On the Influence of Microstructure on the Neutron Irradiation Response of HIPed SA508 Steel for Nuclear Applications

Abstract The neutron irradiation response of a novel hot isostatically pressed SA508 Grade3 steel was studied, such to deduce any influence this unconventional RPV microstructure has on radiation response. In particular, the role of elevated ferrite fraction was investigated. Neutron irradiation was conducted at 155 ± 10˚C to induce 0.1dpa of damage, this corresponded 2.53 ± 0.63GPa hardening for the ferrite and 1.94 ± 0.57GPa for the bainite as measured by nanoindentation. Atom probe tomography detected the presence of Mn-Ni-Si type clusters in both microconstituent phases. The ferrite microstructure showed a greater percentage of solute atoms available to form clusters than bainite, but it also contained a lower cluster volume fraction and number density compared to the bainite.