Determination of caesium and its isotopic composition in nuclear samples using isotope dilution-ion chromatography-inductively coupled plasma mass spectrometry

Abstract

As the natural isotopes of Ba give isobaric interferences on the radioactive isotopes of Cs at nominal masses of 134, 135 and 137, a chemical separation of Cs from Ba has been necessary for the determination of the isotopic composition of Cs by mass spectrometric techniques in highly active nuclear wastes (HAW), dissolved spent nuclear fuels or radioactively contaminated environmental samples. Ion chromatography (IC), which allows Cs and Ba to be chemically separated according to their different cationic charge, was coupled to an ICP-MS instrument and the chemical separation was performed on-line and followed directly by mass spectrometry. Three separation schemes were compared with respect to chromatographic resolution, accuracy and precision in irradiated spent fuel samples. The mass discrimination factors for the radioactive Cs isotopes were calculated by using a solution of natural Ba for the different chromatographic processes. They were found to be less than –2.5%. The results obtained by IC-ICP-MS were compared with those obtained by γ-spectrometry and with simulation calculations based on the KORIGEN code. The method using a CS5 cation-exchanger column and 1 M HNO₃ as eluent gave a detection limit of 16 pg g^–1 for total Cs with a precision of 2.5% at a concentration level of 100 ppb (n=7). Under the same chromatographic conditions, the accuracy of the ratio ¹³⁴Cs/¹³⁷Cs, calculated considering the γ-spectrometry measurements, was 2.5%.

References

1. L. Moens and N. Jakubowski, Anal Chem., 1998, 70, 251A.
2. Modern Isotope Ratio Mass Spectrometry, ed. I. T. Platzner, Wiley, New York, 1996.
3. Radioecology after Chernobyl, Biogeochemical Pathways of Artificial Radionuclides, ed. F. Warner and R. M. Harrison, Wiley, New York, 1993.
4. M. Betti, J. Chromatogr., 1997, 789, 369.
5. L. Koch, G. Cottone and M. W. Geerlings, Radiochim. Acta, 1968, 10, 122.
6. S. Guardini and G. Guzzi, BENCHMARK—Reference Data on Post-irradiation Analysis of Light Water Reactor Fuel Samples, EUR-7879-EN, 1983.
7. K. G. Heumann, S. M. Gallus, G. Rädlinger and J. Vogl, Spectrochim. Acta, Part B, 1998, 53, 273.
8. L. Ebdon, S. J. Hill and C. Rivas, Spectrochim. Acta, Part B, 1998, 53, 289.
9. J. I. Garcia Alonso, F. Sena, Ph. Arbore, M. Betti and L. Koch, J. Anal. At. Spectrom., 1995, 10, 381.
10. J. M. Barrero Moreno, M. Betti and J. I. Garcia Alonso, J. Anal. At. Spectrom., 1997, 12, 355.
11. J. M. Barrero Moreno, I. J. Garcia Alonso, Ph. Arboré, G. Nicolaou and L. Koch, J. Anal. At. Spectrom., 1996, 11, 929.
12. M. Betti, J. I. Garcia Alonso, Ph. Arbore, I. Sato and L. Koch, in Application of Plasma Source in Mass Spectrometry II, ed. G. Holland and A. N. Eaton, Royal Society of Chemistry, Cambridge, 1993, p. 205.
13. J. Weiss, Ion Chromatography, VCH, Weinheim, 2nd edn., 1995.
14. H. Small, Ion Chromatography, Plenum Press, New York, 1990.
15. P. R. Haddad and P. E. Jackson, Ion Chromatography. Principles and Applications, Elsevier, Amsterdam, 1990.
16. J. I. Garcia Alonso, Anal. Chim. Acta, 1995, 312, 57.
17. P. J. De Bievre and P. D. P. Taylor, Int. J. Mass Spectrom. Ion Processes, 1993, 123, 149.
18. U. Fischer and H. W. Wiese, Verbesserte Konsistente Berechnung des Nuklearen Inventars Abgebrannter DWR-Brennstoffe auf der Basis von Zell-Abbrand-Verfahren mit KORIGEN, Kernforschungszentrum, Karlsruhe, Report 3014, 1983.