Depressurization device for reactor container

In a depressurization device of a reactor container, a means for maintaining the level of pool water to a predetermined range is disposed to a wet cleanup device, and a water recycling channel is also disposed for recycling the pool water. Preferably, a cooling means is disposed to a portion of the water recycling channel. Further, a means for cleaning a radioactive material adsorbing filter device is disposed. Then, reduction of water amount is prevented by maintaining the level of the pool water and the concentration of captured water soluble radioactive material is not increased to prevent re-evaporation of radioactive materials. Further, flow in the pool water is stabilized by a water recycling channel to, eliminate interference between an uprising stream and a downstream. Since re-evaporation of radioactive materials is prevented during operation of the depressurization device and the amount of pool water is not decreased, effective radioactive material removing function is always provided. Further, abnormal elevation of the pool water level or disturbance on the liquid surface are suppressed, to decrease the amount of scattering liquid droplets. The wet type cleanup device can be made compact and the volume of radioactive materials released to surrounding circumstance can be reduced remarkably. (N.H.)