Prediction of the effects of neutron irradiation on the Charpy ductile to brittle transition curve of an A508 pressure vessel steel

Nuclear pressure vessel steels are subjected to irradiation embrittlement which is monitored using Charpy tests. Reference index temperatures, such as the temperature for which the mean Charpy rupture energy is equal to 56 J (T56 J), are used as embrittlement indicators. In this work a material model integrating a description of viscoplasticity, ductile damage and brittle fracture is used to simulate the Charpy test. The model is adjusted on an unirradiated material. It is then applied to irradiated materials assuming that irradiation affects hardening. It is shown that irradiation probably also affects brittle failure. The decrease of the Charpy upper shelf energy is also interpreted.