Nuclear power stations use a chain reaction inside a nuclear reactor to produce heat, which is used to create steam to make electricity in the same way as a conventional coal fired station. Reactors use uranium or thorium fuel rods to create the chain reaction. Each atom that decays stimulates the decay of one additional atom. Eventually, the fissionable atoms are consumed and the reaction cannot be sustained, at which point the reactor must be refueled. Nuclear power is reliable, but requires a substantial investment on safety. 

Advantages
Nuclear power has historically been more expensive than coal-fired power because of multipe regulatory delays and higher upfront reactor costs. However, the Energy Policy Act of 2005 addresses the regulatory delays and may make nuclear energy competitive with coal.  Nuclear power does not produce pollutants such as sulfur, mercury or carbon dioxide, so it does not contribute to the greenhouse effect. It is very reliable, and it produces a significant amount of energy from a small amount of fuel and produces a small amount of waste.

Issues
Although not much waste is produced, the remains are radioactive and can be used to produce plutonium, a substance that is suitable for nuclear weapons if extracted and is a potential enabler for weapons proliferation. The disposal of such waste is the major impediment to the growth of nuclear power in the U.S. Additionally, nuclear power is less flexible than traditional power, as production cannot be easily increased or decreased based on short-term consumer demand.