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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](UO2)2(SiO4)2(H2O)3) 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
  • Poster
    Actinide-XAS 2008, 15.-17.07.2008, Saint Aubin, France

Publ.-Id: 11681 - Permalink