Environmentally-assisted cracking behaviour of EUROFER97 under simulated water-cooled breeder blanket conditions

Abstract The reduced activation ferritic martensitic (RAF/M) EUROFER97 steel is the candidate structural material for the water-cooled lithium lead breeding blanket (WCLL-BB) section in the DEMO fusion reactor. Its performance under environmentally-assisted cracking (EAC) conditions was evaluated under simulated WCLL-BB coolant water chemistry at 300 °C using compact tension specimens under cyclic loading conditions. Results show that EAC susceptibility increased when switching from air to water, particularly at high loading frequencies. At very low frequencies, crack growth was retarded, consistent with oxide-induced crack closure effect. Alkalinity was controlled using LiOH or KOH, with no systematic difference observed between the two alkalising agents. No consistent or systematic effect of zinc additions on EAC behaviour was observed under the conditions investigated. Nonetheless, these findings support the EAC resistance of EUROFER97 under the tested water-side environmental conditions.