Thermal evolution effects on the properties of converting Cs-polluted soil into pollucite-base glass-ceramics for radioactive cesium immobilization

The Fukushima nuclear accident in Japan on March 11, 2011, produced large amounts of Cs-polluted soil which must be controlled to prevent the spread of hazardous Cs into the environment. In this paper, the effects of heat treatment on the structure and properties of Cs-containing glass-ceramics, as a simulated nuclear waste form, were systematically investigated. Cesium atoms are chemically bonded in the pollucite structure, and the amorphous phase further encapsulates the pollucite crystals in the glass-ceramics, thus providing an extra protective layer for the immobilized Cs. XRD analysis, Raman and FT-IR studies on the glass-ceramics synergistically indicated that the optimum crystallization temperature for pollucite is around 1000 °C. The pollucite is predominantly the main crystalline phase with a narrow crystal size distribution between 0.5 and 2 μm. Standard leaching test results show that the leaching rate of Cs was very low (3.0 × 10−3 g/(m2·d)). The study offers a practical method for immobilizing Cs in pollucite-base glass-ceramics. Moreover, the experimentally obtained data may provide some important references for converting Cs-polluted soil into pollucite-base glass-ceramics waste form.