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 prope rties were measured and compared to explore possible correlations for react or pressure vessel (RPV) forging and weld surveillance Charpy specimens whi ch were irradiated to the neutron fluence of 2.3x10(19) n/cm(2) (E > 1.0 Me V) in a typical pressurized water reactor environment at 290 degrees 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, res pectively. Results of mechanical property measurements showed an increase i n yield and tensile strength, Vickers microhardness, 30 ft. lb indexed RTND T and a decrease in Charpy upper-shelf energy irrespective of forging and w eld metals. Hysteresis loops appeared to turn clockwise, resulting in an in crease in H-c, and BNA appeared to decrease after irradiation. Both magneti c parameters showed viable correlations to the changes in mechanical parame ters (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 param eter changes due to neutron irradiation. (C) 1999 American Institute of Phy sics. [S0021-8979(99)18508-6].