Electrically controlled load activating mechanisms that can be used inside the containment vessel of a nuclear reactor in conjunction with bellows-loaded DCB crack growth sensors installed inside the reactor pressure vessel or piping of a nuclear reactor. One mechanism is a liquid-filled, double-bellows master/slave arrangement connected by a capillary tube to transmit the loading provided by a linear motion device. Another mechanism uses a heat-resistant gas bottle that can be heated in a furnace to increase the gas pressure to expand the bellows of the DCB sensor. A third mechanism uses a pump or compressor to provide the necessary expansion force. The loading is controlled via electrical connections that do not require special pressure boundary penetrations of the containment vessel.