Changes in magnetic parameters of neutron irradiated SA 508 Cl. 3 reactor pressure vessel forging and weld surveillance specimens

Irradiation-induced changes in the magnetic parameters and mechanical properties were measured and compared to explore possible correlations for reactor pressure vessel (RPV) forging and weld surveillance Charpy specimens which were irradiated to the neutron fluence of 2.3×10¹⁹ n/cm² (E≫1.0 MeV) in a typical pressurized water reactor environment at 290 °C. For mechanical property parameters, Vickers microhardness, tensile and Charpy impact tests were performed and saturation magnetization (M_s), remanence (M_r), coercivity (H_c), and Barkhausen noise amplitude (BNA) were measured for magnetic parameters for both unirradiated and irradiated specimens, respectively. Results of mechanical property measurements showed an increase in yield and tensile strength, Vickers microhardness, 30 ft. lb indexed RT_NDT and a decrease in Charpy upper-shelf energy irrespective of forging and weld metals. Hysteresis loops appeared to turn clockwise, resulting in an increase in H_c, and BNA appeared to decrease after irradiation. Both magnetic parameters showed viable correlations to the changes in mechanical parameters (Vickers microhardness, Charpy upper shelf energy) due to irradiation. Even limited, the present study seems to show additional possibilities for the application of this magnetic method in monitoring the mechanical parameter changes due to neutron irradiation. © 1999 American Institute of Physics.