Application of advanced Master Curve approaches on WWER-440 reactor pressure vessel steels

The Master Curve (MC) approach used to measure the transition temperature, T0, has been standardized in the ASTM Standard Test Method E 1921 in 1997. The basic MC approach for analysis of fracture test results is intended for macroscopically homogeneous steels with a body centered (ferritic) structure only. In reality, due to the manufacturing process, the steels in question are seldom fully macroscopically homogeneous. The fracture toughness values measured on Charpy size SE(B) specimens of base metal from the Greifswald Unit 8 RPV show a large scatter. The basic MC evaluation following ASTM E1921 supplies a MC with many fracture toughness values which lie below the 1% fracture probability line. It is therefore suspected that this material is macroscopically inhomogeneous. In this paper, two recent extensions of the MC for inhomogeneous material are applied on these fracture toughness data.