Reactor container

Non-radioactive materials comprising elemental substances or compounds of the same elements as fissile products which evaporate by molten leached fuels from a pressure vessel and are converted into aerosols upon occurrence of reactor core melt down are disposed below the pressure vessel. This non-radioactive materials are surrounded by insoluble materials gasified or melted easily by after-heat of the molten fuels. Further, the outside of the insoluble materials is surrounded by water soluble non-radioactive materials which are elemental substances or compounds of the same elements as the fissile products released upon occurrence of a severe accident. Moreover, the surface of the water soluble non-radioactive materials is surrounded by materials which are water soluble but having no or scarce deliquescence. Then, the specific radioactivity of fissile products in suppression pool water is decreased, volatile organic iodine is mostly deactivated, and transfer of radioactive inorganic iodine to a gas phase is suppressed, to thereby remarkably suppress the radioactive materials releasing from the reactor container. (N.H.)