Non-destructive examination of helium implanted HTRs construction materials

High chromium steels belong to the most prospective materials for reactor pressure vessel of High Temperature Reactors as well as for more components used in GEN IV facilities. Radiation resistance of GEN IV materials is a significant attribute. Therefore the process of microstructure deterioration due to irradiation followed by degradation of mechanical properties must be consistently investigated.This paper is focused on microstructure study of 9% chromium steels (T91, P91) and observation of residual stress as well as open volume defect accumulation after helium ion implantation performed at room temperature. Helium ion implantation should simulate changes of structure due to knocking-out of atoms during neutron irradiation. Investigated materials were studied by non-destructive experimental techniques based on the positron annihilation in the matter (Positron Annihilation Spectroscopy, Doppler Broadening Spectroscopy) and magnetic properties of iron alloys (Magnetic Barkhausen Noise Measurement). Results indicate higher resistance of T91 to defect formation during implantation than P91, although T91 shows higher residual stress in microstructure prior to implantation.