A procedure using inductively coupled plasma mass spectrometry (ICP-MS) has been developed for determining traces of 237Np in isotopically enriched solutions of U. The chemical treatment of the samples consists of: extracting 237Np in a 1 mol dm-3 solutions of nitric acid using 0.5 mol dm-3 thenoyltrifluoroacetone in xylene, leaving 99% of the U matrix in the aqueous phase; re-extracting 237Np in 10 mol dm-3 nitric acid; heating the extracted solution to white fumes in order to remove the excess of acid; and diluting the resulting solution with 2% HN03. Optimization of the analytical parameters involved suppressing the spectral overlap between 237Np and 238U. By applying an additive continuous tension to the quadrupole on m/z 237 only, the interfering part of the 238U peak is eliminated and good resolution can be achieved between m/z 237 and 238, if the concentration of U is less than 100 mg dm-3. The operating conditions adopted result from a compromise between resolution and sensitivity. The suppression of the analyte signal, arising from U at a high concentration, is corrected for by adding an internal standard to the calibration and measuring solutions. The detection limit is about 0.005 pg of Np per gram of U, for an initial sample of 1 g of U and an additive continuous tension of 7.5 V. The analytical performance of ICP-MS is compared with that of a-spectrometry. The radiochemical determination of 237Np involves a tedious pre-treatment and measurement procedure. In contrast, ICP-MS appears to be a good alternative to a-spectrometry (for the determination of long-lived radionuclides) because of its simplicity, accuracy, excellent detection limits and rapidity of analysis.
This study presents the combined analysis of leftover zirconium in irradiated fuel dissolution solution through time. Thermo-ionisation mass spectrometry was used to analyse the kinetics start and final aliquots with uncertainties lower than 3%, while inductively coupled plasma-mass spectrometry (ICP-MS) was used for intermediary aliquots. In order to obtain low uncertainties using ICP-MS, dissolution solutions were spiked with lutetium, used as a process tracer, in order to perform a relative analysis. The analytical parameters were optimised and uncertainties were lower than 3% for real nuclear samples. This method shows the input of ICP-MS for concentration evolutions determination.
Five chromatography extraction separation methods using Triskem columns were developed for the measurement of minority elements present in high level activity solutions produced by various programs (processes of hydrometallurgical extraction, dissolution of hulls and spent fuels) implemented in the Atalante facility at CEA Marcoule. The first three concern the Purex process, for which it is necessary to quantify Np + Pu traces in the main raffinate, Np traces in the “U-Pu production” step, and Tc traces in the “U production” to qualify its performances. Total recovery of these traces was obtained with a good macro-element decontamination factor, thus permitting their determination by L-line X-ray fluorescence or by ICP-QMS. The fourth separation focussed on the total recovery of U and Pu traces from a hull dissolution solution. The decontamination and recovery performances were very good and enabled the determination of U and Pu by L-line X-ray fluorescence. The last method concerns the separation of Zr from an irradiated fuel dissolution solution, for its isotopic composition determination by ICP-QMS. Excellent agreement was obtained between the experimental measurements and computer code estimates.
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