Immobilization of zirconolite-based glass-ceramics and investigation on analogue of actinides

After decades of using nuclear power, high level nuclear waste is highly hazardous and has been a global environmental issue. Disposal of actinides which are the major contributions to the long term potential radioactivity after 2∼3 hundred years is a challenge to engineers. This study aims to investigate the immobilization of actinides in form of glass-ceramics. Nd₂O₃ was used as surrogate of actinides. Techniques of Transmission Electron Microscopy (TEM) and quantitative X-ray diffraction analysis through using Rietveld refinement method were used to characterize the glass-ceramic samples. Results from the effect of temperature on crystallization in the glass system indicated that single zirconolite phase was obtained after heat treatment at 950℃ for 2 hours. The highest amount of zirconolite phase in the glass-ceramic samples was also at 950℃. As the heat increases, other crystalline phases like titanite, anorthite and beddeleyite appeared in the samples. And the amounts of them keep the highest with increasing temperature to 1200℃, and the glass phase keeps the lowest at 950℃. The thermostability of the glass-ceramic samples was studied at 950℃. Results from the X-ray diffraction patterns showed that the glass-ceramic system is not stable at 950℃ for long time heat treatment. (authors)