Kinetic Monte Carlo modeling of cascade aging and damage accumulation in Fe-Cu alloys

Irradiation embrittlement in nuclear reactor pressure vessel steels results from the hardening produced by a high number density of nanometer scale features. This paper describes a kinetic lattice Monte Carlo model to simulate the cascade aging and damage accumulation of neutron irradiated Fe-Cu alloys, including new algorithms to introduce additional displacement damage, including self-interstitial atom-vacancy recombination, and to introduce a flux of diffusing vacancies due to the supersaturated vacancy concentrations under irradiation. The results of initial KLMC simulations of damage accumulation in an Fe-0.3% Cu alloy at 290 °C and 10−11 dpa/s are presented and reveal the continuous formation and dissolution of three-dimensional vacancy-Cu clusters from the remnants of the vacancy-rich displacement cascade core, in addition to the formation of a high number density of copper clusters that grow with increasing irradiation dose. To our knowledge, this represents the first kinetic Monte Carlo model simulation that captures both Cu precipitate formation and vacancy-Cu cluster formation, as is experimentally observed. KLMC simulation results that investigate the effect of increasing irradiation dose rate from 10−13 to 10−9 dpa/s are also presented. Future modeling efforts will evaluate the effect of the model parameters, perform multiple simulations to provide statistical evaluation of the copper precipitate and vacancy-Cu cluster evolutions, and quantitatively compare the results to available experimental data.