Atomic Energy Agency (IAEA) as part of their environmental sampling program. A grid was created such that extraction locations covered the center circle (n = 34 without overlapping). Uranium (U) particulates (<20 μm) of varying U isotopic abundance and chemical form (i.e., uranyl fluoride and uranyl nitrate hexahydrate) were mechanically placed on the swipes in random locations and detected via the microextraction-ICP-MS methodology. Heat maps were subsequently generated to show the placement of the particulate with their respective intensity and isotopic determination. This detection of the uranium particulates, via isotopic determination, agreed with reference values for these materials. Additionally, depleted (235U/238U = 0.002) uranium particulates were placed directly within a clay matrix, on the swipe surface, and subjected to analysis by microextraction-ICP-MS. The mapping of the swipe demonstrated, for the first time, the employment of the microextraction-ICP-MS method for extracting sample from a complex matrix, and correctly identifying the uranium isotopic composition. This example ultimately demonstrates the utility of the methodology for detecting particles of interest in complex matrices.

The effect of ancillary ligands on hydrocarbon C-H bond functionalization by uranyl photocatalysts.

The aqueous uranyl dication has long been known to facilitate the UV light-induced decomposition of aqueous VOCs (volatile organic compounds), via the long-lived highly efficient, uranyl excited state. The lower-energy visible light excited uranyl ion is also able to cleave unactivated hydrocarbon C-H bonds, yet the development of this reactivity into controlled and catalytic C-H bond functionalization is still in its infancy, with almost all studies still focused on uranyl nitrate as the precatalyst. Here, hydrocarbon-soluble uranyl nitrate and chloride complexes supported by substituted phenanthroline (Ph2phen) ligands are compared to each other, and to the parent salts, as photocatalysts for the functionalization of cyclooctane by H atom abstraction. Analysis of the absorption and emission spectra, and emission lifetimes of Ph2phen-coordinated uranyl complexes demonstrate the utility of the ligand in light absorption in the photocatalysis, which is related to the energy and kinetic decay profile of the uranyl photoexcited state. Density functional theory computational analysis of the C-H activation steps in the reaction show how a set of dispersion forces between the hydrocarbon substrate and the Ph2phen ligand provide control over the H atom abstraction, and provide predictions of selectivity of H atom abstraction by the uranyl oxo of the ring C-H over the ethyl C-H in an ethylcyclohexane substrate.

Research new type of cation-exchange resin for waste water treatment

This article presents the studies obtaining and research new polycondensation type phosphoric cation-exchange resin. The conditions for the phosphorylation of this polymer were selected from the experiments accumulated in relation to the phosphorylation reactions of low- and high-molecular compounds. The resulting polymer had an exchange capacity for a 0.1 N NaOH solution – 5,5-5,6 mEq/g and contained 16,5% phosphorus. Based on the studies carried out, the optimal conditions for the synthesis of the styrene-furfural polymer are assumed to be: the reaction temperature is 90°C, the concentration of the ZnCl2 catalyst is 0.07 mol per mole of furfural, and the molar ratio of styrene to furfural is 1:1. There was studied an interaction of the cation exchanger in Na- and H-forms with solutions of salts of copper sulfate, nickel, cobalt, sodium chloride, calcium and uranyl nitrate. In order to elucidate the mechanism of sorption of the cations of these metals, were taken the IR-spectra of the cation exchanger in the H- and Na- form, saturated with copper ions. The less dissociated phosphoric acid groups, the stronger hydrogen bond forms phosphoryl oxygen with OH-groups. Therefore, it can be expected that as the cation exchanger is saturated with sodium, the maximum of the band corresponding to the phosphorus-oxygen bond vibrations will slightly shift to longer wavelengths as a result of the destruction of the weaker hydrogen bond.

