Immobilization of Actinides in Garnets
EMSL Project ID
47956
Abstract
The garnet structure is a promising nuclear waste form due to its potential of accommodating various actinide elements. Study of tetravalent cation substitution in a simple garnet system may shed light on the substitution mechanisms and their energetics. Initial experiments have chosen iron garnet as a starting garnet host, and study the substitution of U and its analogs (Ce, Th) in this project. Formation of the single phase of synthetic substituted garnets indicates that a charge coupled substitution reaction involving Fe3+/Fe2+ facilitates the incorporation of tetravalent cations. However, the oxidation state of Fe and other cations (Ce, U) in the system are not well studied. Mossbauer spectroscopy, electron loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) as a complement can help us quantify Fe2+/?Fe and estimate oxidation state of Ce, U in the substitution system, and further clarify the substitution mechanism. Also accurate determination of oxidation state of cations is crucial for the interpretation of the calorimetric measurements.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Guo X., A. Navrotsky, R.K. Kukkadapu, M.H. Engelhard, A. Lanzirotti, M. Newville, and E.S. Ilton, et al. 2016. "Structure and Thermodynamics of Uranium-Containing Iron Garnets." Geochimica et Cosmochimica Acta 189. PNNL-SA-113283. doi:10.1016/j.gca.2016.05.043
Guo X., E. Tiferet, L. Qi, J. Solomon, A. Lanzirotti, M. Newville, and M.H. Engelhard, et al. 2016. "U(v) in Metal Uranates: A Combined Experimental And Theoretical Study of MgUO4, CrUO4 and FeUO4." Dalton Transactions 45, no. 11:4622-4632. PNNL-SA-113798. doi:10.1039/C6DT00066E