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The energy spectrum of uranium in irradiated fuels is known to give key information on the oxidation state of uranium at the sample surface. In this respect, it is essential to know the operating conditions applied to measure energy spectra by secondary ion mass spectrometry in order to obtain reliable data. Using a focussed beam on CAMECA IMS6f, the acquisition of an energy spectrum is performed along a line on the sample surface because the primary beam position moves as a function of the high voltage. Depending on the size of UO2 grains, the analysed area can be limited within one single grain or spread among many grains. The consequences of such acquisition conditions are discussed in this paper. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The energy spectra of UO2 samples with slight hyper-stoichiometry were measured. In addition to the regular peak detected at 20 eV, it was observed that another peak at 80 eV would grow with the increasing stoichiometry. The relative intensities of the two peaks were used to determine the surface O/U ratio of the sample. We discuss how it would be possible to determine bulk O/U ratio from these results. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The energy spectra of UO2 samples with slight hyper-stoichiometry were measured. In addition to the regular peak detected at 20 eV, it was observed that another peak at 80 eV would grow with the increasing stoichiometry. The relative intensities of the two peaks were used to determine the surface O/U ratio of the sample. We discuss how it would be possible to determine bulk O/U ratio from these results. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]