Dr Klaus Szielasko has been working in the field of reactor safety research for more than 20 years. Currently he is head of the Materials Characterization department at Fraunhofer IZFP. His main background is electrical engineering, materials science and micromagnetic NDE.
Physical principles of NDE methods for characterization of embrittlement
The aging management of safety-critical, large, expensive or irreplaceable nuclear power plant (NPP) components such as the reactor pressure vessel and primary piping like surge or spray line requires nondestructive testing and evaluation (NDT/NDE) for flaw detection and materials characterization. Over the years it has been demonstrated that NDE methods detect signs of possible embrittlement significantly before the material degradation reaches critical levels, i.e. before any damage would occur. As opposed to NDT techniques, which focus on flaw detection, NDE detects changes in material behavior and mechanical properties. This contribution focuses on the physical principles of electromagnetic nondestructive evaluation based on electromagnetic acoustic transducers (EMAT) and micromagnetic techniques such as 3MA. These techniques are sensitive for changes in microstructure and stress via acoustoelastic, magnetoelastic and micromagnetic effects. Machine learning enables the prediction of virtual degradation classes or even the quantitative approximation of mechanical characteristics like Vickers hardness and ductile-brittle-transition temperature shift after training on on reference sample sets or in reference experiments. Besides the possible application for recurrent inspection, these NDE techniques are also well suited for continuous condition monitoring at elevated temperatures and for instrumentation of laboratory experiments to understand general material characteristics in service conditions.