PHOTOMETRIC DETERMINATION OF URANIUM CONCENTRATION

An evaluation into the feasibility of using photometric techniques to determine in-process uranium concentrations is being conducted. An in-line process monitor that uses the optical absorption at two wavelengths to determine solution levels from 20 to 200 grams uranium per liter (gU/liter) solutions is currently under evaluation. Initial tests used an absorption feature at 416 nm to determine gU/liter concentrations, and absorption at 550 nm was used to make solution turbidity corrections. Total uranium concentration was found to be linearly proportional to the absorbance at 416 nm for constant levels of nitric acid (HNO3), but errors of 15–50% were seen as a result of variations in nitric acid concentration. Several methods have been proposed in the literature to minimize the effects of HNO3 on the photometric determination of uranium concentrations, although most require the monitoring of several wavelengths or a priori knowledge of total uranium or HNO3 concentration. This report will present preliminary results from a dual-wavelength technique that utilizes absorption at 385 nm that is less sensitive to both uranium and HNO3 concentration.