Pulse columns have been studied long and a great variety of experimental investigations have been carried out, using them. In this study, two 5 m pulse columns with the same cartridge geometries are installed to investigate the performances. First of all, the characteristic differences of the aqueous continuous and the organic continuous columns were investigated experimentally. Secondly, a ternary system of 30 % TBP in dodecane-acetic acid-water was adopted for the mass-transfer study. It was concluded that the overall mass-transfer coefficient Kx was independent of whether the mass-transfer is from the dispersed to the continuous phase or from the continuous to the dispersed phase. Next, thorium nitrate was extracted and reextracted using both modes of operation for comparison. Both HETS and HTU were obtained. According to the results for the extraction, the aqueous continuous column gave much shorter HTU than the organic continuous column. On the other hand, in reextraction the organic continuous column gave shorter HTU. Finally, the Thorex-processes for uranium and thorium co-extraction, co-stripping, and partitioning were studied. As for the extraction process, both acid feed solution and acid deficiend feed solution were investigated for comparison. The concentration profiles along the column height were obtained. The data were analysed with McCabe-Thiele diagrams to evaluate HETS
