Evaluation of the n(235U)/n(238U) isotope ratio measurements in a set of uranium samples by thermal ionization mass spectrometry

The measurement of n(235U)/n(238U) isotope amount ratio in a set of representative uranium samples with enrichment levels ranging from 0.5 to 20.0 wt.% of 235U was carried out by thermal ionization mass spectrometry using the traditional and the total evaporation methods. The uncertainties of the measurement results were evaluated according to the recommendations of the ISO guide to the expression of uncertainty in measurement. They were then compared to the requirements of the IAEA international target values for measurement uncertainties in safeguarding nuclear materials.