Nature can efficiently recognize specific ions by exerting second-sphere interactions onto well-folded protein scaffolds. However, a considerable challenge remains to artificially manipulate such ...affinity, while being cost-effective in managing immense amounts of water samples. Here, we propose an effective approach to regulate uranyl capture performance by creating bio-inspired nano-traps, illustrated by constructing chelating moieties into porous frameworks, where the binding motif's coordinative interaction towards uranyl is enhanced by introducing an assistant group, reminiscent of biological systems. Representatively, the porous framework bearing 2-aminobenzamidoxime is exceptional in sequestering high uranium concentrations with sufficient capacities (530 mg g
) and trace quantities, including uranium in real seawater (4.36 mg g
, triple the benchmark). Using a combination of spectroscopic, crystallographic, and theory calculation studies, it is revealed that the amino substituent assists in lowering the charge on uranyl in the complex and serves as a hydrogen bond acceptor, boosting the overall uranyl affinity of amidoxime.
Featured Cover Yu, Xiao‐Ying; Yao, Jennifer; Buck, Edgar C. ...
Surface and interface analysis,
July 2020, 2020-07-00, 20200701, Letnik:
52, Številka:
7
Journal Article
Recenzirano
The cover image is based on the Short Communication In situ liquid SIMS analysis of uranium oxide by Xiao‐Ying Yu et al., https://doi.org/10.1002/sia.6799.
The radionuclide sup.99Mo, which has a half-life of 65.94 h was produced from sup.238U(γ, f) and sup.100Mo(γ, n) reactions using a 10 MeV electron linac at EBC, Kharghar Navi-Mumbai, India. This has ...been investigated since the daughter product sup.99mTc is very important from a medical point of view and can be produced in a generator from the parent sup.99Mo. The activity of sup.99Mo was analyzed by a γ-rays spectrometric technique using a HPGe detector. From the detected γ-rays activity of 140.5 and 739.8 keV, the amount of sup.99Mo produced was determined. For comparison, the amount of sup.99Mo from sup.238U(γ, f) and sup.100Mo(γ, n) reactions was also estimated using the experimental photon flux from sup.197Au(γ, n) sup.196Au reaction. The amount of sup.99Mo from the detected γ-lines is in agreement with the estimated value for sup.238U(γ, f) and sup.100Mo(γ, n) reactions. The production of sup.99Mo activity from sup.238U(γ, f) and sup.100Mo(γ, n) reactions is a relevant and novel approach, which provides alternative routes to sup.235,238U(n, f) and sup.98Mo(n, γ) reactions, circumventing the need for a reactor. The viability and practicality of the sup.99Mo production from the sup.238U(γ, f) and sup.100Mo(γ, n) reactions alternative to sup.235,238U(n, f) and sup.98Mo(n, γ) reactions has been emphasize. An estimate has been also arrived based on the experimental data of present work to fulfill the requirement of DOE. Keywords Medical isotope sup.99Mo-sup.99mTc * Photo-fission and reaction * sup.238U(γ, f), sup.100Mo(γ, n) * E.sub.γ = 10 MeV * Off-line γ-ray spectrometry
This manuscript deals with the development of ICP-OES based methodology for the determination critical elements: B, Cd, Eu, Sm, Gd and Dy in U.sub.3Si.sub.2 matrix. The sample was dissolved in ...HNO.sub.3 with catalytic amount of HF. To avoid spectral interference of uranium, five contacts of TOPO-CCl.sub.4 have been given for preferential separation of U, leaving behind the critical elements into the aqueous phase. Though measurable quantity of Si was also co-extracted with U into the organic phase; however, the critical elements remained in aqueous phase. Five contacts of organic phase were found to be sufficient in bringing down concentration of U below tolerance level in aqueous raffinate. This methodology was validated using synthetic samples. The optimization was done by choosing interference free analytical lines of the analytes, determination of detection limits, linear dynamic range, sensitivity and precision. Actual samples were analyzed using the optimized methodology and the results were found to be satisfactory.
