Charged defects during alpha-irradiation of actinide oxides as revealed by Raman and luminescence spectroscopy

Abstract

We have recently evidenced an original Raman signature of alpha irradiation-induced defects in UO 2. In this study, we aim to determine whether the same signature also exists in different actinide oxides, namely ThO 2 and PuO 2. Sintered UO 2 and ThO 2 were initially irradiated with 21 MeV He 2+ ions using a cyclotron device and were subjected to an in situ luminescence experiment followed by Raman analysis. In addition, a PuO 2 sample that has previously accumulated self-irradiation damage due to alpha particles was investigated only by Raman measurement. Results obtained for the initially white ThO 2 showed that a blue color appeared in the irradiated areas as well as luminescence signals during irradiation. However, Raman spectroscopic analysis showed the absence of Raman signature in ThO 2. In contrast, the irradiated UO 2 and PuO 2 confirmed the presence of the Raman signature but no luminescence peaks were observed. These findings lead to propose a mechanism involving electronic defects in ThO 2 while a coupling between electronic defects and phonons is needed to explain the Raman signal in UO 2 and PuO 2 .

Quantification of irradiation-induced defects in UO2 using Raman and positron annihilation spectroscopies

“…The intensity of the defect peaks increases as a function of electron energy and is consistent with the increase defects concentration in the UO 2 samples. However, the intensity increase observed in this study is less prominent compared to data reported for alpha and heavy-ion irradiation [10,11,25]. Though the Raman defect bands appear clearly for the 2.5 MeV irradiated disk, it is difficult to estimate the electron energy threshold for the defect peaks from Figure 1.…”

“…Figure 1 shows that electron irradiation induces the apparition of the Raman triplet defect bands in the 500-700 cm -1 spectral range, denoted by U1 (~532 cm -1 ), U2 (~574 cm -1 ) and U3 (~636 cm -1 ). First of all, these spectra look rather similar to those previously obtained under ionic irradiation [10,11]. The T 2g mode looks only slightly affected and the three defect lines occur.…”

“…Raman spectroscopy offers an alternative approach for the characterization of irradiation-induced defects in nuclear fuels. The occurrence of a specific Raman signature referred to as the Raman triplet defect bands, in doped or irradiated UO 2 , appears as a promising path for the understanding of irradiation effects on UO 2 fuels [10,11,12,13].…”

Effect of ballistic damage in UO2 samples under ion beam irradiations studied by in situ Raman spectroscopy

“…We must note that our Raman measurements have been performed with a 532 nm wavelength laser. In these analysis conditions, the LO band is much more intense compared to the U1 and U3 bands due to a resonance effect [16].…”

Lattice thermal expansion of Pu1−y Am y O2−x plutonium–americium mixed oxides

“…Estimated O/M ratio T (K) y = 0.018 y = 0.077 y = 0.21 y = 0.49 y = 0.80 y = 1.00 disorder induced by the recoil nuclei of the decays (Chikalla & Turcotte, 1973;Noe & Fuger, 1974;Hurtgen & Fuger, 1977;Weber, 1984;Sykora et al, 2005;Baclet et al, 2007;McCall et al, 2008;Kato et al, 2009;Belin et al, 2009;Prieur et al, 2011Prieur et al, , 2014Horlait et al, 2013;Lebreton et al, 2014;Strach et al, 2014;Mohun et al, 2016). Since the present samples were annealed in situ prior to the measurements and because the analysis duration was relatively short (about 1 d), the swelling effect induced by selfirradiation on the lattice was not observed.…”