Yury A. Teterin

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.

XPS study of U, Cs and Sr ionic forms in the “hot” particles formed due to the nuclear power plant accident simulation

The X-iay photoelectron spectroscopy (XPS) ionic and quantitative analysis of the reactor fuel containing masses (FCM) doped with the Cs, Sr ions before and after the up to 2300°C heating, as well as the “hot” particles formed during the laboratory simulated nuclear power plant accident under various conditions, was carried out. The U and Cs were shown to sublime within the first 20 seconds of the heating. Within the next 60 seconds the sublimation of U, Cs and Sr. was shown to take place. The “hot” particles collected within the first 20 seconds of heating and extra heated to 900°C in the air flow were shown to contain 68% of U and 32% of Cs, while the particle collected within the next 360 seconds and extra heated - 51% of U, 13% of Cs, and 36% of Sr. The “hot” particles were suggested to include the uranyl compounds like UO2CO3, Cs2UO4, Cs4UO2(CO3)3, CsUO2(OH)3, SrUO4, Sr3UO6, SrUO2CO3(OH)2. The Ar+treatment of the “hot” particles results in the change of their compositions.

XPS study of the An5f electronic states in actinide (Th, U, Np, Pu, Am, Cm, Bk) compounds.

In the present work it was found that the relative intensity of the quasiatomic An5f- electron line correlates with the number n5f of such electrons in actinide compounds. The experimental dependence of the relative An5f line intensity for Th, U, Np, Pu, Am, Cm, and Bk in various compounds on the number n5f (I5f = 0.02 n5f) in the range from 0 to 7 was obtained. It gave a unique opportunity to determine the oxidation state of actinides in compounds, to conduct the X-ray photoelectron quantitative ionic analysis on the basis of the An5f line intensity, to study the participation degree of electrons in the chemical binding, and to carry out the comparison with the results of the theoretical calculations of the photoemission cross-sections.

The structure of the valence electronic orbitals in uranium trioxide γ-UO3

The role of the U6p,5f electrons in the chemical bond in γ-UO3 was studied on the basis of the low-energy X-ray photoelectron, conversion electron spectra from uranium trioxide, and the calculations for the [UO2O4]6− (D4h) cluster.