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The current mission of the US Department of Energy's Hanford Site is one of environmental restoration. A major task within this mission is the disposal of large volumes of high-level wastes (HLW) that are stored in underground tanks on the site. Under the current planning assumptions, all high-level tank waste will be vitrified as borosilicate glass and then disposed of in a geologic repository. The costs associated with this disposal scheme are very high. Thus, methods to reduce the volume of glass required to vitrify these wastes are currently being investigated. Plutonium Finishing Plant (PFP) sludge is a unique transuranic waste that is stored in tank 241- SY-102 on the Hanford site. As the name implies, the bulk of this material consists of waste from operations at the Plutonium Finishing Plant; but, other wastes have also been added (e.g., wastes from decontamination activities). Because the quantities of plutonium and americium in the PFP sludge are greater than 100 nCi/g, this sludge must be handled as a HLW. Approximately 6000 glass canisters would result from vitrifying this waste directly. Sludge washing would reduce the required number of canisters to [approximately]2500, with the volume of glass being driven by the low allowablemore » concentration limit for Cr in the vitrification plant feed. The cost of production and subsequent geologic disposal of each canister of glass is expected to be $0.5 M to $1 M. Thus, an economic incentive exists to develop methods of pretreating the sludge to reduce the number of glass canisters needed to contain the final vitrified product.« less |
