Micromagnetic characterization of thermal degradation in cu-rich alloys and results of neutron-irradiation

The Cu-rich German martensitic/bainitic structural steel WB36 (15 NiCuMoNb 5, 1.6368) is in service in fossil power plants as well as in pipes and pressurizer vessels of German nuclear power plants. That material - when exposed at elevated temperatures in between 280°C - 350°C - shows the effect of precipitation hardening by Cu-rich precipitates and a shift FATT = 70°C can be observed. Micromagnetic measurements based on multiple linear regression or pattern recognition algorithms and taking into account different micromagnetic quantities were applied in order to characterize the material degradation. In parallel a different approach was employed to evaluate in the same way alloys based on pure iron with different contents of Cu. Because Cu-rich precipitates play an essential role when nuclear pressure vessel material is exposed to neutron irradiation, micromagnetic measuring quantities are also of interest to characterize these materials. Therefore the paper reports ex periments performed in the hot cells of AREVA NP in Germany.