EXAFS and XANES analysis of plutonium and cerium edges from titanate ceramics for fissile materials disposal.
We report x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra from the plutonium L{sub III} edge and XANES from the cerium L{sub II} edge in prototype titanate ceramic hosts. The titanate ceramics studied are based upon the hafnium-pyrochlore and zirconolite mineral structures and will serve as an immobilization host for surplus fissile materials, containing as much as 10 weight % fissile plutonium and 20 weight % (natural or depleted) uranium. Three ceramic formulations were studied: one employed cerium as a ''surrogate'' element, replacing both plutonium and uranium in the ceramic matrix, another formulation contained plutonium in a ''baseline'' ceramic formulation, and a third contained plutonium in a formulation representing a high-impurity plutonium stream. The cerium XANES from the surrogate ceramic clearly indicates a mixed III-IV oxidation state for the cerium. In contrast, XANES analysis of the two plutonium-bearing ceramics shows that the plutonium is present almost entirely as Pu(IV) and occupies the calcium site in the zirconolite and pyrochlore phases. The plutonium EXAFS real-space structure shows a strong second-shell peak, clearly distinct from that of PuO{sub 2}, with remarkably little difference in the plutonium crystal chemistry indicated between the baseline and high-impurity formulations.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 750468
- Report Number(s):
- ANL/CMT/CP-99271; TRN: US0204607
- Resource Relation:
- Conference: MRS '99 Fall Meeting, Boston, MA (US), 11/29/1999--12/03/1999; Other Information: PBD: 16 Nov 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Characterization of phase assemblage and distribution in titanate ceramics with SEM/EDS and x-ray mapping.
Preparation and characterization of {sup 238}Pu-ceramics for radiation damage experiments