Synthesis and characterization of oxyapatite [Ca₂Nd₈(SiO₄)₆O₂] and mixed-alkaline-earth powellite [(Ca,Sr,Ba)MoO₄] for a glass-ceramic waste form

Journal Article · Thu Nov 01 00:00:00 EDT 2018 · Journal of Nuclear Materials

DOI:https://doi.org/10.1016/j.jnucmat.2018.08.048· OSTI ID:1485422

Peterson, Jacob A.; Crum, Jarrod V.; Riley, Brian J. ; Asmussen, R. Matthew ; Neeway, James J.

This paper discusses the synthesis, characterization, and chemical durability assessment of oxyapatite [Ca₂Nd₈(SiO₄)₆O₂] and mixed-alkaline-earth powellite [(Ca,Sr,Ba)MoO₄]. These are the major crystalline phases that precipitate from the melt during cooling of a glass ceramic waste form currently being evaluated for immobilizing wastes produced during the aqueous reprocessing of used nuclear fuel. The oxyapatite was made at 99.7% purity using a solution-based process followed by heat treatments. The powellite, made by melting carbonates and slow-cooling the melt, formed two different phases, one rich in Ca (74.7%) and Sr (19.4%) (balance is Ba) and the other rich in Sr (25.6%) and Ba (65.6%) (balance is Ca). Following the product consistent test after 5 days, the oxyapatite phase had a maximum normalized loss of 0.024 g m^-2 for Ca and the powellite phases showed a higher normalized loss from the Ba-powellite (0.22 g m^-2) compared with the Sr-powellite (0.06 g m^-2) and Ca-powellite (0.02 g m^-2).

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1485422
• Report Number(s): PNNL-SA-133874
• Journal Information: Journal of Nuclear Materials, Vol. 510, Issue C; ISSN 0022-3115
• Publisher: Elsevier
• Country of Publication: United States
• Language: English