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Communication Dans Un Congrès Année : 2022

Application of coupling between capillary electrophoresis and mass spectrometry for precise isotope ratio measurements

Résumé

Introduction: The accurate determination of isotopic and elemental compositions of nuclear fuels is essential for management of nuclear reactors and for treatment and recycling of radioactive waste. Chemical separation of elements present in nuclear fuel samples is necessary before mass spectrometry measurements in order to avoid isobaric interferences. Various analytical developments are performed in our laboratory with the goal to reduce the amounts of samples required, the handling time on radioactive samples and the radioactive wastes produced. The objective of this work is to validate a new miniaturized analytical method based on the coupling of capillary electrophoresis (CE) and multicollector inductively coupled plasma mass-spectrometry (MC ICP-MS) to determine, at uncertainty around several per thousand, both the isotopic composition and the elemental content of three important elements present in fuels, uranium, plutonium and neodymium. Materials and methods: A home-made module of capillary electrophoresis implanted in glove box was used and the separation of the three elements was performed through a capillary (inner diameter : 50 µm) using hydroxymethyl butyric acid (HMB) as electrolyte at a concentration of 120 mM. The capillary was coupled to the ICP source using a commercial nebulizer inserted in a double entry cyclonic spray chamber. The second entry is dedicated to a second nebulizer allowing automatic addition of an isotopic reference standard during the separation to correct mass bias that must be taken into account by MC ICP-MS to obtain accurate isotope ratio measurements. Approach: Firstly, the CE separation and on-line measurement by MC ICP-MS were performed on a "qualified" Pu-Nd reference material in order to validate the correction of mass bias. Then, the MC CE-ICP-MS method was applied on a nuclear fuel sample and U/Pu and U/Nd elemental ratios were determined using the double isotope dilution technique. Results and discussions: A total of 9 electrophoretic injections of the Pu-Nd reference material were performed by MC CE-ICP-MS. The electropherograms show the presence of three redox states of plutonium in solution: Pu (+IV), Pu (V), Pu (+VI). The precision and trueness are less than 0.1% for all plutonium species and less than 0.2% for neodymium, in agreement with the uncertainties of the isotopic reference material. For elemental and isotope ratio measurements of the nuclear fuel sample, a redox cycle was performed before separation to fix the redox state of Pu at valence (+VI) and ensure isotopic equilibration in the case of isotope dilution. The evolution of the speciation of Pu for the successive samples injections will be discussed. The results obtained for isotopic and elemental compositions are in good agreement at uncertainty of several per thousand to those obtained by "conventional" methods. Conclusions: Compared to conventional method, this miniaturized technique allowed to decrease volume of radioactive waste from several hundred milliliters to a few milliliters and quantities of elements analyzed from microgram to nanogram, which is of great interest for nuclear applications.
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Dates et versions

cea-04327890 , version 1 (06-12-2023)

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  • HAL Id : cea-04327890 , version 1

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Julie Stevenin, Erwan Dupuis, Hélène Isnard, Frédéric Chartier. Application of coupling between capillary electrophoresis and mass spectrometry for precise isotope ratio measurements. Analytics, Sep 2022, Nantes, France. ⟨cea-04327890⟩
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