Investigation of Condensed Liquid Film Flow on Chamber Ceiling of Laser-Fusion Reactor

To protect from high-energy fluxes caused by nuclear fusion reaction to a first wall of a laser-fusion reactor such as KOYO reactor, the cascade-type falling liquid-metal film flow was proposed as a liquid-wall concept which was one of the reactor chamber cooling and wall protection schemes. In this concept, vapor released by fuel targets and the liquid wall will be condensed on the chamber ceiling which is kept relatively cold. The condensed liquid-metal vapor makes many droplets on the ceiling, and then the droplets will agglomerate, and eventually make the liquid film on the ceiling surface. The liquid-metal film will flow from the ceiling to the liquid first-wall. In this study, the proof-of-principal (POP) experiments and numerical simulations were conducted regarding the liquid-film flow on the ceiling wall. It is found that if the liquid film is formed on the ceiling surface, the liquid flows along the ceiling wall and from the ceiling wall down to the reactor core as long as the vapor is supplied. Moreover, the measurements of the liquid-film thickness were taken by using a confocal laser scanning microscopy, and the effects of the wettability of the wall on the liquid film flow behavior were obtained.