The terms used nuclear fuel and spent nuclear fuel are both used to describe nuclear fuel that has been used in a nuclear reactor. There is no liquid in used nuclear fuel. Used nuclear fuel is a solid material, in the form of ceramic pellets. Each pellet is about the size of a pencil eraser. The pellets are stacked inside long metal zirconium tubes approximately 12 feet long, which are sealed on each end to form a fuel rod. Between 100 and 300 fuel rods are arranged in a square pattern to form a fuel assembly. Depending on the design, a reactor core may have between 120 and 800 fuel assemblies. A used fuel storage cask may contain up to 89 fuel assemblies. Learn more about nuclear fuel by watching this Nuclear Energy Institute video.
