Abstract
Zircaloy-4 is widely used as structural material for the fuel cladding of nuclear reactors due to its low neutron absorption cross-section, excellent corrosion resistance and good mechanical stability under neutron irradiation. In nuclear reactors, helium ions (He+) are produced during (n, alpha) reactions that can affect the structural performance of the Zircaloy-4. Therefore, it is important to investigate the structural properties of Zircaloy-4 after irradiation with helium ions. In this work, structural properties of He(+)irradiated Zircaloy-4 are investigated at different ion fluences. The samples of Zircaloy-4 were irradiated with 300 keV He+ at different fluences (1x10(13), 1 x 10(15) and 1 x 10(16) ions/cm(2)) by using Pelletron Accelerator at room temperature. The ion range inside the samples was 0.84 mu m as estimated through the SRIM software. Structural properties of the pristine and He(+)irradiated samples were studied through x-ray diffraction that revealed polycrystalline Zr peaks whose intensity and width were changed after irradiation. The diffraction peaks of Zr corresponding to (002) plane were found to be higher in intensity as compared to its other diffraction peaks. The changes in peaks positions at lower and higher diffraction angles were also noticed that was attributed to the generation of stresses inside the irradiated samples. The Williamson-Hall (W-H) analysis of the samples depicted a decrease in material's crystallinity after exposure to He+ up to 1 x 10(15) ions/cm(2) whereas the crystallinity was started to improve with increase of the ion fluence to 1 x 10(16) ions/cm(2). These results were explained on the basis of collisional cascades process and defects annihilation under the thermal spike model.