Dependence of irradiation defects evolution on dose rate and PKA energy spectrum in tungsten

Abstract

Heavy-ion irradiation is considered as an effective method to study the performance of nuclear materials under neutron irradiation, while these two types of experiments show the striking difference in microstructure evolution and thermo-mechanical properties. In this work, taking tungsten (W) as an example, we systematically investigated how dose rate and primary knock-on atom (PKA) energy spectrum affect the evolution of displacement damages in materials using object kinetic Monte Carlo (OKMC) method. It is found that the increase of dose rate promotes the nucleation of vacancy clusters and dislocation loops but inhibits their growth, which is in agreement with the experimental results. This should be attributed to shortened evolution time, which suppresses the migration and dissociation of defects and promotes their nucleation, which can be compensated by the increase of temperature. Accordingly, a modified predictive model has been proposed to characterize the compensatory effect of temperature on different dose rates. However, different from the dose rate, the influence of PKA energy spectrum cannot be compensated by temperature variation, because the high-energy PKAs may generate large and stable defect clusters directly during collision cascade. These results clarify the influence of dose rate and PKA energy spectrum on the evolution of displacement defects in W, and provide valuable insights for assessing the performance of materials under neutron irradiation.