Nuclear Power allows the building of nuclear plants, which increase factory production of a city but with a risk of meltdown.
It is a prerequisite of fusion power.
Civilopedia
The development of Nuclear Power was an attempt to find a peaceful application for the energy released by Nuclear Fission. The heat given off created steam that drove electric turbines, producing electricity. Nuclear Power held the promise of being cleaner and less costly than burning fossil fuels. However, the radioactive materials consumed in the process were extremely lethal, the disposal of nuclear waste was difficult, and the risk of nuclear meltdown could not be eliminated. Continuing work may lead to a safer application. For example, employing reactors built on the principles of nuclear Fusion, rather than Fission, may yet provide safe, clean power.