The Research Of Helium Irradiation Effect And Dislocation Defects Affect He Behavior In Stainless Steel

The stainless steel structure material of nuclear reactor is the basic research object in the field of nuclear material, which is research hotspot. The stainless steel in domestic nuclear reactor primary circuit pipe and coolant pump contains 304, 316 L etc. In this article, we selects the pure iron metal as the reference, the 304 and 316 L stainless steel as the mainly research object. These are all austenitic stainless steel, and the main elements have Fe, Cr, Ni and other trace elements. In this paper, the ion irradiation technology is the main introduced way of the helium atom.This paper has carried out different energy(low and high) helium irradiation experiment. Different irradiation energy leads to different irradiation effects, through the analysis results of the simulation software SRIM and positron annihilation spectroscopy technique, we can know the low energy of helium irradiation will not cause serious irradiation damage(point defects generated);High energy of helium atom will leads to a lot of vacancy defects. And the helium diffusion depth is connected with the introduced energy. The low energy(150 eV) of He+ irradiated 304 stainless steel is performed, and the injection depth is only a few nanometer; The 5 keV He+ irradiated pure Fe, the depth of ion implantation is dozens of nanometers; and the 50 keV He+ irradiated 304 stainless steel, the particle injection depth is several hundred nanometers.In order to introduce dislocation defects, we used the method of cold-rolled deformation combine with annealing. On this basis we studied the existence of dislocation defects affect helium atom diffusion in the process of helium irradiation, and the influence of the evolution mechanism of action. Through the measured by slow positron technique to the deformation samples, the positron annihilation mechanism have big changed compared with the undeformed material on the surface region. The Doppler results show S parameter drops rapidly, and the bigger deformed the faster decline. The S parameter on the matrix region still increases with deformation. Using 5 keV He+ irradiated deformation of pure iron samples, we can found that the existence of dislocation would lead to helium atom diffusion and large number of helium atoms aggregate in the dislocation fault. For the 304 and 316 L stainless steel, the deformation variable contrast is increasing(10%, 20%), and the He+ irradiation was performed at room temperature, the dose of 1 × 10 /m and1 × 10 /m.The size of deformation affect the content of dislocation, the more dislocation the stronger of the ability to attract helium atom, the greater affect to radiation effects and helium behavior evolution. Dislocation defect is not only attracting a lot of helium atoms diffusion rapidly, and the vacancy defects will also be attracted. Vacancies gather and group in the dislocation line or form the complex with different amount of helium atoms. The existence of dislocation will weakens irradiation damage, in other words, the existence of dislocation can enhance the irradiation resistance of materials.In order to determine the existence form of helium atoms in the material and the influence of dislocation existence, the helium thermal desorption measurement experiment is performed by thermal desorption spectrometer. For the irradiated samples, the helium atom mainly exists in clearance, vacancy, and dislocation line or grain boundary. The state of being contains the free of helium atom, the He-vacancy complex, the He-dislocation complex and helium bubble. The existence of dislocation will directly affect the content of original helium atoms in each position and state, the directly performance is the amount of helium bubble reduced. And the increase of dislocation density causes the number of small clusters will increase, and not lead to large helium bubble formation directly. Thermal desorption energy can received by calculation, the helium surface adsorption energy was about 0.9 eV, and the dissociation energy of helium from the dislocations and vacancies was about 2.3 eV and 3.2 eV, respectively. The decomposition energy of helium bubble was about 3.7 eV.