Fluorescence and absorbance spectroscopy of the uranyl ion in nitric acid for process monitoring applications

Near real time process monitoring of the uranium content in an aqueous fuel recycling plant is a desired component of an advanced safeguards suite; Ultraviolet-Visible spectroscopy and Time Resolved Laser induced Fluorescence Spectroscopy can contribute to this technology gap. This work presents the observation of the spectroscopic parameters (molar absorptivities, fluorescent response) of the uranyl ion across the range of conditions expected in reprocessing chemistry. From this data, a monitor using the ratio of the absorbance of the uranyl ion at 403 and 426 nm has been developed. This technique can determine the nitrate solution concentration and can be coupled with a condition appropriate molar absorptivity to determine the uranyl concentration. This method provides a reliable technique for online, real time process monitoring of the uranyl and nitrate concentration under a wide range of solution compositions.