Application of the ASTM C1308 Semi-Dynamic Dissolution Methodology to Ceramic Materials for Radioactive Waste Immobilisation

Semi-dynamic dissolution experiments were performed using the ASTM C1308 methodology, where the dissolution media is renewed periodically, to understand more about the fundamental chemistry of the corrosion behaviour of ceramic wasteforms [1]. Zirconolite (CaZrTi₂O₇) and pyrochlore (Gd₂Ti₂O7) have frequently been proposed as ceramic wasteform compositions, due to their passive safety, and are known to be chemically flexible and radiation tolerant with excellent overall aqueous durability [2]. However, a recent literature review highlighted a gap in the understanding of the dissolution mechanism of these wasteforms, which the semi-dynamic nature of the C1308 test could elucidate. In this study, the dissolution of a zirconolite and a pyrochlore composition was investigated using the ASTM C1308 test, with an extensive test matrix, where the temperature (40, 60, 90 °C) and dissolution media (0.01M HNO₃, FIN groundwater and 0.01M LiCL / 0.011M LiOH) were varied. The results have contributed to the understanding of the application of the ASTM C1308 methodology to ceramic materials dissolution, highlighting the merits of this test procedure compared to other commonly used dissolution protocols. This research also supported the development of a standard operating procedure for a series of round robin experiments with partners worldwide to further verify the efficacy and reproducibility of this methodology (allowing direct comparison between different formulations and wasteforms).