Abstract
Molten salt has rapid mass transfer and nucleation process, so it can synthesize ceramic solid solution of immobilized high-level radioactive waste at low temperature. The chemical stability in the process of interaction with groundwater determines the ability of matrix phase to prevent radionuclides from entering the biosphere and the release form of radionuclides. Nd-doped ZrSiO4 ceramics with different sintering temperature (1100-1500 ℃), sintering time (3-24 h) and molar ratio of salt to oxide (3:1, 7:1 and 10:1) were prepared by molten salt method. The sintered ceramic is Zr1−xNdxSiO4−x/2, where x is the solubility of Nd in ZrSiO4. The results show that the optimum molar ratio of molten salt to oxide is 10:1, which can quickly synthesize zircon waste form at low temperature. The chemical stability test shows that the normalized leaching rate of trivalent nuclides in zircon structure is in the order of ~10−5 g·m−1·d−1, and the surface layer is dissolved. The experimental results show that zircon structure is an excellent waste form.
Immobilized nuclide and leaching mechanism of zircon waste forms efficient synthesized by molten salt
