On the required toughness for the application of the net section yield criterion on nuclear power plant components

The principles of plastic limit load are recaptured. A method is developed to calculate lower bound estimates of critical crack sizes for nuclear plant components. More than 250 fracture mechanics experiments on specimen and component geometries have been evaluated focussing on the material toughness in terms of Charpy-V energy. The thus determined Charpy threshold value for the application of the aforementioned method is 45 J regardless whether the material has already reached the upper shelf toughness or is still within the transition region. The method is not able to cope with the phenomenon of “ductile tearing”. However when predicting critical crack sizes the method yields conservative results even when ductile tearing must be expected.