Transport mechanism of uranyl nitrate in nanopore of geopolymer with different Si/Al ratios: Molecular dynamics simulation

Geopolymer is an amorphous cementitious material produced by geopolymerization using minerals or industrial waste as the main raw material under the action of activators. It can be used for safe treatment of heavy metal and radioactive pollution. This study applied molecular dynamics simulation to investigate the transport behaviour of uranyl nitrate in nanochannel of geopolymer, and focused on the influence of changes in the Si/Al ratio of geopolymer on the adsorption and diffusion of ions and water molecules. The simulation results described by density distribution, radial distribution function (RDF), hydrogen bonding network structure, mean square displacement (MSD) and diffusion coefficient. The density distribution shows that geopolymer has the strongest adsorption capacity for UO22+, followed by NO3−, and finally H2O. The results also indicate that the changes in molecular composition of geopolymer have a significant impact on kinetic characteristics of UO22+, NO3− and H2O. As the Si/Al ratio decreases, the adsorption capacity of geopolymer shows an upward trend, with the most significant improvement in the adsorption of UO22+. In addition, when the Si/Al ratio reduces, the migration rate of UO22+ and NO3− slows down. It could hinder the diffusion of ions in nanopores of geopolymer. The work could optimize the preparation of geopolymer adsorbent, and reveal the transport mechanism of uranyl nitrate in nanopore of geopolymer with different Si/Al ratios at the atomic scale.

Encapsulation of Uranium Oxide in Multiwall WS2 Nanotubes.

Uranium is a high-value energy element, yet also poses an appreciable environmental burden. The demand for a straightforward, low energy, and environmentally friendly method for encapsulating uranium species can be beneficial for long-term storage of spent uranium fuel and a host of other applications. Leveraging on the low melting point (60°C) of uranyl nitrate hexahydrate and nanocapillary effect, a uranium compound is entrapped in the hollow core of WS2 nanotubes. Followingly, the product is reduced at elevated temperatures in a hydrogen atmosphere. Nanocrystalline UO2 nanoparticles anchor within the WS2 nanotube lumen are obtained through this procedure. Such methodology can find utilization in the processing of spent nuclear fuel or other highly active radionuclides as well as a fuel for deep space missions. Moreover, the low melting temperatures of different heavy metal-nitrate hydrates, pave the way for their encapsulation within the hollow core of the WS2 nanotubes, as demonstrated herein.

Using life cycle assessment to quantify the environmental benefits of circular economy strategies in the nuclear industry

In the United Kingdom nuclear energy is expected to play a key role in decarbonising the power generation sector. The implementation of circular economy approaches in the nuclear industry can minimize the amount and the associated environmental impacts of nuclear wastes. In this article, we demonstrate how Life Cycle Assessment (LCA) can be used to investigate the environmental benefits of two circular economy strategies that aim at reducing the amount of intermediate level waste (ILW) destined for disposal in a geological disposal facility. The first case study focuses on a novel technology for recycling zirconium alloy cladding waste, whilst the second case study investigates the environmental benefits of using depleted (instead of natural) uranium to produce uranyl nitrate, a chemical used in the PUREX process. Our results show that both circular approaches outperform conventional ones across all environmental categories and particularly in terms of resources depletion, with reductions up to 25% and 94% for respectively zirconium alloy recycling and depleted uranium reuse. The environmental benefits of both approaches are due not only to a reduction in the amount of ILW to be disposed of, but also because they are assumed to induce a reduction in the demand for mining of primary zirconium or uranium respectively. When both approaches are combined, the environmental benefits range from 4% in the category freshwater and up to 94% in the category resource use, energy carriers.

In Situ Liquid Cell Transmission Electron Microscopy Study of Studtite Particle Formation and Growth via Electron Beam Radiolysis.

This study presents in situ observations of studtite (UO2O2(H2O)2·2H2O) crystal growth utilizing liquid phase transmission electron microscopy (LP-TEM). Studtite was precipitated from a uranyl nitrate hexahydrate solution using hydrogen peroxide formed by the radiolysis of water in the TEM electron beam. The hydrogen peroxide (H2O2) concentration, directly controlled by the electron beam current, was varied to create local environments of low and high concentrations to compare the impact of the supersaturation ratio on the nucleation and growth mechanisms of studtite particles. The subsequent growth mechanisms were observed in real time by TEM and scanning TEM imaging. After the initial precipitation reaction, a post-mortem TEM analysis was performed on the samples to obtain high-resolution TEM images and selected area electron diffraction patterns to investigate crystallinity as well as energy-dispersive X-ray spectroscopy spectra to ensure that studtite was produced. The results reveal that studtite particles form through various mechanisms based on the concentration ratio of uranyl to H2O2 and that studtite is initially produced through an amorphous intermediary prior to formation of the crystalline material commonly reported in the literature.

