Visualization of single micro-particle behavior on an interface using a laser manipulation

Horiguchi, Naoki   

In severe accidents of LWRs, it is expected that radioactive micro-particles are captured by the interfaces of bubbles in a pool, and the capture controls the discharge of radioactive micro-particles to the exterior environment. In recent research on the visualization of bubbles, which include insoluble micro-particles, the accumulation of particles on the interfaces of bubbles is reported. However, numerical studies for severe accident management commonly ignore this accumulation and treat a single particle to move from a gas phase to a liquid phase irreversibly. Therefore, experimental studies for the visualization of the single micro-particle behavior on an interface is required in order to improve severe accident management. In the experiments for this purpose, the manipulation of a micro-particle near an interface in a non-contact manner is required too. Although laser manipulation techniques can not only manipulate a micro-particle in a single liquid phase in a non-contact manner but also visualize its behavior, there is no report related to a micro-particle on an interface. In this study, we developed a visualization method of single micro-particle behavior on an interface using a laser manipulating technique. We prepared an apparatus to manipulate and visualize an insoluble micro-particle in a single water phase using a laser manipulating technique; we developed a method to form an interface using water and silicon oil in the apparatus. We conducted the experiment using the apparatus and confirmed that a micro particle was captured by the interface. Another micro-particle was captured by an interface with small curvature but returned to the original phase after a short time. We considered that the Brownian motion of the particle itself and the curvature of the interface affect the behavior.