The world’s first commercial nuclear power plantThermal power plant, primarily used for electricity generati... in Seascale, England. The Calder Hall Nuclear Power PlantThermal power plant, primarily used for electricity generati... consists of four gas-graphite reactors, each with an electrical power of 55 MWMegawatt, million times the power unit of watt (W). 1 MW = 1.... First connection to the grid on August 27, 1956. Final shutdown due to commercial reasons March 31, 2003.