A novel Sr2Nd8(SiO4)6O2 glass-ceramics for rapid immobilization of FP and An3+ co-doped uranium tailings by microwave sintering: mechanism and performance

Oxyapatite (general formula:A2IA8II(BO4)6O2) is a potential material for immobilization of nuclear waste. Here, a novel Sr2Nd8(SiO4)6O2 glass-ceramics (GCs) derived from uranium tailings were synthesized by consecutive microwave sintering technology at 1200 °C for simultaneous immobilization of simulated bivalent fission product (FP) Sr and trivalent actinide (An3+) Nd. Sr and Nd were successfully immobilized into A2I and A8II acceptor sites of oxyapatite respectively, and glass structures. The phase evolution, microstructure, physical property, and radon exhalation of as-prepared sintered forms were systematically investigated by XRD, FT-IR, SEM-EDS, TEM, and RAD7 radon meter. The experimental results demonstrated that the ultimate solid solubility of Sr reached 25 wt.%, while Nd exceeded 30 wt.% at 1200 °C. Importantly, the solidified samples exhibited homogenous and dense microstructure, and the radon exhalation rate improved with the increase of pore. It was indicated that oxyapatite glass-ceramics could be a potential matrix for the simultaneous immobilization of bivalent FP and An3+.