New Synthesis Route and Characterization of Siderite (FeCO_3) and Coprecipitation of 99Tc

摘要

Technetium-99 is a long-lived product of nuclear fission. In the ground-waters of European disposal sites Tc is expected to be in the tetravalent state since the geochemical conditions are reducing due to the presence of redox couples such as Fe(II)/Fe(III), and the presence of reducing minerals such as pyrite and siderite (FeCO_3). Siderite is expected to be formed as well as container corrosion product. Experiments of coprecipitation of Fe~(2+) and Tc(IV) were conducted in the laboratory under an inert atmosphere at room temperature. High resolution transmission electron microscopy shows that the coprecipitate is around 3 nm sized particles. Analytical electron microscopy indicates that the precipitate contains 30 atom % of Tc and 70 atom % Fe. The Tc was homogeneously distributed. Selected Area Electron Diffraction doesn't reveal the formation of siderite, which suggests that the presence of technetium in high concentration inhibit the formation of this phase.