HIPed Tailored Pyrochlore-Rich Glass-Ceramic Waste Forms for the Immobilization of Nuclear Waste

Abstract

Hot isostatically pressed (HIPed) glass-ceramics for the immobilization of uranium-rich intermediate-level wastes and Hanford K-basin sludges were designed. These were based on pyrochlore-structured Ca (1-x) U (1+y) Ti 2 O 7 in glass, together with minor crystalline phases. Detailed microstructural, diffraction and spectroscopic characterization of selected glass-ceramic samples has been performed, and chemical durability is adequate, as measured by both MCC-1 and PCT-B leach tests.

Glass–ceramic nuclear waste forms obtained by crystallization of SiO2–Al2O3–CaO–ZrO2–TiO2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

“…These radioactive wastes must be isolated from the biosphere for very long times until their radiotoxicity level drops back to a radiotoxicity level close to that of the initial uranium natural ores [6][7][8][9]. GCM are also envisaged for the immobilization of separated minor actinides [9], U-rich [10] and Pu-rich [11,12] wastes. GCM would benefit at the same time from the ease of glassy waste forms preparation by melting + casting and from the very good long term behavior and the high incorporation capacity of ceramic waste forms such as zirconates, titanates and phosphates.…”

Development of brannerite glass‐ceramics for the immobilization of actinide‐rich radioactive wastes

“…The primary consideration was based on a typical sodium borosilicate glass with half of the boron replaced by aluminum in order to improve its chemical durability. Such a baseline glass was successfully used in the development of pyrochlore‐based glass‐ceramics . As part of the design brief, the actinide is directed toward the more durable ceramic phases and away from the glass.…”

“…Some durable titanate mineral phases identified in Synroc, [6][7][8][9][10][11][12][13][14][15][16] e.g., zirconolite and pyrochlore, have been considered for such an application. Consequently, both zirconolite-and pyrochlore-based glass ceramics [20][21][22][23][24][25][26][27][28] have been investigated as potential waste forms for the immobilization of some compositionally diverse actinide-rich radioactive wastes, e.g., plutonium (Pu) residue wastes and separated minor actinides. Considering their actinide waste loadings and radiation resistance, pyrochlore-based glass-ceramics are more favorable.…”

Pyrochlore based glass-ceramics for the immobilization of actinide-rich nuclear wastes: From concept to reality

“…However, the internal crystallization of pyrochlore in glass had hardly been studied and remained challenging until recently when we reported some conceptual work on the internal crystallization of U pyrochlore in glass by using both sintering and HIP techniques [15]. However, the formed crystalline pyrochlore was quite fine and the partitioning of U between pyrochlore and glass was far from satisfactory.…”