Fracture toughness behavior of high-Ni/high-Mn Barsebäck 2 reactor pressure vessel welds after 28 years of operation

• The surveillance samples describe the aging of the RPV. • The scatter in T 0 is connected to the ratio between the sampled as-welded and reheated regions ahead of the crack. • The upper bound for the trend curve was determined using the MML Master Curve assessment. • The difference between fracture toughness based T 0 and impact toughness based T 41J increases with fluence. The safety assessment of reactor pressure vessels (RPV) is based on knowledge obtained from surveillance programs. In this study, the fracture toughness characteristics in the ductile-to-brittle transition region were determined for samples extracted from Barsebäck 2 RPV’s beltline and head high Ni/Mn welds, and the results were compared to the surveillance welds. The fracture toughness results from the surveillance program describe the RPV core welds after 28 years of operation associated to a fluence of 0.1·10 19 n/cm 2 in the beltline region. The results show that the microstructural features of the multilayer weld increase the uncertainty in the reference temperature T 0 to 34 °C. The inhomogeneity of the weld affects more the fracture toughness properties in comparison to impact toughness. The T 0 based embrittlement trend curve obtained for Barsebäck 2 weld subjected to a maximum fluence of 5.9·10 19 n/cm 2 is compared to similar welds. The results contribute to improvements in reliability of aging management programs of nuclear power plants important for availability of carbon free energy.