U.S. Department of Energy

Pacific Northwest National Laboratory

An in-situ investigation of γ-AlOOH dissolution under high pH conditions

Please join us on Wednesday, January 6, 2016, from Noon to 1:00 p.m. in the RPL Plutonium Room for a monthly Seminar Series featuring LDRD PI Dr. Edgar Buck presenting on project An In-situ Investigation of γ-AlOOH Dissolution under High pH Conditions.

Research Team: Edgar Buck, Eugene Ilton, Frances Smith, Michele Conroy, Eric Jensen, Sayan Chatterjee, Chongmin Wang

Wednesday, January 6, 2016
Dr. Edgar Buck
Scientist, Irradiated Materials
PNNL
Reactions at solid or particle surfaces include dissolution, precipitation, and sorption. Heterogeneities of the mineral surface include defects and dislocations, and expression of different crystallographic faces represent intrinsic factors that cause variability in reactivity. Extrinsic factors that may affect reactivity include sorbed molecules and colloids, tenacious nano-scale surface coatings, and, particularly relevant to nuclear system, nano-bubbles, from radiolytic processes. We propose that by probing dissolution processes relevant to Hanford waste processing and spent fuel dissolution at the nanoscale with modern in situ electron microscopy techniques, we will be able to test the role of both intrinsic and extrinsic factors on the variability of mineral reactivity. The dissolution and precipitation of gibbsite [alpha-Al(OH)3] and boehmite [gamma-AlOOH] is of prime importance to the final disposition of high-level nuclear waste stored at the Hanford Site. The high aluminum content in the Hanford tank waste stream is incompatible with current durable glass formulations and needs to be minimized prior to vitrification. The aluminum oxide that formed from the precipitation of waste streams from plutonium weapons processing is present as colloidal-sized particles in a highly alkaline and high ionic strength solution. Although the high radioactivity of the waste is a significant challenge to waste processing, the influence of radioactivity on the behavior of the aluminum phases and their subsequent processing is unknown. Gibbsite and sodium aluminate, which are common in the tanks, are easily dissolved by heating under caustic conditions; however, boehmite is more stable and requires more aggressive conditions.
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