Molecular dynamics analysis of primary radiation damage evolution in nickel, iron, and tungsten

Abstract

BackgroundNickel-, iron- and tungsten-based alloys are commonly used as structural materials of reactors. During their operational life, these alloys undergo intense neutron irradiation.PurposeThis study aims to analyze the post-irradiation defect evolution and its mechanisms in these materials for comprehending the effects of irradiation on them.MethodsThe displacement cascades in nickel, iron, and tungsten were examined at various temperatures (300⁓500 K), primary knock-on atom (PKA) energies (, and ) by using molecular dynamics (MD) simulations. Firstly, the model was initially relaxed at each specified temperature under a canonical ensemble for 10 ps, applying periodic boundary conditions in every direction. Then, an atom was randomly chosen as a PKA and assigned kinetic energy to initiate the cascade collision simulation in the micro-canonical ensemble. Finally, the Open Visualization Tool package was employed for visualization and data analysis of the irradiation cascade processes.ResultsThe simulation results reveal that nickel and iron exhibit similar steady-state defects. At lower PKA energies (<5 keV), nickel exhibits marginally fewer defects than iron. However, as the PKA energy surpasses 5 keV, the number of defects in nickel becomes slightly more than that in iron. Furthermore, under identical irradiation conditions, tungsten demonstrates superior radiation resistance, with fewer steady-state defects when compared with both nickel and iron.ConclusionsThe defect evolution during various cascade displacement phases in three metals and their defect recombination rates are crucial to understanding the disparities in radiation damage resilience. The derived results help to comprehend the radiation characteristics of these metals. Additionally, the primary radiation damage dataset compiled for these metals lays a foundation for further larger-scale simulations of their radiation attributes using rate theory or cluster dynamics methods.

Keywords

• nickel
• iron
• tungsten
• neutron irradiation
• primary radiation damage
• molecular dynamics