Unveiling fungal diversity in uranium and glycerol-2-phosphate-amended bentonite microcosms: Implications for radionuclide immobilization within the Deep Geological Repository system

Uranium (U) represents the preeminent hazardous radionuclide within the context of nuclear waste repositories. Indigenous microorganisms in bentonite can influence radionuclide speciation and migration in Deep Geological Repositories (DGRs) for nuclear waste storage. While bacterial communities in bentonite samples have been extensively studied, the impact of fungi has been somewhat overlooked. Here, we investigate the geomicrobiological processes in bentonite microcosms amended with uranyl nitrate and glycerol-2-phosphate (G2P) for six-month incubation. ITS sequencing revealed that the fungal community was mainly composed of Ascomycota (96.6 %). The presence of U in microcosms enriched specific fungal taxa, such as Penicillium and Fusarium, potentially associated with uranium immobilization mechanisms. Conversely, the amendment of U into G2P-suplemented samples exhibited minimal impact, resulting in a fungal community akin to the control group. Several fungal strains were isolated from bentonite microcosms to explore their potential in the U biomineralization, including Fusarium oxysporum, Aspergillus sp., Penicillium spp., among others. High Annular Angle Dark-Field Scanning Transmission Electron Microscopy (HAADF) analyses showed the capacity of F. oxysporum B1 to form U-phosphate mineral phases, likely mediated by phosphatase activity. Therefore, our study emphasizes the need to take into account indigenous bentonite fungi in the overall assessment of the impact of microbial processes in the immobilization of U within DGRs environments.

Irradiation and analysis of Uranyl Nitrate solutions in different Uranium concentrations for use in subcritical reactors for 99Mo production

Different Uranyl Nitrate Solution concentrations and undiluted Uranyl Nitrate Hexahydrate were irradiated in the Kartini TRIGA Mk II reactor to qualitatively assess the radioisotope production feasibility in different neutron fluxes within reactor irradiation facilities. Multiple radioisotope gamma spectrums’ were obtained using the Neutron Activation Analysis method without chemical separation prior to detection. The presented methodology serves as a preliminary experiment toward the Subcritical Assembly for 99Mo Production (SAMOP) application in the Kartini reactor. The results show that the concentration and crystallization of Uranyl Nitrate can change the detectability of some radioisotopes in gamma spectrometry. Through a combination of depletion calculation and standardized measurement, some dominant isotopes’ gamma peaks from irradiated Uranyl Nitrate are identifiable, and their activity is quantifiable. Although chemical separation is inseparable from fission product analysis using gamma spectrometry, the presented direct measurement establishes a practical and rapid assessment method for the next isotope production development in the Kartini reactor.

Structural features of early fuel cycle taggant incorporation for intentional nuclear forensics

To develop strategies for incorporating transition metal taggants (Fe, Cr, and Ni) into oxide fuels and to understand how these taggant candidates persist through early fuel cycle processes, synthetic procedures are modified from established production routes to yield intentionally tagged early fuel cycle intermediates including uranyl nitrate hexahydrate (UNH, UO2(NO3)2·6H2O), uranyl peroxide tetrahydrate (studtite, UO2O2·4H2O), and uranyl peroxide dihydrate (metastudtite, UO2O2·2H2O). First, Fe, Cr, and Ni nitrate solutions are introduced to an aqueous solution of UNH followed by precipitation to produce tagged UNH. Then, studtite is precipitated from UNH followed by dehydration to metastudtite. Structural influences of taggant incorporation within all synthesized phases are investigated using powder X-ray diffraction (PXRD) and Raman spectroscopy to provide insight into crystallographic modifications resulting from the addition of tags to these early fuel cycle materials and elucidate the chemical form of taggants introduced at these stages. The possibility of segregation of taggant species into discrete phases within U matrices was examined using scanning electron microscopy with energy dispersive X-ray spectroscopy. Taggant concentrations in solid-phase materials were determined using inductively coupled plasma-optical emission spectroscopy. Observations from Raman spectroscopy and PXRD indicate that introducing transition metal tags during uranyl nitrate precipitation results in potential impurity phase segregation in UNH, but transition metal incorporation is suggested by results for tagged uranyl peroxide materials. Results from this study will inform strategies for optimizing taggant incorporation in UO2.

