Leaching resistance of simulated radioactive graphite waste forms prepared by SHS

In order to study the SHS immobilization effect of the radioactive graphite, the exothermic reaction (3C + 4Al + 3TiO₂ = 2Al₂O₃ + 3TiC + Q), in which Sr²⁺ was used to simulate ⁹⁰SrO, and Nd³⁺, Ce⁴⁺ were used to simulate An³⁺, An⁴⁺, respectively, was introduced in the air and N₂ atmosphere by SHS equipment self-designed. The addition amount of simulated radionuclide was SrO 1%~8 %, Nd₂O₃ 1%, CeO₂ 1%~3% in the air and SrO 1%~8 %, Nd₂O₃ 1%, CeO₂ 1%~2% in N₂ atmosphere, respectively. The leaching experiments of waste forms prepared were conducted in synthetic sea water at 40°C and 70°C. X-ray diffractometer (XRD) and inductively coupled plasma source mass spectrometer were used to test and analyze the phase composition and leaching data of these samples. The anti-leaching properties were studied on the basis of a detailed research on the phase changes of waste forms within solid solution. The results indicated that leaching concentration of Sr²⁺, Nd³⁺, Ce⁴⁺ in waste forms prepared in both air and N₂ atmosphere increased gradually with extending immersion time, and it was higher at 70°C than 40°C. The leaching concentration of simulated nuclides was higher in waste forms prepared in N₂ atmosphere than in the air.