Performance Research Of A Nuclear Micro Extractor Based On Coanda Effect

The reprocessing of spent nuclear fuel(SNF) is becoming necessary with the rapid development of the nuclear power industry in China, as it is efficient and safe. However, the extraction equipment widely used in the Purex process, the worldwide generally applied reprocessing method of SNF, all has varying degrees of deficiencies. In comparison with the traditional equipment, the microextraction equipment shows a number of advantages such as higher mixing efficiency, smaller equipment scale, larger surface area, better mass transfer performance, shorter residence time, less remaining material in device and so on. Thus, it meets the requirements of Purex process well and is very promising. Based on the Coanda effect, this paper researched the biphasic mass transfer and enrichment as well as problems concerning interstage transfer, and proposed an efficient design concept of a multistage countercurrent microextraction system.For this system, a new type of Passive Feedback Oscillation Micro Mixer(PFOMM) is constructed, making use of the Coanda effect, namely the adhesion-wall effect of jet. With the help of mixing experiments of mutually soluble liquids, three mixing mechanisms of this new micro mixer(vortex mixing, internal recirculation mixing and oscillation mixing) are illustrated. It is ensured that asymmetric feedback tunnel and splitter design can enhance the mixture performance of PFOMM. Also, the prospect of PFOMM by high Reynolds number or high throughput is quantitative validated through digital image processing.Furthermore, this paper researched the mixing characteristics of immiscible biphasic liquids in PFOMM and discovered four biphasic liquid-liquid flow patterns under different Reynolds numbers. In addition, the mass transfer performance by extraction of two types of PFOMM in nitric acid/TBP system and in Zr4+/TBP system is examined, so that the high extraction performance of PFOMM under high Reynolds number is ensured.To conclude: Based on the new type of multistage PFOMM, this paper proposed and validated the design concept of a microextraction system that enables biphasic mass transfer, enrichment and interstage transfer by controlling the operation methods of circulating. A multistage countercurrent extraction becomes possible, which is twice to four times more efficient than concurrent flow equipment by Zr4+ extraction and thus has a good potential prospect in Purex process.Using CFD simulations, this paper also discusses the formation and correlation of the three mixing mechanisms of PFOMM and proved that the fluid oscillation frequency is proportional to the Reynolds number. This lays the theoretical foundation for the further optimization of micromixers.