Synthesis and Property of SrCeTi₂O₇ Synroc for Immobilization of High Level Radioactive Waste

Simulating radionuclide ⁹⁰Sr with ⁸⁸Sr and tetravalent actinides radionuclides with Ce⁴⁺, using analytical SrCO₃, CeO₂ and TiO₂ as raw materials, the SrCeTi₂O₇ synroc was synthesized through a high temperature solid-state method. The synthesis technology, physical properties, crystal structure and microstructure of SrCeTi₂O₇ synroc were researched. The thermal stability and leaching performance were also investigated. The results show that when selecting formulation as n(SrCO₃)∶n(CeO₂)∶n(TiO₂)＝1∶1∶2, sintering at 1 450 ℃ with holding time 5 h can synthesize SrCeTi₂O₇ synroc with dense structure and well crystallized. Indexing results show that SrCeTi₂O₇ synroc crystallizes as a tetragonal structure with the lattice parameters are a=0.387 33(4) nm, c=0.388 07(5) nm. The SrCeTi₂O₇ synroc has excellent thermal stability, and it maintains the SrCeTi₂O₇ phase after 800 ℃ heat treatment. Product consistency test shows SrCeTi₂O₇ synroc has good leaching performance, and the leaching rate of Sr, Ce and Ti are 3.51×10^-4, 8.23×10^-8 and 2.02×10^-7 g/(m²·d) in 28 days, respectively.