Nuclear reactor fuel loading. Worker using binoculars to check the correct loading of fuel rods into a nuclear power station's reactor core. She is standing on the lifting machinery being used to lower fuel rods (not seen) into the core, which is immersed in water. Uranium and plutonium fuel are used to produce a controlled nuclear fission reaction. This releases large amounts of energy from a small amount of fissionable material. The addition of new rods to replace used ones is part of the process of controlling the reaction, and needs to be done with great care. This is the Chooz B1 nuclear power station in the Ardennes region of France. Brought online in May 2000, this pressurized water reactor generates 1500 megawatts of power. Photographed in 2004.