Separation processes for highly radioactive and chemically complex spent nuclear fuel require advanced safe technologies and process models based on large databases. Availability of advanced methodologies for on-line control and safeguarding of aqueous reprocessing flowsheets will accelerate implementation of the closed nuclear fuel cycle. This report reviews application of the absorption and vibrational spectroscopic techniques supplemented by physicochemical measurements for radiochemical process monitoring. In this context, our team experimentally assessed potential of Raman and spectrophotometric techniques for on-line real-time monitoring of the U(VI)/nitrate ion/nitric acid and Pu(IV)/Np(V)/Nd(III), respectively, in the solutions relevant to spent fuel reprocessing. Both techniques demonstrated robust performance in the repetitive batch measurements of each analyte in the wide concentration range using simulant and commercial dissolved spent fuel solutions. Static spectroscopic measurements served as training sets for the multivariate data analysis to obtain partial least squares predictive models, which were validated during on-line centrifugal contactor extraction tests. Achieved satisfactory prediction of the analytes concentrations in these preliminary experimentation warrants further development of the spectroscopybased methods for radiochemical process control and safeguarding.
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