Thermally responsive trigger devices and their use in shut-down devices for nuclear reactors

摘要

A thermally responsive trigger device comprises a closed bellows (14) having a filling of liquid metal and acting on a trigger (19) responsive to the free end of the bellows. The bellows and trigger are located at a temperature measuring location which is the coolant flow outlet (15) from a demountable sub-assembly vehicle (10) having a fuel unit (11) and a triggerable absorber unit (12). The outlet flowing coolant sweeps over the bellows (14) and once the expansion of the bellows exceeds a threshold a pin (26) and cam (28) at the free end of the bellows causes a plate (21) to move to release the absorber unit (12).