Effect of carbon on irradiation-induced grain-boundary phosphorus segregation in reactor pressure vessel steels using first-principles-based rate theory model

Ebihara, Kenichi   ; Yamaguchi, Masatake   ; Nishiyama, Yutaka ; Onizawa, Kunio ; Matsuzawa, Hiroshi*

According to the experiment, the grain-boundary (GB) phosphorus (P) segregation in neutron-irradiated reactor pressure vessel (RPV) steels causes intergranular embrittlement. However the dependence of the segregation on variables such as dose and dose-rate is not clear due to the lack of experimental databases. In this paper, we incorporated the effect of carbon atoms into the rate theory model, and simulated the GB P coverage in the neutron-irradiated RPV steels. As a result, the simulation reproduced the experimental GB P coverage. It was observed that the GB P coverage does not depend on the dose rate regardless of the presence of carbon atoms. Furthermore, it was confirmed that vacancies scarcely transport P atoms to grain-boundaries as compared to the transport by self-interstitial atoms and it was found that carbon atoms influence the irradiation-induced P segregation mainly by suppressing the migration of vacancies.