Comparison of mass spectrometric methods (TE, MTE and conventional) for uranium isotope ratio measurements

Abstract

The isotope ratio measurement techniquestotal evaporation (TE), modified total evaporation (MTE), and conventional-used for characterization measurements of certified reference materials by thermal ionization mass spectrometer instruments are compared. The advantages of each method, the fractionation profiles resulting from the measurement techniques, and factors affecting systematic components of bias in the isotope ratio measurements are discussed. The TE and MTE techniques yield major ratios and the conventional and MTE techniques yield minor ratios of comparable quality (in terms of precision and accuracy).

Development and comparison of high accuracy thermal ionization mass spectrometry methods for uranium isotope ratios determination in nuclear fuel

“…The TE method is an accurate and simple analytical method for major isotope ratio measurements (typically 235 U/ 238 U isotope ratio) [7]. However, the TE method has limitations for the minor isotope ratios measurements because these measurements require other corrections such as: the SEM calibration, changes in the peak centering and focusing during the filament heating, or peak tailing corrections [6].…”

“…One of the reference techniques for the isotope ratio measurement is the Thermal Ionization Mass Spectrometry (TIMS) [6]. Two TIMS measurement methods are commonly used: the classical and the total evaporation method [6][7][8]. In the classical method, the different isotopes are collected in a limited period of the sample evaporation and the isotope ratios are mathematically corrected of the isotope fractionation.…”

“…In the total evaporation method (TE method), the isotopes are collected during the entire sample evaporation. Thus, this method is barely affected by the isotope fractionation and is a reference technique for major isotope ratio determinations like 235 U/ 238 U [1,2,7].…”

Investigation of the crucial factors affecting accurate measurement of strontium isotope ratios by total evaporation thermal ionization mass spectrometry

“…Since the lighter isotopes are preferentially evaporated according to the Rayleigh distillation law, the lighter‐to‐heavier isotope ratio decreases with time, resulting in mass fractionation . Theoretically, if the sample loaded on the filament is totally exhausted and the ion currents are integrated, the mass‐dependent bias will be completely avoided, which is the basic concept of total evaporation thermal ionization mass spectrometry (TE‐TIMS), first described by Callis et al By using TE‐TIMS, the repeatability and accuracy of isotopic analysis can be significantly improved without additional internal normalization or external normalization using certified reference materials (CRMs) . Therefore, its applications quickly expanded from U and Pu to other elements such as Ra, Nd, B, Re, Cr, Zr, Eu, Yb, etc.…”

Contribution of the Faraday cup coupled to 10 12 Ω current amplifier to uranium 235/238 and 234/238 isotope ratio measurements by thermal ionization mass spectrometry

“…That generated in an important contribution of the 238 U and 235 U on the 234 U signal and a higher bias on the 234 U/ 238 U isotope ratio measurement. Unfortunately, further peak tailing correction was not possible with the total evaporation method, as it is one of its limitation [2,14]. A solution for further peak tailing correction would be using the modified total evaporation (MTE) [2,[15][16][17].…”