An improved method for determination of isotope ratios in individual uranium particles by thermal ionization mass spectrometry

• Published in: Spectrochimica acta. Part B: Atomic spectroscopy Vol. 182; p. 106252
• Main Authors: Gao, Jie, Xu, Changkun, Zhao, Yonggang
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01-08-2021; Elsevier BV
• Subjects: Emitters; Ionization; Isotope ratio; Isotope ratios; Isotopes; Mass spectrometry; Mass spectroscopy; Micromanipulation; Nuclear accidents & safety; Nuclear safeguards; Nuclear safety; Ratios; Reference materials; Sample preparation; Scanning electron microscopy; Scientific imaging; SEM; Spectroscopy; TIMS; Uranium; Uranium isotopes; Uranium particle; X ray spectrometers; SEM; Uranium particle; Nuclear safeguards; TIMS; Isotope ratio
• ISSN: 0584-8547; 1873-3565
• DOI: 10.1016/j.sab.2021.106252

The determination of isotope ratios of individual uranium particles in environmental swipe samples is very important for nuclear safeguards. A new technique to measure isotope ratios for individual uranium particle was developed in this work, which was a combination of particle transfer by scanning electron microscope (SEM) and isotope ratios analysis by thermal ionization mass spectrometry (TIMS). The technique was verified by measuring isotope ratios in individual micrometer-size uranium particles of known isotopic abundance. The particles were identified by SEM combined with energy dispersive X-ray spectrometer (EDX) and transferred by micromanipulator, which could improve the efficiency of sample preparation and simplify the procedure. The experimental condition was optimized by using a new kind of thermal ion emitter to enhance the ionization efficiency of uranium. Several individual uranium particles from certified reference materials were successfully measured by SEM-TIMS. The results show that the measured isotope ratios were in good agreement with the reference values. The relative errors of 13 particles were within 2.7% for 234U/238U, 1.1% for 235U/238U and 4.5% for 236U/238U isotope ratios, respectively, and the relative standard deviation (RSD) were within 1.6% for 234U/238U, 0.5% for 235U/238U and 3.3% for 236U/238U, respectively. It is expected that this method will become a promising alternative technique for determining uranium isotope ratios in particle analysis. The particles used in this study had sizes between 1.3 and 4.7 μm.
A new technique to measure isotope ratios for individual uranium particle was developed in this work. The particles were identified by SEM combined with energy dispersive X-ray spectrometer (EDX) and transferred by micromanipulator, which simplify the procedure of sample preparation. A new type of thermal ion emitter was used to enhance the ionization efficiency of uranium. Several micrometer-size (1–5 μm) individual uranium particles from certified reference materials (CRM U200 and U850) were measured by SEM-TIMS. The results show that the relative errors of 13 particles were within 2.7% for 234U/238U, 1.1% for 235U/238U and 4.5% for 236U/238U isotope ratios, respectively, and the relative standard deviation (RSD) were within 1.6% for 234U/238U, 0.5% for 235U/238U and 3.3% for 236U/238U, respectively. [Display omitted]
•The sample preparation was improved and simplified by using SEM.•The experimental condition was optimized by using a new kind of thermal ion emitter.•The relative errors and relative standard deviations of minor isotope ratios were within 5%.