UO₂, or uranium dioxide, is a compound of uranium used primarily as fuel in nuclear reactors. It is a ceramic material that efficiently absorbs neutrons, making it suitable for sustaining nuclear fission reactions. UO₂ is typically formed into pellets and housed in fuel rods, which are then assembled into nuclear fuel assemblies. Its properties allow for high thermal conductivity and stability under operational conditions, making it a key component in the nuclear energy industry.