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Stephen Liddle, Erli Lu, Ashley Wooles, Mathew Gregson, Philip Cobb
Reaction of the uranium silyl-phosphino-carbene complex [U{C(SiMe3)(PPh2)}(BIPM)(μ-Cl)Li(TMEDA)(μ-TMEDA)0.5]2 (1, BIPM = C(PPh2NSiMe3)2; TMEDA = Me2NCH2CH2NMe2) with the rhodium chloride compound [Rh(μ-Cl)(COD)]2 (COD = cyclo-octadiene) affords the unprecedented heterotrimetallic UIV-RhI2 complex [U(Cl)2{C(PPh2NSiMe3)(PPh[C6H4]NSiMe3)}{Rh(COD)}{Rh(CH(SiMe3)(PPh2)}] (2). Complex 2 exhibits one, very short, uranium-rhodium distance that is by some margin the shortest uranium-rhodium bond on record, one of the shortest absolute uranium-metal distances generally, and the shortest actinide-transition metal bond in terms of formal shortness ratio...
April 17, 2018: Angewandte Chemie
Hao Wang, Nathan Lau, Ryan M Gerdes
OBJECTIVE: The aim of this study was to apply work domain analysis for cybersecurity assessment and design of supervisory control and data acquisition (SCADA) systems. BACKGROUND: Adoption of information and communication technology in cyberphysical systems (CPSs) for critical infrastructures enables automated and distributed control but introduces cybersecurity risk. Many CPSs employ SCADA industrial control systems that have become the target of cyberattacks, which inflict physical damage without use of force...
April 1, 2018: Human Factors
Beatriz Baselga-Cervera, Julia Romero-López, Camino García-Balboa, Eduardo Costas, Victoria López-Rodas
The extraction and processing of uranium (U) have polluted large areas worldwide, rendering anthropogenic extreme environments inhospitable to most species. Noticeably, these sites are of great interest for taxonomical and applied bioprospection of extremotolerant species successfully adapted to U tailings contamination. As an example, in this work we have studied a microalgae species that inhabits extreme U tailings ponds at the Saelices mining site (Salamanca, Spain), characterized as acidic (pH between 3 and 4), radioactive (around 4 μSv h-1 ) and contaminated with metals, mainly U (from 25 to 48 mg L-1 ) and zinc (from 17 to 87 mg L-1 )...
2018: Frontiers in Microbiology
Alexander Timofeev, Artaches A Migdisov, Anthony E Williams-Jones, Robert Roback, Andrew T Nelson, Hongwu Xu
The behavior of uranium in environments, ranging from those of natural systems responsible for the formation of uranium deposits to those of nuclear reactors providing 11% of the world's electricity, is governed by processes involving high-temperature aqueous solutions. It has been well documented that uranium is mobile in aqueous solutions in its oxidized, U6+ state, whereas in its reduced, U4+ state, uranium has been assumed to be immobile. Here, we present experimental evidence from high temperature (>100 °C) acidic brines that invalidates this assumption...
April 16, 2018: Nature Communications
Katherine E Zychowski, Vamsi Kodali, Molly Harmon, Christina Tyler, Bethany Sanchez, Yoselin Ordonez Suarez, Guy Herbert, Abigail Wheeler, Sumant Avasarala, José M Cerrato, Nitesh K Kunda, Pavan Muttil, Chris Shuey, Adrian Brearley, Abdul-Mehdi Ali, Yan Lin, Mohammad Shoeb, Aaron Erdely, Matthew J Campen
Background: Exposure to windblown particulate matter (PM) arising from legacy uranium (U) mine sites in the Navajo Nation may pose a human health hazard due to their potentially high metal content, including U and vanadium (V). Objective: To assess the toxic impact of PM derived from Claim 28 (a priority U mine) compared to background PM, and consider the putative role of metal species U and V. Methods: Two representative sediment samples from Navajo Nation sites (Background PM and Claim 28 PM) were obtained, characterized in terms of chemistry and morphology, and fractioned to the respirable (≤10μm) fraction...
April 5, 2018: Toxicological Sciences: An Official Journal of the Society of Toxicology
Zhengyang Li, Zhenbing Cai, Yanping Wu, Xiandong Meng, Dongxu Zhang
A fretting wear experiment with uranium has been performed on a linear reciprocating tribometer with ball-on-disk contact. This study focused on the fretting behavior of the uranium under different atmospheres (Ar, Air (21% O₂ + 78% N₂), and O₂) and vacuum conditions (1.05 and 1 × 10−4 Pa). Evolution of friction was assessed by coefficient of friction (COF) and friction-dissipated energy. The oxide of the wear surface was evaluated by Raman spectroscopy. The result shows that fretting wear behavior presents strong atmosphere and vacuum condition dependence...
