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Characterization of the fuel debris has been required for decommissioning Fukushima Daiichi Nuclear Power Station. To understand the reaction mechanisms involved for mixed UO2 – ZrO2 compounds, these materials were treated at high temperatures (1473 to 1873 K) under oxidizing, inert, and reducing atmospheres. The reaction products were analysed by a combination of powder X-ray diffraction (PXRD) and X-ray absorption spectroscopic measurements of the U LIII- and Zr K-edges. Principal component analysis of the X-ray absorption near edge structure and extended X-ray absorption fine structure of U LIII- and Zr K-edges provided a breakdown of the composition of each species within the products, these results were further supported by PXRD. Under an oxidizing atmosphere, the formation of U3O8 and U2Zr5O15 was observed in equilibrium with UO2, monoclinic-ZrO2, and tetragonal-ZrO2. However, when O2 gas was purged through the reaction tube during the cooling process to room temperature, pentavalent U in ZrU2O7 was produced by the oxidation of solid solution UO2 formed at > 1774 K during the temperature dropped at 1673 K due to a low concentration of O2 impurity with the Ar gas. Although the oxidized UO2 was able to form in such a system, tetravalent UO2 and its solid solution were instead present throughout the whole temperature range examined under a reducing atmosphere (H2 gas). This study can pave the way for understanding the interaction between the nuclear fuels and the cladding materials in damaged reactors enabling further simulation of possible decontamination procedures.

Characterization of uranium accumulated in the micro-regions of renal tubules of rats exposed to uranyl acetate was examined by micro-X-ray absorption fine-structure analysis and the results showed the possible biotransformation of uranium in this in vivo system., The kidney is the critical target of uranium exposure because uranium accumulates in the proximal tubules and causes tubular damage, but the chemical nature of uranium in kidney, such as its chemical status in the toxic target site, is poorly understood. Micro-X-ray absorption fine-structure (µXAFS) analysis was used to examine renal thin sections of rats exposed to uranyl acetate. The U L III-edge X-ray absorption near-edge structure spectra of bulk renal specimens obtained at various toxicological phases were similar to that of uranyl acetate: their edge position did not shift compared with that of uranyl acetate (17.175 keV) although the peak widths for some kidney specimens were slightly narrowed. µXAFS measurements of spots of concentrated uranium in the micro-regions of the proximal tubules showed that the edge jump slightly shifted to lower energy. The results suggest that most uranium accumulated in kidney was uranium (VI) but a portion might have been biotransformed in rats exposed to uranyl acetate.

Although the kidneys comprise a critical target of uranium exposure, the dynamics of renal uranium distribution have remained obscure. Uranium is considered to function physiologically in the form of uranyl ions that have high affinity for phosphate groups. The present study applied microbeam-based elemental analysis to precisely determine the distribution of phosphorus and uranium in the kidneys of male Wistar rats exposed to uranium. One day after a single subcutaneous injection of uranyl acetate (2 mg/kg), areas of concentrated phosphorus were scattered in the S3 segments of the proximal tubule of the kidneys, whereas the S3 segments in control rats and in rats given a lower dose of uranium (0.5 mg/kg) contained phosphorus without concentrated phosphorus. Areas with concentrated phosphorus contained uranium 4- to 14-fold more than the mean uranium concentration (126&ndash, 472 vs. 33.1 &plusmn, 4.6 &mu, g/g). The chemical form of uranium in the concentrated phosphorus examined by XAFS was uranium (VI), suggesting that the interaction of uranyl ions with the phosphate groups of biomolecules could be involved in the formation of uranium concentration in the proximal tubules of kidneys in rats exposed to uranium.

Kidneys are critical targets of uranium exposure, meaning that effective analytical methods for characterizing uranium accumulated in kidneys are required in toxicological studies of uranium. In this work, synchrotron radiation micro-X-ray fluorescence (SR-μXRF) imaging and two-dimensional μXAFS measurements were combined to analyze renal section specimens. By histochemical staining of the serial sections, the distribution of uranium chemical condition within the uranium-concentrated areas of the proximal tubules, which are toxic target sites of uranium, were obtained with 1 µm × 1 µm spatial resolution.

Silicalite-1 zeolites with high manganese contents isomorphously incorporated within the framework were synthesized by using mechanochemical pretreatment. First, manganese and silica sources were mixed in a planetary ball mill to obtain a composite material comprised of Mn, Si, and O. The composite was subsequently hydrothermally treated to crystallize Silicalite-1 zeolites. The synthesis was performed using a condition with a small amount of water to directly convert the composite material into a zeolite crystal while preventing manganese from leaching into water, which may cause manganese oxide/hydroxide species to precipitate. X-ray fluorescence analysis showed that the obtained products displayed a high manganese content of up to 6.3 mol%. The importance of utilizing mechanochemical treatment was confirmed through a number of characterization techniques, such as X-ray diffraction, catalytic activity assessments, diffuse reflectance UV-vis spectroscopy, Raman spectroscopy, and X-ray absorption fine structure analysis. Our findings suggest that this procedure using mechanochemical pretreatment can produce zeolites with various heteroatoms within their framework structures at contents difficult to achieve through conventional methods.

