Characterization of defect clusters in ion-irradiated A533B steel

A weak-beam transmission electron microscopy study was carried out for matrix damage in A533B reactor pressure vessel (RPV) steel produced by 3MeV Ni2+ ion irradiation to a dose of 1dpa at 290°C. The matrix damage was found to consist of small dislocation loops. The observed and analyzed dislocation loops have Burgers vectors b=a〈100〉. The dislocation loops have a mean image size d=2.5nm and the number density is about 1×1022m−3. Most of the loops are stable after thermal annealing at 400°C for 30min. This indirect evidence suggests that their nature is interstitial.