In nuclear reactors, uranium rods will undergo fission reaction after being hit by neutrons, releasing a lot of energy and radioactive substances. These energy and radioactive substances will produce high temperature and radiation. If the uranium rod is not cooled in time, it will overheat and be damaged, and even lead to a nuclear accident.
The cooling time of uranium rod is related to the flow rate of coolant, the size and material of uranium rod. Generally speaking, coolant needs to flow through the whole nuclear reactor to take out and discharge the heat generated by uranium rods and prevent them from overheating.
The cooling time of uranium rods usually takes several years or even longer, because uranium rods will gradually release residual heat and radioactive substances during the cooling process. These waste heat and radioactive substances need enough time to be gradually released to avoid harm to the environment and human beings.
Therefore, uranium rods need to be cooled for 10 years or longer to ensure the safety and reliability of nuclear reactors.