RADIATION-DAMAGE IN UO2 BY SWIFT HEAVY-IONS

Specimens of sintered UO2, a high melting point ceramic with the fluor ite structure, were irradiated with heavy ions (Xe-129, U-238) with di fferent fluences (5 x 10(10) to 7 x 10(13) ions/cm(2)) acid energies ( 173 MeV for Xe ions to 2.713 GeV for U ions). The influence of the ele ctronic energy loss on the mechanisms of damage formation was studied in the range of 29 to 60 keV/nm. Transmission Electron Microscopy (TEM ) was performed to identify and characterize the damage induced by the se ions. Tracks produced by U ions of 2713 and 1300 MeV and by Xe ions of 173 MeV were observed, The radii of the observed tracks were calcu lated using a thermal-spike model, taking into account the thermodynam ic parameters of the material and the energy and velocity of the incom ing ions. The TRIM code was used to determine the displacement profile and the energy distribution along the ion paths. Good agreement with the experimental results was found. The dependence of damage formation on the ion dose was also studied. For instance, defect clusters and l oops were produced in UO2 irradiated with Xe-129 of 173 MeV (dE/d x si milar to 29 keV/nm) between 7 x 10(10) and 7 x 10(13) ions/cm(2).