Extraction and Stripping Tests of Engineering-Scale Centrifugal Contactor Cascade System for Spent Nuclear Fuel Reprocessing

The Japan Atomic Energy Agency has been developing centrifugal contactors for solvent extraction to apply to next-generation reprocessing plants. The centrifugal contactor has some attractive advantages such as more compact design and shorter liquid residence times than conventional contactors. Many kinetic studies using a miniature centrifugal contactor have been carried out worldwide. However, there are few engineering-scale studies in which stage efficiencies, transition behavior of concentration profiles, and robustness under maloperation conditions have been comprehensively discussed for a contactor cascade system. In this study, we carried out extraction and stripping tests of an engineering-scale centrifugal contactor cascade system based on a flowsheet of 10 kg-HM/h using uranyl nitrate solution. As a result, the stage efficiencies on uranium extraction and stripping were quite high, nearly 100% for extraction and 97-98% for stripping. The uranium concentration profiles became stable within 10 minutes for both extraction and stripping sections. No overflow or entrainment was observed under normal operation during the extraction and stripping tests. During the stripping test, it was estimated that an increase in temperature of the feed stripping solution from 308 to 333 K or a decrease in the flow rate ratio of the organic to aqueous phase from 1.0 to 0.8 corresponded to the distribution capacity of the two contactors. The maloperation test, in which a motor at a stage of the contactor cascade system was intentionally stopped, showed that the system could maintain stable operation with no emergency shutdown following the installation of at least two additional stages.