Flashing phenomenon via microwave heating and influence of high dielectric constant solution

Kobayashi, Shohei*; Abe, Yutaka*; Kaneko, Akiko*; Fujiwara, Kota*; Futsuta, Akihiro*; Segawa, Tomoomi ; Kawaguchi, Koichi  ; Ishii, Katsunori 

In the reprocessing process in the nuclear fuel cycle, a solution of plutonium nitrate and uranyl nitrate is converted into a mixed oxide by microwave heating denitration method. The objective of this study is to clarify the mechanism of the flashing phenomenon and to clarify the effect of the microwave heating characteristics of a high dielectric constant solution on the flashing phenomenon. Microwave heating experiments were conducted using KCl aqueous solution, which is the high dielectric constant solution simulating the reprocessing solution. It was clarified that the growth rate of bubbles in the KCl aqueous solution decreased with the time of microwave heating compared with distilled water. It is thought that in the KCl aqueous solution, the heating efficiency at the center of the solution is lower than that in the surroundings, and the growth rate of bubbles is reduced so that the flashing phenomenon does not easily occur in the high dielectric constant solution.