Resonant inelastic x-ray scattering from UOand UN.

Resonant inelastic x-ray scattering (RIXS) using an incident energy tuned to the uraniumN4,5absorption edges is reported from epitaxial films of-UOand UN. Theory shows that for UOthe multiplets associated with a 5configuration with a ground state of2F5/2and the excited state of2F7/2are observed. However, the strong transition predicted at a transfer energy of 1.

Temperature-dependent anisotropy in the bond lengths of UOas a result of phonon-induced atomic correlations.

Previous experiments on cubic UOhave suggested that the temperature dependences of the nearest-neighbour U-O and U-U distances are. We have acquired total-scattering neutron diffraction patterns out to = 23.5 Åfor50 View Article and Find Full Text PDF

Thermal Energy Transport in Oxide Nuclear Fuel.

To efficiently capture the energy of the nuclear bond, advanced nuclear reactor concepts seek solid fuels that must withstand unprecedented temperature and radiation extremes. In these advanced fuels, thermal energy transport under irradiation is directly related to reactor performance as well as reactor safety. The science of thermal transport in nuclear fuel is a grand challenge as a result of both computational and experimental complexities.

X-ray synchrotron radiation studies of actinide materials.

By reviewing a selection of X-ray diffraction (XRD), resonant X-ray scattering (RXS), X-ray magnetic circular dichroism (XMCD), resonant and non-resonant inelastic scattering (RIXS, NIXS), and dispersive inelastic scattering (IXS) experiments, the potential of synchrotron radiation techniques in studying lattice and electronic structure, hybridization effects, multipolar order and lattice dynamics in actinide materials is demonstrated.

Water corrosion of spent nuclear fuel: radiolysis driven dissolution at the UO2/water interface.

X-ray diffraction has been used to probe the radiolytic corrosion of uranium dioxide. Single crystal thin films of UO(2) were exposed to an intense X-ray beam at a synchrotron source in the presence of water, in order to simultaneously provide radiation fields required to split the water into highly oxidising radiolytic products, and to probe the crystal structure and composition of the UO(2) layer, and the morphology of the UO(2)/water interface. By modeling the electron density, surface roughness and layer thickness, we have been able to reproduce the observed reflectivity and diffraction profiles and detect changes in oxide composition and rate of dissolution at the Ångström level, over a timescale of several minutes.

Local structure and charge distribution in the UO(2)-U(4)O(9) system.

Analysis of X-ray absorption fine structure spectra of UO(2+x) for x = 0-0.20 (UO(2)--U(4)O(9)) reveals that the adventitious O atoms are incorporated as oxo groups with U--O distances of 1.74 A, most likely associated with U(VI), that occur in clusters so that the UO(2) fraction of the material largely remains intact.

Higher order speciation effects on plutonium L(3) X-ray absorption near edge spectra.

Pu L(3) X-ray near edge absorption spectra for Pu(0-VII) are reported for more than 60 chalcogenides, chlorides, hydrates, hydroxides, nitrates, carbonates, oxy-hydroxides, and other compounds both as solids and in solution, and substituted in zirconolite, perovskite, and borosilicate glass. This large database extends the known correlations between the energy and shape of these spectra from the usual association of the XANES with valence and site symmetry to higher order chemical effects. Because of the large number of compounds of these different types, a number of novel and unexpected behaviors are observed, such as effects resulting from the medium and disorder that can be as large as those from valence.