Void swelling in reduced activation ferritic/martensitic steels under ion-beam irradiation to high fluences

Swelling behavior of a 9Cr–2.0W–V,Ta reduced activation ferritic/martensitic steel (JLF-1) and a tungsten-enriched 9Cr–2.5W–V,Ta steel (JLS-1) under ion-beam irradiation was studied. A technique of dual-beam ion irradiation utilizing a pair of electrostatic accelerators was employed to achieve high fluence levels and a helium production rate that are relevant to fusion power reactor blanket environments. Under single ion-beam irradiation at 743 K, a cavity structure was formed only in regions of more than 40 dpa. Cavities were in the martensite lath structure. Cavities did not form at the displacement peak about 1400 nm. Under dual ion-beam irradiation at 743 K, a cavity structure was formed at dual ion-beam irradiated regions. A bi-modal size distribution of faceted voids and spherical helium bubbles of diameter up to 2 nm were observed.