Oxidative leaching of plutonium from simulated Hanford tank-waste sludges

IEC 119

Kenneth L. Nash, Melissa Hancock, Ivan Laszak, and Marian Borkowski. Chemistry Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439
The behavior of Pu(IV) and Pu(VI) during alkaline permanganate leaching of 4 synthetic sludges (Bismuth Phosphate (B), Modified Bismuth Phosphate (M), Purex (P) and Redox (R)) has been investigated. The amount of Pu leached from the sludge increased in order P > R > B > M, in reverse order to the chromium leaching. The content of plutonium was independent of its initial oxidation state. The reverse trends can be understood in terms of Pu re-adsorption onto the MnO2 generated (as Cr(III) and other substrates are oxidized by permanganate/manganate). The effect of chelating agents known to be present in tank wastes (EDTA, gluconate, glycolate, oxalate and citrate) on KMnO4 reduction/MnO2 production and re-deposition of plutonium was also studied and found to have varied effects on the process of oxidative dissolution/Pu redeposition. The results will be reported with discussion of their potential impact on oxidative leaching of actual tank-waste sludge. Work performed under the auspices of the Environmental Management Science Program (EMSP) of the U.S. Department of Energy under contract number W-31-109-ENG-38