An emergency device for cooling a nuclear reactor core

The emergency cooling system for a nuclear-reactor comprises a pressurized enclosure tightly sealed by an obturating head forming a pressure chamber, a reactor-core in said enclosure, an inlet and an outlet for allowing the coolant to flow, characterized in that it comprises an accumulator containing a pressurized neutron-absorbent connected to the obturating head for providing said pressure-chamber with an emergency-coolant when the coolant pressure within the reactor falls below the pressure within the accumulator, and means in communication with the pressure-chamber and the core for introducing the emergency coolant into the latter