Self-Propagating High-Temperature Synthesis of Simulated An~(3+)-Contained Radioactive Graphite in N_2 Atmosphere

摘要

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 N_2 atmosphere, in our study, with the exothermic reaction (3C + 4Al + 3TiO_2 = 2Al_2O_3 + 3TiC + Q), we used the following raw powdery materials including graphite (C), aluminum (Al), titanium dioxide (TiO_2) and neodymium oxide (Nd_2O_3, where Nd~(3+) was used to simulate An~(3+)). 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 Nd_2O_3 of 0 16 wt% could maintain the self-sustainable reaction. And in the designed reaction, the Nd_2O_3 solid solubility was 1 wt%. The samples were mainly in pieces, with grain sized mainly in 5 10 m. The samples without adding Nd_2O_3 content were composed of Al_2O_3, TiC, C, TiO_2 and AlN. With adding Nd_2O_3 content of 1 wt%, the samples were composted of Al_2O_3, TiC, C, TiO_2, AlN and NdAlO_3. While in case of adding Nd_2O_3 content of over 1 wt%, the occurrence of the Nd_2O_3 phase was observed in the XRD patterns of the samples.