Fracture mechanics concepts for evaluation of irradiated reactor pressure vessel material behavior

Within the German research program Forschungsvorhaben Komponentensicherheit (FKS), irradiation experiments were performed with ferritic reactor pressu re vessel (RPV) steels and welds. The materials cover a wide range of chemi cal composition and initial toughness to achieve different susceptibility t o neutron irradiation. Different neutron flux was applied and the neutron e xposure extended up to 8 x 10(19) cm(-2). The change in material properties was determined by means of tensile, Charpy impact, drop-weight and fractur e mechanics tests, including crack arrest. The results have provided more i nsight into the acting embrittlement mechanisms and shown that the fracture mechanics concept of the Code provides in general an upper bound for the m aterial which can be applied in the safety analysis of the RPV. (C) 1999 Pu blished by Elsevier Science S.A. All rights reserved.