Influence of Xe Ion Irradiation on Surface Morphology and Electrochemical Corrosion Behavior of Zr-1Nb Alloy

Zirconium alloy cladding suffers from the synergetic effect of irradiation and corrosion degradations in reactor environment. In order to evaluate the effect of irradiation on the electrochemical corrosion behavior of the Zr-1Nb alloy before and after irradiation in 0.5 mol/L LiOH solution at room temperature, the alloy was irradiated with 6.37 MeV Xe ions. The microhardness, surface morphology and phase composition of Zr-1Nb alloy before and after irradiation were measured. After the Xe ion irradiation, the surface of Zr-1Nb alloy has a bump formed by ion denudation. The microhardness and surface roughness are increased with the increase in irradiation dose. The polarization current density of the 0.5 dpa dose irradiated sample is increased by 18 times than that of the unirradiated sample, while it is about 82 times higher of the 2.7 dpa irradiated sample, compared with the unirradiated sample. After the ion irradiation tests, the polarization potential and polarization resistance of the samples decrease significantly. In addition, the lower-frequency impedance is decreased, and the curvature radius of the capacitance curve is also decreased with the increase in irradiation dose. The polarization curves and EIS results show that the ion irradiation increases the corrosion tendency of the Zr-1Nb alloy, and its corrosion resistance is decreased with the increase in irradiation dose. After electrochemical corrosion test, the surface of Zr-1Nb alloy has a strip structure, and the strip is finer after ion irradiation. The reduced corrosion resistance after the ion irradiation tests is considered to be mainly caused by the irradiation induced damage on the alloy matrix.