The technology development for surveillance test of RPV materials 2

Irradiation-induced changes in mechanical properties and magnetic parameters were measured and compared to explore possible correlations for Mn-Mo-Ni low alloy steel surveillance specimens which were irradiated to a neutron fluence of 2.4 x 1019n/cm2(E≥1.0 MeV) in a typical pressurized water reactor environment at about 288 deg C. For mechanical property parameters, microvickers hardness, tensile and Charpy impact test were performed and Barkhausen Noise(BN) amplitude, coercivity, maximum induction were measured for magnetic parameters, respectively. Results of mechanical property measurements showed an increase in yield and tensil strength, microvickers hardness 41J indexed RT NDT and a decrease in upper shelf energy irrespective of base and weld metals. In the case of magnetic measurements, it is found that magnetic remanence, BN amplitude, BN energy have dropped significantly but coercivity has increased rapidly after irradiation. For isothermally heat treated condition of irradiated specimen, BN energy has increased while Vickers microhardness has decreased. Results of BNE and Vickers microhardness are reversed to the results on irradiated condition. All these consistent changes in magnetic parameter and Vickers microhardness measurement, which are thought to be resulted from the interaction between irradiation-induced defects and dislocation, and magnetic domain, respectively, show a possibility that magnetic measurement may be used to the evaluation of material degradation and recovery due to neutron irradiation and heat treatment, respectively, if a relevant large database is prepared. (author). 49 refs., 7 tabs., 23 figs