The steam turns a turbine-generator that produces electricity. The big difference between Columbia Generating Station and other thermal plants is in how the heat is produced. Nuclear power plants produce heat by fissioning atoms of uranium. Fissioning occurs when a subatomic particle, a neutron, strikes and is absorbed into the nucleus of a uranium atom. This makes the nucleus unstable and causes it to split.
Heat is produced as the result, as are additional neutrons.
These free neutrons cause other uranium atoms to fission, resulting in a self-sustaining chain reaction. Each fission releases a small amount of heat, but in a nuclear reactor there are billions of atoms fissioning every second. The fissioning takes place within the nuclear fuel core, which is housed in a heavy steel reactor vessel. The fuel core contains 153 tons of uranium dioxide fuel enclosed in 764 fuel assemblies. The uranium fuel contains an enormous amount of energy.