Depending on the neutron fluence and the special design of the pressure vessel of nuclear power plants (NPP) the microstructure of the steels change by neutron induced embrittlement. Embrittlement is on the basis of vacancies and Curich precipitates which in the size range of 1–3 nm contribute with coherent residual stresses of the 3rd kind to an increase in hardness and strength (yield strength and tensile strength) as well as with a reduction of the upper shelf value of Charpy energy and a shift in the brittle-to-ductile transition temperature to higher temperatures. Micromagnetic investigations sponsored by the German minister of economics were performed at full Charpy specimen and material of the last generation of German NPP in order to characterize the material degradation. The contribution reports to the results obtained by the application of the Micromagnetic-, Multiparameter-, Microstructure-, and stress-Analysis (3MA) and the magnetostrictive excitation of ultrasound using an EMAT. Both technologies document potential to be further developed to an in-service inspection technique.
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