Open AccessOxidative dissolution of chromium from Hanford Tank sludges under alkaline conditions
Author(s) -
Brian M. Rapko,
G.J. Lumetta,
Michael J. Wagner
Publication year - 1996
Language(s) - English
Resource type - Reports
DOI - 10.2172/266870
Subject(s) - hanford site , leaching (pedology) , borosilicate glass , savannah river site , hazardous waste , high level waste , waste management , chromium , radioactive waste , chemistry , reagent , environmental science , plutonium , dissolution , radiochemistry , pulp and paper industry , environmental chemistry , nuclear chemistry , engineering , soil water , organic chemistry , soil science
Because of the expected high cost of vitrifying and disposing of high-level waste at the U.S. Department of Energy`s Hanford Site, pretreatment processes are being developed to reduce the anticipated volume of borosilicate glass. Sludge washing and caustic leaching, the baseline sludge pretreatment process, is expected to leach out a substantial portion of the {sup 137}Cs, possibly other radionuclides, and a significant portion of such major nonradionuclides as Al or P. The decontaminated solution will be routed to the low-level waste stream, where it will be immobilized in a glass matrix. The leached solids, which will contain the transuranic elements and {sup 90}Sr, will be handled as high-level waste. Previous studies indicate that poor removal of chromium in the +3 oxidation state [Cr(III)] occurs during baseline pretreatment. Because the concentration of Cr allowed in high level waste glass is low, a relatively small amount of Cr in the sludge can have a relatively large impact on the volume of high level waste glass produced. For this reason, additional leach steps to remove Cr would be desirable, and oxidative alkaline leaching has been proposed as a simple addition to the baseline sludge pretreatment. This report describes small-scale screening tests on the oxidative alkaline leaching of Cr performed with actual Hanford tank sludges