Core emergency shutdown device of pebble bed type reactor

Purpose: To provide the subject device wherein at the time of emergency shutdown of a reactor a high-pressure gas is caused to flow therein through a gas passage to cause pellets of neutron absorbers to flow out into a fuel ball filled layer, thereby imparting to the reactor substantially the same effect as inserting control rods deeply into the core and improving the reliability and safety of the device. Constitution: The core emergency shutdown device is arranged at the upper part of the pebble bed core together with a number of control rods. In the center of the device there is provided a gas passage, which is communicated with a hollow portion applied with a neutron absorber lining, said hollow portion being filled ordinarily with a number of pellets of a neutron absorber such as boron, and a plurality of outlet holes for causing the same pellets to flow out are provided at the lower end of the device. At the time of emergency shutdown of the reactor, supporting metal fittings are opened, and the above described device falls onto the core together with the control rods. Simultaneously, the high pressure gas flows through the gas passage to cause the pellets to flow out into the fuel ball filling layer. (Yoshino, Y.)