Reactor container

Metals are disposed below a reactor pressure vessel, which evaporate by the heat of fuels melted out of the pressure vessel and generates aerosols upon occurrence of a rector core melt-down accident. Simultaneously with melting of the pressure vessel upon occurrence of reactor core melt-down accident, the molten fuel is dropped on the metals. The metals evaporate into aerosols by the afterheat of the molten fuels. Accordingly, upon occurrence of the accident, radioactive aerosols and the aerosols generated by the evaporation of the metals are present together in the reactor container. When the concentration of the aerosol exceeds a predetermined level in this state, aerosols are coagulated to increase the grain size thereof. Then, a gravitational settling velocity is increased and they are segmented in a short period of time. Further, the aerosols having increased grain size are removed more efficiently upon scrubbing. (T.M.)