Fuel rods are cylindrical tubes that contain nuclear fuel, typically made of enriched uranium or plutonium. They are used in nuclear reactors to produce heat through a process called nuclear fission, where the nuclei of atoms split apart, releasing energy. This heat is then used to generate steam, which drives turbines to produce electricity. Each fuel rod is designed to withstand high temperatures and radiation. They are bundled together in groups called fuel assemblies, which are placed in the reactor core. The arrangement of these rods is crucial for maintaining a controlled nuclear reaction and ensuring the safety of the nuclear reactor.