Development of sodium conversion technology; Development of sodium conversion basic experiment apparatus

Matsumoto, Toshiyuki; Yoshida, Eiichi; Suzuki, Shigeaki*; Yasu, Tomohisa*

In the future, a large amount of sodium (Na) containing radioactive wastes must be processed at the time of final shutdown/ decommissioning of FBR plant or radioactive sodium facilities in Japan. Therefore, its disposal technology should be established in consideration of economical efficiency, safety, etc. In the existing technology, since the method of processing sodium directly into radioactive waste is not established, conversion of sodium into chemically stable material can be considered. Then, basic experiments in which sodium was injected at 10 kg/h into solution of sodium hydroxide (NaOH) were conducted, with the improved Sodium Conversion Test Apparatus (SCOT). The conditions of NaOH solution were temperature of 100C, and NaOH concentration of 45-50 wt%. Consequently, the injected sodium reacted completely in the NaOH solution, and NaOH temperature, NaOH concentration, etc. were controlled properly. It validated that the system of this apparatus was appropriate. Moreover, in case sodium is injected into NaOH solution, a nozzle blockades sometimes. Therefore, the methods to eliminate the cause of nozzle blockage were examined.