IMMOBILIZATION OF INTERMEDIATE-LEVEL WASTES IN GEOPOLYMERS

Intermediate-level wastes (ILW) are immobilized in monolithic solids of low dispersibility. Alkali-activated aluminosilicate binders, known as geopolymers, are investigated in this work for possible application in ILW solidification. Results show that Sr is reasonably immobilized. Its concentrations in water were below the detection limit. In Q-brine, 2-7 wt% of Sr were leached in 6 months. Cs was leached more rapidly than Sr. Leached fractions were 1-11 wt% and 14-28 wt% in water and Q-brine, respectively, depending on the geopolymer composition. 20-40 wt% of Mo were leached in water, and 4-18 wt% were leached in Q-brine. Tolerance of the solidified matrix to water was quite adequate. Samples maintained their shape, dimensions, and strength to the end of experiments. On the contrary, tolerance of most compositions to Q-brine was poor. Cement-glass, for comparison, gave better results under the same conditions. Concentrations of Mo and Sr were below the detection levels in all cases. Cs was also not detectable in Q-brine. Only 4-6 wt% of Cs were leached into water. In addition, tolerance to both water and Q-brine was quite good.