A new series of uranium isotope reference materials for investigating the linearity of secondary electron multipliers in isotope mass spectrometry

Development of an improved method to perform single particle analysis by TIMS for nuclear safeguards

“…By use of the total evaporation module, the filament current was regulated to keep a maximum count rate of 8000 cps for the 238 U signal during the run. Due to the low count rate of less than 20,000 cps even for the major isotope 238 U non-linearity effects for the ion counters are negligible [29]. Having the same count rate conditions for standard and sample additionally serves to cancel out any remaining non-linearity effects in the ion counting detectors.…”

Certification of uranium hexafluoride reference materials for isotopic composition

“…In addition, it was shown in [8], that the major isotope ratios n( 235 U)/n( 238 U) in IRMM-074 were confirmed by TIMS measurements using the major amount ratios of the predecessor series IRMM-072 (similar isotope amount ratios [9,10], prepared about 10 years earlier) as calibrant. Using IRMM-072, also the isotopic composition of two further gravimetric mixtures, the IRMM-199 ( 233 U/ 235 U/ 238 U = 1/1/1) and the NBL (New Brunswick Laboratory) CRM U500 ( 235 U/ 238 U = 1/1), was confirmed at the same time [8]. This shows the 'consistency' of the gravimetrically prepared reference materials with time using different equipment at IRMM.…”

“…For this method, six TIMS evaporation filaments were loaded with 4 lg of uranium for each solution and six replicates of the certified reference material IRMM-074/10 were also measured on this turret. The IRMM-074 series of gravimetric mixtures is characterized by major isotope ratios n( 235 U)/n( 238 U) of about 1.00026 with relative expanded uncertainties of 0.015 % (k = 2) and isotope ratios n( 233 U)/n( 235 U) ranging between 10 -6 and 1, with relative expanded uncertainties of 0.025 % (k = 2) [8]. In addition, it was shown in [8], that the major isotope ratios n( 235 U)/n( 238 U) in IRMM-074 were confirmed by TIMS measurements using the major amount ratios of the predecessor series IRMM-072 (similar isotope amount ratios [9,10], prepared about 10 years earlier) as calibrant.…”

“…The IRMM-074 series of gravimetric mixtures is characterized by major isotope ratios n( 235 U)/n( 238 U) of about 1.00026 with relative expanded uncertainties of 0.015 % (k = 2) and isotope ratios n( 233 U)/n( 235 U) ranging between 10 -6 and 1, with relative expanded uncertainties of 0.025 % (k = 2) [8]. In addition, it was shown in [8], that the major isotope ratios n( 235 U)/n( 238 U) in IRMM-074 were confirmed by TIMS measurements using the major amount ratios of the predecessor series IRMM-072 (similar isotope amount ratios [9,10], prepared about 10 years earlier) as calibrant. Using IRMM-072, also the isotopic composition of two further gravimetric mixtures, the IRMM-199 ( 233 U/ 235 U/ 238 U = 1/1/1) and the NBL (New Brunswick Laboratory) CRM U500 ( 235 U/ 238 U = 1/1), was confirmed at the same time [8].…”

“…The 234 U is also measured on the SEM in order to determine the intercalibration factor between the Faraday cups and the ion counter [6,7]. The IRMM-074 series was used to assess the linearity of the secondary electron multiplier of the TIMS instrument and to determine the linearity correction parameter [8]. For this method, five TIMS-filaments were loaded with 4 lg of uranium for each solution.…”