The results of this report indicate that in-tank evaporation (ITE) should be continued to reduce the inventory of supernate in the Melton Valley Storage Tanks (MVST) until additional storage tanks and/or treatment facilities can be installed. Several equipment problems were encountered during the initial operation of the ITE. All of these have been addressed with the exception of the replacement of the air compressor that was originally used in the hydrofracture process and the intermittent wetting of the high efficiency particulate air (HEPA) filters. The compressor is being replaced with a unit that is designed for continuous operation. Filter wetting needs further investigation. ITE will help reduce the supernate inventory in the MVST using the existing equipment but will not eliminate the need for solidification campaigns. Several options are available to increase the evaporation rate above that achieved in this study to minimize dependence on solidification campaigns until new tanks and/or treatment systems become available. These include increasing the air sparge flow rate through the MVST, adding heat to the MVST, and pumping the supernate to an evaporator located near the MVST. Evaluations of the feasibility and cost effectiveness for the more promising options began in FY 1991 and will continue in FY 1992.
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