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

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 0.1·1019n/cm2 in the beltline region. The results show that the microstructural features of the multilayer weld increase the uncertainty in the reference temperature T0 to 34 °C. The inhomogeneity of the weld affects more the fracture toughness properties in comparison to impact toughness. The T0 based embrittlement trend curve obtained for Barsebäck 2 weld subjected to a maximum fluence of 5.9·1019n/cm2 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.