The isotopic composition of commercially available uranium chemical reagents

Abstract

The uranium isotopic compositions of 12 commercially available uranium chemicals, obtained from various suppliers, were measured by high accuracy isotope mass spectrometry. The goal was to establish the range of isotopic compositions in currently available commercial uranium chemicals, offered in different chemical forms and used for different purposes (e.g., atomic absorption spectrometry or inductively coupled plasma mass spectrometry). The relative isotope abundances of ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸U were determined by thermal ionisation mass spectrometry with high abundance sensitivity (Finnigan MAT262-RPQ-Plus), using the n(²³⁵U)/n(²³⁸U) amount ratio measurements of a gravimetrically prepared Isotopic Reference Material (IRMM-183) for mass fractionation correction. All uncertainties were calculated according to the ISO Guide to the Expression of Uncertainty in Measurement (International Standards Organization, Geneva, Switzerland), using a coverage factor k=2. For n(²³⁵U)/n(²³⁸U) relative uncertainties of 0.2-0.3% and for n(²³⁴U)/n(²³⁸U) and n(²³⁶U)/n(²³⁸U) of 0.4-3.0%, depending on the relative amounts of the ²³⁴U and ²³⁶U isotopes, were achieved. All samples were found to be depleted in ²³⁵U by a factor of two compared with its natural molar abundance (0.72%). The non-natural isotope ²³⁶U was present in all samples analyzed. The range found for the molar abundances of ²³⁴U is 0.0022-0.000 81%, for ²³⁵U 0.35-0.21%, for ²³⁶U 0.021-0.000 011% and for ²³⁸U 99.788-99.634%.

References

1. P. De Bièvre, Z. Anal. Chem., 1973, 264, 365.
2. K. J. Rosman and P. D. P. Taylor, Pure Appl. Chem., 1998, 70(1), 217.
3. P. v. Calsteren and J. B. Schwieters, Int. J. Mass Spectrom. Ion Processes, 1995, 146/147, 119.
4. R. Ovaskainen, K. Mayer, W. De Bolle, D. Donohue and P. De Bièvre, Proceedings of 19th Annual Symposium on Safeguards and Nuclear Material Management, May 13–15, 1997, Montpellier, France, ed. C. Foggi and F. Genoni, ESARDA, Ispra, no. 28.
5. Guide to the Expression of Uncertainty in Measurement, ISO1993, ISBN 92–67–10188–9.
6. S. Richter, A. Alonso, W. De Bolle, M. Berglund, A. Verbruggen, R. Wellum and P. D. P. Taylor, in preparation.