Evaluating the Solubility and Homogeneity of Plutonium in an Alkali Borosilicate Glass

Glass waste forms have been considered as candidate immobilization matrices for long-term Pu disposal. A disposition approach that involves immobilizing plutonium in alkali borosilicate high level radioactive waste (HLW) glass is now being considered. In typical HLW glasses, the concentration of plutonium is low (typically on the order of 0.01 wt % PuO2 in the glass). The behavior of plutonium in the glass at these low concentrations has been analyzed and determined not to impact processing, criticality safety or glass performance. If Pu levels in the glass are increased to significantly higher levels, an understanding of the behavior of Pu during processing and in the produced glass is needed. In this study, the behavior of plutonium in an HLW glass of nominal composition was evaluated at concentrations up to 2 wt % Pu in the glass. The homogeneity of Pu in the glass was assessed using scanning electron microscopy coupled with energy dispersive spectroscopy. X-ray diffraction analysis was used to assess crystallization within the glass. The results will be related to previous testing involving higher concentrations of plutonium in a lanthanide borosilicate (LaBS) glass.