Soft and Tender X-Ray Synchrotron Radiation Spectromicroscopy for Nuclear Forensics

The development of new methods and signatures is crucial to ensure that nuclear forensics activities remain effective. Synchrotron radiation analysis offers one way to extend the scope of nuclear forensics investigations in elemental, chemical, and structural analysis which all can be done in imaging modes that in some cases, reaches to the nanoscale. X-ray techniques are particularly useful because of their elemental specificity and non-destructive nature. The ability to use tunable, focused beams makes synchrotron radiation sources a potentially key tool for addition into the array of characterization techniques currently employed, particularly when it comes to the investigation of particles or areas of interest in very small specimens.<br/><br/>There have been recent efforts at the Advanced Light Source (ALS) conducting tender and soft spectromicroscopy using primarily x-ray fluorescence and chemical speciation coupled with selective X-ray absorption near-edge structure (XRF and XANES; Beamline 10.3.2); and with a scanning transmission x-ray microscope (STXM; Beamline 11.0.2). The tender XRF/XANES measurements provide elemental analysis at the low-single micron scale, whereas the STXM can probe electronic structure with ligand K-edge spectroscopy and chemical speciation via XANES with a spatial resolution of better than 25 nm. Several uranium, plutonium, and along with other relevant specimens, from both particle-based systems and monoliths fabricated by focused ion beam (FIB) methods, have been investigated utilizing these specific aforementioned techniques. The potential signatures obtained from this data, as well as the significance of the results, will be presented and discussed. The outlook for synchrotron radiation within nuclear forensics including the strengths and drawbacks of these techniques will also be discussed.