April 16, 2018: Materials
M Tirmarche
The International Commission on Radiological Protection (ICRP) mandated a task group (Task Group 64) to review recently published epidemiological studies related to cancer risk and incorporated alpha emitters, and to evaluate whether the results might consolidate or challenge assumptions underlying the current radiation protection system. Three major alpha emitters were considered: radon and its decay products, plutonium, and uranium. Results came mainly from cohorts of workers, while for radon, major studies of the general population contributed to a better understanding of the risk of lung cancer at low and chronic exposure...
January 1, 2018: Annals of the ICRP
Jamal Asfahani
Multifractal Concentration-Number (C-N) modeling approach has been developed and applied to Airborne Gamma Spectrometry (AGS) data related to Area-3, Northern Palmyrides, Syria. The application of the multifractal approach basically aimed at separating uranium anomalies from background. The AGS technique has been applied for uranium exploration in Syria, where four radioactive parameters were recorded, T.C, eU, eTh, and K%. Log-log plots practiced on those radioactive variables indicate the presence of different uranium anomaly ranges...
March 19, 2018: Applied Radiation and Isotopes
Santiago Hurtado-Bermúdez, María Villa-Alfageme, José Luis Mas, María Dolores Alba
The development of Deep Geological Repositories (DGP) to the storage of high-level radioactive waste (HLRW) is mainly focused in systems of multiple barriers based on the use of clays, and particularly bentonites, as natural and engineered barriers in nuclear waste isolation due to their remarkable properties. Due to the fact that uranium is the major component of HLRW, it is required to go in depth in the analysis of the chemistry of the reaction of this element within bentonites. The determination of uranium under the conditions of HLRW, including the analysis of silicate matrices before and after the uranium-bentonite reaction, was investigated...
April 5, 2018: Applied Radiation and Isotopes
Hang Wen, Zezhen Pan, Daniel E Giammar, Li Li
Phosphate amendment has shown promise for enhancing uranium immobilization. The mechanism of the enhancement however has remained unclear with contrasting observations under different geochemical conditions. A dual-domain reactive transport model (RTM) is developed here based on batch and column experimental data to understand the mechanisms and to explore the effectiveness of enhanced U(VI) immobilization under variable geochemical and flow conditions. Modeling results indicate that under low U(VI) conditions in natural waters, phosphate addition promotes immobilization through the formation of U(VI)-phosphate ternary surface complexes and the precipitation of calcium phosphate, both decreasing the concentrations of mobile U(VI)-Ca-CO3 aqueous complexes...
April 12, 2018: Environmental Science & Technology
Jiahui Zhu, Qi Liu, Zhanshuang Li, Jingyuan Liu, Hongsen Zhang, Rumin Li, Jun Wang
In this paper, titanate nanotubes/cobalt ferrite/tetraethylenepentamine (TNTs/CoFe2 O4 /TEPA) adsorbents were prepared for the adsorption of uranium (VI) from the solution. Its morphology was observed by transmission electron microscopy (TEM) and exhibited the uniform well tubular structure. TNTs/CoFe2 O4 /TEPA composites were easily separated from solution by an external magnetic field. The removal of uranium (VI) from aqueous solution (ppm level) and simulated seawater (ppb level) were investigated by the TNTs/CoFe2 O4 /TEPA composites...
March 22, 2018: Journal of Hazardous Materials
Divya T V, Pallavi Chandwadkar, Celin Acharya
Metallothioneins (MTs) are low molecular weight, sulfhydryl-containing, cysteine-rich, metal-binding proteins. Eukaryotes have multiple metallothionein genes; however, there is dearth of reports on prokaryotic metallothioneins. Bacterial MTs with SmtA from Synechococcus PCC 7942 as prototype have been studied in the context of cadmium detoxification. In this study, a smtA related ORF, namely nmtA, was identified in the heterocystous, nitrogen-fixing cyanobacterium, Anabaena PCC 7120. A recombinant N-terminal histidine-tagged Anabaena NmtA protein was overexpressed in Escherichia coli and purified...
March 30, 2018: Aquatic Toxicology
X Y Zheng, Y H Shen, X Y Wang, T S Wang
Biosorption of radionuclides by microorganisms is a promising and effective method for the remediation of contaminated areas. pH is the most important factor during uranium biosorption by Saccharomyces cerevisiae because the pH value not only affects the biosorption rate but also affects the precipitation structure. This study investigated the effect of pH on uranium (VI) biosorption and biomineralization by S. cerevisiae. Cells have the ability to buffer the solution to neutral, allowing the biosorption system to reach an optimal level regardless of the initial pH value...
