Numerical Modeling of Mixing of Chemically Reacting, Non-Newtonian Slurry for Tank Waste Retrieval

Fifty-four million gallons of wastes containing 180-million curies of radioactivity are stored in single (SSTs)- and double-shell underground tanks (DSTs) at the U.S. Department of Energy's Hanford Site in eastern Washington (Gephart and Lundgren 1997). They are a multiphase, multicomponent, high-ionic strength, and highly basic mixture of liquids, solids, and, in some cases, gases. Mixer pumps will be installed in twenty-eight 4,0000-m DSTs to stir radioactive sludge/saltcake and supernatant liquid (and possibly a solvent) so the waste can be retrieved from the tanks for subsequent treatment and disposal. During the retrieval operation, complex interactions occur between waste mixing, chemical reactions, and rheology. Thus, decisions made about waste retrieval must account for these complex interactions