TiO2 addition into nuclear glass ceramic : study of the crystalline phases, structure and chemical durability

Abstract

This paper studies the nuclear glass ceramic based on aluminosilicate glass. It is proposed the addition of TiO2 on the crystalline phase. The structure and chemical durability have been investigated. The materials with four TiO2 contents, ranging from 4.11 to 7.11 wt.%, are synthesized by a discontinuous method. The 7.11 wt.% TiO2 glass ceramic synthesis was not successful and crystallizes during the melting stage. For the others materials, Archimedes density ranges between 2.891 and 2.962 g/cm3. For the majority of materials, X-ray diffraction analysis allows the identification of an aluminosilicate that belongs to pyroxenes silicates family as the initial phase, powelite and calzirtite. These phases are known as radionuclides’ sequestration minerals. Both SEM and DTA analyses confirm these findings. The FTIR analysis of materials reveals the complex glass-ceramics chemical composition. MCC1 and MCC2 tests, performed on selected glass ceramic materials, indicate that the materials containing 4.11 and 5.11 wt.% TiO2 are the most durable against Si, Al, Mg and Ce elements release, in MCC2 test; the Ce (minor actinide surrogate) leaching rate being negligible (193.7☓10-9 kg/m2d after 28 leaching days for 5.11 wt.% of TiO2 content). These results make valuable conclusions for the selection of the glass ceramic suitable to the high-level waste disposal