Molecular Dynamics Simulation Of Irradiation Damage In Zirconium

The irradiation damage behavior of materials under intense radiation is the key for nuclear technology. Zirconium alloy is considered for use as one of nuclear structural materials in fission reactors because of its outstanding physical and nuclear properties. Computer simulations can offer an efficient approach to observe the evolution of initial irradiation damage at atomic level and obtain some information which can't be obtained by experiments so far. thus we can make further understanding about radiation damage, which is helpful for design and improvement of nuclear structural materials.In present paper, molecular dynamic (MD) simulations based on a modified EAM potential are applied to investigate the process of irradiation damage and the defects forming mechanisms of displacement cascades in HCP-Zr that is the main component of Zr alloy. This paper focuses on the effect of temperature,PKA energy and relative atomic mass on the process of initial irradiation damage. And the displacement threshold energy of Zr is calculated.The simulation results show that the lifetime of displacement cascade of HCP Zr caused by radiation is very short, about-ps. During the radiation process, there is a rapid build-up in the number of defects in the initial stage and a maximum number is reached at about lps. During the subsequent relaxation stage, due to recombination of interstitial atoms and vacancies occurs, the number of defects decreases to a certain amount and a steady state is reached.The influences of temperature and radiation energy are investigated. In present paper, we investigate the radiation process at temperature of 100K,200K and 300K respectively. After the visualization of the simulation results, we found that the number of defects increases and the tendency for defects to form as clusters increases with the temperature rising. Then at 100K, radiation processes with different PKA energy (500eV, 1keV,2keV) were investigated respectively. The results show that more intensive of the radiation energy will induce more serious radiation damage, which indicates that more atoms get enough energy exceeding Ed to overcome the binding force and removed from the crystal lattice.By comparing the number of defects of Zr and Ti which have the same crystal structure (HCP) under the same radiation energy, the metal with heavier atomic mass (Zr) has fewer defects through the process of displacement cascade, which indicates that relative atomic mass is important factor for the evolution of radiation damage. By raising the initial incident energy Eo of PKA, we found that defects appears when the energy Eo is higher than-30eV, which indicates that atoms can overcome the binding force and become displacement atoms only when they get energy exceed this value. So it is certain that the critical value of Eo is the displacement threshold energy Ed and it is generally coordinate with the experimental value.