Uranium bioprecipitation mediated by a phosphate-solubilizing Enterobacter sp. N1-10 and remediation of uranium-contaminated soil

Uranium (U) pollution in soils is prevalent worldwide and poses a significant health risk that will require remediation approaches. However, traditional U bioreduction by sulfate reducing bacteria (SRB) are sensitive to oxygen and are not suitable for treating aerobic topsoil. Bioprecipitation of U into uranyl phosphate (UP) mediated by phosphate-solubilizing microorganism (PSM) is not affected by oxygen. In this study, PSM strains were isolated and used for U-contaminated soil remediation. Microbial metabolites and the mechanism of PSM bioprecipitation were revealed. The results showed that strain Enterobacter sp. N1-10 had the highest phosphate-solubilizing capacity (dissolved P was 409.51 ± 8.48 mg/L). Uranium bioprecipitation was investigated by culturing the bacterium in the presence of 50 mg/L U and in the cell-free culture supernatant. The results showed that strain N1–10 had a high U removal rate (99.45 ± 0.43 %) after adding 50 mg/L U to the culture medium. A yellow precipitate was immediately formed when uranyl nitrate solution was added to the cell-free culture supernatant. The analysis indicated that bacterium produced lactic acid (37.58 mg/L), citric acid (4.76 mg/L), succinic acid (2.03 mg/L), and D-glucuronic acid (1.94 mg/L); the four organic acids solubilized Ca3(PO4)2 to form stable uranyl phosphate precipitate. The application of strain N1-10 and Ca3(PO4)2 significantly decreased the bioavailability of soil U (43.54 ± 0.52 %). In addition, pot experiments showed that PSM N1-10 and Ca3(PO4)2 promoted plant growth and markedly reduced U accumulation by pakchoi. These results demonstrate that PSM N1-10 and Ca3(PO4)2 exhibit a great potential for U bioremediation.

Electric field gradients at rubidium sites in rubidium uranyl nitrate and quadrupole moments of 85Rb and 87Rb

The electronic structure along the axial direction of the uranyl ion in rubidium uranyl nitrate (RbUO2(NO3)3) has been probed by nuclear quadrupole resonance and nuclear magnetic resonance measurements of 85Rb and 87Rb quadrupole couplings. The parameter of interest in these experiments is the electric field gradient at the Rb sites, which may be compared with values computed by various theoretical approaches. From this analysis a refinement of the ratio of the quadrupole moments of 85Rb and 87Rb has also been obtained.

Comparison of Raman and mid-infrared spectroscopy for quantification of nitric acid in PUREX-relevant mixtures