March 26, 2018: Chemosphere
Andrew Miskowiec
The DFT+U approach, where U is the Hubbard-like on-site Coulomb interaction, has successfully been used to improve the description of transition metal oxides and other highly correlated systems, including actinides. The secret of the DFT+U approach is the breaking of d or f shell orbital degeneracy and adding an additional energetic penalty to non-integer occupation of orbitals. A prototypical test case, UO2, benefits from the +U approach whereby the bare LDA method predicts UO2 to be a ferromagnetic metal, whereas LDA+U correctly predicts UO2 to be insulating...
April 3, 2018: Physical Chemistry Chemical Physics: PCCP
(no author information available yet)
No abstract text is available yet for this article.
April 2018: Journal of Nuclear Medicine: Official Publication, Society of Nuclear Medicine
F Luo, R Han, Z Chen, Y Nie, Q Sun, F Shi, S Zhang, G Tian, L Song, X Ruan, M Y Ye
The accelerator driven subcritical system (ADS) is regarded as a safe and clean nuclear power system, which can be used for the transmutation of nuclear waste and the breeding of nuclear fuel. In this study, in order to validate nuclear data and the neutron transportation performance of the materials related to ADS, we measured the leakage neutron spectra from multiple-slab sample assemblies using 14.8 MeV D-T neutrons. Two types of assemblies comprising A-1 (W+U+C+CH2 ) and A-2 (U+C+CH2 ) were both built up gradually starting with the first wall...
March 26, 2018: Applied Radiation and Isotopes
Haijian Li, Philip Kegler, Dirk Bosbach, Evgeny V Alekseev
Four novel uranyl silicates and germanates with framework structures, K4 Na2 (UO2 )3 (Si2 O7 )2 ·3H2 O, K4 Na2 (UO2 )3 (Ge2 O7 )2 ·3H2 O, H3 O(UO2 )2 (HGe2 O7 )·2H2 O, and Na2 (UO2 )GeO4 , have been synthesized by means of the hydrothermal method. The structures of the title compounds were refined by single-crystal X-ray diffraction and characterized by Raman spectroscopy. We used the method of secondary building units (SBUs) for a crystal chemical analysis of the 3D framework and their topologies. The framework of the K4 Na2 (UO2 )3 (T2 O7 )2 ·3H2 O (T = Si, Ge) series exhibits large 14-membered rings and smaller 8-membered rings which are built upon [UT4 ] pentamers...
April 2, 2018: Inorganic Chemistry
Kristen A Pace, Vancho Kocevski, Stavros G Karakalos, Gregory Morrison, Theodore Besmann, Hans-Conrad Zur Loye
The first entirely pentavalent uranium borate, Na2 (UO2 )(BO3 ), was synthesized under mild hydrothermal conditions. The single-crystal structure was solved in the orthorhombic space group Cmcm with a = 10.0472(3) Å, b = 6.5942(2) Å, and c = 6.9569(2) Å. Magnetic susceptibility measurements revealed an antiferromagnetic transition at 12 K and an effective magnetic moment of 2.33 μB . Density functional theory calculations indicated dynamic stability of the structure above 0 K.
April 2, 2018: Inorganic Chemistry
F R M Matamet, D M Bonotto
The Constant Flux and Constant Sedimentation (CF:CS) of supported/excess210 Pb model was successfully used to study sediment profiles from Antas stream, located in the region of Poços de Caldas city, Minas Gerais State, Brazil. Historical changes in the region were tracked from evaluating the sedimentation rate by the210 Pb method. In that site, Osamu Utsumi mine was the first mining-industrial complex for the production of concentrated uranium in Brazil. Four sediment testimonies were sampled along Antas stream in order to determine sedimentation rates using210 Pb as geochronometer...
March 22, 2018: Applied Radiation and Isotopes
Jungjin Kim, HyunJu Kim, Won-Seok Kim, Wooyong Um
This study determined the dissolution rate of studtite, (UO2 )O2 (H2 O)4 , which can be formed by reaction between H2 O2 and UO2 2+ that leaks from spent nuclear fuel (SNF) in deep geological repositories. The batch dissolution experiments were conducted using synthesized studtite under different solution conditions with varying pHs and concentrations of HCO3 - and [H2 O2 ] in synthetic groundwater. The experimental results suggested that carbonate ligand and H2 O2 in groundwater accelerated the dissolution of studtite and uranium (U) release...
March 28, 2018: Journal of Environmental Radioactivity
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