The leaching behaviour of various ceramics was studied as part of a program to evaluate their potential use as container material for very long term containment of nuclear fuel waste under conditions of deep geologic disposal.
Samples of four grades of Al2O3, stabilized ZrO2, TiO2, a cermet (70% A12O3 - 30% TiC) and porcelain have been leached in deionized distilled water, Standard Canadian Shield Saline Solution (SCSSS), and SCSSS plus 20% Na-bentonite under static conditions at 100°C for periods up to 120 d.
The results of these ongoing leaching experiments suggest that the controlling features of the ceramic leaching process were leachant composition, and the presence and concentration of ions in the solution capable of preferentially precipitating on the ceramic surface, i.e., silicon, Mg2+, Ca2+, etc. Weight losses were determined after leaching. The initial leach rates showed a dependence upon ceramic purity and the processing used to prepare the ceramics, as well as the leachant composition. Also, it was apparent that the decrease of leach rates with time occurred as a result of the ceramic components in the leachant approaching their saturation limits.