Contribution of the Faraday cup coupled to 10 12 ohms current amplifier for uranium 235/238 and 234/238 isotope ratio measurements by Thermal Ionization Mass Spectrometry

Alexandre Quemet (1) , Melody Maloubier , Vincent Dalier (1) , Alexandre Ruas

1 DMRC - Département de recherche sur les procédés pour la mine et le recyclage du combustible

This work highlights the possibility of improving, for given deposited quantities, the accuracy of uranium isotope ratio determination by Thermal Ionization Mass Spectrometry (TIMS) using Faraday cups coupled to a 10 12 current amplifying system. This system improves the electronic sensitivity compared to the same Faraday cups coupled to 10 11 current amplifiers. The analytical procedure developed in a previous work (Quemet et al., 2014) was applied in order to study the improvements in accuracy using the Faraday cups equipped with 10 12 current amplifier. The 234 U/ 238 U and 235 U/ 238 U isotope ratios were measured on the Certified Reference Material IRMM 052 (natural uranium). Results were evaluated relying on NF T 90-210 norm regarding method validation. The 234 U/ 238 U and 235 U/ 238 U isotope ratios were studied by total evaporation using different configurations. First, 234 U or 235 U was measured with a Faraday cup coupled to a 10 12 current amplifier and 238 U was measured with a Faraday cup coupled to a 10 11 current amplifier. Then, 234 U or 235 U was measured by discrete dynodes electron multiplier and 238 U was measured with a Faraday cup coupled to a 10 12 current amplifier. In comparison to the configurations using the 10 11 current amplifier, the analyzable quantity was reduced from 250 ng to 100 ng for the 235 U/ 238 U isotope ratio and from 50 ng to 3 ng for the 234 U/ 238 U isotope ratio with extended uncertainty below 0.28% for the 235 U/ 238 U isotope ratio, in compliance with the International Target Values (ITV 2010), and below 5% for the 234 U/ 238 U isotope ratio.

Mots clés: TIMS; uranium; isotope ratio; 10 12 Ω current amplifier; SEM; Faraday cup

Domaines: Chimie analytique

Alexandre Quemet, Melody Maloubier, Vincent Dalier, Alexandre Ruas. Contribution of the Faraday cup coupled to 10 12 ohms current amplifier for uranium 235/238 and 234/238 isotope ratio measurements by Thermal Ionization Mass Spectrometry. International Journal of Mass Spectrometry, 2016, 404, pp.35 - 39. ⟨10.1016/j.ijms.2016.04.005⟩. ⟨cea-03470752⟩