Hybrid x-ray fluorescence and K-edge densitometry (KED) is used at nuclear fuel reprocessing facilities to determine the concentrations of uranium and plutonium in the input accountability vessel. The uranium concentration is determined by KED, that is, from the step-difference in transmission on either side of the K-absorption edge measured using a continuous x-ray spectrum on a vial of the solution defining a well- known geometry. In parallel with the transmission measurement, the relative plutonium-to-uranium concentration is obtained from the relative strength of the x-ray–induced K-shell x-ray fluorescence production measured at a backward angle in energy-dispersive mode. The HKED analysis method has recently been extended to accommodate more complex solutions providing concentration values for an arbitrary mixture of actinides representative of the evolving nuclear fuel cycle. The extension to these solutions and the correspondingly complex spectra has been hampered by challenges in accurately representing the backscatter Bremsstrahlung spectrum, correcting for self-irradiation effects from high fission product loadings, predicting the relative fluorescence yields and limitations in the available atomic data (e.g., mass attenuation coefficients). This work discusses the impact of these challenges on the HKED measurement and Oak Ridge National Laboratory’s efforts to address them.
Year
2021
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Abstract