FUELLING THE SUN | SPECIAL REPORT


Left: Recycled batteries could become an important source of fuel for the fusion industry


The second catch: only one isotope of lithium – Li-6 –


produces heat during the nuclear reaction (2kg of Li-6 is required to produce 1kg of tritium) and the excess neutrons required for both tritium production and heat transfer. The more abundant isotope, Li-7, which represents between 92% and 98% of naturally occurring lithium is not conducive to the reaction. It is not clear what proportion of Li-6 will be required in the lithium blanket but proportions in the literature vary upwards from 40%. Furthermore, once it has been ‘bred’ the tritium gas


has to be extracted from the lithium blanket and it is not clear what efficiency can be achieved in the capture and extraction process. As the nuclear fission industry has found time and again, even small volumes of nuclear fuel rely on an extensive global supply chain to source, transporting and processing fuel, and that can mean bottlenecks that may represent major risks to industry or the environmental damage that comes with resource extraction.


Lithium production Lithium production is not free from environmental issues. It is produced in two ways. Some accumulations of saline groundwater are rich in dissolved lithium. It is also found in minerals hosted in pegmatites, rock units formed when mineral-rich magma intrudes from magma chambers into the Earth’s crust. For the brine option, drilling at the site allows the brine


to be pumped to the surface. It is kept in evaporation ponds for months or years until most of the liquid water content has been removed through evaporation, although this may be sped up with reverse osmosis. Extracting the lithium then requires several stages of purification, chemical separation of other by-products, filtration, and treatment to produce product for sale, such as using sodium carbonate to produce lithium carbonate. Mineral deposits may have a higher lithium content but the material has to be mined and pulverised before the lithium can be extracted with chemical reagents that form a slurry that is heated, filtered, and concentrated through an evaporation process to form saleable lithium salts. The higher energy consumption, chemicals, and materials involved in extracting lithium from mineral ore mean typical lithium costs are twice those of brine extraction. According to the US Geological Survey four mineral


operations in Australia, two brine operations each in Argentina and Chile, and two brine and one mineral operation in China accounted for the majority of global lithium production in 2021.


The IEA says anticipated capacity additions would lead


supply in 2030 to be only slightly more diverse than it is now, mostly thanks to the start-up of mining in Canada. Australia and Chile will still account for around 70% of all mining once all those additions are fully operational. China has more than half of all capacity for refining lithium into specialised battery chemicals. Separation of Li-6 from Li-7 presents another potential


environmental issue. The World Nuclear Association lists two options. Mercury-


based separation relies on Li-6’s greater affinity to mercury. It says that when a lithium-mercury amalgam is mixed with lithium hydroxide, the Li-6 concentrates in the amalgam and the Li-7 in the hydroxide. A counter-flow of amalgam and hydroxide passes through cascades. This requires a lot of mercury and today this is undertaken only in Russia and China. The process is currently banned in the USA, where 11,000t on mercury was used in a previous process that involved significant losses to “wastes, spills and evaporation”. WNA says the alternatives are laser processes on metal vapour or chemical separation using crown ethers.


Meeting commercial needs If the fusion industry is to be significant in meeting our electricity needs it will have to have not one 1000MW plant but hundreds or thousands. The Statista website shows global lithium production


hovered just above the 30,000 tonne mark during the early 2010s (up a third from the previous decade). Production began to step up from 2017 (when it was nearly 70,00o tonnes) and it was estimated at 100,000 tonnes in 2021. In its January report, IEA estimated global demand for lithium – almost entirely for electric vehicle batteries and motors – would be 700,000 tonnes per year by 2050. If fusion reactors were to represent 5GW of supply by then – with five of the 1000MW units noted above – the industry’s annual lithium demand would be less than 1 tonne of Li-6 but up to twenty times as much unseparated lithium, along with 100 tonnes of start-up volumes. Extra would be required to ‘top up’ those figures after losses along the lithium conversion and tritium production and collection process. That total remains a rounding error in the lithium


industry. But the industry will aim to be larger than this: if it matches the current fission industry, with closer to 500GW of capacity, its demand for lithium will increase to the hundreds of tonnes – with the complexity that a large proportion of the lithium, in the form of discarded Li-7-rich material, can be offered back to the market. U


www.neimagazine.com | February 2023 | 17


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