Abstract: A self-actuated mechanism within a safety assembly in a liquid metal nuclear reactor comprising sensor fuel pins located in a reactor coolant flow path, a sensor bulb containing NaK located near the upper end of the sensor fuel pins and in the reactor coolant flow path, and a sensor tube connecting the sensor bulb to a metal bellows and push rod. The motion of the push rod resulting from the temperature dependent change in the NaK volume actuates a safety rod release mechanism when a predetermined coolant temperature is reached.

Abstract: An apparatus for holding, releasing, and resetting a multiplicity of neutron absorbing balls within a safety assembly of a liquid metal nuclear reactor comprising vertically hinged trap doors resting on the shoulders of a generally cylindrical release valve, the actuation of which disengages the doors, permitting the poison balls above the doors to drop into the core. In the reset mode of operation a platform is raised, lifting the balls from the bottom of the core and swinging the trap doors upward until the balls are above the door hinges. The release valve is reset and the platform is lowered to reset the doors against the valve shoulders. In the disclosed embodiment, the valve is operated by a self-actuated, temperature responsive scram mechanism.