EXAFS investigation of U(VI) speciation in cementitious materials
EXAFS investigation of U(VI) speciation in cementitious materials
Macé, N.; Harfouche, M.; Dähn, R.; Tits, J.; Scheinost, A.; Wieland, E.
Cement in the Swiss radioactive waste management program is used as a waste matrix for the long-lived intermediate-level waste (ILW) disposal, where Uranium is an important radionuclide. Calcium Silicate Hydrates (C-S-H) are one of the major components of Hardened Cement Paste (HCP). In such a context, the understanding of Uranium uptake processes occurring in cementitious materials is necessary.
U(VI) uptake by C-S-H (CaO/SiO2 = 1.07) in Artificial Cement pore-Water (ACW) and HCP has been investigated using X-Ray Absorption Spectroscopy (XAS) technique in order to determine the chemical environment of sorbed and precipitated U(VI) species in cementitious matrices.
Phase X (CaUO4(H2O)x) and a uranophane (Ca(H3O)2 have been chosen as relevant reference compounds.
Similar coordination environment of U(VI) taken up by C-S-H and HCP
U(VI) sorbed species a-uranophane-like structure
U(VI) precipitated species phase-X-like structure
No split equatorial shell is observed
Complementary informations are expected using Time-Resolved Laser Fluorescence spectroscopy (TRLFS)
Keywords: Uranium; cement; EXAFS
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Poster
Actinide-XAS 2008, 15.-17.07.2008, Saint Aubin, France
Permalink: https://www.hzdr.de/publications/Publ-11681