The surfaces of the pellets are polished and smoothed, and the finished pellets go through an inspection process that culls out misshapen pellets. When the pellets have passed inspection, they are loaded into thin metal tubes called fuel rods. These fuel rods are made of Zircaloy, an alloy of zirconium, tin, and iron that possesses a greater strength and resistance to corrosion from water and steam. After close inspection, the rods are bundled into fuel assemblies at the fuel fabrication plant and sent to a nuclear power plant. From Kilotons to Kilowatts At the nuclear power plant, fuel assemblies are placed in a nuclear reactor.
Energy is released when a controlled chain reaction causes uranium or plutonium atoms to fission.
The energy from fission heats water that is circulated through the reactor. The steam from the hot water drives the turbines that make electricity. After some time in the reactor, the fuel assemblies at the center of the core use up so much of their fuel that those assemblies inhibit the chain reaction. At that point, the most depleted fuel assemblies are replaced. Currently, nuclear power plants in the U.S. use uranium fuel.