Improvements in or relating to nuclear reactor control elements

908,456. Nuclear reactor control rods. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. May 5, 1961 [May 10, 1960], No. 16445/60. Class 39 (4). A control device for a pressurized gas-cooled nuclear reactor comprises a neutron absorbing body 5 housed within a neutron absorbing body 4 in a container 3 in a vertical channel in the reactor core, and means for releasing the body 5 so that it falls under gravity, thus increasing the neutron absorption capacity of the device. In the device shown, on a sudden reduction of coolant gas pressure, gas escapes more quickly through holes 22, 23 than through hole 21, thus creating a pressure difference across diaphragm 11 which moves and lowers plug 13, allowing boron steel shot 5 to fall out of boron steel tube 4 into tube 18. Other neutron absorbing elements referred to are cadmium, mercury and rare earths.