Application of Collision Reaction-cell Based MC-ICPMS to In-situ Interferences Resolution for Elemental and Isotopic Ratios Measurements of Nuclear Fuel Samples

摘要

Two direct applications of a collision-reaction cell based Multiple-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) for the resolution of isobaric interferences are presented. The first one is the determination of ~(90)Sr/~(238)U elemental ratio by double isotope dilution technique and the second one concerns the ~(33C)s/~(135)Cs and ~(137)Cs/~(135)Cs isotope ratios measurements in spent nuclear fuel samples. The results obtained for both type of measurements using respectively O_2 and N_2O as reaction gas for the in-situ Sr/Zr and Cs/Ba separation in the collision reaction cell of the instrument are compared to the classical "two-step" chemical purification results obtained with further Thermal Ionization Mass Spectrometry (TIMS) and MC-ICPMS measurements. Accuracy and reproducibility obtained on both ~(90)Sr/~(238)U elemental ratio and ~(133)Cs/~(135)Cs and ~(137)Cs/~(135)Cs isotope ratios measurements are found to be similar (<0.5% in all cases) between the two approaches, leading to the validation of the direct "in-cell" measurements. In addition to the obvious time gain associated with the reduction of chemical purification procedure, this approach allows to reduce the risk of natural contamination, the amount of analytical radioactive wastes, and the time contact of analysts with radioactive samples.