High UO2 embeding ratios by rapid synthesis of zircon-based glass-ceramic waste forms

In order to enhance the uranium immobilization conditions in zircon silicate ceramics, 5 wt% CaO was introduced as an effective mineralizer. This additive promoted the phase transformation from monoclinic to tetragonal zirconia, enabling successful sintering at a reduced temperature of 1500 °C with a shortened holding time of 6 h. A stable Zr (1-x) U x SiO 4 solid solution formed when uranium content x ≤ 0.1, confirming successful U 4 + substitution for Zr 4+ in the crystal structure. When x exceeded 0.1, a UO 2 secondary phase appeared, indicating the solid solution limit. Using this optimal loading, zirconium-based borosilicate glass-ceramic composites were prepared. In this work, Pb-doped borosilicate glass was selected as the glass component, because Pb exhibits better radiation resistance compared with traditional borosilicate glass. Increased glass content further enhanced immobilization performance, achieving an exceptionally low uranium leaching rate of 1 × 10 −5 g·m −2 ·d −1 after 28 days at 90 °C, demonstrating superior durability.