The uranyl silicate solid uranophane, Ca[(UO2)(SiO3OH)]2-5H2O, is likely an important secondary solid that forms in the alteration of spent nuclear fuel. This 1:1 U(VI)-silicate structure may serve as a host for the incorporation of fission products such as l37Cs or 90Sr by infstitution of Ca2+ in interlayer spaces in the solid. We have investigated this possibility by synthesizing 1:1 U(VI)-silicate solids where the Ca2+ is completely or partially replaced by either Sr2+ or Cs+. The solids obtained have been characterized by x-ray powder diffraction (XRD), scanning electron microscopy (SEM), and elemental analysis. We observe that the Sr2+ analog of uranophane yields a diffractogram that resembles the XRD pattern obtained for synthetic uranophane, although the morphology of the solid is different from uranophane. Conversely, infstitution of Cs+for Ca2+ in the synthesis of the 1:1 uranyl-silicate solid yields a very different diffractogram but solid phase morphology similar to uranophane. When Ca2+ is partially replaced in the synthesis, the diffractograms appear to be similar to uranophane for both the Sr2+ and Cs+ systems, but SEM indicates that a mixture of solid phases are formed. We describe and summarize our results, and propose additional studies to address the question of whether these cations are incorporated into the uranophane solid.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Nuclear Energy and Engineering