NDE for material characterization of aging due to thermal embrittlement, fatigue and neutron degradation

The contribution reports to R&D results obtained in both, a German programme sponsored by the minister of economics and social affairs and the European EURATOM programme. Whereas in the first project material degradation due to thermal aging is investigated, in the second project neutron exposed specimens from national surveillance programmes of nuclear power plant (NPP) pressure vessels were characterized in the hot cell of the research reactor in Petten, The Netherlands, and fatigue specimens especially prepared in LCF-tests were measured by electromagnetic and micro-magnetic non-destructive testing and evaluation (NDT / NDE)-techniques. The objective was to characterize the material degradation in terms of mechanical parameters like hardness, Charpy-energy, transition temperatures and usage factor. The proposed NDT is especially sensitive for mechanical properties degradation because of the similarities between the impeding of dislocation movement by lattice defects in the microstructure under mechanical loads and the impeding of Bloch-wall movement by the same microstructure under magnetic loads. Both is described, the state of the art of the techniques and the development steps needed to come to reliable in-service inspection (ISI) procedures.