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Sven Boden, Koen Vints, Simone Cagno, Dominic Maertens, Karen Van Hecke, Thomas Cardinaels
Thorium-229 is a valuable, but scarce, radionuclide for nuclear clock applications or targeted alpha therapy. While it is mostly produced by the decay of (233)U, (229)Th can also be produced by neutron irradiation of (226)Ra. At SCK•CEN, capsules containing mainly (228)Th (by-product of (226)Ra irradiation) were characterized to quantify the present amounts of (229)Th, (228)Th, (227)Ac, (226)Ra with high resolution gamma spectroscopy, after a decay period of 40 years in which (228)Th has decayed. High purity (229)Th was quantified, and after recovery using radiochemical separation processes, it can be used to support ongoing research...
November 24, 2016: Applied Radiation and Isotopes
Andrew C Behrle, Alexander J Myers, Pokpong Rungthanaphatsophon, Wayne W Lukens, Charles L Barnes, Justin R Walensky
The synthesis and characterisation of a rare U(iii) alkyl complex, U[η(4)-Me2NC(H)C6H5]3, using the dimethylbenzylamine (DMBA) ligand has been accomplished. While attempting to prepare the U(iv) compound, reduction to the U(iii) complex occurred. In the analogous Th(iv) system, C-H bond activation of a methyl group of one dimethylamine was observed yielding Th[η(4)-Me2NC(H)C6H5]2[η(5)-(CH2)MeNC(H)C6H5] with a dianionic DMBA ligand. The utility of these complexes as starting materials has been analyzed using a bulky dithiocarboxylate ligand to yield tetravalent actinide species...
November 16, 2016: Chemical Communications: Chem Comm
Gina E Moseley, Yuri V Dublyansky, R Lawrence Edwards, Kathleen A Wendt, Mathieu Pythoud, Pu Zhang, Hai Cheng, Yanbin Lu, Ronny Boch, Christoph Spötl
Winograd and Coplen question the thorium-230 distribution model proposed to explain the age bias observed with increasing depth during Termination II. We have evaluated both criticisms and find that all samples display virtually identical fabrics, argue that the modern setting is not analogous to the conditions during Termination II, and reiterate the robustness of our age models. Our conclusions remain unchanged.
October 21, 2016: Science
Tyler B Coplen
Moseley et al's (Reports, 8 January 2016, p. 165) preferred-Termination-II age is subjective, as evidenced by variation in their Termination-II ages of 2500 years per meter. Termination-II-age bias decreases to zero at ~1.5 meters below the present-day water table, if one assumes linear variation with core-sample height. Maintaining the required gradient of thorium isotope (230)Th over 3.6 meters for 1000 years, much less 10,000 years, seems exceedingly unlikely.
October 21, 2016: Science
Isaac J Winograd
Moseley et al (Reports, 8 January 2016, p. 165) postulate an increase in dissolved thorium isotope (230)Th with depth below the water table as the explanation for the differing ages of Termination II. Flow of geothermal water through the Devils Hole caverns precludes this explanation. Deposition of younger secondary calcite into the initial porosity of the calcite comprising their cores is a plausible alternate explanation.
October 21, 2016: Science
Peter N Eze, Valiant S Mosokomani, Theophilus K Udeigwe, Opeoluwa F Oyedele, Adeniyi F Fagbamigbe
Geospatial dataset of trace elements including manganese (Mn), iron (Fe), titanium (Ti), rubidium (Rb), strontium (Sr), thorium (Th), Vanadium (V) and Zirconium (Zr) of near-surface soils in a Cu-Ni prospecting field at Airstrip North, Central Botswana were statistically analysed. Grid sampling method was used in the field data collection. The relatively new portable X-ray fluorescence spectrometer (Delta Premium, 510890, USA) technology in a "soil" mode was used to measure the concentrations of trace elements in the soils...
December 2016: Data in Brief
Ashley E Sharpe, George D Kamenov, Adrian Gilli, David A Hodell, Kitty F Emery, Mark Brenner, John Krigbaum
We examined the potential use of lead (Pb) isotopes to source archaeological materials from the Maya region of Mesoamerica. The main objectives were to determine if: 1) geologic terrains throughout the Maya area exhibit distinct lead isotope ratios (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb), and 2) a combination of lead and strontium ratios can enhance sourcing procedures in the Mesoamerica region. We analyzed 60 rock samples for lead isotope ratios and a representative subset of samples for lead, uranium, and thorium concentrations across the Maya region, including the Northern Lowlands of the Mexican Yucatan Peninsula, the Southern Lowlands of Guatemala and Belize, the Volcanic Highlands, the Belizean Maya Mountains, and the Metamorphic Province/Motagua Valley...
