Efforts are underway to qualify the Next-Generation Solvent for the Caustic Side Solvent Extraction (CSSX) process. Researchers at multiple national laboratories have been involved in this effort. As part of the effort to qualify the solvent extraction system at the Savannah River Site (SRS), Savannah River National Laboratory (SRNL) researchers performed a number of tests at various scales. A series of batch equilibrium, or Extraction-Scrub-Strip (ESS), tests were conducted first. These tests used similar to 30 mL of Next-Generation Solvent and either actual SRS tank waste, or waste simulant solutions. The results from these cesium mass transfer tests were used to predict solvent behavior under a number of conditions. For larger-scale testing, twelve stages of 2-cm (diameter) centrifugal contactors were assembled. This rack of contactors is structurally similar to one tested in 2001 during the demonstration of the baseline CSSX process. No issues were encountered during assembly and mechanical testing. A non-radiological test was performed using 35 L of cesium-spiked caustic waste simulant followed by a test with 39 L of actual tank waste. Test results are discussed, particularly those related to the effectiveness of extraction.