A test program has been conducted to determine the extent to which irradiation of a calixarene-based cesium extractant affects separation of the organic (solvent) phase from aqueous solutions with which it is contacted in a prototype extraction flowsheet. A caustic-side solvent extraction process, known as CSSX, has been developed for the selective removal of cesium from wastes generated by the processing of irradiated nuclear reactor fuels. This process consists of a cascade of mass transfer stages in which cesium is transferred from an aqueous feed into the CSSX extractant (BOBCalixC6), the extract is scrubbed with 0.05 M nitric acid to remove coextracted elements, and the solvated cesium is stripped (or back-extracted) into 0.001 M HNO3-Removal of cesium from stored waste supernatants is desirable as a means of segregating high-activity cesium-137 (137Cs) from the solution, thereby reducing the volume of material that must be processed and disposed of as high-level waste. The CSSX process is one of three cesium removal technologies currently being considered for deployment for treatment of wastes that are stored at the U.S. Department of Energy's (USDOE's) Savannah River Site (SRS).
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