(339d) Modeling of Hanford C Farm Waste Retrievals Using the Environmental Simulation Program (ESP)

Evaluation of the potential difficulties associated with cleanup of the Hanford site tank wastes has indicated that tank farm operations are limited by the lack of available space in the existing double shell tank (DST) system. Part of the difficulty in controlling the available space lies in the underlying chemistry associated with salt cake and sludge retrievals.  Sludge retrievals typically employ sluicing. Owing to the limited solubilities of metal hydroxides and oxides, only minimal dissolution is expected during sludge retrievals.  The resulting slurry feed must also meet specific requirements such as percent solids by weight, and the ability to effectively blend the waste with that already present in the DST, etc.

Efforts at the Institute for Clean Energy Technology at Mississippi State University  have led to the development of an equilibrium-based model for use in predicting tank and stream parameters during retrieval of low level radioactive wastes from Hanford C farm tanks.  The model uses the Environmental Simulation Program (ESP, OLI Systems Inc.) structured as a batch process for each stage of retrieval processing and delivers outputs relating thermodynamically predicted compositions.  The model is augmented with various stage and process constraints that are based on use of the Modified Sluicing with Recycle and the Mobile Retrieval System methods for waste retrieval.

The ESP simulation model was used to predict tank and stream parameters corresponding to the retrieval of waste from tanks in the Hanford C farm.  The proposed schedule for retrieval for C farm tanks was used as a basis for waste tank sequencing and receiver tank usage.  Each C tank retrieval was modeled, and selected data are presented to show the applicability and possibilities of the use of ESP modeling for equilibrium predictions within Hanford waste recovery processes.