Liquid metal cooling reactor

A liquid surface area restricting mechanism is disposed in the upper portion of a reactor container for decreasing coolant liquid surface, and it comprises inner and outer cylindrical portions and a disk-like bottom for closing the lower edge thereof which are integrated and inserted from the upper portion of the reactor vessel such that coolants are introduced to the inside of the inner cylinder. A plurality of control rod supports are suspended from annular floats passing through the reactor structure, and control rod receivers are mounted to the control rod supports. A reactor power control rods are supported by the control rod receivers so as to insert and withdraw the reactor power control rods to and from a lower portion of the reactor core. Along with the elevation of the liquid level of the coolants, the floats are also raised to drive the connected control rods and insert them to the reactor core thereby suppressing reactor reaction. That is, an inherent nuclear reaction suppression mechanism utilizing physical phenomenon is disposed without interposing any intermediate system such as electron circuits. Reactor safety is improved to mitigate an operator's psychological burden. (N.H.)