Hydrogen inventory and embrittlement in low activation steels

Results on hydrogen permeation and diffusion in virgin and preirradiated iron and martensitic MANET II are compared to literature data on iron and other ferritic/martensitic steels. Both permeability and diffusivity decrease with increasing alloying content. While preirradiation to 1.5 .10-3 dpa has negligible effect on permeation and diffusion, simultaneous irradiation enhances permeability in Fe and MANET II below ∼300 C. Diffusivity shows a strong pressure dependence and deviation from Arrhenius-type temperature dependence. Diffusion of implanted hydrogen shows a behaviour different from that derived from gas permeation. The hydrogen inventory in a fusion reactor blanket is roughly estimated and compared to the critical concentration for hydrogen embrittlement. Hardness of hydrogen implanted MANET II and F82H shows no pecularities compared to helium implantation and only slightly differs from irradiation without implantation. Tensile tests on F82H at 30 C and 200 C after implantation to hydrogen concentration above ∼10 wtppm show large variation, possibly due to formation of microcracks, while measurements at 350 C show no effect of implantation. (orig.)