Electromagnetic characterization of materials degradation due to neutron irradiation and fatigue

Most of the materials used in practice show degradation due to fatigue, i.e. cyclic loading. Very often other degradation mechanisms like corrosion and in the high temperature regime also creep are superimposed. In the primary circuit of nuclear power plants the material is additionally exposed to neutron irradiation. According to the licensing conditions the main focus is on the pressure vessel material. The contribution describes measurement results collected at surveillance programme specimens of different nuclear power plants in different European countries. The set of Charpy specimen was measured in the hot cell of the research reactor in Petten in the Netherlands. Electromagnetic non-destructive testing techniques were applied for characterization. The second part of the contribution is to the early detection of fatigue. Austenitic stainless steel and plain carbon steel have been exposed under cyclic loading in the high as well as in the low cycle fatigue regime. Beside electromagnetic NDE also positron annihilation and a thermographic technique was applied to characterize to damage states. The contributions is discussion of the results.