Manometer type reactor shutdown assembly

A manometer type reactor shutdown assembly comprises vacant hexagonal reflective tubes each tightly sealed at the upper portion thereof and disposed at the periphery of a reactor core for the shutdown of nuclear reactions in the nuclear reactor. Different from conventional reactor shutdown devices using control elemtns, they can actively shsutdown the nuclear reactor without requiring external scram signals. When the pressure at the inlet aperture changes during normal operation, the liquid level of the coolants fluctuates by which the axial neutron leakage is changed making the reactor control complicate. In view of the above, a gas plenum is disposed in the upper portion of the hexagonal tube between the tightly sealing plate in which a plurality of apertured buffle plates are disposed. If the pressure near the coolant inlet aperture is fluctuated, since the apertured buffle plate constitutes a flow resistance, the liquid level change can be reduced as compared with the conventional case. It is possible to rapidly and effectively shutdown the nuclear reactor and unnecessary liquid level vibrations can be suppressed, and the controllability can be improved. (K.M.)