Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide

Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O-2 lattice in an irradiated (60 MW d kg(-1)) MOX sample was performed employing micro-X-ray fluorescence (mu-XRF) and micro-X-ray absorption fine structure (mu-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (similar to 0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am3+ species within an [AmO8](13-) coordination environment (e.g. >90%) and no (<10%) Am(IV) or (V) can be detected in the rim zone. The occurrence of americium dioxide is avoided by the redox buffering activity of the uranium dioxide matrix. (C) 2013 Elsevier Inc. All rights reserved.