The combined application of hydroxyapatite and ferrihydrite can simultaneously immobilize lead and antimony(V) in oxic soil. However, this has not been demonstrated for antimony(III). In this study, antimony(III) sorption experiments in solution and dissolution experiments in oxic soil were conducted using the combined application of hydroxyapatite and ferrihydrite to elucidate the contribution of the materials to antimony(III) sorption and to evaluate the amount of antimony dissolved from the antimony(III)-sorbed materials by the change in redox state in oxic soil. All the antimony(III) in 50 mg l−1 solution at pH 5 was sorbed on the combined materials without oxidation. The contribution of ferrihydrite and hydroxyapatite on antimony(III) sorption was 92.6 and 7.4 %, respectively. The antimony(III) sorbed on the combined materials was not oxidized within 7 days of incubation period in oxic soil. However, after 90 days of incubation period, all the antimony(III) was oxidized to antimony(V). The percentage of antimony dissolution from the simulative-immobilized soil with the antimony(III)-sorbed combined material was constant at less than 1 % during incubation periods. Therefore, no enhancement in the antimony soil mobility in the soil with the combined application was observed, although antimony(III) was oxidized. These results suggest that the combined application of hydroxyapatite and ferrihydrite could immobilize antimony(III) without re-dissolving antimony through oxidation. Thus, the combined application would be applicable to lead- and antimony-contaminated soil.

Effect of SiO2 addition on the microstructures of calcium-deficient hydroxyapatite prepared by the heat-treatments was examined. Obtained hydroxyapatites substituted with Si ion were characterized by XRD, FT-IR and XAFS measurements. XANES results of Si K-edge and P K-edge in these modified hydroxyapatites indicated the shift of peaks of P K-edge with the SiO2 contents, although no change of Si local structures. In this study, the effect of Si ion on micro- and local structure of hydroxyapatite with SiO2 addition was mainly clarified.

Manganese-incorporated MCM-41 with high manganese content of Mn/(Mn + Si) = 9.2 mol % and BET specific surface area of 750 m2 g−1 was obtained by utilizing mechanochemical treatment. Clear differen...

The origin of the ruby color of Satsuma glass, a famous copper-ruby glass produced in Japan in the mid-19th century, has been examined by electron microprobe analysis (EPMA), X-ray absorption fine structure (XAFS), and optical absorption spectroscopy analyses. CuK XAFS analysis reveals that the major component of copper in the ruby glass consists of Cu(I) ions in the glass structure. This species is distinct from Cu2O (cuprite), which we conclude is not responsible for the ruby color. Optical absorption spectra measured at 300 and 77 K clearly distinguishes the absorptions due to the colloidal particles of metallic copper and Cu2O. It is concluded that the trace amount of copper in the ruby glass, which is below the detection limit of the EPMA and XAFS techniques, exists as metallic copper particles of nanometer size and is responsible for the ruby-red appearance of the Satsuma glass.

Ten mole percent ytterbium-doped SrZrO 3 , which has the highest proton conductivity among the ytterbium-doped SrZrO 3 , has been studied by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and differential thermal analysis (DTA) to elucidate the effect of dopant amount of ytterbium ions. The results are compared with those of 5 mol% ytterbium-doped SrZrO 3 of our previous work. The orthorhombic unit cell volume increases monotonously with increasing temperature but exhibits a bent between 500 and 600 °C, which is about 300 K lower than that of 5 mol% ytterbium-doped SrZrO 3 and then increases again with temperature. This bent of the unit cell volume is considered to be due to a loss of oxygen, which is consistent with the result of a weight loss in TGA observed in the same temperature range. The weight loss and gain on heating and on cooling, respectively, were observed in TGA but do not exhibit so clear hysteresis loop as observed for 5 mol% ytterbium-doped SrZrO 3 . The displacements of oxide ions were observed in the Fourier syntheses followed by a loss of oxygen at high temperature.

