Computer simulations of the effects of temperature change on defect accumulation in copper during neutron irradiation

Kinetic Monte Carlo (kMC) computer simulations were used to study the effects of temperature change during low-dose 14-MeV fusion neutron irradiations on defect accumulation in copper. Instantaneous temperature changes from 300 to 473 K, from 300 to 673 K and from 373 to 573 K were simulated. All the high temperatures are above the Stage-V annealing temperature for copper, approximately 400 K. The total simulated dose was 0.01 dpa for all temperature-change simulations, at a dose rate of 10−6 dpa/s. In general, the concentrations of both self-interstitial atom (SIA) clusters and vacancy clusters decrease when the temperature is changed from low to high. The relative decrease in concentration of defect clusters when the temperature is increased is determined by the level of accumulation of vacancy clusters in the initial low-temperature part of the irradiation as well as by the specific temperatures involved. If the vacancy clusters are small and their concentration is high, the decrease of cluster density is prominent when the temperature increases, and the higher the second temperature, the easier it is for defect clusters to dissolve.