| Aimed at the helium damages in Plutonium caused by a decay, He+ ions were implanted in aluminum and the behaviors of helium in aluminum were investigated both theoretically and experimentally to simulate those effects in Plutonium. At the same time, the diffusion of helium-3 produced by tritium decay in stainless steels, which were served as the structural materials in tritium and fusion technologies, was also investigated in this thesis. The sense of this work is to gain a further understanding of helium in the two metals.On the diffusion of helium-3 in two spherical shell samples made of 21-6-9 type of stainless steel, during the storage of tritium at the pressure of 6.13MPa for about 4 and 6 years at room temperature and later exposed to air for another 3 and 1 year. First, a calculation based on the analytical and numerical method to the diffusion and decay theories was developed to evaluate the concentration distribution of helium-3 by tritium diffusion and decay in the samples. The numerical method was also used to solve the diffusion problem involved with several steps. By etching the inner surface with an acid solution and collecting the released helium-3 simultaneously and analyzing it later, the distribution of helium-3 in the shells was determined experimentally. Results showed that most helium-3 atoms were preferential segregated to the surface, and some accumulated at some local sites inward the shells. This is due to the incompatibility of helium with the matrix atoms. But on the whole, the trend of helium distribution by the determination was similar to that by calculation. And the depth which helium-3 could reach in both samples were 350 microns and 500 microns respectively.In the theoretical simulation on the behavior of single helium atom in aluminum, the varieties of energy data including the formation, migration, binding, and dissociation energies for single helium atom at the interstitial, vacancy, grain boundary, and dislocation sites in aluminum lattice were calculated, based on the density functional theories, general gradient approximation and pseudopotential plane wave method. Results showed that the most fittable sites for containing helium atoms inside the cell are vacancies. But in the view of the whole lattice, grain boundaries are the best. Dislocations can also contain helium with a relatively poorer ability than vacancies and grain boundaries. In the two interstitial sites in fcc-Al cell, He prefers to occupying the tetrahedron site. Helium interstitials are movable. It is easy for the accumulation of helium interstitials or being trapped by vacancies, grain boundaries and dislocations through the migration of helium interstitials.In the experimental studies on the behaviors of helium in aluminum, ion implantation technique was adopted to introduce helium with different energies, doses and distributions into some specimen of monocrystal, polycrystal, and preferred orientation as to the structure of aluminum. The energies varied in the range of 50eV to 4.87MeV. The corresponding helium peak depths by TRIM simulation varied in the range of 16 angstrom to 20.7 microns.The thickness of the helium layer varied in the range of 10 angstrom to 1 micron. Then varieties of methods were used to study the implanted helium in the specimen. Determination of the helium distribution by enhanced proton back scattering spectroscopy revealed that most helium has escaped out of the specimen during the long term of storage and the hugest loss by escape was found in the monocrystal aluminum which is lack of the grain boundaries for containing helium atoms. Lattice aberrance could be seen in the He+ implanted layers by small angular X-ray diffraction measurement. The largest swelling in the lattice parameter lies in the low index crystal face in monocrystal aluminum for the same implantation and storage process. S parameters in the slow positron annihilation spectroscopy denoted the distributions of helium-vacancy defects (HenVm) sensibly. Through annealing the samples above 450℃, he...
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