Molecular Dynamics Simulation Of Radiation Damage And Interaction With Grain Boundaries In Tungsten

Due to the many advantages of fusion energy compared to fossil fuels, it has been vigorously developing. If fusion energy can be successfully used in large scale, the energy problem might be fundamentally solved. Meanwhile researches on first wall materials of fusion reactor have become a key topic. The first wall material would be irradiated by high-energy neutrons produced by nuclear fusion reactor. Irradiation-induced point defects would lead to changes of the material’s microstructure after a long period of accumulation and evolution, and finally resulting in deterioration of the macroeconomic performance, at last causes the failure of material. Tungsten(W) has become a big concern as the most promising plasma facing material (PFM) of fusion reactor. Therefore, in-depth study of W radiation damage process is of great significance for better understanding the behavior of W under neutron irradiation. In this work, molecular dynamics method has been improved for the simulation of radiation damage to explore the atomic mechanism of formation and evolution of irradiation-induced defects in bcc-W in the early stage of neutron irradiation.For single crystal W(SC-W), the number and distribution of defects produced by displacement cascades has been studied; the influence of PKA direction and temperature on the number of steady Frenkel pairs has also been researched;defect clusters and the threshold energy has been simulated. For W system with symmetrical tilt boundaries(GB-W), different effects on survival interstitials and vacancies have been seperately analyzed, and Σ13 [001] (230) GB and 117 [001] (140) GB have also been explored to study the different absorption capacity of the defects.The results of SC-W showed that for morphologies distribution of defects induced in the peak time of cascade, the more intensive the defects are, the less the steady Frenkel pairs numbers are, on the contrary, the more decentralization the defects are, the more the steady Frenkel pairs numbers are; the number of steady Frenkel pairs is insensitive to PKA direction, but has a trend to decline with the temperature elevating; the percentage of interstitial clusters is higher than that of the vacancy clusters, while vacancy tend to form larger clusters; the average threshold energy of W is less affected by temperature and has certain anisotropy. For GB-W, by separating analyzing the number of survival interstitials and vacancies quantitatively, the effect of the GB in W has a dual nature for radiation-induced defects in the timescale of picosecond(ps), that is to absorb interstitials and to cause simultaneously more vacancies in grains, which, as a whole, may lead to a larger number of total survival defects of GB-system than that of single crystal. Our research also refers that Σ17 [001] (140) GB has better "absorbing" capability of radiation-induced point defects than that of Σ13 [001] (230) GB, which may attribute to the less matching degree level of atoms, the greater ratio of grain boundaries and the higher GB energy compared with Σ13 [001] (230) GB.The results of this work can provide data for analyzing the behavior of W material under nuclear environment, meanwhile lay a good foundation for the radiation damage of tungsten alloy.