## 1 Introduction
[7], the embrittlement of nuclear pressure vessel steels (A508 Cl.2 and 15 Kh2 NMFA) was investigated on Charpy specimens by applying two different magnetic nondestructive testing methods: 3 MA-X8 (micromagnetic multiparameter microstructure and stress analysis [8]) and MAT (magnetic adaptive testing) [9]. Well detectable modification of the material properties due to neutron irradiation was found on the same specimens. A reasonable correlation between magnetic properties and neutron-irradiation-generated damage was found, regardless of the type of material or the measurement method used. As a conclusion, the results of the individual micromagnetic measurements demonstrated their suitability for characterizing RPV steel degradation under simulated operating conditions. A calibration procedure was also applied on the merged outcome of both methods, giving excellent results in predicting the transition temperature, yield strength, and mechanical hardness in both materials. In spite of the generally good correlation between the embrittlement and magnetic characteristics, large scattering of the points was also observed [7]. To perform a kind of interpretation of the scattering of the points, the results of MAT measurements performed on irradiated 15 Kh2 NMFA Chappy specimens were analyzed. Magnetic parameters were considered as functions of the DBBT. The scattering of points could originate either in errors of the magnetic measurement itself, or in some inhomogeneity of the investigated samples. Possible error in the MAT measurements was carefully analyzed in [10], and it was demonstrated that the point scatter cannot be explained by measurement error. As a conclusion, it was stated that the neutron-irradiation-induced embrittlement depends very much on local material conditions/inhomogeneities. Surprisingly, samples cut from the same block of reactor steel were different from a magnetic point of view, implicating different trajectories of neutron-irradiation-generated degradation, with identifiable differences in the results of the nondestructive magnetic evaluation. Magnetic parameters seem to result in more reliable and precise determination of the local embrittlement in pressure vessel steel than the traditionally used mechanical characteristics. This conclusion is rather striking, and not all nuclear reactor experts can accept it. Because of the importance of these measurement results for the potential application of magnetic measurements in the future, our previous result needs further verification. The purpose of the present work was to repeat the measurement on irradiated reactor steel blocks, and not only on Chappy specimens, as conducted in previous studies. Furthermore, in this work, instead of the transition temperature (which is an estimated value with large error, as mentioned above), individually measured Vickers hardness data were used to characterize the mechanical properties of the material. The same magnetic preselection was applied as described in [10], and the results obtained on block and Chappy specimens were compared with each other. The main goal of the present work is to prove on both irradiated Chappy and block specimens that by suitable magnetic separation of the investigated samples, the scattering of points can be significantly reduced, verifying the efficiency of magnetic measurements. As outlined in Ref. [10], the scatter was mainly attributed to the original inhomogeneity of the samples. To prove this assumption, another (not irradiated) set of samples cut from the _same_ reactor steel block was also investigated to study the homogeneity of individual samples. In this experiment, we systematically measured the individual samples--both mechanically and magnetically--to reach a conclusion about the scattering of mechanical and magnetic parameters and to obtain a correlation between mechanical hardness and magnetic parameters.