AbstractThe neutron irradiation resistance of the reduced-activation ferritic/martensitic (RAFM) steel EUROFER97 and international reference steels (F82H-mod, OPTIFER-Ia, GA3X and MANET-I) have been investigated after irradiation in the Petten High Flux Reactor up to 16.3 dpa at different irradiation temperatures (250-450 ¡ãC). The embrittlement behavior and hardening are investigated by instrumented Charpy-V tests with subsize specimens.Neutron irradiation-induced embrittlement and hardening of EUROFER97 was studied under different heat treatment conditions. Embrittlement and hardening of as-delivered EUROFER97 steel are comparable to those of reference steels. Heat treatment of EUROFER97 at a higher austenitizing temperature substantially improves the embrittlement behaviour at low irradiation temperatures. Analysis of embrittlement vs. hardening behavior of RAFM steels within a proper model in terms of the parameter C=DDBTT/Ds indicates hardening-dominated embrittlement at irradiation temperatures below 350 ¡ãC with 0.17 ¡Ü C ¡Ü 0.53 ¡ãC/MPa. Scattering of C at irradiation temperatures above 400 ¡ãC indicates non hardening embrittlement. A role of He in a process of embrittlement is investigated in EUROFER97 based steels, that are doped with different contents of natural B and the separated 10B-isotope (0.008-0.112 wt.%).Testing on small scale fracture mechanical specimens for determination of quasi-static fracture toughness will be also presented in a view of future irradiation campaigns.