During the plutonium uranium reduction extraction (PUREX) process, nitric acid facilitates the extraction of actinides from the aqueous phase into the organic phase by forming neutral, organic soluble complexes with tri-n-butyl phosphate (TBP). The concentration of nitric acid is generally measured by titration; however, titration is a time-consuming method that generates significant volumes of additional waste. Optical spectroscopic techniques can be used to perform fast, automated measurements off-line or on-line, without generating any waste. In this work, the effectiveness of Raman and mid-infrared (MIR) spectroscopy has been compared for the first time as an alternative to titration for the quantification of nitric acid in PUREX-relevant mixtures. Samples of 0–12 M nitric acid in the aqueous phase and 0–1.10 M nitric acid in the organic phase (TBP/odourless kerosene (OK)–H2O–HNO3 model system) were analysed and partial least squares (PLS) regression models were built to predict nitric acid concentration. MIR spectra required less pre-processing than Raman spectra and more accurate predictions of nitric acid concentration were obtained for MIR spectroscopy than for Raman spectroscopy, with root mean square error of prediction (RMSEP) values of 0.099 M versus 0.148 M obtained for the aqueous phase and root mean square error of cross validation (RMSECV) values of 0.006 M versus 0.013 M obtained for the organic phase. To investigate the ability to predict nitric acid concentration in the presence of uranyl nitrate, samples containing uranium (0–100 g/L) and nitric acid (0.15–0.64 M) in the organic phase (U-TBP/OK-H2O–HNO3 model system) were analysed by Raman and MIR spectroscopy. The RMSECV was 0.027 M and 0.066 M for MIR and Raman spectroscopy, respectively; these values are higher than those obtained in the absence of uranyl nitrate owing to differences in the experimental approaches employed. Therefore, the results obtained demonstrate that MIR or Raman spectroscopy could be used to measure the concentration of nitric acid in the organic and aqueous phases in the PUREX process.

Exploring band-free Raman microspectrometry combined with PCA and MCR-ALS for size-resolved forensic analysis of uranium in aerosols in a model nuclear atmosphere

Achieving non-destructive micrometer-scale molecular and structural analysis of uranic materials in atmospheric aerosols with traditional methodologies is a challenge. Spatially resolved analysis of uranium in actinide-bearing aerosols is critical for nuclear forensics. Although laser Raman microspectrometry enables this, for the normally low uranium concentrations in the aerosols the spectra are indiscernible (band-free) against pronounced background: trace analysis requires a push in analytical strategy. We combined laser Raman microspectrometry (utilizing two lasers (λ = 532 nm, λ = 785 nm)) with principal component analysis (PCA) and multivariate curve resolution–alternate least squares (MCR-ALS) to perform size-resolved analysis of uranium in aerosols. Uranium-specific Raman scatter bands corresponding to uranyl nitrate (860 cm−1), uranium sulphate (868 cm−1), uranyl chloride (816 cm−1) and uranium trioxide (839 cm−1) were detected. The 816 cm−1, 854 cm−1, 868 cm−1 bands were resolved by MCR-ALS and used to identify and map uranium in PM4.5 size aerosols. Based on spectral feature selection of the signature bands, PCA identified two sources of aerosol particles in model nuclear atmosphere - Sea spray for PM4.5 and re-suspension of ‘nuclear’ dust from a rare earth element (REE) mine for PM2.5. The MCR-ALS-resolved uranium bands showed the potential for attributive nuclear forensic analysis.

Cation-heterogeneity in internally gelated U1-zCezO2-x, 0.15 ≤ z ≤ 0.3 microspheres

Internal gelation of aqueous mixtures of metal (M = Ln, An) nitrate with Uranyl Nitrate is generally assumed to yield cation homogeneity and a fluorite type single phase U1-zMzO2±x solid solution. As-sintered (U,Ce)O2 internally gelated microspheres, manufactured with target z values up to 0.3 using Ce(NO3)3, were observed to exhibit systematic peak broadening and splitting at higher 2θ angles in their X-Ray diffraction (XRD) patterns, correlating with increasing z≥0.15. This was interpreted as an unexpected departure from a single phase material. Thermogravimetry was used to make an initial assessment whether these peak anomalies were caused by an oxygen hypostoichiometry. Results indicated global oxygen stoichiometry for all compositions. The subsequent detailed characterization study via Electron Probe Micro Analysis of cross-sections of the as-sintered microspheres revealed the systematic presence of spherical Ce concentration gradients, as well as µm-sized highly Ce-enriched features. EDS and TEM studies on focused ion beam lamellae extracted from the cross-sections of as-sintered microspheres revealed a hexagonal Ce4.67(SiO4)3O minor phase manifesting as single grain precipitates and clusters uncovering the presence and critical role of Silicon as an unexpected contaminant and Ce-scavenger from surrounding (U,Ce)O2 grains. Characterization at intermediate heat treatment steps revealed that the systematic U/Ce heterogeneity features are already present post-gelation and are independent of the superimposed trace Ce-Si-O phase. This work constitutes the first systematic cation distribution study on cross-sections of (U,Ce)O2±x microspheres, executed on a series of compositions, using a combination of elemental mapping techniques.

