Microwave chemical durability of an iron-rich glass-ceramic dedicated for high-level radioactive waste

Abstract

This study investigates the effect of crystallization time (t _c ) in the structure of an iron-rich glass-ceramic (GC) dedicated for high-level radioactive waste (HLW), ceramized by nucleation–crystallization treatment at 790 °C for 2 h and 950 °C, for different periods ranging from 3 to 12 h. Density, XRD, SEM, FTIR, and Microwave chemical durability results are shown. Considering all the materials, Archimedes’ density is between 2.607 and 2.634 g cm ^−3 . Both XRD and SEM analyses revealed the development of two main crystalline phases, spodumene (LiAlSi _2 O _6 ) and (Zr, Ln) molybdate La _2 Zr _3 (MoO _4 ) _9 , during the heat treatment. These phases regularly grow by the increase of crystallization time. They are known as radionuclides’ sequestration minerals. FTIR analysis confirms the complex GCs chemical composition. The microwave chemical durability test performed on GCs crystallized at t _c = 9 h was conducted to evaluate their chemical stability. The leachates of the elements: Al, Fe, Mg, Li, Mo, Na, Si, and Zr were analyzed by ICP-OES. RL _i values of Al, Mg, Mo, and Zr elements representing the radioactive waste (RW), vary between 2.3218 × 10 ^−8 and 2.9204 × 10 ^−8 kg m ^−2 d. For Fe and Li, were slightly lower. However, RL _Si was highest reaching 1.7457 × 10 ^−6 kg m ^−2 d ^−1 . The elementary percentages extracted during the dissolution test for all elements are less than 0.5%, which makes our material chemically stable. Its resistance to such an aggressive dissolution test makes it a good candidate for the confinement of some RW elements.

Keywords

• nuclear glass ceramics
• crystallization time
• microwave
• chemical durability