Characterization of actinides in simulated alkaline tank waste sludges and leach solutions

Nash, K. L. ; Rao, L. ; Jensen, M. P. ; Bond, A. H.

Argonne National Laboratory

关键词: Leaching;    Sludges;    Uranium;    Radiolysis;    Neptunium;   

DOI  :  10.2172/755844
RP-ID  :  ANL/CHM/RP-101703
RP-ID  :  W-31109-ENG-38
RP-ID  :  755844

美国|英语

来源: UNT Digital Library

【 摘 要 】

Current plans call for an alkaline scrub of actinide-bearing sludges in the Hanford Waste tanks prior to their incorporation in glass waste forms. Though it is assumed that actinides will remain in the sludge phase during this procedure, this assumption is based on insufficient supporting thermodynamic and kinetic data. In this project the authors will investigate the fundamental chemistry of actinides in strongly alkaline solution and solid phases to strengthen the foundation and identify potential limitations of this approach. They will focus on the characterization of the leaching of actinides from simulated BiPO{sub 4}, REDOX, and PUREX sludges, the identification of actinide mineral phases in the sludge simulants, and the possible solubilization of actinides by complexation and radiolysis effects. This program will provide new fundamental information on the chemical behavior and speciation of uranium, neptunium, plutonium, and americium in simulated alkaline tank waste sludges and alkaline scrub liquors. Sludge simulants will be prepared from the appropriate matrix components using published data for guidance. Actinide ions will be introduced in the oxidation states pertinent to process conditions. The authors will characterize the speciation of the actinides in the sludges using a variety of techniques. In parallel studies, they will address the chemistry of actinide ions in alkaline solutions, principally those containing chelating agents. The third critical element of this research will be to assess the impact of radiolysis on actinide behavior. By correlating actinide speciation in the solid and solution phases with sludge composition, it will be possible to predict conditions favoring mobilization (or immobilization) of actinide ions during sludge washing. The new information will increase predictability of actinide behavior during tank sludge washing, and so contribute to minimization of the volume of high level waste created.