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

Abstract

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.

Accumulation of Particles in an Annular Centrifugal Contactor Cascade and the Effect upon the Extraction of Nitric Acid

“…Rev. [1]; the flowsheets demonstrated are PUREX [69,70], Advanced PUREX [71][72][73][74], URanium EXtraction [75], Next Extraction system for Transuranium Recovery [76,77], TRansUranium EXtraction [78,79], DIAMide EXtraction [80,81], Selective ActiNide EXtraction [53,54,[56][57][58][59][82][83][84][85][86][87], UNiversal Extraction [88][89][90][91][92], StRontium EXtraction [60,93], and others [1,94]. The feeds used in these flowsheets are genuine nuclear fuel solutions or simulated compositions, several of which generate solids in situ [1,4,51,[55][56][57][58][59][60][61]64,86].…”

Ultrasonic Method for Online Tracking of Interface and Dispersion Band in Gravity Settlers

“…In gravity settling, the driving force for separation of the two phases is gravity while in centrifugal settling, the driving force is a radially outward directed centrifugal force. Centrifugal settling is typically incorporated in centrifugal contactors and is preferred when the process requires very short residence time (like reprocessing of highly radioactive fuel). − As the driving force in these units can be 2 orders of magnitude higher than in gravity settlers, centrifugal settler is associated with very fast settling, low settler volume/hold up, and entrainment free operation. However, these units are highly power intensive, expensive, as well as maintenance intensive.…”

Design Modification in the Stationary Bowl of Annular Centrifugal Extractors to Handle Adverse Conditions

“…The ACE has several advantages such as a compact design, less holdup, high throughput, high mass transfer performance, low residence time, small footprint, low height, etc. Owing to these advantages, these equipment are also being used in nuclear fuel reprocessing, − especially in fast breeder reactor fuel reprocessing.…”