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I. Key Causes of Corrosion: Pure helium itself has stable chemical properties and does not cause direct corrosion of materials. Actual corrosion arises mainly from trace impurities in helium such as CO, H₂, H₂O, CH₄, etc., which undergo oxidation, carburization/decarburization reactions with the alloy at high temperatures. In nuclear environments, helium embrittlement induced by radiation also occurs, leading to a degradation of the material’s mechanical properties. II. Typical corrosion behaviors: Oxidation and element migration: Chromium-containing superalloys develop a chromium-based oxide layer on their surface; when the temperature exceeds a critical value, this protective layer can be damaged, leading to issues such as internal element segregation and intergranular penetration. Carbon migration damage: Different alloys exhibit carburization or decarburization behavior. Incoloy 800H can resist such damage spontaneously thanks to the silica layer formed on its surface, whereas alloys such as Inconel 617 lack this self-protection mechanism. Helium embrittlement effect: In nuclear reactor environments, helium is deposited and accumulates within materials through nuclear reactions, forming bubbles that cause localized stress cracking and lead to a significant reduction in the material’s toughness. III. Common corrosion-resistant candidate materials: Inconel 617, Hastelloy X, and Incoloy 800H are the mainstream candidate structural materials for high-temperature gas-cooled reactors, and they can operate for extended periods in an environment of impure helium at temperatures of 700–1000°C. Specially modified fluororubber sealing materials have an extremely low permeability to small-molecule media such as helium, making them suitable for sealing applications in high-temperature helium environments. Radiation-resistant ferritic/martensitic steels and SiC/SiC composites can replace conventional austenitic stainless steels to more effectively suppress helium embrittlement.