Numerical simulation of irradiation induced precipitates in low copper RPV steels based on cluster dynamics

Irradiation induced defects such as matrix damage and solute atom precipitates are the main causes of irradiation embrittlement. Based on the reaction rate theory, a cluster dynamics model considering multiple nucleation mechanisms of Mn-Ni-Si precipitates is established, and the generation of irradiation induced defects, the irradiation dose dependence of mean size, number density of Mn-Ni-Si precipitates and dislocation loops in low-copper RPV steels are simulated. The comparative analysis with experimental data shows that the modified cluster dynamics model considering both the precipitates formation mechanism of interstitial dislocation loops domination and vacancy cluster domination can better simulate the irradiation damage behavior of materials. On this basis, the sensitivity analysis of the irradiation parameters shows that the effect of the neutron flux on the irradiation induced precipitates is related to the neutron fluence, the larger the irradiation flux is, the less the precipitates will be generated at low fluence, and the more the precipitates will be at high fluence. Further more, the precipitates is more likely to be produced at lower temperature. (authors)