Experimental And Computational Studies Of Uranium Extraction Microchip Laminar Flow

Tributylphosphate (TBP)-kerosene is widely used to extract uranyl from aqueous, no matter in uranium metallurgy, uranium material and nuclear fuel cycle. However the extraction process has a problem of phase separation, because of severe shaking which results in emulsification. Moreover, the process consumes a lot of organic reagents and generates large amount of radioactive wastes. Microfluidic is one of the most developed technology during the recent three decades. Because of its micron size, the channel has high interface-to-volume ratio and short transition distance, which can reduce the consumption of reagents, time of mass transfer and accelerate the process of analysis. Application of microfluidic in radioactive extraction process could provide significant improvements, by shortening analysis time, generating less waste in safeguards and minimizing radiation exposure for analytical personnel. Here in this thesis, extraction of uranium in microchannel were studied experimentally and theoretically.Firstly, a high liquid pressure and organic resistance device was constructed by connecting microchip and capillary by elastic O-ring and special capillary end which was turned outside. The flow rates of the aqueous and organic were changed for investigating the flow type. A relationship between the organic width to channel width ratio and the flow rates ratio of aqueous to organic was found. And computation fluid dynamic combined with level set method was used to simulate the flow type of two phases. Simulation results were agreed well with experimental phenomena.To acquire automatic phase separation, octadecyltrichlorosilane diluted in xylene was used to partly modify the microchannel. One-half of the glass wall was modified to be hydrophobic by OTS, while the other half remain hydrophilic. Aqueous and organic phase were automatically, completely, stably separated at the Y-type exit in the experiment. Then the stability of modified surface was investigated by soaking glass plates in different solutions for several days. The modified surface is stable in nitric acid (3mol/L), TBP-kerosene (20%), and uranyl nitrate solution (concentration of nitric acid is3mol/L, concentration of uranium is1,5,10mg/ml), while it is not stable in sodium hydroxide (lmol/L) and impurities solution (Al, Cu, Fe, Mn, Ni, Si,10mg/ml,concentration of nitric acid is3mol/L).Then modified channels were used to achieve the extraction process. Extraction ratio increases with contact time increasing, and has no relationship with initial concentration, when initial concentration of uranium is from1to10mg/ml. Also, one dimension simulation and experimental data are fitting well.At last, impurities in uranium were tested by microchennel. Comparing the results of microchannel with conventional results, there is no obviously difference by t-test. From the research in this thesis, microchannel could be used as a new way to pretreat for analysing impurities in uranium by ICP-AES.