Background effect on the measurement of trace amount of uranium by thermal ionization mass spectrometry

열이온화 질량분석에 의한 극미량 우라늄 정량에 미치는 바탕값 영향

  • Received : 2008.10.06
  • Accepted : 2008.11.05
  • Published : 2008.12.25

Abstract

An experiment was performed for zone refined Re-filament and normal (nonzone refined) Re-filament to reduce the background effect on the measurement of low level uranium samples. From both filaments, the signals which seemed to come from a cluster of light alkali elements, $(^{39}K_6)^+$, $(^{39}K_5+^{41}K)^+$ and $PbO_2$ were identified as the isobaric effect of the uranium isotopes. The isobaric effect signal was completely disappeared by heating the filament about $2000^{\circ}C$ at < $10^{-7}$ torr of vacuum for more than 1.5 hour in zone refined Refilaments, while that from the normal Re-filaments was not disappeared completely and was still remained as 3 pg. of uranium as the impurities after the degassing treatment was performed for more than 5 hours at the same condition of zone refined filaments. A threshold condition eliminating impurities were proved to be at 5 A and 30 minutes of degassing time. The uranium content as an impurity in rhenium filament was checked with a filament degassing treatment using the U-233 spike by isotope dilution mass spectrometry. A 0.31 ng of U was detected in rhenium filament without degassing, while only 3 pg of U was detected with baking treatment at a current of 5.5 A for 1 hr. Using normal Re-filaments for the ultra trace of uranium sample analysis had something problem because uranium remains to be 3 pg on the filament even though degassed for long hours. If the 1 ng uranium were measured, 0.3% error occurred basically. It was also conformed that ionization filament current was recommended not to be increased over 5.5 A to reduce the background. Finally, the contents of uranium isotopes in uranium standard materials (KRISS standard material and NIST standard materials, U-005 and U-030) were measured and compared with certified values. The differences between them showed 0.04% for U-235, 2% for U-234 and 2% for U-236, respectively.

Keywords

Uranium isotope;thermal ionization mass spectrometer;background test;rhenium filament

References

  1. G. R. Choppin and J. Rydberg. Pergamon Press, Nuclear Chemistry, Theory and Applications, p. 460-461(1980)
  2. J. B. Osmond and Cowart, Atomic Energy review 14(4), (1976)
  3. R. L. Holden, Martin and I. L. Barnes, International Union of Pure & Appl. Chem., 55(7), 1119-1136(1983) https://doi.org/10.1351/pac198355071119
  4. E. W. Becker and W. Welcher, Mass Spectroscopy in Physics Research, National Bureau of Standards, Circular 522, Washington, DC, p. 225(1953)
  5. Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright-2005 by The McGraw-Hill Companies, Inc
  6. K. G. Heumann, Int. J. Mass Spectrom. Ion Phys., 45, 87(1982) https://doi.org/10.1016/0020-7381(82)80101-0
  7. Finnigan MAT Application Flash Report No. 7, 8. (1995)
  8. A. P. Dickin, Radiogenic Isotope Geology, Cambridge University Press, Cambridge, UK, p.452 (1995)
  9. D. L. Donohue, Journal of Alloys and Compounds, 11-18(1998)
  10. G. H. Palmer, Advances in Mass Spectrometry, p. 89, Pergamon Press (1959)
  11. S. R. Hart and A. Zindler, Int. J. Mass Spectrom. Ion Processes 89, 287301(1989)
  12. S. Richter, A. Alonso, W. De Bolle, R. Wellum and P. D. P. Taylor, International Journal of Mass Spectrometry, 193, 9-14(1999) https://doi.org/10.1016/S1387-3806(99)00102-5
  13. R. Ovaskainen, K. Mayer, W. DeBolle, D. Donohue and P. De Bievre, Proceedings of the 19th Annual Symposium on Safeguards and Nuclear Material Management, Montpellier, C. Foggi, F. Genoni (Eds.) Ispra, ESARDA No. 28 (1997)
  14. G. Lafaye, F. Weber and H. Ohmoto, Economic Geology, 84(1989)
  15. K. Habfast, I. T. Platzner, A. J. Walder and A. Goetz, Modern Isotope Ratio Mass Spectrometry, John Wiley & Sons Ltd, West Sussex, England, pp. 182(1997)
  16. P. de Bievre, Adv. Mass Spectrom., 7A, 395(1978)

Acknowledgement

Supported by : 교육과학기술부