Crystallization of Simulated High-Level Nuclear Waste Glasses Under Heat Treatment and Its Impacts on Glass Durability

• Published in: He huaxue yu fangshe huaxue
• Main Authors: CHANG Jiong, ZHU Dong-dong, WANG Jia-teng, HE Cheng, LIU Xiao, ZHANG Hua, TAN Sheng-heng
• Format: Article
• Language: Chinese
• Published: Editorial Office of Journal of Nuclear and Radiochemistry 2023-02-01
• Subjects: vitrification; molybdate; rare earth oxides; crystallization; glass chemical durability
• Online Access: http://www.jnrc.org.cn/CN/10.7538/hhx.2023.45.01.0022
• ISSN: 0253-9950

Vitrification is currently the primary choice worldwide for high-level nuclear waste immobilization. This study investigated the crystallization behaviors of glasses containing 24%(mass fraction) and 30% simulated high-level nuclear waste, respectively, under different temperatures. According to X-ray diffraction, Raman spectroscopy and scanning electronic microscopy results, dendritic powellite(CaMoO4) phase and string-like Zr-cerianite (ZrxCe1-xO2) are the main crystalline phases when the glasses are heat treated at 800 ℃, while a great amount of hollow hexagonal oxyapatite(Ca2Ln8(SiO4)6O2) phases are observed in addition when the glasses are heated at 950 ℃. The chemical durability test shows that the heat treatment decreases the total normalized leaching mass loss of glass by about 1/3, with main contributions from B, Na, Mo and Ca. The normalized leaching mass loss of the glasses after heat treatment at 950 ℃ is smaller than that after heat treatment at 800 ℃. It indicates that the heat treatment of glass for crystallization improves glass durability.