Nuclear Forensics & Attribution

Signatures at the Nanoscale

Interrogating interdicted materials at the nanoscale

Seaborg scientists are analyzing interdicted illicit nuclear, biological and radioactive materials for clues to the material's origins and routes of transit.

Scientists from the Seaborg Institute are leaders in nuclear and biological forensics — the chemical, isotopic, and morphological analysis of interdicted illicit nuclear, biological, radioactive materials and any other associated materials. A major focus of nuclear and biological forensics is identifying signatures, which are the physical, chemical, and isotopic characteristics that distinguish one material from another. Signatures enable researchers to identify the processes used to initially create a material.

Photo of Ian Hutcheon and Peter Weber with the NanoSIMS machine

Ian Hutcheon (left) and Peter Weber (right) use NanoSIMS, a secondary-ion mass spectrometer to look at the elemental and isotopic signatures of nanoparticles.

Current efforts, led by Peter Weber and his research group are focused on developing signatures for a variety of nuclear materials. NanoSIMS is their tool of choice to detect chemical and isotopic signatures at the nanoscale, combining nanometer-scale spatial resolution with part-per-million (μg/g) sensitivity.

Micrographs showing isotopic information

Left shows a scanning electon microscope (SEM) micrograph of UO2 particles. Right shows a nanoSIMS image of 16O in UO2 particles. The image shows isotopic information on an unprecedented nanoscale.

Unirradiated uranium reactor fuel pellets have inherent elemental oxygen content. Because the ratio of naturally occurring isotopes of oxygen-18 to oxygen-16 varies worldwide, these ratios could correlate with the locations of production sites. See S&TR; Jan./Feb. 2007, Identifying the Source of Stolen Nuclear Materials for further reading.

NanoSIMS images of a Bacillus thuringiensis spore that was sectioned using a focused ion beam.

NanoSIMS images of a Bacillus thuringiensis spore showing abundances of elements such as (a) phosphorus, (b) sulfur, (c) chlorine and (d) fluorine. Brighter colors indicate areas of higher ion ion centration.

Weber's team is studying chemical and isotopic signatures of biological materials that can provide information on the origin and source of biological agents. In a native spore, the microstructural distribution of some elements, such as phosphorus, is biologically determined. They are researching microstructural signatures in spores that can be used to determine how biological weapons were produced. See S&TR; Sept. 2006, Decoding the Origin of a Bioagent for further reading.