Development and testing of centrifugal extractors for the reprocessing of fast breeder reactor fuels

The reprocessing of fuels of future breeder reactors is regarded as being necessary and extremely important. Solvent extraction and extraction apparatus will have a key part to play here. This report should represent a design basis for centrifugal extractors, by which one can comply with the great requirements for such a project. The requirements for high reliability in operation and remote maintenance have led to a simple vertical extractor shape with drive motor at the top. Equipped with an EK drive motor and air bearing, the developed model is practically without wear. The factors affecting the throughput were examined with models which could easily be converted and which gave a good idea. With TBP (30%) in dodecan and dilute nitric acid as the experimental medium, a rotor of 50 mm diameter and 115 mm settling length, a total throughput of 200 litres/hour was achieved with an organic/aquaeous ratio of 0.5. 0.5% entrainment in one of the separate phases was fixed as the criterion for the limit of throughput. The relationship between Covette flow mixing, drop size distribution and efficiency of settling was examined and maximized with reference to the above-mentioned rotor size. The stage efficiency, losses of refined material and the behaviour of a 3-stage extractor battery to variations of material flow were determined by experiments with uranium. A surprisingly high stage efficiency of nearly 100% was achieved with throughputs up to 250 kg/d. A starting process up to reaching a state of equilibrium is finished after less than 20 minutes. (orig.)