| ABSTRACT: | IRRADIATION DEGRADATION IN REACTOR PRESSURE VESSEL WELD SURVEILLANCE
SPECIMENS
K.-o.Chang, B.-c. Kim, S.-L. Lee
Korea Atomic Energy Research Institute(KAERI), Daejeon, South Koreo
Irradiation-induced changes in the magnetic parameters and mechanical properties were measured and
compared to explore possible correlations for reactor pressue vessel(RPV) weld Charpy specimens. The
specimens employed in the present study were obtained from a RPV surveillance programme. The materials
were tested in the unirradiated and three different post-irradiation conditions in a typical pressurized water
reactor environment.For mechanical property parameters, Vickers microhardness, tensile and Charpy impact
tests were performed and saturation magnetization, remanence, coercivity and Barkhausen noise amplitude
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 RTNDT and a decrease in Charpy upper-shelf energy irrespective of weld
materials. Hysteresis loops appeared to turn clockwise, resulting in an increase in coercivity and Barkhauen
noise amplitude appeared to decrease after irradiation. Both magnetic parameters showed viable correlations
to the changes in mechanical parameter(Vickers microhardness, Charpy upper shelf energy)due to
irradiation. If we consider many intrinsic and extrinsic factors that affect defect microstructures of RPV
steels, comparisons of magnetic measurement data reported on irradiated RPV samples may need careful
consideration of factors, including, but not limited to, irradiation temperature, flux, fluence, chemical
composition and heat treatment conditions of the specimens.
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