Features of fracture faces in synroc C

Fracture faces and polished surfaces of Synroc C specimens with 10% and 20% simulated high-level nuclear waste (HLW) have been studied with X-ray photoelectron spectroscopy. Elemental abundances and chemical environments for all matrix and most HLW atomic species have been investigated in the surface and near-surface layers before and after chemical attack. These observations suggest that the fracture mechanism is mainly intergranular, that particular phases are not preferentially exposed in the fracture faces, that some HLW species (caesium and molybdenum) are found in the grain boundaries, that intergranular regions are thin amorphous films or larger “glassy” triple points and that the intergranular films exhibit low chemical durability in an aqueous environment. These effects are independent of waste loading up to 20% and are consistent with the very good chemical durability reported for large monoliths.