Development of LIBS for online analysis of solid nuclear materials

With the objective to implement a fast, online analysis technique for control of solid metal nuclear materials, laser-induced breakdown spectroscopy (LIBS) technique is developed for quantitative analysis in uranium and plutonium. Since these matrices have a very dense emission spectrum in the UV-Visible range, the Vacuum Ultra-Violet (VUV) spectral range, less rich in lines, is explored. The aim of this thesis is to perform the analytical development of VUV-LIBS for quantitative analysis between 500 and 5000 ppm with an uncertainty of 3%. For that purpose, four steps were defined. First, for practical and safety reasons, it is generally better to perform experiments on surrogate materials. LIBS based on laser-material interaction, it is relevant to seek a surrogate of material of interest from the viewpoint of the ablated mass. Thus, a complete study of laser ablation of several metals was enabled to build a predictive model of the ablation efficiency. Titanium and stainless steel were defined as surrogate materials of plutonium and uranium for laser ablation. Secondly, the VUV-LIBS setup analytical performances were optimized for several elements of interest in four metals. Then, two calibration methods are used to determine the analytical performances. The limits of quantification are of the order of a few hundreds of ppm for all studied matrices, which validates the objective of impurities quantitation in the 500-5000 ppm range. Uncertainty is lower than 3% in the best cases. Finally, the calibration transfer between the four matrices was studied. A normalization of the nickel net signal measured in three matrices was presented. (author)