Radiation damage studies in fusion reactor steels by means of small-angle neutron scattering (SANS)

Abstract

In this contribution, small-angle neutron scattering (SANS) studies of the micro-structural radiation damage in technical steels, developed for application in future fusion reactors, are presented. The effect of neutron irradiation at 250 °C–450 °C, up to dose levels of 16 dpa (displacement per atom), has been investigated in the European reference ferritic/martensitic steel Eurofer97 (0.12 C, 9 Cr, 0.2 V, 1.08 W wt%), both in its standard composition and mechanically alloyed with B (up to 1000 appm) to enhance the helium production, via transmutations, and reproduce fusion relevant helium/dpa ratios. The obtained SANS results suggest that in the irradiated standard Eurofer97 micro-voids distributions are present, with very small average radii (a few Å) and volume fractions (around 0.01); such low values, close to the SANS resolution limit, are consistent with the good resistance of this steel to radiation damage, for low helium concentrations. In the irradiated B-alloyed Eurofer97, more complex changes are observed: the helium bubble distributions appear strongly dependent on the irradiation temperature and on the helium concentration; furthermore, micro-structural effects possibly related to modifications in the steel matrix are detected.