Present study evaluates distribution of .sup.210Pb and .sup.210Po in soil around uranium mineralized region of East Singhbhum district, Jharkhand, India. The overall median activity concentration of ....sup.210Pb and .sup.210Po in soil was observed to be 95 ± 35 Bq kg.sup.-1 and 79 ± 35 Bq kg.sup.-1, respectively. Based on KS test, both the radionuclides follow normal distribution in the study area. The extent of disequilibrium in soil is evaluated using .sup.210Po/.sup.210Pb activity ratio. Also, comparison between cultivated and virgin (uncultivated) lands based on activity concentration of .sup.210Pb and .sup.210Po and .sup.210Po/.sup.210Pb activity ratio has been carried out. Higher median activity concentration of both the radionuclides were observed in cultivated soil compared to uncultivated soil. Comparison of .sup.210Po/.sup.210Pb ratio indicates higher degree of radioactive disequilibrium in cultivated soils (.sup.210Po/.sup.210Pb = 0.70) compared to uncultivated soils (.sup.210Po/.sup.210Pb = 0.99). Further, correlation study indicated significant difference between cultivated and uncultivated soils with respect to .sup.210Po and .sup.210Pb. The observed difference between cultivated and uncultivated soil could be due to physical and chemical alterations of cultivated land during farming practices.
Uranium speciation and physical–chemical characteristics were studied in solids precipitated from synthetic acidic to circumneutral wastewaters in the presence and absence of dissolved silica and ...phosphate to examine thermodynamic and kinetic controls on phase formation. Composition of synthetic wastewater was based on disposal sites 216-U-8 and 216-U-12 Cribs at the Hanford site (WA, USA). In the absence of dissolved silica or phosphate, crystalline or amorphous uranyl oxide hydrates, either compreignacite or meta-schoepite, precipitated at pH 5 or 7 after 30 d of reaction, in agreement with thermodynamic calculations. In the presence of 1 mM dissolved silica representative of groundwater concentrations, amorphous phases dominated by compreignacite precipitated rapidly at pH 5 or 7 as a metastable phase and formation of poorly crystalline boltwoodite, the thermodynamically stable uranyl silicate phase, was slow. In the presence of phosphate (3 mM), meta-ankoleite initially precipitated as the primary phase at pH 3, 5, or 7 regardless of the presence of 1 mM dissolved silica. Analysis of precipitates by U LIII-edge extended X-ray absorption fine structure (EXAFS) indicated that “autunite-type” sheets of meta-ankoleite transformed to “phosphuranylite-type” sheets after 30 d of reaction, probably due to Ca substitution in the structure. Low solubility of uranyl phosphate phases limits dissolved U(VI) concentrations but differences in particle size, crystallinity, and precipitate composition vary with pH and base cation concentration, which will influence the thermodynamic and kinetic stability of these phases.
