The XPS study of physical and chemical forms of neptunium group on the surface of minerals

The sorption behavior and the physical and chemical forms of neptunium on the surface of minerals of the two chlorate samples, biotite and kaolin, with different contents of Fe(II) was studied. The liquid-liquid extraction and the X-ray photoelectron spectroscopy were employed to identify the valence forms of neptunium. On the basis of the obtained data the quantitative elemental composition of the surface of the studied minerals, as well as the ionic composition of the formed neptunium complexes was determined. It was shown that the Np(IV) and Np(VI) containing compounds did not form, while the complexes Np(V)O+ -hydroxyl did form on the surface. The oxygen ions bonded with iron and oxygen belonging to water and/or of carboxyl were suggested to be present in the equatorial plane of the neptunyl group NpO+

Localization of the gamma-radiation sources using the gamma-visor

The search of the main gamma-radiation sources at the site of the temporary storage of solid radioactive wastes was carried out. The relative absorbed dose rates were measured for some of the gamma-sources before and after the rehabilitation procedures. The effectiveness of the rehabilitation procedures in the years 2006-2007 was evaluated qualitatively and quantitatively. The decrease of radiation background at the site of the temporary storage of the solid radioactive wastes after the rehabilitation procedures allowed localizing the new gamma-source

An X-ray photoelectron spectroscopy study of uranyl-chitosan interaction

An X-ray photoelectron spectroscopy study of uranium sorption by spherically-granulated chitosan in sulphate solutions, as well as the study of the nature of the U(VI) - chitosan interaction was carried out in this work. The X-ray photoelectron spectroscopy analysis showed that the uranyl - chitosan interaction results in the formation of complexes with aminogroup nitrogen, and possibly chitin ring oxygens and free hydroxyl groups in the equatorial plane. Under the UHV in the spectrometer chamber, the uranyl-amin and uranyl-hyroxide bonds were shown to break and tetravalent uranium compounds were shown to form on the sample surface. Hydroxyl groups were shown to evaporate. The calculated DG0 = -1,3 kJ/mol can be an evidence of several concurrent processes, some of which require energy, as well as of the formation of a surface chemical compound

XPS Investigation of ceramic matrixes for disposal of long-living radioactive waste products

The synthesis of ceramic matrixes for the long-term storage of highly active radionuclide wastes and determination of physical and chemical forms of radionuclides in them is one of the important problems in radioecology. It enables to create purpose fully materials for the long-term storage of radionuclides. In the present work the samples of ceramics [CaCe0.9Ti2O6.8(I) and CaCeTi2O7(II}] formed under various conditions were investigated with the X-ray photo electron spectroscopy. It is necessary for synthesis of ceramic matrixes, for the disposal of the plutonium and others tetravalent actinides. A technique was developed for the determination of cerium oxidation state (Ce3+ and Ce4+) on the basis of the X-ray photo electron spectroscopy spectral structure characteristics. It was established that the sample (I) formed at 300 MPa and T = 1400 °C in the air atmosphere contained on the surface two types of cerium ions in the ratio – 63 atomic % of Ce3+ and 37 atomic % of Ce4+, and the sample (II) formed at 300 MPa and T= 1300 °C in the oxygen atmosphere contained on its surface two types of cerium ions also, but in the ratio – 36 atomic % of Ce3+ and 64 atomic % of Ce4+. It was established that on the surface of the studied ceramics carbonates of calcium and/or cerium could be formed under influence of the environment that leads to the destruction of ceramics

An X-ray photoelectron spectroscopy study of the products of the interaction of gaseous IrF6 with fine UO2F2

Nuclear fuel reprocessing by fluorination, a dry method of regeneration of spent nuclear fuel, uses UO2F2 for the separation of plutonium from gaseous mixtures. Since plutonium requires special treatment, IrF6 was used as a thermodynamic model of PuF6. The model reaction of the interaction of gaseous IrF6 with fine UO2F2 in the sorption column revealed a change of color of the sorption column contents from pale-yellow to gray and black, indicating the formation of products of such an interaction. The X-ray photoelectron spectroscopy study showed that the interaction of gaseous IrF6 with fine UO2F2 at 125 °C results in the formation of stable iridium compounds where the iridium oxidation state is close to Ir3+. The dependence of the elemental compositions of the layers in the sorption column on the penetration depth of IrF6 was established

The electronic structure and the nature of the chemical bond in CeO2.

