Technical assistance in nuclear forensics

The methods developed and applied by the Institute of Isotopes for the categorization and characterization of nuclear material of unknown origin are based on (low-background) high-resolution gamma-spectrometry, mass spectrometry (ICP-SFMS), prompt gamma activation analysis (PGAA) and electron microscopy. The purpose of these investigations is to determine the origin of the material, its intended use and possibly its last legal owner.


Categorization of nuclear material involves a quick determination of the isotopic composition, in order to assess what is the threat posed by the material. The categories are depleted, natural, low-enriched and high-enriched uranium, and plutonium. Using the gamma-spectroscopic equipment available at the Institute, on-site categorization of nuclear material can be performed (e.g. at a border crossing). If the material is shielded, but one suspects that the package contains nuclear material, categorization can also be performed in our PGAA laboratory without opening the package, using prompt gamma activation analysis.


Characterization of the material in the laboratory includes, e.g. the following
  • a precise determination of the isotopic composition by low-background high-resolution gamma-spectrometry
  • a precise determination of the isotopic composition by ICP-SFMS
  • in particular U-232, determined by gamma-spectroscopy, and U-236, determined by ICP-SFMS, give information about the production process (i.e., they help decide whether the material was produced from reprocessed uranium)
  • age dating of uranium by low-background high-resolution gamma-spectroscopy
  • impurity determination by ICP-SFMS
  • surface morphology by electron microscopy