Application of NDE techniques to operating reactor materials is useful for the determination of deviations resulting from material inhomogeneity and long-term degradation of properties from irradiation damage. A new programme, Nondestructive Evaluation System for the Inspection of Operation-Induced Material Degradation in Nuclear Power Plants (NOMAD), focuses on the non-destructive investigations of Reactor Pressure Vessel (RPV) steels in ageing reactors to better assess the integrity for lifetime management. In this study, Magnetic Barkhausen Noise (MBN) is used to characterise the effect of inhomogeneties in a Jominy end-quench test specimen subjected to differential cooling rates. The effect of material state encompassing different variables such as surface roughness, microstructure, hardness and residual stress is correlated with the MBN Root Mean Square (RMS) parameter in order to enhance the understanding of the embrittlement phenomena. These studies will contribute to the development of a tool that can monitor and quantify the extent of material degradation in operating nuclear power plants.