The nuclear fuel cycle is the process of producing energy from nuclear fuel. It begins with the mining and milling of uranium ore, followed by the conversion of the ore into uranium hexafluoride gas. The uranium gas is then enriched and formed into fuel rods which are placed into nuclear reactors to generate energy. The used fuel rods are then removed from the reactor and processed to extract the remaining uranium and plutonium, which is then recycled into new fuel rods to be used again. Finally, the spent fuel rods are stored safely in secure facilities until their radioactivity has decayed to acceptable levels.