Development of an analysis method of minor uranium isotope ratio measurements using electron multipliers in Thermal Ionization Mass Spectrometry

Abstract

a b s t r a c tA simple analytical procedure was developed to measure with high accuracy the isotope ratio of minor isotope of natural uranium present in small quantities using a thermal ionization mass spectrometer (TIMS). The reduction of quantities used for analysis and the measurement of non-abundant isotopes are of prime interest in the nuclear industry. Indeed it is necessary to reduce the analyst received dose and the effluent released, as well as realizing measurement at trace level. The new generation of TIMS is equipped with a multicollection system of electron multipliers: discrete dynode electron multiplier (SEM) and continuous dynode electron multiplier (MIC), that improve the sensitivity compared to faraday cups. The procedure developed was verified using Certified Reference Material IRMM 052. Results were evaluated relying on NF T 90-210 norm regarding method validation. First, the isotope ratio 234 U/ 238 U was examined by total evaporation using the SEM and MIC to measure 234 U and the faraday cup to measure 238 U. In a second approach, the isotope ratio 235 U/ 238 U was studied by total evaporation using the SEM to measure 235 U and the faraday cup to measure 238 U. The classical method with peak-jumping SEM measurement was also used. Total evaporation method employing only the faraday cup was used to confront the results obtained. The analyzable quantity was reduced from 250 ng to 50 ng for the 235 U/ 238 U isotope ratio and from 1270 ng to 50 ng for the 234 U/ 238 U isotope ratio with acceptable uncertainties thanks to the use of electron multipliers. For all experiments were the accuracy was achieved, the calculated uncertainties were below to 0.28% for the 235 U/ 238 U isotope ratio and 5% for the 234 U/ 238 U isotope ratio.

Determination of zirconium isotope composition and concentration for nuclear sample analysis using Thermal Ionization Mass Spectrometry

“…The method employed in this study was previously described and was transposed to zirconium [21]. "Peak center" (mass calibration and ion beam centering in the detector) and lenses optimization were realized using the major zirconium isotope: 90 Zr + for the SPEX solutions isotope determinations and the nuclear samples concentration determinations or 91 Zr + for the enriched 91 Zr spike solutions isotope and concentration determinations.…”

“…Several studies for zirconium isotope measurement have been reported in literature. They are mainly two principal techniques used for this kind of measurement: multiple collector-inductively coupled plasma mass spectrometer [2][3][4]9,10] (MC-ICP-MS) and thermal ionization mass spectrometry [1,2,5,6,8,[18][19][20] (TIMS). TIMS is a reference technique for isotope measurement [21][22][23]. TIMS allows reaching isotope ratio with high measurement trueness and precision.…”

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

“…There have also been different opinions on the influence of sample amount. Suzuki et al and Fujii et al separately reported that the sample amount had little influence on the measured rhenium and chromium isotopic ratios, whereas Foster et al found that the 11 B/ 10 B ratio decreased linearly with the sample amount and Quemet et al found that the 235 U/ 238 U ratio also decreased with the sample amount.…”

Recent Developments in Nuclear Forensic and Nuclear Safeguards Analysis Using Mass Spectrometry

“…TIMS has been used for the detection of minor U isotopes by Quemet et al and they obtained less than 5% uncertainty for a 234 U/ 238 U isotope ratio with 50 ng samples using a peak jumping method with an electron multiplier. 78 They concluded that the use of a multi-ion counter (MIC) or SEM can improve the detection sensitivity, and decrease the analyzable quantity, from 1,270 ng for a Faraday cup-only case to 50 ng for cases of a Faraday cup with SEM, or a Faraday cup with MIC. Although ICP-MS is more commonly used in isotope analysis, TIMS remains one of the bestperforming mass spectrometers in a nuclear material analysis of environmental samples and nuclear forensics analysis.…”