Nuclear energy is mostly used for electric power generation. According to the World Nuclear Association, there were over 430 commercial nuclear power reactors operating in 31 countries as of April 2014, with over 370,000 MW of total capacity. Approximately 70 more reactors were under construction as of April 2014.
Nuclear energy is generated by splitting uranium atoms (specifically U-235 atoms) through a process called nuclear fission. At nuclear power plants, nuclear fission generates heat to produce steam that is used by a turbine to generate electricity. As of April 2014, about 15 percent of the world?s electricity was generated by nuclear power plants.