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 3 MeV Ni2+ ion irradiation to a dose of 1 dpa 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〈1 0 0〉. The dislocation loops have a mean image size d = 2.5 nm and the number density is about 1 × 1022 m−3. Most of the loops are stable after thermal annealing at 400 °C for 30 min. This indirect evidence suggests that their nature is interstitial.