The caustic-side solvent extraction process to remove radioactive cesium from Department of Energy salt waste was developed using small-scale annular centrifugal contactors. A scale-up factor of 750X is required. Testing with commercially available centrifugal contactors identified key design and operational parameters. Air flow is significant and the rotor bottom must remain covered to prevent surging flow. The Clean-in-Place feature was modified to allow hands-on maintenance. Flow rates and rotor speeds were optimized to reduce other-phase carryover. Startup, operation, and recovery methods were confirmed. Testing validated a Decontamination Factor 12 and a strip Concentration Factor of 12 to 15.