Ion irradiation is a promising tool to emulate neutron-irradiation effects on reactor pressure vessel (RPV) steels, especially in the situation of limited availability of suitable neutron-irradiated material.This approach requires the consideration of ion-neutron transferability issues, which are addressed in the present study by comparing the effect of ions with neutron-irradiation effects reported for the same materials.The first part of the study covers a comprehensive characterization, based on dedicated electron microscopy techniques, of the selected unirradiated RPV materials, namely a base Perfume metal and a weld.
The results obtained for the grain size, dislocation density, and precipitates are put in context in terms of hardening contributions and sink strength.The second part is focused on the depth-dependent characterization of the dislocation loops formed in ion-irradiated samples.This work is based on scanning transmission electron microscopy applied to cross-sectional samples prepared by the focused ion beam technique.
A band-like arrangement of loops is observed in the depth range close to the peak of injected interstitials.Two levels of displacement damage, 0.1 and 1 dpa (displacements per atom), as well as post-irradiation annealed conditions, are included for both RPV materials.
Compared with neutron irradiation, ion irradiation creates a similar average size but a higher number density of loops presumably due to the higher dose Weight Loss rate during ion irradiation.