The primary fuel used in nuclear power plants is uranium. Specifically, uranium-235 is the isotope commonly used due to its ability to undergo nuclear fission. When the nucleus of uranium-235 absorbs a neutron, it splits, releasing a substantial amount of energy, which is harnessed to generate electricity. The process also produces more neutrons, which can initiate further fission reactions in a chain reaction. Nuclear power plants are designed with safety systems to control these reactions and contain radioactive materials, making them a significant source of low-carbon energy worldwide, but they also raise concerns regarding waste disposal and safety.