Recovery of Damage Indued by Irradiation Reactor Pressure Vessel Steels

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The main purpose of the present study was to investigate the mechanism of miorostructural evolution in dilute Fe-Cu alloys, the model alloys of the reactor pressure vessel steels, and the range of vary temperature under vary temperature irradiation.Before investigation of effect of vary temperature on the microstructural evolution, it is necessary to investigate the miorostructural evolution at constant temperature. Two Fe-Cu alloys, namely Fe-0.3Cu and Fe-0.6Cu, were tested in this study. The neutron irradiations were carried out at the Kyoto University Reactor at 573 K. The results indicate that there are three stages in the formation of Cu precipitates. First, the precipitates nucleate by vacancy migration. Second, microvoids form and grow at these precipitates sites, and then the aggregation of Cu atoms is promoted at these microvoids because the surface energy of Cu is lower than that of Fe. Third, the microvoids form and grow in the matrix without any connection with Cu precipita … More tes.Two types of vary temperature irradiations, 573 K/723 K and 573 K/673 K, were carried out to investigate the recovery behavior of defect clusters Fe-Cu alloys. Microvoids and interstitial clusters disappeared, and Cu precipitates grew under vary temperature irradiation. The disappearance of microvoids and interstitial clusters was more prominent in the irradiation than in the annealing at 723 K. The recovery of microvoids and interstitial clusters and the formation of Cu precipitates in the irradiation of 573 K/723 K were more prominent than those in the irradiation of 573 K/673 K. In addition, the irradiation dose at low temperature also influenced the microstructural evolution during subsequent irradiation at high temperature. The results suggest that the lower the irradiation dose at 573 K, the greater the extent recovery of defect clusters in Fe-Cu alloys during irradiation at 673 K. They also suggest that a higher irradiation dose is needed to recover the defect clusters formed at 573 K with low irradiation dose. Inversely, a lower irradiation dose is needed to recover the defect clusters formed at 573 K with high irradiation dose. Less