X-ray study of radiation damage in UO2 irradiated with high-energy heavy ions

In order to characterize the radiation damage due to ion-track formation in UO2, polycrystalline samples have been irradiated with 210 MeV Xe ions, and characterized with X-ray diffraction technique and with extended X-ray absorption fine structure (EXAFS) technique using X-ray near U L-3-edge. The result of the XRD measurement shows that the change in XRD profile is observed at relatively low fluence of 10(16) ions/m(2), where the ion-tracks should occupy about 20% of the sample when the typical diameter of 5 nm is assumed. The damages detected by XRD increase monotonically with increasing fluence up to relatively high fluence of 10(19) ions/m(2). The irradiation-induced change in EXAFS spectra near U L-3-edge is not observed in UO2 irradiated with 210 MeV Xe ions at highest fluence of 10(19) ions/m(2). The failure of the damage detection in EXAFS spectra may be due to a deep penetration of high-energy X-ray, which results in smearing of the signal from the damaged shallow region. The depth profile of X-ray penetration may critically affect the detection efficiency of the damage introduced by energetic ion irradiation. (C) 2011 Elsevier B.V. All rights reserved.