Emergency core cooling device

The purpose of the present invention is to ensure the reactor safety upon loss of coolant accident (LOCA) in a BWR type reactor. That is lowering of the water level in a shroud is suppressed upon rupture of pipeways in an emergency core cooling system of a nuclear reactor containing recycling pump. In view of the above, openings of a reactor pressure vessel in each system constituting the cooling device are formed to the outside of the shroud contained in the reactor pressure vessel and above the uppermost end of the reactor core contained in the shroud. In the thus constituted emergency reactor core cooling device, ruptured openings situate above the reactor core even when a part of each system is ruptured. Accordingly. flow rate of coolants discharged to the outside due to the rupture can be reduced. Further, since the openings are formed at the outside of the shroud, direct discharge of the coolants from the shroud to the outside can be prevented. Therefore, a greater amount of water can be stored in the reactor core upon LOCA and the safety margin is improved. (I.S.)