Densification study of sodium zirconium phosphate-type ceramic for immobilizing radionuclides of Sr prepared with microwave sintering from uranium tailing sand

Strontium zirconium phosphate (SrZr 4 (PO 4 ) 6 ) ceramics has high density and chemical inertness, which can safely and effectively immobilize the divalent fission product Sr in the ceramic matrix. In this study, a novel SrZr 4 (PO 4 ) 6 ceramic was synthesized using microwave sintering of uranium tailings. This method features shorter sintering times and efficient energy use. Sr replaces Na in sodium zirconium phosphate (NaZr 2 (PO 4 ) 3 ) due to similar ionic radii, transforming it into SrZr 4 (PO 4 ) 6 ceramics. The results showed that the sintered samples prepared by holding at 1200 °C for 50 min, which the density of the solidified body reached up to 3.2 g/cm 3 .The ceramics showcase outstanding leach resistance, with Sr leaching rates far below the nuclear industry standard (1 × 10 −2 g m −2 d −1 ). Similarly, the leaching rates for Na, Zr, P, and Si (10 –4 –10 –6 , 10 –6 –10 –8 , 10 –3 –10 –4 , and 10 –2 –10 −3 g m −2 d −1 ) are significantly lower than industry standards.