The promise of fusion energy is cheap and abundant power for the entire planet. Scientists have made startling advances towards achieving it at scale, but there are still many problems holding it back. One of them is the production of fuel, which requires vast amounts of enriched lithium. Enriching lithium has been an environmental catastrophe, but researchers in Texas believe they’ve found a way to do it cheaply and at scale without poisoning the world.
A team of researchers at Texas A&M University discovered the new process by accident while working on a method for cleaning groundwater contaminated during oil and gas extraction. The research has just been published in the scientific journal Chem under the title “Electrochemical 6-Lithium Isotope Enrichment Based on Selective Insertion in 1D Tunnel-Structured V2O5.”
The effect the research has on nuclear fusion might be enormous. “Nuclear fusion is the primary source of energy emitted by stars such as the Sun,” Sarbajit Banerjee, a professor and researcher at ETH Zürich and Texas A&M and one of the authors of the paper, told Gizmodo. The simplest method of doing fusion on Earth instead of space involves tritium and deuterium isotopes. Tritium is rare and radioactive so reactors currently “breed” it on demand to generate energy.
They breed the tritium by bombarding lithium isotopes with neutrons. Most lithium on the planet, more than 90% of it, is lithium-7. Breeding tritium works way more efficiently with the ultra-rare lithium-6. “When 7Li, the most commonly occurring lithium isotope, is used, tritium production is much less efficient as compared to 6Li,” Banerjee said. “As such, modern reactor designs are based on breeding blankets with enriched 6Li isotope that has to be specifically extracted from natural lithium.”
You can turn naturally abundant mixtures of lithium isotopes into Lithium-6, “enriching” it, but the process is a toxic nightmare. “From 1955 to 1963, the United States produced 6Li at the Y12 plant at Oak Ridge National Laboratory in Tennessee for thermonuclear weapons applications, taking advantage of the slight difference in solubility of 6Li and 7Li isotopes in liquid mercury,” Banerjee said. “This did not go so well.”
“About 330 tons of mercury were released to waterways and the process was shut down in 1963 because of environmental concerns,” he said. Mercury is a toxic nightmare substance that’s difficult to clean up. After 60 years, heavy metals from the process of extracting Lithium-6 from naturally abundant mixtures are still poisoning Tennessee today. Cleaning up the remnants of the environmental disaster is a major project for Oak Ridge National Lab’s current residents.
During a different project, the team at Texas A&M developed a compound called zeta-V2O5 that it used to clean groundwater. As it ran water through this membrane it noticed something strange: it was really good at isolating Lithium-6. The team decided to see if it could harvest Lithium-6 from mixtures of Lithium isotopes without mercury.
It worked.
“Our approach uses the essential working principles of lithium-ion batteries and desalination technologies,” Banerjee said. “We insert Li-ions from flowing water streams within the one-dimensional tunnels of zeta-V2O5…our selective Li sponge has a subtle but important preference for 6Li over 7Li that affords a much safer process to extract lithium from water with isotopic selectivity.”
Banerjee this could lead to a massive change in how fuel is developed for fusion generators. It also doesn’t require a massive re-design of the existing reactors. “Our work outlines a path to overcoming a key supply chain issue for fusion. However, to be clear we are not redesigning the actual reactors—tokamaks or stellarators—although there is tremendous recent excitement about new innovations and designs in plasma physics,” he said.
A lot of people are banking on fusion being the path towards cheap and abundant energy. My entire life I’ve heard that the breakthrough that will make it real is “just around the corner.” It’s been a constant refrain that’s become a bit of a joke. