Simultaneous spectrophotometric determination of uranium, nitric acid and nitrous acid by least-squares method in PUREX process

Multi-wavelength linear regression spectrophotometry combined with method of least squares for simultaneous determination of uranium, nitric acid and nitrous acid in PUREX (Plutonium/URanium EXtraction) process was developed. The molar absorbance matrix was calibrated with absorbance data measured in the wavelength range of 350-500 nm for a series of standard solutions by linear least-squares regression. This method used information from the absorption spectra of U(VI)-nitrous acid-nitric acid solutions to determine U(VI), nitrous acid and nitric acid. In the range of 0.95-74.1 g/L U(VI), 5 x 10(-4)-2 x 10(-3) mol/L nitrous acid and 3-5 mol/L aqueous nitric acid solution, the measuring precision for determination of U(VI), nitrous acid and nitric acid was 0.46, 4.09, and 0.68 % respectively. In the solution of 30 % TBP-kerosene, the measuring precision for determination of U(VI) and nitrous acid was 0.42 and 4.2 % respectively in the range of 0.95-74.1 g/L U(VI) and 5 x 10(-4)-2x10(-3) mol/L nitrous acid. The spectrophotometric method can be valuable for monitoring and controlling of both species in PUREX process operation, thanks to its simplicity, efficiency and accuracy.