Leaching resistance of alkali-activated binder contaminated with cesium

Abstract

Leaching is a phenomenon of fundamental interest in low-level radioactive waste disposal, and the measurement of the leaching resistance of different wasteforms is very important for proper waste management. In general, alkali-activated binders (AABs) can be considered as a sustainable solution for safe immobilization of hazardous wastes containing different toxic or radioactive elements. In this paper, the leaching resistance of AAB based on blast furnace slag (BFS), contaminated with 2% cesium (i.e., solidified simulated low-level radioactive waste), was investigated according to the ANSI/ANS-16.1-2003 standard procedure. Based on the leaching results obtained for different elements, in particular for Cs, Si, Al, Ca, Na, and K, it was concluded that the short (up to 5 days) semi-dynamic process of leaching from AAB can be divided into two distinct stages: a) fast leaching of non-bound or loosely bound ions during the initial 24 hours, which occurred mostly between the surface of AAB and the leachant, and b) slower leaching in the later stages of the experiment, which was controlled by diffusion of ions through AAB matrix. By calculating the diffusion coefficient (D) and the leachability index (L) of cesium, it was also concluded that AAB based on blast furnace slag, synthesized under the given experimental conditions, can be considered as a potentially efficient matrix for immobilizing up to 2% cesium in hazardous wastes.