Large area quantitative X-ray mapping of (U,Pu)O2 nuclear fuel pellets using wavelength dispersive electron probe microanalysis

The work presented is an example of how large area compositional mapping (≥1 mm2) can be used to provide quantitative information on element distribution and specimen homogeneity. High-resolution was accomplished by producing a collage of X-ray maps acquired using classical conditions; magnification ×400, spatial resolution 256×256 pixels. The individual images, each measuring roughly 250×250 μm, were converted to quantitative maps using the Himax® software package and the Xmas® matrix correction from SAMx. The quantitative gray-level large area X-ray picture was pieced together using the ‘Multiple Image Alignment’ function of the AnalySIS® image processing software. This software was also used to convert the gray-level pictures to false color images. The specimens investigated were transverse sections of MOX fuel pellets. Results are presented for the distribution of Pu by area fraction and cumulative area fraction, the size distribution of regions of high Pu concentration and average separation of these regions.