Chemical stability of Ce-doped zircon ceramics: Influence of pH, temperature and their coupling effects

• Published in: Journal of rare earths Vol. 35; no. 2; pp. 164 - 171
• Main Authors: XIE, Yi, FAN, Long, SHU, Xiaoyan, CHI, Fangting, DING, Yi, MA, Dengsheng, LU, Xirui
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2017
• Subjects: chemical durability; high-level radioactive waste; rare earths; waste form; zircon; chemical durability; waste form; high-level radioactive waste; zircon; rare earths
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/S1002-0721(17)60895-0

Zircon was employed to immobilize simulated tetravalentactinide nuclide (Ce4+). Zr1−xCexSiO4 (0≤x≤0.10) ceramics were synthesized and their chemical durabilities were investigated systematically. The effects of pH and temperature on the chemical durability of the as-prepared compounds were investigated using the MCC-1 static leaching test, and their coupling effects were also explored. It was found that the normalized release rates of Ce in deionized water and alkaline solutions (pH=10) were smaller than those in acid solutions (pH=4). At a certain pH value, the normalized release rate of Ce (LRCe) increased with the temperature in the initial period. However, the leaching progress almost reached a balance after 14 days, and both of the pH and the temperature had slight impact on the leaching of Ce element. Moreover, the LRCe were below 10−5 g/m2/d after 42 days, which was lower than those of other nuclear waste forms in all discussed leachates. Normalized release rates of Ce in all discussed leachates