Abstract: A device is disclosed for generating electricity and is of particular use in the event of a Beyond Design Basis Event at a nuclear power plant. The device includes a first string including a first plurality of thermoelectric generator cells, each of the thermoelectric generator cells of the first plurality operable to generate a voltage and current across a pair of electrical terminals, based upon a temperature differential between two fluids, a second string including a second plurality of thermoelectric generator cells and circuitry adapted to control, dependent upon the temperature differential between the two fluids a switch between a first configuration and a second configuration. In the first configuration the two strings are electrically in parallel and the second configuration, the two strings are electrically in series.