(224c) Speciation of Aluminum Phases at the Hanford Site

Treatment of the tank waste at the Hanford Nuclear Reservation in Washington State is one of the largest environmental challenges facing the world today. Disposition of the insoluble solids poses the greatest hurdle to achieving long-term stabilization of the tank waste. The single largest component of the insoluble solids is aluminum. An assessment of the characterization of this waste has identified that the aluminum is roughly split into thirds between sodium aluminate, gibbsite, and boehmite mineral phases. The largest single source of aluminum in the Hanford tank farms is associated with the tanks located in the southwest corner of the site. These tanks contain relatively high concentrations of aluminum such that the mass of insoluble solids present could be reduced by up to 90% through caustic leaching of the materials in these tanks. Chromium is also present and has been suspected of inhibiting aluminum dissolution. An assessment of the impact of chromium (and other metals) on the dissolution of boehmite will be provided.