By 2040, at least 100 tonnes of isotopically pure lithium-6 will be required to fabricate and fuel the breeder blankets for STEP (Spherical Tokamak for Energy Production), the UK’s prototype fusion power plant. There is currently no established supply chain or large-scale lithium isotope enrichment plant to provide the needed quantities of lithium-6 for tritium breeding blankets, which are used to generate tritium for Deuterium-Tritium (D-T) reactions. While deuterium can be easily extracted from seawater, tritium is much harder to obtain, as it is only found in trace amounts and has a 12-year half-life.[1]
The industrially proven process for lithium-6 enrichment, COLEX (COLumn EXchange), relies on massive quantities of liquid mercury which presents problematic handling issues and hazardous environmental and health implications. Alternative methods with similar separation performance, such as liquid-liquid extraction, have only been tested at a laboratory scale and lack trials for successful industrial-scale deployment.
The UKAEA’s Fusion Industry Programme (FIP) awarded £1.3 million to Dr. Kathryn George from the University of Manchester for the project “Demonstration of a Viable Process for Li-6 Enrichment to Support Tritium Breeding” to develop lithium technologies for fusion. This project aims to deliver a ‘proof of concept’ liquid-liquid extraction method using crown ethers to produce enriched lithium at the scale needed for breeder blanket formation.[2]
The best-performing lithium enrichment liquid-liquid extraction system has been identified, and the back-extraction conditions optimised. Different diluted acids have been trialed, and several recommendations for the enrichment process were devised. Lithium-6 enrichment by two-phase liquid-liquid separation has not been studied in detail, making this research a valuable contribution to the field of liquid-liquid extraction and facilitating the deployment of fusion power plants.