Influence of Diffusing Hydrogen on Corrosion Properties of Reduced Activation Ferritic/Martensitic Tube of Nuclear Fusion

The water-cooled blanket can be used for fusion reactors, and the working condition of its structural materials is a water environment under 280°C/325°C and a pressure of 15.5 MPa. Besides, materials are also affected by diffusible hydrogen generated during fusion reactions, in which hydrogen can induce internal defects, potentially leading to stress corrosion cracking (SCC). Based on these, this study simulates the operating conditions of cooling tubes in fusion reactors, aiming to investigate the impacts of diffusible hydrogen. With the application of a reduced activation ferritic/martensitic steel developed by Southwestern Institute of Physics (SWIP) in China, CLF-1 tubes were immersed in a pressurized and deoxygenated water environment for 400 h. According to the results of transmission electron microscopy, the oxide films exhibited a dual-layer structure. Moreover, the results of x-ray photoelectron spectroscopy revealed that the diffusible hydrogen degraded the stability of oxide films of CLF-1 tubes. Specifically, diffusible hydrogen would result in an increase in the Fe2+/Fe3+ ratio within the oxide films of CLF-1 tubes, and the residual stress in CLF-1 steel exhibited an initially increasing and subsequently decreasing trend with the increase of hydrogen pressure.