Recent small-angle neutron scattering (SANS) investigations of radiation effects in nuclear materials

Due to the capability of cold neutron beams to non-destructively probe massive samples, to separate effects relating to elements of close atomic number (such as Fe and Cr), to detect H effects and to investigate magnetic materials, small-angle neutron scattering (SANS) provides a very useful experimental technique to study the micro-structural effects of irradiation in nuclear materials for GenIV fission reactors and for the future fusion reactors. The utilization of polarized neutron beams offers an additional and unique tool to characterize magnetic structural materials. Furthermore, the problems relating to preparation and manipulation of irradiated samples for SANS measurements are considerably reduced when comparing with other micro-structural techniques, such as electron microscopy.

Results of SANS experiments carried out to characterize the European reference ferritic/martensitic steel EUROFER97 for first-wall application will be presented. The micro-structural effects produced in this steel by neutron irradiation, at different temperature and doses as well as by different irradiation facilities, have been investigated. Additionally, SANS measurements have been carried out on a variant of EUROFER97 doped with B to artificially increase under fission irradiation the He/dpa ratio, for simulating the effect of 14 MeV neutron irradiation. Regarding high-heat flux materials, neutron irradiated high purity W single crystals have also been investigated by SANS. All these results will be discussed comparing with micro-structural information provided by electron microscopy on the same samples investigated by SANS.