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Area of Science:

  • Nuclear analytical chemistry
  • Isotope ratio mass spectrometry
  • Particle analysis

Background:

  • Accurate measurement of uranium isotopes, particularly 236U, is crucial for nuclear safeguards and environmental monitoring.
  • Traditional methods often struggle with molecular interferences, complicating direct 236U measurements in uranium-bearing particles.
  • The International Atomic Energy Agency (IAEA) provides certified reference materials for validating analytical techniques.

Purpose of the Study:

  • To demonstrate the direct measurement of 236U in uranium-bearing particles using the NAUTILUS spectrometer.
  • To assess the NAUTILUS's capability to overcome molecular isobaric interferences.
  • To compare NAUTILUS performance with established techniques like LG-SIMS.

Main Methods:

  • Direct analysis of uranium-bearing particles using the Naval Ultra-Trace Isotope Laboratory's Universal Spectrometer (NAUTILUS).
  • Utilized IAEA-provided particles with varying 235U and 236U enrichments.
  • Generated raster ion images to visualize particle distribution and composition.

Main Results:

  • Successfully measured 236U directly from uranium particles, free from molecular interferences.
  • Achieved direct measurement of 236U concentrations as low as 3 μmol mol-1, irrespective of 235U concentration.
  • Results agreed with certified values, except for one sample with particle size limitations.
  • Demonstrated comparable performance to Large Geometry Secondary Ion Mass Spectrometry (LG-SIMS).

Conclusions:

  • NAUTILUS enables direct, interference-free 236U quantification in individual uranium particles.
  • The instrument's raster imaging capability aids in identifying small, low-intensity particles.
  • This technique offers potential for more targeted and efficient particle screening in nuclear material analysis.