A robust alkaline-side CSEX solvent suitable for removing cesium from Savannah River high level waste

A robust solvent suitable for extracting cesium from alkaline nitrate media like that of the high-level liquid waste stored at the U.S. Department of Energy Savannah River Site has been developed. The solvent is composed of t he cesium extractant calix[4]arene-bis-(tert-octylbenzo-crown-6) ("BOBCalix C6") at 0.01 M, the modifier 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylp henoxy)-2-propanol ("Cs-7SBT") at 0.50 M, trioctylamine ("TOA") at 0.001 M, and the aliphatic diluent Isopar(R) L. The solvent holds up exceptionally well under various stresses, such as sustained contact with waste simulant and dilute nitric acid; repeated extraction, scrubbing, and stripping cycle s; and excessive loading. The behavior of the solvent in batch-equilibrium flowsheet tests conducted at 15, 25, and 45 degreesC is presented. Flowshee t calculations show that the Savannah River Site requirements for a deconta mination factor of 40,000 and a cesium concentration factor of 12 could be met in a 22-stage bank of 25-cm centrifugal contactors at 25 degreesC with conservative assumptions regarding hydrodynamics and stage efficiency. Expl oiting the temperature dependence of extraction and stripping could reduce the number of stages to 18.