Self-propagating high-temperature synthesis of simulated An ³⁺-contained radioactive graphite in N₂ atmosphere

The self-propagation synthesis (SHS) technology is characterized exclusively in multiple aspects, including: higher reaction rate, simplified procedure, shortened flow-process, facilitated process, lower energy consumption and remote control. In order to evaluate the performance of the self-propagating high-temperature synthesis (SHS) to treat An ³⁺-contained radioactive graphite in N₂ atmosphere, in our study, with the exothermic reaction (3C + 4Al + 3TiO₂ = 2Al ₂O₃ + 3TiC + Q), we used the following raw powdery materials including graphite (C), aluminum (Al), titanium dioxide (TiO ₂) and neodymium oxide (Nd₂O₃, where Nd ³⁺ was used to simulate An³⁺). After a serial pretreatment including mixing, refinement and formation, a self-developed SHS reactive facility was used to prepare the simulated waste form for the An ³⁺-contained radioactive graphite. Then, X-ray diffractometer(XRD) and scanning electron microscope (SEM) were used to test and analyze the morphology, phase composition and solid solubility of the prepared waste forms. According to the results, the samples with the adding Nd₂O ₃ of 0∼16 wt% could maintain the self-sustainable reaction. And in the designed reaction, the Nd₂O₃ solid solubility was 1 wt%. The samples were mainly in pieces, with grain sized mainly in 5∼10μm. The samples without adding Nd₂O₃ content were composed of Al₂O₃, TiC, C, TiO₂ and AlN. With adding Nd₂O₃ content of 1 wt%, the samples were composted of Al₂O₃, TiC, C, TiO₂, AlN and NdAlO₃. While in case of adding Nd₂O₃ content of over 1 wt%, the occurrence of the Nd₂O₃ phase was observed in the XRD patterns of the samples.