The Process Simulation & Safeguards group conducts simulations and experiments in support of nuclear materials safeguards for both aqueous and pyrochemical spent fuel reprocessing processes. This presentation will give an overview of two completed projects: i) implementation of an in-line, fiber optic UV-vis measurement system for monitoring Pu oxidation states in aqueous reprocessing streams; and ii) validation studies of the dyAMUSE model using experimental data collected on lab-scale countercurrent centrifugal contactors. In 2014, Argonne successfully conducted a test at the Savannah River Plant that demonstrated the utility of an in-line, fiber optic UV-vis measurement system for monitoring Pu oxidation states in aqueous reprocessing streams. That success resulted in the monitoring system becoming a permanent installation of the plant. During 2013-2015 a study to validate the dynamic, time-dependent version of the Argonne Model for Universal Solvent Extraction (dyAMUSE) code was conducted. The study involved comparing modeling predictions against experimental data collected in a controlled setting. The experiments involved operating PUREX-like (Pu URanium EXtraction) solvent extraction flowsheets on a 20-stage bank of 2-cm rotor O.D. countercurrent centrifugal contactors. Captured samples were analyzed by liquid scintillation counting and x-ray flurorescence (EDXRF) analysis. A 16-detector in-line flow cell, fiber optic UV-vis system was used to capture in-process absorbance spectra. The detectors were distributed as pairs over eight stages with one detector of each pair monitoring the aqueous or organic phase at the stage. Each stage was fitted with seven thermocouples to monitor the temperature profile of the system. The validation studies demonstrated that the dyAMUSE model correctly captures the time-dependency and predicts uranyl concentrations to within ±10% when the [UO22+] ≥ 10 g/L. The error becomes progressively larger as the [UO22+] decreases.

Experiments in support of safeguards for aqueous spent nuclear fuel reprocessing

255th National Meeting (2018)

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