Proliferation of nuclear weapons programs, terrorism, and the potential for theft and diversion of special nuclear materials (i.e. enriched uranium and plutonium) pose grave threats to national security. Detecting released materials and forensically determining not only its phase identity, isotope composition, but also its chemical processing history is crucial to establishing likely points of origin. While established baseline methods are often effective, microscale synchrotron radiation-based x-ray fluorescence (SR-XRF) chemical analyses can provide an additional complementary layer of signature recognition and classification capabilities for micro-particle analysis of nuclear materials. SR-XRF is well suited to forensic analyses of small particles because it is rapid, non-destructive, highly sensitive, has good spatial resolution, and can provide chemical information on the elements that are present when combined with x-ray absorption spectroscopy (XAS).<br/><br/>However, the conventional XAS capability in the near edge region as commonly implemented is often inadequate for the sensitivity required for forensics applications. A higher detail of spectroscopic information is required. The particular power of a newly developed x-ray microprobe beamline at the Stanford Synchrotron Radiation Lightsource at the SLAC National Acceleratory Laboratory will be presented, that combines micro SR-XRF and XAS, integrated with a high energy resolution fluorescence detector crystal analyzer. The combination of these techniques with the highly energy sensitive detector, provides a higher information content of the spectral data. This allows for the rapid location and imaging of particles and provides non-destructive analysis that gives chemical and structural information, as well as the distribution of phases across different particles at the micro-scale. We have used this instrument to develop detailed chemical signatures to provide links between the determination of molecular composition, morphological distribution, and nuclear fuel cycle processes.

Application of micro-HERFD-XAS spectrometer to nuclear forensics

ACS Fall 2021

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