Effects of Gamma Irradiation on Early Age Properties of MetakaolinBased Geopolymer for the Immobilization of Radioactive Waste Containing Cesium and Strontium

Partitioning of heat and radiation-emitting Cesium (Cs) and strontium (Sr) is regarded as a viable pathway for the safe disposal of spent nuclear fuel and reprocessing waste without exceeding the temperature limits of geological disposal. The partitioned Cs and Sr have similar physical characteristics and could be immobilized together in a suitable matrix. Geopolymer is a potential candidate for immobilization of Cs and Sr, owing to its good thermal performance and radiation resistance. This PhD research explored the possibility for immobilization of Cs and Sr by metakaolin-based geopolymer matrix. The results demonstrate that the co-immobilization of Cs and Sr even at higher waste loading (4 wt.% Cs and 4 wt.% Sr) into a single matrix is feasible. On the other hand, gamma ionizing radiation and decay heat negatively impacts the strength development and alters the pore structure. Despite that, metakaolin-based geopolymer containing Cs and Sr maintained satisfactory strength, and the binding phase (N-A-S-H gel) demonstrated chemical stability upon exposure to a high dose of 4032 kGy of gamma a dose rate of 6 kGy/h and a temperature of 75 °C. Bases on the results, metakaolin-based geopolymer is promising for the immobilization of Cs and Sr-containing wastes.