Simulation of the kinetics of defect accumulation in copper under neutron irradiation

Stochastic annealing simulations were originally developed for and successfully used to describe the short-term annealing stage of defect evolution within individual displacement cascades. Applied to a sufficiently large volume with periodic boundaries. stochastic annealing simulations can also provide a description of the evolution of defects produced during continuous irradiation. The irradiation is simulated by successive introduction of collections of defects representing the primary damage state of individual cascades placed in the simulation volume randomly in time and space. Cascade energies and the rate of their occurrence are chosen to approximate the damage due to the neutron flux of the 14 MeV neutron source Rotating Target Neutron Source-II (RTNS-II). The cascades are chosen from a library of cascades generated in molecular dynamics (MD simulations for recoil energies from 5 to 25 keV. The numbers of each type of defect, defect cluster size distributions. as well as the positions of the defects within the crystal, are monitored as a function of time. Simulated defect cluster densities as a function of dose up to 0.1 dpa at room temperature are compared to experimental results. The simulated cluster densities are within about a factor of two of the experimental results over several orders of magnitude of dose. The effects on damage accumulation due to dose, dose rate, cascade overlap and interstitial cluster mobilities are demonstrated with examples. (C) 1999 Elsevier Science B.V. All rights reserved.