Ytterbium-doped SrZrO3 has been studied by thermogravimetric analysis (TGA), differential thermal analysis (DTA), powder X-ray diffraction (XRD), and XAFS spectroscopy. A broad endothermic peak was observed in the DTA curve for 5 mol% Yb-doped SrZrO3 at 812°C, accompanied with a small weight loss, which is considered due to a mass loss of oxygen. The weight recovered its value in the cooling process at the lower temperature of 740°C. The weight loss and gain in the heating and cooling process, respectively, shows a hysteresis loop. There exist at least 2.3 atom% oxide ion vacancies at high temperature. The two lattice constants become the same value above about 800°C, indicating a phase transition for 5 mol% Yb-doped SrZrO3, which is consistent with the results from TGA and DTA. The oxide ion vacancies produced by substitution of tetravalent zirconium ions by trivalent ytterbium ions are localized not near zirconium ions, but near ytterbium ions.

The fluorescence XAFS (X–ray absorption fine structure) technique using synchrotron radiation was applied to characterize zinc in the Hg–Zn, Cd–Zn, and Bi–Zn coprecipitates, and to elucidate the reaction mechanism of the coprecipitation of zinc from a strong acidic solution. Hg LII–, Cd K–, and Bi LIII–edge XAFS spectra suggested that the respective host materials of the coprecipitates listed above are metacinnabar (HgS), greenockite (CdS), and bismuthinite (Bi2S3) and that existence of zinc has not affected the local structure of the host metal sulfides in each system. On the other hand, the Zn K–edge XAFS spectra of each coprecipitate indicated that the chemical forms of zinc compounds are controlled by the crystal structure of the host sulfides.The shapes of the Zn K–XAFS spectra of the Hg–Zn and Cd–Zn coprecipitates showed a strong resemblance to those of crystalline standards ZnS, wurtzite and spharelite. It was suggested that the two coprecipitated phases (HgS, ZnS) and (CdS, ZnS) may form a solid solution in the Hg–Zn and Cd–Zn coprecipitates. The local structure around the zinc(II) ion in the Bi–Zn coprecipitate is the same as that around hexaaqua–zinc(II) ions, and adsorption of soluble ions or mechanical occlusion from the mother liquor is regarded as a driving force of coprecipitation in the Bi–Zn system.

Local structure around arsenic atoms in K-T boundary clays was studied by As K-edge XAFS spectroscopy. The threshold E0 energy of As and the characterization of the white peak of XANES spectra agree well with the values of As(+5) minerals like Zn2(AsO4)2(OH) 22H2O and CaCu(AsO4)(OH) according to the comparison with several types of arsenic minerals. This indicates that arsenic is in a high oxidation state As(+5) and occupies the AsO4 tetrahedral site of a mineral in K-T boundary clays.

International audience; Four calcium silicate hydrates (C-S-H) with structural calcium/silicon (Ca/Si) ratios ranging from 0.82 +/- 0.02 to 0.87 +/- 0.02 were synthesized at room temperature, 50, 80, and 110 degrees C. Their structure was elucidated by collating information from electron probe micro-analysis, transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, and powder X-ray diffraction (XRD). A modeling approach specific to defective minerals was used because sample turbostratism prevented analysis using usual XRD refinement techniques (e.g. Rietveld analysis). It is shown that C-S-H with Ca/Si ratio of similar to 0.8 are structurally similar to nano-crystalline turbostratic tobermorite, a naturally occurring mineral. Their structure thus consists of sheets of calcium atoms in 7-fold coordination, covered by ribbons of silicon tetrahedra with a dreierketten (wollastonite-like) organization. In these silicate ribbons, 0.42 Si per bridging tetrahedron are missing. Random stacking faults occur systematically between successive layers (turbostratic stacking). Layer-to-layer distance is equal to 11.34 angstrom. Crystallites have a mean size of 10 nm in the a-b plane, and a mean number of 2.6-2.9 layers stacked coherently along the c* axis. (C) 2013 Elsevier Ltd. All rights reserved.

XAFS analysis was used to reveal local atomic environment of manganese hydroxide precipitates, the reaction products of the Winkler method which is used in the determination of dissolved oxygen in analytical chemistry. From the comparison with the XANES spectra of standard materials, it is suggested that the brown manganese, hydroxide precipitates oxidized from dissolved oxygen or H2O2 contain both divalent and trivalent ions, and are not MnO(OH)2 nor MnO2, which have been often referred as the Winkler product in general text books of analytical chemistry.

XAFS analysis was used to reveal local atomic environment of manganese in the intracellular and extracellular granules from kidney tissues in several kinds of marine bivalves. The Mn K-absorption spectra of the kidney granules were measured in a fluorescence mode. The overall spectral shapes and the positions of the Mn K-absorption edge of the kidney granules of the bivalves are similar to each other and somewhat resemble those of eosphorite (MnAl(PO4)OH)2·H2O) which contains Mn(II). These results, combined with those of IR analysis, suggest that manganese in the kidney granules exist as a phosphate with 6-fold coordination of oxygen atoms.