Determination of the safe analysis zone in proton irradiated steels

Proton irradiation has been widely used as a surrogate for neutron damage due to its low cost and high damage introduction rate, particularly for studies concerning corrosion and mechanical property testing. However, characterization of post-irradiated steels encounters difficulties in accurately and quantitatively determining the depth regions that are not affected by surface and hydrogen effects. The safe analysis zone is identified as the region where all data points exhibit consistent void swelling as a function of local damage levels. The comparison of low-dose and high-dose irradiation reveals the depth boundaries where inconsistencies start to appear. This method greatly maximizes data extraction from proton-irradiated steels, making it possible to obtain a swelling curve from a single-dose ion irradiation. Using 316L as an example, the safe analysis zone was determined to range from 2 to 16 μm. Unlike heavy ion irradiation, which shows suppressed void swelling around the projected range of implants, proton irradiation enhances void swelling around the projected range of protons. The proposed safe zone determination method is particularly useful for micro-mechanical testing on proton-irradiated specimens, especially when cross-sectional analysis is involved.