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This study presents the development and the comparison of high accuracy methods for uranium isotope determination by thermal ionization mass spectrometry. Two methods for uranium minor isotope ratio determination were compared in term of accuracy, analysable quantity, analysis time and versatility: the total evaporation and the classical method with multi-dynamic sequences. The mathematical correction of the abundance sensitivity and the detector calibration within the classical method helps decreasing the uncertainties and the biases compared to the total evaporation method. This comparative study was conducted within the framework of the "2017 Nuclear Material Round Robin" participation organized by the International Atomic Energy Agency.

This study compares the two analytical methods for uranium concentration determination with high accuracy in uranium pellet: K-edge densitometer (KED) and the isotope dilution with Thermal Ionisation Mass Spectrometry measurements (ID-TIMS). Both techniques are compared in terms of time, generated radioactive effluent, simplicity, uncertainty estimation and detection limit. ID-TIMS shows lower detection limit and uncertainties than KED. However, the KED analysis time is shorter and generates less effluent. Both techniques were used for metrological analysis of uranium concentration in nuclear materials. The optimization of sample spike mixture isotope ratio for ID-TIMS to decrease uncertainties is also discussed.

This report describes a key comparison of monoelemental calibration solutions, organized under the auspices of the Consultative Committee for Amount of Substance (CCQM) in 1999-2000 and piloted by the Federal Laboratories for Materials Testing and Research (EMPA, Switzerland) and the Laboratoire National d'Essais (BNM-LNE, France). Solutions of aluminium, copper, magnesium and iron were measured. Although different methods of measurement were applied, most of the thirteen participating national metrology institutes achieved results within the required target range for a combined standard uncertainty of 0.5 % relative for each element. The methods used were titrimetry, coulometry, gravimetry, isotope dilution mass spectrometry and inductive coupled plasma/emission spectrometry.

The Joint Research Centre, in cooperation with the Commissariat à l’Energie Atomique et aux Energies Alternatives, produced a novel 243Am spike reference material for mass spectrometry. Americium solution with an isotopic composition of 88% 243Am and 12% 241Am was used as the source for the preparation of the spike material. The certified value of 5.696 (11) nmol g−1 for the amount content of 243Am and 0.136138 (54) for the n(241Am)/n(243Am) amount ratio were assigned. The assigned values from mass spectrometry were confirmed by alpha-particle spectrometry, alpha-particle counting at a defined solid angle, and high-resolution gamma-ray spectrometry. Furthermore, an external validation of the certified values was obtained from the results of an interlaboratory comparison exercise, using this americium reference solution as the test sample.

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In nuclear activities such as reprocessing plants, safeguard laboratories, or research centers, U and Pu are regularly analyzed. Fast and accurate analytical devices are favored such as K-edge densitometer. This paper presents the results obtained by this device from assay samples with high U and Pu concentrations. Two processing methods without calibration (except energy calibration) are compared and discussed. Despite literature advising against the use of estimated mass attenuation coefficients for near edge energy, this study shows that these values can contribute to very good results for uranium and plutonium concentration estimations, with a bias less than 1%.