LAUSR

Abstract The effects of ion irradiation on the atomic local structure of GH3535, a nickel based alloy and candidate of pressure vessel material for molten salt reactor, were investigated by X-ray absorption fine structure (XAFS). We investigated the local structure of the three major solid solution atoms: Mo, Cr, and Fe under the irradiation of two species of ions: He+ and Ni13+. The changes to the coordination number of these atoms after irradiation were determined from XAFS data. The results reveal that ion irradiation causes selective damage to the elements in alloy. No matter for He+ and Ni13+, Cr is the most vulnerable atom in the alloy to the irradiation with the most decrease in its local coordination number. Mo, on the contrary, changes little under either type of ion irradiation. The irradiation damage to Fe lies in between. The degree of ion damage, however, is closely related to the ion species and energy. XRD results show slight increase of lattice constant in the alloy after irradiation with Ni13+, while the lattice remains unchanged after irradiation with He+. The MD simulation in pure nickel system suggests the lattice expanse effect by the competition between interstitials and vacancies.