Microstructural study of EC316LN and its welds irradiated in SINQ target-3

Solution-annealed (SA) austenitic stainless steel EC316LN and its welds were irradiated in SINQ Target-3. The irradiation dose was up to 11 dpa and the temperature ranged from around 70 °C to 350 °C. For the SA metal, TEM investigations show that the main features of irradiation damage for the SA metal are high-density small black dot defects and large Frank loops. The density and size of the small dot defects are independent of irradiation dose with a mean size of about 1.2 nm and a density of about 4.5 × 1023 m−3. The density of Frank loops also varies little with dose, while the size increases with dose. No bubbles or voids were found in specimens irradiated up to 9.3 dpa at below 290 °C, while high-density small bubbles were observed in the specimens irradiated to 11 dpa at 350 °C. For the welds metal (namely in the fusion zone), the main features are the same, high-density small defect clusters and large Frank loops formed after irradiation. However, high-density small bubbles were observed in a specimen irradiated to 10 dpa at a temperature of around 290 °C.