Contribution of the surface contamination of uranium compounds on the quantitative analysis by electron probe microbeam analysis
Résumé
Electron Probe Microbeam Analysis (EPMA) is largely used for nuclear fuels to support R &D studies as fuel fabrication, post irradiation examination, chemical compatibility between fuel and structural materials and severe accident post-test (CORIUM) to determine chemical composition of material with high accuracy.
The present contribution is related to the optimisation of analyses by EPMA of uranium compounds. Uranium materials (metallic alloys or ceramic) are sensitive to oxidation even at room temperature after metallographic preparation; it induces an overestimation of oxygen measurements. In some case, it could be difficult to distinguish the difference between an oxidized surface and an oxide compounds based on EDS measurements.
The quantification of light elements (C, N, O) in uranium compounds could be altered by surface contamination or native oxidation.
Electron probe microanalysis (EPMA), originally developed for determining the composition of bulk samples, has become well established techniques for determining thickness but also composition of multi-elements thin films deposited on a substrate.
The present contribution is related to the optimisation of analyses by EPMA of uranium compound in taking into account surface contamination or native oxidation.
Some example of quantification operated on reduction of UO2 in molten salts media (1123 K), UC arc melted fabrication, USiC prototype nuclear fuel mixed carbide of uranium composite in the study of Generation IV reactor. Auger Spectroscopy could be used to complete the quantification of the oxidation.