"This book examines the prospects and challenges of a global phase-out of highly enriched uranium and the risks of this material otherwise being used by terrorists to make atom bombs. Terrorist ...groups, such as Al Qaeda, have demonstrated repeatedly that they seek to acquire nuclear weapons. Unbeknownst even to many security specialists, tons of bomb-grade uranium are trafficked legally each year for ostensibly peaceful purposes. If terrorists obtained even a tiny fraction of this bomb-grade uranium they could potentially construct a nuclear weapon like the one dropped on Hiroshima that killed tens of thousands. Nuclear experts and policymakers have long known of this danger but - so far - have taken only marginal steps to address it. This volume begins by highlighting the lessons of past successes where bomb-grade uranium commerce has been eliminated, such as from Argentina's manufacture of medical isotopes. It then explores the major challenges that still lie ahead: for example, Russia's continued use of highly enriched uranium (HEU) in dozens of nuclear facilities. Each of the book's thirteen case studies offers advice for reducing HEU in a specific sector. These insights are then amalgamated into eight concrete policy recommendations for U.S. and world leaders to promote a global phase-out of bomb-grade uranium. This book will be of much interest to students of nuclear proliferation, global governance, international relations and security studies"--
Small modular reactor's development provides an alternative option for potentially using nuclear power more economically and effectively. SMART is the world's first licensed, integral, small ...pressurised water reactor. However, it should still be optimised for the UK's energy market. This thesis has used the stochastic method Monte Carlo codes MONK and OpenMC to investigate the neutronic related behaviours and assess the proposed optimisations. The numerical models based on both codes have been validated and verified, especially to the open-source code OpenMC. The neutron transport simulation and depletion calculation results show that a beryllium-based reflector material would significantly improve fuel assemblies' utilisation rate at the core edge area. This would give higher power output and reduce the frequency of reactor shutdown and refuelling. In addition to the beryllium oxide reflector, three types of variant fuel layout were designed. They respectively occupy 57,44,28 high enrichment fuel assemblies at different positions. This thesis then proposes two hypothetical construction paths to the staggered build of a giga-watt scale,10 SMART unit power station by combining and switching the core layout. Both paths could self-sustain the reloading fuels and, most importantly, decrease the demand for fresh fuel in every refuelling period.
The eastern boundary region of the southeastern Pacific Ocean hosts one of the world's most dynamic and productive upwelling systems with an associated oxygen minimum zone (OMZ). The variability in ...downward export fluxes in this region, with strongly varying surface productivity, upwelling intensities and water column oxygen content, is however poorly understood. Thorium-234 (.sup.234 Th) is a powerful tracer to study the dynamics of export fluxes of carbon and other elements, yet intense advection and diffusion in nearshore environments impact the assessment of depth-integrated .sup.234 Th fluxes when not properly evaluated. Here we use vessel-mounted acoustic Doppler current profiler (VmADCP) current velocities, satellite wind speed and in situ microstructure measurements to determine the magnitude of advective and diffusive fluxes over the entire .sup.234 Th flux budget at 25 stations from 11 to 16.sup." S in the Peruvian OMZ. Contrary to findings along the GEOTRACES P16 eastern section, our results showed that weak surface wind speed during our cruises induced low upwelling rates and minimal upwelled .sup.234 Th fluxes, whereas vertical diffusive .sup.234 Th fluxes were important only at a few shallow shelf stations. Horizontal advective and diffusive .sup.234 Th fluxes were negligible because of small alongshore .sup.234 Th gradients. Our data indicated a poor correlation between seawater .sup.238 U activity and salinity. Assuming a linear relationship between the two would lead to significant underestimations of the total .sup.234 Th flux by up to 40 % in our study. Proper evaluation of both physical transport and variability in .sup.238 U activity is thus crucial in coastal .sup.234 Th flux studies. Finally, we showed large temporal variations on .sup.234 Th residence times across the Peruvian upwelling zone and cautioned future carbon export studies to take these temporal variabilities into consideration while evaluating carbon export efficiency.
Extraction of uranium from seawater is critical for the sustainable development of nuclear energy. However, the currently available uranium adsorbents are hampered by co-existing metal ion ...interference. DNAzymes exhibit high selectivity to specific metal ions, yet there is no DNA-based adsorbent for extraction of soluble minerals from seawater. Herein, the uranyl-binding DNA strand from the DNAzyme is polymerized into DNA-based uranium extraction hydrogel (DNA-UEH) that exhibits a high uranium adsorption capacity of 6.06 mg g
with 18.95 times high selectivity for uranium against vanadium in natural seawater. The uranium is found to be bound by oxygen atoms from the phosphate groups and the carbonyl groups, which formed the specific nano-pocket that empowers DNA-UEH with high selectivity and high binding affinity. This study both provides an adsorbent for uranium extraction from seawater and broadens the application of DNA for being used in recovery of high-value soluble minerals from seawater.
PDF