2016: PloS One
Ilya Captain, Gauthier J-P Deblonde, Peter B Rupert, Dahlia D An, Marie-Claire Illy, Emeline Rostan, Corie Y Ralston, Roland K Strong, Rebecca J Abergel
Targeted α therapy holds tremendous potential as a cancer treatment: it offers the possibility of delivering a highly cytotoxic dose to targeted cells while minimizing damage to surrounding healthy tissue. The metallic α-generating radioisotopes (225)Ac and (227)Th are promising radionuclides for therapeutic use, provided adequate chelation and targeting. Here we demonstrate a new chelating platform composed of a multidentate high-affinity oxygen-donating ligand 3,4,3-LI(CAM) bound to the mammalian protein siderocalin...
November 1, 2016: Inorganic Chemistry
Per Søstrand, Langård Sverre, Tor Erik Danielsen
Inhalation of escaping radon from groundwater comprises the largest part of radiological hazard from groundwater radionuclides in the uranium and thorium series. Groundwater containing 1.5 mg dm uranium and 3 kBq dm radon activity concentration supplied an ordinary bathroom of 15 m in a home. Using the showerhead, atmospheric levels of radon activity in the bathroom exceeded 100 kBq m within a period of about 1 h.
December 2016: Health Physics
J R Griswold, D G Medvedev, J W Engle, R Copping, J M Fitzsimmons, V Radchenko, J C Cooley, M E Fassbender, D L Denton, K E Murphy, A C Owens, E R Birnbaum, K D John, F M Nortier, D W Stracener, L H Heilbronn, L F Mausner, S Mirzadeh
Actinium-225 and (213)Bi have been used successfully in targeted alpha therapy (TAT) in preclinical and clinical research. This paper is a continuation of research activities aiming to expand the availability of (225)Ac. The high-energy proton spallation reaction on natural thorium metal targets has been utilized to produce millicurie quantities of (225)Ac. The results of sixteen irradiation experiments of thorium metal at beam energies between 78 and 192MeV are summarized in this work. Irradiations have been conducted at Brookhaven National Laboratory (BNL) and Los Alamos National Laboratory (LANL), while target dissolution and processing was carried out at Oak Ridge National Laboratory (ORNL)...
September 28, 2016: Applied Radiation and Isotopes
Alvaro Muñoz-Castro, R Bruce King
The experimentally characterized endohedral metallic fullerenes involving the small C28 cage, has shown to be able to encapsulate zirconium, hafnium, and uranium atoms, among other elements. Here, we explore the formation and nature of concentric bonds from purely d- to f-block elements, given by Zr, Hf, and uranium, along a borderline metal between such blocks, thorium. We explore the interplay of d- and f-orbitals in the chemistry of the early actinides, where the features of a d- or f-block metal can be mixed...
January 5, 2017: Journal of Computational Chemistry
Adel Mesbah, Nicolas Clavier, M Janeth Lozano-Rodriguez, Stephanie Szenknect, Nicolas Dacheux
Pure powdered compounds with a general formula Th1-xErx(SiO4)1-x(PO4)x belonging to the zircon-xenotime family were successfully synthesized under hydrothermal conditions (250 °C, 7 days) as recently reported for the preparation of coffinite. Therefore, a thorough, combined PXRD, EDX, EXAFS, Raman, and FTIR analysis showed the formation of a solid solution in agreement with Vegard's law. Moreover, the examination of the local structure shows that the Th-O distances remain close to those found in ThSiO4, whereas the Er-O distances show a significant decrease from 2...
October 17, 2016: Inorganic Chemistry
Hilary P Emerson, Katherine A Hickok, Brian A Powell
Previous field experiments have suggested colloid-facilitated transport via inorganic and organic colloids as the primary mechanism of enhanced actinide transport in the subsurface at former nuclear weapons facilities. In this work, research was guided by the hypothesis that humic substances can enhance tetravalent actinide (An(IV)) migration by coating and mobilizing natural colloids in environmental systems and increasing An(IV) sorption to colloids. This mechanism is expected to occur under relatively acidic conditions where organic matter can sorb and coat colloid surfaces and facilitate formation of ternary colloid-ligand-actinide complexes...