Nucleation kinetics of reactive crystallization of ammonium di-uranate

ABSTRACT The reactive crystallisation of ammonium di-uranate (NH4U2O7) from uranyl nitrate (UO2 (NO3)2) and ammonia (NH3) is a key process in the nuclear fuel cycle towards uranium-bearing fuel preparation. However, the process kinetics and mechanism remain poorly understood and the modelling of the reactive crystallisation of NH4U2O7(ADU) is not available. Hence, this work aims to determine the kinetics and mechanisms of the nucleation and growth of ADU through induction time measurements by comparing sonochemical and conventional precipitation methods. Induction was measured as functions of initial supersaturation starting from S = 1.07 to S = 1.875 and in a temperature range of 30 °C to 80 °C. The solubility data of ADU were also found experimentally. The trends in the experimental data suggest that two nucleation mechanisms co-exist: heterogeneous and homogeneous nucleation at low and high supersaturations respectively. Due to acoustic cavitation of the ultrasound prompting micromixing, the induction time is markedly reduced in the sonochemical route owing to the reduction of the energy barrier for nucleation. The induction time data were also analysed to calculate the interfacial energy (γ) and other parameters including the radius of the critical nucleus (r*), critical free energy of the nucleus (ΔG*) and nucleation rate (J). Determination of nucleation kinetics gives us insights into the fundamentals of the ADU crystallisation process for control and optimisation. Highlights: Nucleation kinetics of the reactive crystallisation of ADU was studied through classical nucleation theory Induction time data with supersaturation are interpreted by classical nucleation theory and different crystallisation kinetic parameters were determined Homogeneous and heterogeneous nucleation was determined from the correlation A comparison of sonochemical and conventional precipitation shows that in the sonochemical route, the nucleation happens at lower supersaturation with lower induction time because of much lower activation energy requirement All the model data gives us an insight into the crystallisation kinetics to optimise and control the crystallisation process of ADU

Preparation and properties of visible light-cured strippable film for radioactive decontamination

In this research, solutions of styrene-butadiene-styrene block copolymer (SBS) in 2-ethoxyethyl methacrylate (EOEMA) were used to prepare strippable films via rapid visible-light curing, where the mixture of camphorquinone (CQ), diphenylsilane (DPS) and diphenyliodonium hexafluorophosphate (Iod) was employed as the photoinitiating system, LED@405 nm, sunlight or household LED panel light as the light source and no any solvent was involved. The double bond conversion for pure EOEMA under LED@405 nm was firstly monitored by real-time FTIR and it reached 72% within 300 s. The rapid-curing of SBS/EOEMA solutions were systematically investigated and it was found that the solution with 16 wt% SBS became completely dried at the presence of 2.16 mol% crosslinker and 3.6 wt% photoinitiating system after 240 s irradiation under LED@405 nm. The tensile strength, elongation at break and glass transition temperature of the resultant strippable film were determined to be about 4.4 ± 0.5 MPa, 130 ± 11.2% and 6.9 °C, respectively, by mechanical properties testing and DSC measurements. Also, the decontamination efficiencies (DE) of household LED panel light/sunlight cured-strippable film for uranium nitrate on stainless steel, glass, and ceramic surface were evaluated to be higher than 90%. These results indicate that this rapid-curing strippable films would be a good candidate material for large-scale radioactive decontamination.

