Gamma-ray spectrum variations for surface measurements of uranium hexafluoride cylinders

This work aims to characterize features that contribute to the spectral variations that appear in gamma-ray spectra of filled uranium hexafluoride (UF6) cylinders. While the enrichment of the UF6 in a cylinder can greatly affect gamma-ray spectra at peaks such as the 185.7 keV peak and be used to verify enrichment, many other characteristics of a filled UF6 cylinder can affect the spectra. These characteristics vary on a per-cylinder basis and can include: the time between when a cylinder was filled and when it was measured; the previous fill history of a cylinder; how the cylinder was most recently filled; the UF6 geometric distribution within the cylinder; and the measurement location along the cylinder. This work explores spectral variations seen in measurement data and uses validated simulation models to find trends in these uncertainties. These trends are analyzed to observe how each parameter can contribute to the overall uncertainty of UF6 spectral measurements.