Separation methods for the pretreatment of the liquid fraction of high-level nuclear waste (HLW) at the Savannah River Site (SRS) include solvent extraction for the separation of cesium and adsorption/ion exchange for the removal of strontium and alpha-emitting actinides. The solvent extraction process, referred to as Caustic Side Solvent Extraction or CSSX, uses a calixarene extractant in combination with phase modifiers in a hydrocarbon diluent. Monosodium titanate (MST), a hydrous metal oxide, is the baseline material for the removal of strontium and alpha-emitting radionuclides (principally 238Pu, 239Pu, 240Pu and 237Np). Two pretreatment facilities, the Modular Caustic Side Solvent Extraction Unit (MCU) and the Actinide Removal Process (ARP) facility began radioactive operations at SRS in 2008. Together these facilities can treat approximately 4 million liters of waste per year. The same separation processes are also planned for the much larger Salt Waste Processing Facility (SWPF). The SWPF, which has a design throughput of about 27 million liters per year, is scheduled to begin radioactive operations in 2013. This paper presents an overview of the separation processes as well as recent research and development activities aimed at improving separation performance in the pretreatment facilities.

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