Leaching Behavior and Particle Irradiation Response of (1-x)Sr0.5Zr2(PO4)3-xCe0.5Sm0.5PO4 Ceramics for Immobilizing Multiple Nuclides

To explore the application potential of ceramic waste forms for immobilizing multiple nuclides in high-level waste, a systematic study was conducted on (1- x )Sr 0.5 Zr 2 (PO 4 ) 3 - x Ce 0.5 Sm 0.5 PO 4 ( x = 0, 0.5, and 1) ceramics, focusing on their chemical and irradiation stability. The composite ceramics can simultaneously immobilize multiple nuclides (Sr, Ce, and Sm), while retaining a homogeneous microstructure and high relative density (>97%). Static leaching experiment indicated low normalized leaching rates: LR Sr ∼ 10 -4 -10 -3 g·m -2 ·d -1 , LR Ce ∼ 10 -8 -10 -7 g·m -2 ·d -1 , and LR Sm ∼ 10 -7 -10 -6 g·m -2 ·d -1 . Different leaching behaviors of nuclides (Sr, Ce, Sm) were further identified using the de Groot and van der Sloot model. With 5 MeV Xe 20+ irradiation at a fluence of 2.5×10 15 ions/cm 2 , Sr 0.5 Zr 2 (PO 4 ) 3 phase in the composite ceramics can still maintain part of its crystal structure, while Ce 0.5 Sm 0.5 PO 4 phase tends to amorphize. Interestingly, subsequent TEM observation further vitrificated the Xe 20+ -induced amorphous Ce 0.5 Sm 0.5 PO 4 phase recrystallizes under electron-beam (e-beam) irradiation.