The Studies Of The Collision Cascade And The Induced Defects Evolution Behavior In Metal Molybdenum

With the crisis of the energy, nowadays, the nuclear power development and application are very important. At present, the fission can still dominate position in the nuclear power before commercialize the fusion. There has been long standing concern about the safety of nuclear power, especially after the Fukushima disaster last year. The molten salt reactor has a great advantage on it, whether the leakage or the proliferation of the nuclear power. However, the molten salt reactor occurs to a very important technical bottleneck which means that we need to resist neutron irradiation and molten salt corrosion resistant materials, especially the neutron radiation material, which requires that it must have a high intensity radiation damage resistance and corrosion resistance. Nickel-molybdenum tungsten-nickel alloy is one of the most corrosion and neutron radiation resistant metal materials, so it has a great prospect in molten salt reactor design. This paper studied the process of pure metal molybdenum off-normal cascade collision and its evolution process on defects in irradiation environment.In this paper, the displacement cascades in molybdenum have been studied with MD simulation, and we discussed the impact of initial radiation temperature and PKA energy on the cascade process. It was found that the peak number of defects and the time to reach such maximum all increase with increasing of initial temperature and PKA energy. And during the collision, PKA energy reaches a certain value, it will produce sub-cascade. The analysis shows that the PKA energy significantly affected the formation and distribution of defects, the higher the energy, the defect clusters distribution was wider, the greater the size was also relatively. However, the influence of initial irradiation temperature was relatively weak, was regulated by the energy. By combining the MD method and NEB method, we obtained the stable configuration, the binding energy and the migration energy of the partial defect cluster, and it was concluded that the energies increased with the number of defects contained in defects clusters, but for rare exception cases like that who affected by the symmetry of the spatial distribution of defects. In addition, from the comparison of the migration energies of vacancy and interstitial clusters, we could found that interstitial atoms were easy assembling into small size clusters, but its migration barrier was very low and easily to migrate.The object Kinetic Monte Carlo method is applied in this article to simulate the annealing process of different cascade fragments formed after quenching stage, and gain some insights into the recombination behaviors of the defects clusters in fragments. We found during the annealing process, since migration and size differences of the interstitial clusters and vacancy clusters led to several different recombination stages:stage ? almost occurred at the annealing temperature of 90 K, which corresponded to the correlated recombination resulting from the motion of interstitials clusters which were annihilated with nearby vacancy defects or larger clusters; The stage ?, commonly observed at 390-490 K, the mechanisms of this stage relatively complex, multiple mechanisms were involved. The stage ? was affected by the number and size of defects clusters, generally appear to above 700K, it is mainly due to the defects emitting from the larger size clusters and recombination appeared again. Finally, the recombination mechanism of various stages were discussed in detail, we presented the evolution process of the number of vacancy and interstitial clusters as the function of annealing temperature, and it does a good job of explaining the annealing results of OKMC simulation.In this paper, through the detailed simulation study of irradiation damage of pure metal, provided a reference for studies on radiation damage of nickel-molybdenum nickel based alloys, and to provide some guidance for the future experimental research on irradiation properties of molten salt reactor structural materials.