Rapid determination of trace uranium in liquid wastes from spent nuclear-fuel reprocessing plants using on-line solid-phase extraction/electrochemical detection

An on-line analysis system using a solid-phase extraction column coupled to electrochemical detection has been developed for the rapid determination of small amounts of uranium in liquid waste samples of spent nuclear-fuel reprocessing plants. A sample solution with a concentration of 3 M HNO₃ was loaded onto a column: packed with U/TEVA^© resin. The interference elements were rinsed by passing 3 M HNO₃ through the column. The adsorbed uranium was eluted with 0.1 M HNO₃. The eluate was directly introduced into a flow-electrolysis cell. The reduction current of U(VI) → U(V) was monitored and recorded. The uranium concentration was calculated from the relation between the peak current and the concentration of the standard uranium solution. The result of five repeated analyses for a standard solution containing 2.5 μg (0.1 mL at 25 μg mL^-1) of uranium was found to be 2.5 ±0.025 μg (mean ±1σ). The detection limit calculated from 3-times the standard deviation of the background current was 56 ng. The analysis time required for one sample was within 5 min. The recoveries of uranium in actual nuclear waste reprocessing solutions were 92~112%.