Encapsulation of cesium with a solid waste-derived sulfoaluminate matrix: A circular economy approach of treating nuclear wastes with solid wastes

It is of great importance to safely dispose nuclear wastes with the development of nuclear industries. Past approaches to this problem have included immobilizing radioactive cesium in Portland cement-based matrices; however, the leaching rates of cesium are relatively high, especially as the leaching temperature increases. This paper explores a high-efficiency and cost-effective approach for encapsulating cesium using a sulfoaluminate cement (SAC) matrix, which was prepared via synergetic use of industrial solid wastes. Leaching results showed that, the apparent diffusion coefficient values of cesium were only similar to 1.4 x 10(-15) cm(2)/s and similar to 5 x 10(-18) cm(2)/s at 25 degrees C and 90 degrees C leaching conditions, respectively. These values were several orders of magnitude lower when compared with previously reported values, indicating the excellent encapsulation performance of the solid waste-based SAC for cesium. Moreover, the heavy metals contained in the industrial solid waste were also effectively immobilized. A mechanistic analysis revealed that cesium was encapsulated in the SAC matrices stably by a physical effect. Finally, a life cycle assessment and economic analysis indicated that this approach was environmental-friendly, cost-effective, and energy-saving. This work provides a promising strategy for effective encapsulation of cesium and synergetic treatment of industrial solid wastes.

Automated summary

This study presents a high-efficiency and cost-effective method for encapsulating cesium using a sulfoaluminate cement (SAC) matrix prepared from industrial solid wastes, showing excellent encapsulation performance. Leaching tests showed low diffusion coefficient values for cesium, indicating outstanding encapsulation performance. Mechanistic analysis revealed stable encapsulation of cesium in SAC matrices through a physical effect.