He and H effects on structural materials in fusion and accelerator driven systems

In the last two decades, various structural materials were irradiated in the targets of the Swiss spallation source (SINQ). Of the particular interest to develop high power spallation sources for both neutron science and ADS applications, austenitic steels, tempered martensitic steels, Ni- and Al-based alloys have been extensively investigated. Post-Irradiation Examinations (PIE) include mechanical testing using tensile, bend, impact, small punch testing techniques and microstructural analysis employing Transmission Electron Microscopy (TEM), Positron Annihilation Spectroscopy (PAS) and Atom Probe Tomography (ATP). The specimens used for PIE are with irradiation doses up to about 20 dpa and helium (He) concentrations up to about 1800 appm, in the temperature range of 60–500°C. The results of mechanical tests demonstrate pronounced embrittlement effect when the He concentration is above about 500 appm. Meanwhile, additional hardening effect is observed, which can be attributed to high-density He bubbles of 1-2 nm in diameter. (author)