Mechanism of the flashing phenomena induced by microwave heating

Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi ; Yamada, Yoshikazu 

A mixed solution of uranyl nitrate and plutonium nitrate is converted to MOX raw powder by the microwave heating de-nitration method in nuclear fuel reprocessing. Since the microwave heating causes a boiling phenomenon, it is necessary to sufficiently confirm operating conditions to prevent flushing and overflow phenomena of solution. In this study, visualization observation of the microbubble generation and growth behavior near the liquid surface, measuring of bubble diameters, calculating the frequency of nucleation and estimating the quantity of heat of required for generation and growth of microbubbles were performed for the purpose of clarifying the generation mechanism of the flushing phenomena caused by microwave heating. As a result of comparative study with the amount of heat of released by flushing, it was confirmed that the quantities of the heat of released by flushing and the heat of required for generation and growth of microbubbles agree on the order.