## 5 Conclusions  
A nondestructive magnetic method was applied on a reactor steel material for the inspection of neutron irradiation-generated embrittlement, and results were compared with the destructively measured transition temperature. A good and reliable correlation was found between these characteristics, which can be used for the estimation of DBTT (even in case of an unknown sample) from the results of magnetic measurement, in spite of the large scatter of points.  
The reason of this large scatter was also analyzed, and it was attributed to the local material inhomogeneity, to the differences between their initial microstructure state before irradiation, and not to the measurement error. Furthermore, it has been clearly demonstrated by our experiments that, if the microstructure of the reference (not-irradiated) samples is close to each other--which is suspected based on the magnetic measurements--the irradiation embrittlement can be characterized very well, with extremely low scatter of points by magnetic parameters.  
Magnetically measured parameters seem to characterize more precisely the material embrittlement than the traditionally used destructive methods. In addition, the magnetic method can characterize the individual samples, contrary to some destructive methods, which can provide only statistical values. In the future, these facts can be a serious argument for the application of magnetic measurements in a reactor industry.  
Based on the analysis of the measurement conditions, only local material conditions can be responsible for the different embrittlement of a material caused by the same dosage neutron irradiation.  
In order to have similar results as for a Charpy (destructive tests) impact curve, a large variation of samples needs to be tested due to the inhomogeneity. However, the number of samples can be reduced because the fit with a selected number of samples in the average (middle) magnetic hysteresis loops gives similar results as for a large number of samples.  
It was found that the neutron irradiation-generated embrittlement highly depended on the initial material characteristics; even the embrittlement of different parts of the same reactor steel block can be rather different. This result gives important additional information about the whole process of the neutron-generated embrittlement of reactor pressure steel. Our results can be useful for the future potential introduction of this (and in general, any) nondestructive evolution method.  
Conceptualization and original draft preparation: G.V.; investigation and methodology: G.V., I.S., and I.U.; project administration: A.G. All authors have read and agreed to the published version of the manuscript.  
Figure 8: Estimation of the transition temperature from the MAT descriptors, measured on magnetically selected samples (subset). For a better comparison, the linear fit of Figure 7 is also shown as a blue dashed line.  
**Funding:** This research was carried out in frame of the \"NOMAD\" project. This project (Non-destructive Evaluation System for the Inspection of Operation-Induced Material Degradation in Nuclear Power Plants) has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 755330.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data are contained within the article.  
**Conflicts of Interest:** The authors declare no conflict of interest.