Charge Distribution and Local Structure and Speciation in the UO2+x and PuO2+x Binary Oxides for x <= 0.25

Journal Article · Tue Feb 01 00:00:00 EST 2005 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2004.09.029· OSTI ID:15020651

Conradson, Steven D; Begg, Bruce D; Clark, David L; Den Auwer, Christophe J; Ding, Mei; Dorhout, Peter K; Espinosa-Faller, Francisco J; Gordon, Pamela L; Haire, Richard G; Hess, Nancy J; Hess, Ryan F; Keogh, D Webster; Lander, Gerard H; Manara, Dario; Morales, Luis A; Neu, Mary P; Paviet-Hartmann, Patricia; Rebizant, Jean; Rondinella, Vincenzo V; Runde, Wolfgang ; Tait, C DREW; Veirs, D Kirk; Villella, Phillip M; Wastin, Franck

The local structure and chemical speciation of the mixed valence, fluorite-based oxides UO2+x (0.00pxp0.20) and PuO2+x/PuO2+x*y(OH)2y * zH2O have been determined by U/Pu LIII XAFS spectroscopy. The U spectra indicate (1) that the O atoms are incorporated as oxo groups at short (1.75A ? ) U?O distances consistent with U(VI) concomitant with a large range of U displacements that reduce the apparent number of U neighbors and (2) that the UO2 fraction remains intact implying that these O defects interact to form clusters and give the heterogeneous structure consistent with the diffraction patterns. The PuO2+x system, which does not show a separate phase at its x ? 0:25 endpoint, also displays (1) oxo groups at longer 1.9A ? distances consistent with Pu(V+d), (2) a multisite Pu?O distribution even when x is close to zero indicative of the formation of stable species with H2O and its hydrolysis products with O2*, and (3) a highly disordered, spectroscopically invisible Pu?Pu component. The structure and bonding in AnO2+x are therefore more complicated than have previously been assumed and show both similarities but also distinct differences among the different elements.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 15020651
• Report Number(s): PNNL-SA-44836; KP1301020; TRN: US0504636
• Journal Information: Journal of Solid State Chemistry, Vol. 178, Issue 2
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
CHARGE DISTRIBUTION
DEFECTS
HYDROLYSIS
VALENCE
URANIUM OXIDES
PLUTONIUM OXIDES
ELECTRONIC STRUCTURE
X-RAY SPECTROSCOPY
ABSORPTION SPECTROSCOPY
Speciation
Local structure
X-ray absorption fine structure spectroscopy
Urania
Plutonia
Mixed valence actinide oxide
XAFS