The X-ray photoelectron spectral structure of CeO2 valence electrons in the binding energy range of 0 to ∼50 eV was analyzed. The core-electron spectral structure parameters and the results of relativistic discrete-variational calculations of CeO8 and Ce63O216 clusters were taken into account. Comparison of the valence and the core-electron spectral structures showed that the formation of the inner (IVMO) and the outer (OVMO) valence molecular orbitals contributes to the spectral structure more than the many-body processes. The Ce 4f electrons were established to participate directly in chemical bond formation in CeO2 losing partially their f character. They were found to be localized mostly within the outer valence band. The Ce 5p atomic orbitals were shown to participate in the formation of both the inner and the outer valence molecular orbitals (MOs). A large part in the IVMO formation is taken by the filled Ce 5p1/2, 5p3/2 and O 2s atomic shells, while the Ce 5s electrons participate weakly in the chemical bond formation. The composition and the sequent order of the molecular orbitals in the binding energy range of 0 to ∼50 eV were established. A quantitative scheme for the molecular orbitals of CeO2 was built. This scheme is fundamental for understanding the nature of chemical bonding and also for the interpretation of other X-ray spectra of CeO2. Evaluations revealed that the IVMO electrons weaken the chemical bond formed by the OVMO electrons by 37%.The work was supported by the RFBR grant № 17-03-00277a. M.V. Ryzhkov acknowledges financial support of FASO of Russia ISSC of the Ural Branch of RAS № AAAA-A16-116122810214-9. A.J. Popel acknowledges funding from the UK EPSRC (grant EP/I036400/1) and Radioactive Waste Management Ltd (formerly the Radioactive Waste Management Directorate of the UK Nuclear Decommissioning Authority, contract NPO004411A-EPS02), a maintenance grant from the Russian Foundation for Basic Research (projects 13-03-90916) and CSAR bursary

XPS Study of Ion Irradiated and Unirradiated UO2 Thin Films.

XPS determination of the oxygen coefficient kO = 2 + x and ionic (U(4+), U(5+), and U(6+)) composition of oxides UO2+x formed on the surfaces of differently oriented (hkl) planes of thin UO2 films on LSAT (Al10La3O51Sr14Ta7) and YSZ (yttria-stabilized zirconia) substrates was performed. The U 4f and O 1s core-electron peak intensities as well as the U 5f relative intensity before and after the (129)Xe(23+) and (238)U(31+) irradiations were employed. It was found that the presence of uranium dioxide film in air results in formation of oxide UO2+x on the surface with mean oxygen coefficients kO in the range 2.07-2.11 on LSAT and 2.17-2.23 on YSZ substrates. These oxygen coefficients depend on the substrate and weakly on the crystallographic orientation. On the basis of the spectral parameters it was established that uranium dioxide films AP2,3 on the LSAT substrates have the smallest kO values, and from the XRD and EBSD results it follows that these samples have a regular monocrystalline structure. The XRD and EBSD results indicate that samples AP5-7 on the YSZ substrates have monocrystalline structure; however, they have the highest kO values. The observed difference in the kO values was probably caused by the different nature of the substrates: the YSZ substrates provide 6.4% compressive strain, whereas (001) LSAT substrates result only in 0.03% tensile strain in the UO2 films. (129)Xe(23+) irradiation (92 MeV, 4.8 × 10(15) ions/cm(2)) of uranium dioxide films on the LSAT substrates was shown to destroy both long-range ordering and uranium close environment, which results in an increase of uranium oxidation state and regrouping of oxygen ions in uranium close environment. (238)U(31+) (110 MeV, 5 × 10(10), 5 × 10(11), 5 × 10(12) ions/cm(2)) irradiations of uranium dioxide films on the YSZ substrates were shown to form the lattice damage only with partial destruction of the long-range ordering.The irradiation experiment was performed at the Grand Accelé rateur National d ́ ’Ions Lourds (GANIL) Caen, France, and supported by the French Network EMIR. The support in planning and execution of the experiment by the CIMAPCIRIL and the GANIL staff, especially I. Monnet, C. Grygiel, T. Madi, and F. Durantel, is much appreciated. The work was supported by RFBR grant no. 16-03-00914-a and partially supported by M.V. Lomonosov Moscow State University Program of Development. A.J.P. acknowledges funding from the UK EPSRC (grant EP/I036400/1) and Radioactive Waste Management Ltd. (formerly the Radioactive Waste Management Directorate of the UK Nuclear Decommissioning Authority, contract NPO004411A-EPS02), a maintenance grant from the Russian Foundation for Basic Research (projects 13-03-90916) and CSAR bursary. Thanks are given to A.M. Adamska, G.I. Lampronti, V.A. Lebedev, P.G. Martin, L. Payne, and A.A. Shiryaev for their help in characterization of the samples

Modern x-ray spectral methods in the study of the electronic structure of actinide compounds: Uranium oxide UO2 as an example

Fine X-ray photo electron spectral (XPS) structure of uranium dioxide UO2 in the binding energy (BE) range 0-~č40 eV was associated mostly with the electrons of the outer (OVMO) (0-15 eV BE) and inner (IVMO) (15-40 eV BE) valence molecular orbitals formed from the incompletely U5f,6d,7s and O2p and completely filled U6p and O2s shells of neighboring uranium and oxygen ions. It agrees with the relativistic calculation results of the electronic structure for the UO812–(Oh) cluster reflecting uranium close environment in UO2, and was confirmed by the X-ray (conversion electron, non-resonance and resonance O4,5(U) emission, near O4,5(U) edge absorption, resonance photoelectron, Auger) spectroscopy data. The fine OVMO and IVMO related XPS structure was established to yield conclusions on the degree of participation of the U6p,5f electrons in the chemical bond, uranium close environment structure and interatomic distances in oxides. Total contribution of the IVMO electrons to the covalent part of the chemical bond can be comparable with that of the OVMO electrons. It has to be noted that the IVMO formation can take place in compounds of any elements from the periodic table. It is a novel scientific fact in solid-state chemistry and physics