  To evaluate the radiation tolerance of nanocrystalline (NC) materials, the
damage effects of Fe and W as typical body-centered cubic (BCC) metals under
uniform irradiation are studied by a sequential multi-scale modelling
framework. An ideal descriptor, the absorption bias (the ratio of the
absorption abilities of grain boundaries (GBs) to interstitials (I) and
vacancies (V)), is proposed to characterize the radiation tolerance of
materials with different grain sizes. Low absorption bias promotes defects
annihilation through enhancing I-V recombination and optimally tuning its
competition with GB absorption. Thus, the lower absorption bias, the higher
anti-irradiation performance of NC BCC metals is. Furthermore, by
comprehensively considering the mechanical property, thermal stability and
radiation resistance, nano-crystals are recommended for Fe-based structural
materials but coarse crystals for W-based plasma-facing materials. This work
reevaluates the radiation resistance of NC materials, resulting in new
strategies for designing structural materials of nuclear devices through
manipulating grain sizes.
