Microstructural Characterization of Synroc C and E by Electron Microscopy

High‐resolution electron microscopy, analytical electron microscopy, and scanning electron microscopy were used to examine the microstructure and chemistry of the titania‐based nuclear waste ceramics Synroc C and Synroc E. The mineral assemblages of these formulations are dependent upon the level of radwaste incorporation. The principal phases identified are zirconolite, zirkelite, pyrochlore, polymignyte, perovskite, hollandite, magnetoplumbite, and intermetallic alloys. Thin intergranular films and “glassy” triple points were found to exist between different phases. In Synroc formulations containing a large excess of TiO₂the radwaste‐containing minerals are embedded in an inert, continuous rutile matrix; this microencapsulation operates at the level of 10 to 20 nm. Backscattered electron images suggest that the distribution of radwaste ions may not be completely homogeneous throughout the ceramic.