Spent nuclear fuel is the used material that remains after nuclear reactors have generated electricity. It contains a mix of radioactive isotopes, including uranium and plutonium, which have undergone fission during the energy production process. This fuel is highly radioactive and generates heat, requiring careful management and storage. After its removal from the reactor, spent nuclear fuel is typically stored in pools of water for cooling and radiation shielding. Eventually, it may be transferred to dry cask storage or reprocessed to recover usable materials. Proper handling is crucial to ensure safety and minimize environmental impact.