Nuclear power comes from the energy released in fission processes, like the ones we discussed in “Nuclear Chemistry.” The nuclear reactors used for commercial energy production make use of controlled chain reactions of uranium-235. Upon colliding with a neutron, uranium-235 decays spontaneously into two lighter atoms, releasing energy for each atom of uranium that is split. The amount of energy released in the fission process is very large compared to that released from the combustion reactions that we use to obtain energy from fossil fuels. The result is that we can get a lot of energy from a relatively small amount of uranium. In fact, a kilogram of enriched uranium can generate about the same amount of energy as eight million liters of gasoline!