Development of Flow Type Cesium Removing Device Using Fluorinated Solvent

¹ Graduate School of Science and Technology, Niigata University, 2-8050 Ikarashi, Niigata 950-2181, Japan
² Niigata TLO, 2-8050 Ikarashi, Niigata 950-2181, Japan
³ Nanba Ltd., 633-1 Mishimashinbo, Nagaoka, 940-2311, Japan

^* Corresponding Authors: f19b056h@mail.cc.niigata-u.ac.jp (M. Suzuki), h_tajima@eng.niigata-u.ac.jp (H. Tajima)

Abstract

In order to simultaneously achieve separation and volume reduction of radioactive cesium in the aqueous solution, we proposed a solvent extraction using a fluorinated solvent which is a nonflammable liquid having a low boiling point and is easy to distill for regeneration. Firstly optimum conditions for single extraction were determined in a batch operation. The extraction experiment was carried out by changing the pH of 5 mg/L non-radioactive cesium aqueous solution using bis(2-ethylhexyl)phosphoric acid (D2EHPA) as an extractant. The higher the pH of the aqueous phase and the D2EHPA concentration, the better the removal rate. The highest removal rate was about 60% under the pH=13. From the experimental results, the optimum extraction condition was determined as pH=13 and [D2EHPA]=0.15 mol/L. Next multiple extraction test was carried out under this condition, and 90% cesium removal could be achieved in 3 times extraction. Finally, the flow type device using a static mixer for mixing and extracting parts was proposed and then the cesium removal test was performed. The cesium removal performance of this device was equivalent to the batch system.