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ABSTRACT
The accurate prediction of the extraction behaviors of various solutes in PUREX reprocessing process is crucial for the operation and implementation of the actual process. In this paper, an integrated model is developed to predict the extraction behaviors of U, Np, Pu, and HNO3 in the co-decontamination step (1A extraction step) in a pulsed extraction column. The model couples several physical and chemical processes, such as countercurrent flow, mass transfer, and chemical reaction. The mass transfer coefficients and the distribution ratios of U(VI), Pu(IV), Np(IV), Np(V), Np(VI), HNO3 and HNO2 can be obtained using this model. In particular, the redox and disproportion reactions of Np are considered in the model, and the flow direction of Np can be judged under various process conditions and the corresponding influential factors can be analyzed. The judgment is based on the yield calculated from the relative concentration profiles of Np(VI), Np(V), and Np(IV) in the two phases. For neptunium to inter 1AP step, it is necessary to select high nitric acid concentration, low nitrite concentration and especially high flow ratio. For neptunium to inter 1AW step, low nitric acid concentration, high nitrite concentration and low flow ratio are needed. Compared with the experimental data, the relative errors of the distribution ratios of various solutes are less than 30%, and the relative errors of the concentrations of U(VI) and Pu(IV) at the outlet of the organic phase are less than 10%, and our model is indicated to be reliable and applicable for co-decontamination step in the PUREX reprocessing process.
Nomenclature
| List of symbols | = | |
| ∆Z | = | Pulse column plate spacing, cm |
| α | = | Pulsed column plate free area fraction |
| γ | = | Interfacial tension, m/s2 |
| ε | = | Dispersed phase holdup |
| μ | = | Viscosity, Pa·s |
| ρ | = | Density, g/cm3 |
| ς | = | Mechanical power dissipation per unit mass, W/kg |
| Π | = | Function of the energy input per unit mass |
| Φ | = | Function of the effect of two-phase flow |
| Ψ | = | Function of the physical properties of the solute |
| Γ | = | Function of the geometry of the column |
| a | = | Specific surface area, 1/cm |
| d32 | = | Sauter mean diameter of droplet, cm |
| dN | = | Plate hole diameter, cm |
| f | = | Pulse frequency, 1/s |
| fc | = | Fanning friction factor |
| g | = | Acceleration of gravity, cm/s2 |
| m | = | Relative atomic mass |
| u | = | Superficial velocity, cm/s |
| x | = | Aqueous solute concentration |
| y | = | Organic solute concentration |
| A | = | Pulse amplitude, cm |
| D | = | Distribution ratio |
| DM | = | Molecular diffusivity coefficient, cm/s2 |
| DT | = | Column internal diameter, cm |
| E | = | Axial dispersion coefficient, cm/s2 |
| G | = | The number of molecules produced/destroyed per unit of energy absorbed, mol·J−1 |
| H | = | Column height, cm |
| Ka | = | Mass transfer coefficient, cm/s |
| Kdf | = | Mass transfer coefficient of the dropping droplets, cm/s |
| T | = | Temperature, K |
| W | = | Absorbed irradiation power, J·s−1 |
| Subscript | = | |
| a | = | Aqueous |
| e | = | Equilibrium |
| org | = | Organic |
Disclosure statement
No potential conflict of interest was reported by the author(s).
Supplementary material
Supplemental data for this article can be accessed online at https://doi.org/10.1080/07366299.2023.2252859