| High-level radioactive waste (HLW) is the product of spent fuel generated in the commercial and military use of nuclear energy after treatment, with residual Pu, a great deal of radiological hazards take place in the human body. Disposed of a large number of HLW limits the development of related industries. Permanent geological disposal of HLW vitrification is now the only way to actually resolve this problem in large quantities. Actually, the contents of radionuclide process a great ups and downs in HLW with different sources, but there is little research on analysis of immobilization of radionuclide effectively, therefore, we are the first to study effect of radionuclide contents in different systems on structure of HLW vitrification, and change on chemical stability, coming to the relationship between radionuclide contents and chemical stability via leaching resistence performance. However, the glass thermodynamic metastable structures may not meet the need for stable immobilization in thousands of years. So based on the pre-test to select excellent chemical stability of the glass system before adding metal oxide and additional heat treatment, HLW are incorporated into glass-ceramics. Accordingly, high radionuclides incorporated into ceramics and low-level radioactive waste vitrified into glass matrix become a more effective method. At the same time, control composition of glass-ceramics, study effect of radionuclide contents in the optimized structure of glass-ceramics on crystallization and leaching resistence performance. And on the basis, adding Ce as surrogate of Pu by CeO2, via Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) variation studies have been carried out, which are specified as follows:(1) Research on structure and leaching resistance performance of sodium aluminosilicate and aluminum borosilicate glass with different contents of CeO2. Coming to the most effective immobilization of the radionuclide surrogate contents, as well as better leaching resistance performance of glass sistem;(2) Based on aluminum borosilicate glass, CeO2, CaO and different contents of TiO2and ZrO2were added. Single hexagonal phase zirconolite (CaZrTi2O7-3T) can be precipitated by the melting method via adjust the heat treatment temperature, then zirconolite-based glass-ceramics was obtained. Research on effect of TiO2and ZrO2 contents on normalized release rate of Ce ion in zirconolite-based glass-ceramics. Then optimized heat treatment temperature and effective contents of TiO2and ZrO2were obtained;(3) Based on the optimized heat treatment system and proportioning on zirconolite-based glass-ceramics, crystallization behavior and leaching resistance performance of Ce of glass-ceramics with different contents of B2O3and CeO2was studied. And incorporation mechanism of Ce in zirconolite was analysed. Effective contents of radionuclide surrogate in glass-ceramics was obtained. The leaching resistance performance difference between glass-ceramics and glass have been studied.The innovation of this paper include:(1) Via leaching experiments studying radionuclide surrogate contribution to the chemical stability of HLW vitrification, resulting effective proportion of HLW vitrification;(2) Preparation of controllable pure crystalline phase of hexagonal zirconolite-based glass-ceramics, compared to the traditional monoclinic zirconolite, which exhibited more excellent incorporation contents and chemical stability;(3) Study hexagonal zirconolite-based glass-ceramics structure of interaction mechanism with CeO2, providing new ideas to effective immobilization for fission radionuclide. |
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