Research on application of salt-free reductants in uranium/neptunium/plutonium separation

Abstract

In current spent nuclear fuel reprocessing, the predominant method involves chemical extraction, leveraging the differing distribution ratios of elements to achieve separation and purification. Effective separation of uranium (U), plutonium (Pu), and neptunium (Np) typically relies on redox processes that alter their oxidation states during extraction. Therefore, reductants play a critical role in reprocessing processes. An important shift in the advanced reprocessing process is the use of salt-free reagents in the actinide separation process. In addition, the salt content in the reprocessing stream is often indicative of the overall technological sophistication of the process, and it is critical to reform the reductants used in the main process stream. Salt-free reductants have attracted much attention in recent years for basic and applied research in reprocessing processes because of their advantages such as being easily destroyed, not introducing salts, reacting quickly, simplifying the process, and reducing the amount of waste. This study summarizes emerging salt-free reagents with potential applications in reprocessing, and outlines their kinetic and chemical reaction mechanism properties in reducing Pu(IV) and Np(VI). The conclusion discusses the future potential of salt-free reagents in reprocessing. This study summarizes the currently well-studied salt-free reductants and offers recommendations and future research directions in salt-free alternatives.