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Impurities in liquid metal sodium are the core factors that affect the corrosion behavior of materials. The four most critical types of impurities and their effects are as follows: The increased oxygen content of oxygen impurities will significantly accelerate the corrosion rate of structural materials, directly participate in the corrosion reaction to form loose composite oxides, and also promote the dissolution of material component elements in sodium, and even cause preferential erosion of grain boundaries. In severe cases, it will lead to the deterioration of material mechanical properties and blockage of coolant flow channels. Excessive carbon impurities will cause excessive carburization of the material, change the mechanical strength of the material, and will also migrate from the high temperature area to the low temperature area in the non-isothermal system, causing abnormal changes in the carbon content of the material in different areas, destroying the stability of the material performance. Nitrogen impurity Nitrogen has extremely low solubility in sodium, but it will still undergo carbon-like migration behavior from stainless steel to refractory metals, triggering a nitriding reaction in the material, which will have a negative impact on the long-term service performance of the material. Hydrogen impurity Hydrogen will react with some metal components to form solid hydride, causing material embrittlement effect, significantly reducing the toughness of structural materials and increasing the risk of component failure.