Challenges in correlating oxygen stable isotope ratios of hydrates on uranium ore concentrates to process waters

Abstract Exchange of oxygen stable isotopes (δ18O values) between precipitation waters and uranium oxides is governed by thermodynamics or kinetics. It has been assumed that meteoric waters can be related to precipitation waters in uranium ore concentrates and their calcined and reduced uranium oxide products. With this assumption, the δ18O values of uranium materials could provide forensic signatures that identify the production history and geolocation of nuclear materials. To further exploit the potential of δ18O values in nuclear material analysis, this study examines the oxygen stable isotope exchange in two UOCs, magnesium diuranate (MDU) and sodium diuranate (SDU). MDU and SDU were synthesized from solutions of uranyl nitrate hexahydrate using precipitation waters with unique oxygen isotope compositions. The structures of the MDU and SDU were analyzed using powder X-ray diffraction (p-XRD) and thermal mass loss curves, while the δ18O values of waters generated during thermal decomposition were analyzed using a thermogravimetric analyzer coupled to an isotope ratio infrared spectrometer (TGA-IRIS). By p-XRD, the MDU was uniform and amorphous across all syntheses with residual crystalline material incorporated as a minor component. Combined with the TGA results, all of the MDU is likely amorphous MgU2O7·3H2O with MgO impurities present throughout. In contrast, the SDU synthesis resulted in multiple phases with many samples exhibiting crystalline phases including a combination of Na(UO2)4O2(OH)5·5H2O and Na2(UO2)6O4(OH)6·8H2O with a Na2U2O7 minor phase. A small fraction of the SDU samples were amorphous with no crystalline XRD peaks observed. Mass loss curves of the SDU samples revealed that the amorphous samples contained inclusions of similar crystalline phases compared to the crystalline materials. The uniformity of the MDU samples enabled highly reproducible measurements of δ18O values of the water vapor yielded from two dehydration events at 170 °C and 500 °C. In contrast, the multiphase composition of the SDU samples resulted in poor reproducibility in δ18O values. Neither system revealed any correlation between the δ18O values of precipitation water and the waters released during dehydration of the UOCs.

Irradiation-enhanced Interactions at UO2/Al2O3/Al Interfaces

Combustion synthesis is used to prepare thin UO2 films on aluminum alloy substrates. This simple preparation method involves electrospraying uranyl nitrate + acetylacetone + 2-methoxyethanol solution on the substrate, followed by a short annealing at 350 or 550 °C. The irradiation of films with a 40Ar2+ ion beam (energy of 1.7 MeV and fluences of 7.7 × 1016 and 1.3 × 1017 ions/cm2) is conducted to investigate irradiation-induced restructuring processes. High-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) investigations show that the annealing temperature significantly influences the crystallinity and stability of materials during irradiation. A small amount of Mg in the alloy substrate diffuses into the amorphous Al2O3 interfacial layer between the film and the substrate. Local thermal spikes from the incoming ions facilitate the irradiation-induced mixing of immiscible Al2O3 and UO2 for the materials prepared at 350 °C. This mass diffusion produces relatively large cavities at the interface. Selective diffusion of a more significant amount of Mg for the materials prepared at 550 °C suppresses the mixing of the Al2O3 interlayer with the film but forms MgyU1–yO2±x solid solutions during irradiation. Local thermal heating triggers the precipitation of a discontinuous crystalline MgO layer close to the film surface. The enhanced and selective diffusion of Mg into the film makes the materials prepared at 550 °C more robust and mechanically stable than those prepared at 350 °C.

Acute radiation sickness due to critical accidents at a nuclear production facility

Introduction. Nuclear accidents are rare, however, today they cannot be entirely excluded. Thereupon the wealth of global experience is of particular value for prediction of outcomes that potentially follow short-term exposures to ionizing radiation at high dose rates.The objective is to describe clinical simptoms and signs in workers exposed to acute gamma-neutron radiation.Methodology. This paper considers healths effects after radiation exposure due to a critical accident that happened on January, 2 1958 during operations with an experimental flask containing uranium nitrate solution at the Mayak PA. During accident four workers were exposed to short-term gamma-neutron radiation and subsequently suffered from acute radiation syndrome of different severity degree.Results and discussion. Symptoms of the initial response, development of disorders in various organs and systems and the course of the acute radiation syndrome in exposed individuals are described.Conclusion. Multiple organs or tissues are involved in severe acute radiation syndrome at an early period after acute exposure, at that cardiovascular collapse is the most critical physiological state. Multiple organs or tissues failure in the longtrem period after acute exposure is a secondary manifestation both of the primary nonspecific response to radiation and specific radiation-induced direct damage of highly sensitive cells