Study on the effect of Ar9+ ion irradiation of Zr-2.5 wt.% Nb alloy pressure tube

Response of Zr-2.5 wt.% Nb alloy pressure tube, used in PHWR nuclear reactors, to 315 keV Ar9+ ion irradiation at room temperature was investigated in the fluence range of 3.1 x 10(15)-4.17 x 10(16) Ar9+ cm(-2). Changes in microstructural parameters, viz., the size of coherently scattering domains, microstrain and dislocation density, upon irradiation were ascertained through grazing incidence X-ray diffraction. In general, a decrease in domain size was observed with fluence with a corresponding increase in microstrain and dislocation density. Residual stress measurement showed the development of compressive stresses in place of tensile after irradiation. Transmission electron microscopy showed the formation of dislocation loops of ⟨a⟩-type and ⟨c⟩-type during irradiation. The hardness of irradiated samples, probed through nanoindentation technique, was found to be higher in comparison with unirradiated samples. The above findings have been rationalised on the basis of the defects generated during the Ar9+ ion irradiation.