## 5 Discussion  
Apart from the point scatter, a clear tendency is seen in both cases (Charpy samples and blocks) of irradiated specimens: a monotonic correlation exists between magnetic parameters and the dosage of neutron irradiation (Figures 4a and 5a), according to our expectation and previous results [14]. Neutron irradiation generated a 25-40% increase in magnetic parameters as compared with the virgin sample. These results can be considered to validate the usefulness of magnetic measurements for neutron-irradiation-generated embrittlement, regardless of the type or material of the investigated samples. Evidently, this manner of presentation did not reduce the scattering of points. Nevertheless, the tendency between MAT parameters and neutron fluence or Vickers hardness is clearly seen. However, if a preselection of samples is made based on their magnetic behavior, this scatter is significantly decreased. As can be seen very well in Figure 7, if only the magnetically similar samples are taken into account, the point scatter is reduced. The regression of the linear fit increases from R = 0.813 to R = 0.987 in the case of Charpy specimens. The same can be observed in the case of irradiated blocks (Figure 8): the regression of the linear fit increased from R = 0.787 to R = 0.988. The correlation between mechanical hardening and magnetic descriptors is thus excellent. We emphasize that it was not backward reasoning that was used to determine these points, which fit our hypothesis. To clarify this, the whole MAT process is briefly detailed: (1) Large scatter of the MAT descriptors measured on the reference and irradiated specimens was found. (2) Regardless of the result of this evaluation, the magnetic behavior of _reference_ samples was considered. It was found that some samples behaved very similarly from a magnetic point of view. (3) The evaluation was performed once more, but considering only the selected samples. This selection did not provide any information about the mechanical hardening due to neutron irradiation, because samples were measured before irradiation. _Before_ irradiation, we simply did not know how samples will behave _after_ irradiation. It is believed that the fact that the two, very different sample series (different chemical composition blocks and Charpy specimens) revealed the same behavior is a rather strong argument behind our hypothesis: neutron irradiation hardening depends very much on the actual local material parameters, and magnetic measurements properly indicate this behavior. The excellent correlation between destructively measured Vickers hardness values and nondestructively measured magnetic parameters shows that our magnetic method is suitable for the nondestructive characterization of neutron-irradiation-generated embrittlement. Figure 10: Correlation between MAT descriptor and Vickers hardness. The only reason for the large point scatter presented above, if all measured samples are considered, can be material inhomogeneity. We do not dare to provide any explanation or interpretation of this inhomogeneity, but we would like to call the attention of nuclear reactor experts to this fact. To show that this speculation could be true, we cut a single large block of real reactor steel material into 24 Chappy pieces and systematically investigated the different pieces. The result supports our assumption that samples even of the same block behave differently. It can be seen very well that there was a decrease (though not significant) in maximum permeability as a function of sample number, if the majority of samples are considered. However, every fourth sample revealed very different magnetic behavior. It is evident that samples cut from the _same_ block can be magnetically rather different. On the other side, the correlation between optimal MAT descriptors and Vickers hardness was rather good, regardless of the sample number, as can be seen in Figure 10. Both MAT parameters and Vickers hardness values properly characterize the individual samples.