Morphological changes in UO based on calcination temperature have been quantified enabling a morphological feature to serve as a signature of processing history in nuclear forensics. Five separate calcination temperatures were used to synthesize α-UO, and each sample was characterized using powder X-ray diffraction (p-XRD) and scanning electron microscopy (SEM). The p-XRD spectra were used to evaluate the purity of the synthesized U-oxide; the morphological analysis for materials (MAMA) software was utilized to quantitatively characterize the particle shape and size as indicated by the SEM images. Analysis comparing the particle attributes, such as particle area at each of the temperatures, was completed using the Kolmogorov-Smirnov two sample test (K-S test). These results illustrate a distinct statistical difference between each calcination temperature. To provide a framework for forensic analysis of an unknown sample, the sample distributions at each temperature were compared to randomly selected distributions (100, 250, 500, and 750 particles) from each synthesized temperature to determine if they were statistically different. It was found that 750 particles were required to differentiate between all of the synthesized temperatures with a confidence interval of 99.0%. Results from this study provide the first quantitative morphological study of U-oxides, and reveals the potential strength of morphological particle analysis in nuclear forensics by providing a framework for a more rapid characterization of interdicted uranium oxide samples.
The morphological changes that take place during the processing and storage of uranium oxides can provide valuable information on the processing history and storage conditions of an interdicted sample. In this study microstructural changes in two uranium oxides (UO2 and U3O8) due to changes in the aging conditions at elevated temperatures were quantified and modeled using a response surface methodology approach. This allowed the morphological changes to be used as a signature for the aging conditions for nuclear forensic analysis. A Box-Behnken design of experiment was developed using the independent variables: temperature from 100 to 400 °C, aging times from 2 to 48 h, and partial pressure of
${{\rm{O}}_2}({{\rm{P}}_{{{\rm{O}}_{\rm{2}}}}})$
between ~0.0 kPa and 21.3 kPa. The design of experiment consisted of 54 samples per uranium oxide. Each aged sample was characterized using scanning electron microscopy (SEM) for image analysis. Utilizing the Morphological Analysis for Materials (MAMA) software package, particle size and shape were quantified using the acquired SEM images. Analysis of the particle attributes was completed using the Kolmogorov–Smirnov two sample test (K–S test) to determine if the particle size and shape distributions were statistically distinct. This data was then used to create response surfaces of the quantitative morphological changes based on the developed design of experiment. The U3O8 samples showed no statistically quantifiable differences due to the aging conditions. However, the UO2 samples had distinct morphological changes due to the experimental aging conditions. Specifically, the temperature factor had an increasing effect on the particle area, and a decreasing effect on particle circularity.
This paper presents the results of measurements of the changes in strain, as determined from x-ray diffraction line broadening, stored strain energy, particle shape, size and size distribution in samples of yttrium iron garnet powder brought about by a variety of milling treatments. For similar starting material the strain induced by the various milling procedures was found to vary by two orders of magnitude. An example is given of the build-up of strain and the accompanying changes in particle characteristics with milling time.
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