Continuum Background Contributions in K-edge Densitometry

K-edge densitometry is a key technique for safeguarding uranium (U) and plutonium (Pu) in nuclear reprocessing and fuel production. It uses X-ray spectrometry to measure the transmission of X-rays around the K-edge of uranium or plutonium. To improve the uncertainty and robustness of the technique, the influence of two contributions to the spectral continuum background in X-ray transmission spectra of U and Pu was studied: random coincidence summing and the scattering step background. These effects occur when the transmitted X-ray photons and the photons from the Cd-109 source, used for gain stabilization, interact with the detector. This work studied the impact of these effects on the U and Pu concentration measured by K-edge densitometry. It was concluded that the scattering background due to the presence of Cd-109 has the highest impact on the measured concentrations.