X-ray fluorescence microtomography study of trace elements in a SiC nuclear fuel shell

X-ray fluorescence microtomography has been used to measure the trace element spatial distribution in a TRISO SiC shell after exposure to 1.9×1025 neutrons/m2. The bare SiC shell was prepared by laser drilling the TRISO particle and leaching away the core and C. The exposed shell was measured with an X-ray probe having a size of approximately 1×3 μm2 on beamline 2-ID at the Advanced Photon Source. The trace element distribution in the SiC shell was reconstructed after correcting the data for artifacts arising from absorption and experimental restrictions. The trace elements were found in small (<2 μm) regions through the SiC shell and appear to have been introduced during fabrication. X-ray fluorescence microtomography is an ideal tool for this work because it is a penetrating non-destructive probe with good sensitivity to high Z trace elements in a low Z matrix and because it provides a picture of the elemental distribution in the shell.