December 2016: Journal of Environmental Radioactivity
Alasdair Formanuik, Fabrizio Ortu, Christopher Inman, Andrew Kerridge, Ludovic Castro, Laurent Maron, David Paul Mills
Improving our comprehension of diverse CO2 activation pathways is of vital importance for the widespread future utilization of an abundant greenhouse gas. CO2 activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO2 is readily reduced to CO, but isolated thorium(III) CO2 activation is unprecedented. We show that the thorium(III) complex, [Th(Cp'')3] (1, Cp'' = {C5H3(SiMe3)2-1,3}), reacts with CO2 to give the mixed oxalate-carboxylate thorium(IV) complex [{Th(Cp'')2[κ2-O2C{C5H3-3,3'-(SiMe3)2}]}2(µ-κ2:κ2-C2O4)] (3)...
October 7, 2016: Chemistry: a European Journal
Anne E V Gorden, Michael L McKee
The stability of Th(4+) to reduction in water is studied by DFT methods. The standard reduction potential (SRP) of homoleptic complexes including Th(H2O)9(4+), Th(H2O)10(4+), Th(NO3)4, Th(NO2)6(2-), Th(NO3)6(2-), Th(COT)2, Th(acac)4, ThCp4, ThF4, and ThCl4 have been investigated. The values vary widely (from -3.50 V for Th(OH)4 to -0.62 V for Th(NO3)4 depending on whether the ligands are redox active (noninnocent) or not. Several additional topics of thorium chemistry are explored, including the hydrolysis mechanism of ThO2(H2O)n, n = 1, 2, 4, and the solution phase nonzero dipole moment of ThCp4...
October 7, 2016: Journal of Physical Chemistry. A
Mary E Garner, Stephan Hohloch, Laurent Maron, John Arnold
Actinide complexes demonstrate unparalleled reactivity towards small molecules. However, utilizing these powerful transformations in a predictable and deliberate manner remains challenging. Therefore, developing actinide systems that not only perform noteworthy chemistry but also demonstrate controllable reactivity is a key goal. We describe a bis(NHC)borate thorium-bpy complex (1) that is capable of reductively cleaving the R-NC bond in a series of organic isocyanides. In contrast to most actinide-mediated bond activations, the dealkylation event mediated by 1 is remarkably general and yields very well-defined products that assist in mechanistic elucidation...
October 24, 2016: Angewandte Chemie
Elizabeth P Wildman, Gábor Balázs, Ashley J Wooles, Manfred Scheer, Stephen T Liddle
Despite the burgeoning field of uranium-ligand multiple bonds, analogous complexes involving other actinides remain scarce. For thorium, under ambient conditions only a few multiple bonds to carbon, nitrogen, oxygen, sulfur, selenium and tellurium are reported, and no multiple bonds to phosphorus are known, reflecting a general paucity of synthetic methodologies and also problems associated with stabilising these linkages at the large thorium ion. Here we report structurally authenticated examples of a parent thorium(IV)-phosphanide (Th-PH2), a terminal thorium(IV)-phosphinidene (Th=PH), a parent dithorium(IV)-phosphinidiide (Th-P(H)-Th) and a discrete actinide-phosphido complex under ambient conditions (Th=P=Th)...
2016: Nature Communications
Jian Lin, Geng Bang Jin, L Soderholm
A neutral-framework thorium oxohydroxosulfate hydrate has been isolated from aqueous solution. This microporous structure, which self-assembles without a templating agent, is built from [Th6(OH)4O4(H2O)6](12+) hexamers and thorium(IV) monomers linked through bridging sulfates. Solution conditions were chosen to enable an active competition between sulfate and hydroxide for thorium coordination. Synthetic requirements are discussed for this rare example of a thorium(IV) polynuclear complex containing mixed oxo-, hydroxo-, and sulfato-bridging moieties...
October 17, 2016: Inorganic Chemistry
Merve Sasmaz, Erdal Obek, Ahmet Sasmaz
This study focused on the ability of Lemna minor and Lemna gibba to remove U and Th in the tailing water of Keban, Turkey. These plants were placed in tailing water and individually fed to the reactors designed for these plants. Water and plant samples were collected daily from the mining area. The plants were ashed at 300°C for 1 day and analyzed by ICP-MS for U and Th. U was accumulated as a function of time by these plants, and performances between 110 % and 483 % for L. gibba, and between 218 % and 1194 % for L...
December 2016: Bulletin of Environmental Contamination and Toxicology
Kara E Marsac, Pamela C Burnley, Christopher T Adcock, Daniel A Haber, Russell L Malchow, Elisabeth M Hausrath
This study compares high resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (National Uranium Resource Evaluation) aerial gamma-ray survey...
December 2016: Journal of Environmental Radioactivity
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