Laboratory-based characterization of plutonium in soil particles using micro-XRF and 3D confocal XRF

The measurement of plutonium (Pu) in a soil matrix is of interest in safeguards, nuclear forensics, and environmental remediation activities. The elemental composition of two Pu contaminated soil particles was characterized nondestructively using micro X-ray fluorescence spectrometry (micro-XRF) techniques including high resolution X-ray (hiRX) and 3D confocal XRF. The three dimensional elemental imaging capability of confocal XRF permitted the identification two distinct Pu particles within the samples: one external to the Fe-rich soil matrix and another co-located with Cu within the soil matrix. The size and morphology of the particles was assessed with X-ray transmission microscopy (XTM) and micro X-ray computed tomography (micro-CT) providing complementary information. Limits of detection for a 30 mu m Pu particle are <15 ng for each of the XRF techniques. This study highlights the capability for lab-based, nondestructive, spatially resolved characterization of heterogeneous matrices on the micrometer scale with nanogram sensitivity.