Progress in pulsed extraction column for spent nuclear fuel reprocessing

Spent nuclear fuel (SNF) reprocessing is essential for closing the nuclear fuel cycle and enhancing the sustainability and resource efficiency of nuclear energy. Liquid–liquid extraction (LLE) based on the Plutonium Uranium Redox EXtraction (PUREX) process is widely used in large-scale actinide separations and strongly improves uranium resource utilization, reduces high-level radioactive waste (HLW), and lowers the low-carbon environmental footprint of nuclear energy systems. Among various contactors, pulsed extraction columns (PECs) offer high throughput, compact structure, no moving parts, and low holdup, making them highly suitable for remote-operated, high-radiation environments. Because the hydrodynamics and mass transfer of PECs usually govern the throughput, decontamination efficiency, and operating safety margin, reliable design and scale-up are critical. However, current design practice still relies heavily on empirical correlations and pilot-scale validation, and lacks an engineering-scale framework that consistently links hydrodynamics, interfacial mass transfer, and reaction kinetics. This review synthesizes the engineering applications of PECs in SNF reprocessing and critically examines recent advances in experimental diagnostics, modeling, and simulation. Key parameters, including flow regime, holdup, flooding, axial dispersion, mass transfer, and droplet behavior, are reviewed with emphasis on their characterization and correlation. Mainstream scale-up approaches, especially the height of a transfer unit (HTU) and dimensionless-correlation methods, are also assessed. On this basis, the review outlines a pathway toward digital design, model validation, and operational optimization of PECs for next-generation reprocessing plants and sustainable closed nuclear fuel cycles.