Direct Uranium(VI) and Nitrate Determinations in Nuclear Reprocessing by Time-Resolved Laser-Induced Fluorescence

Time-resolved laser-induced fluorescence (TRLIF) has been used for direct uranium(VI) determination in the nuclear reprocessing medium. To take into account the different phenomena that affect the uranyl fluorescence (absorption, quenching, and complexation), a model has been defined. A spectral deconvolution procedure allows uranium speciation in nitric acid and therefore nitrate determination with good accuracy. After normalization of the fluorescence intensity, it is then possible to reach the uranium concentration. Results obtained on synthetic solutions and, above all, on reprocessing samples by the application of this model are presented and compared with results from other techniques. The limit of detection for uranium analysis in reprocessing matrices is in the submilligram per liter range, and a ratio of Pu/U as high as 10 5 can be directly analyzed.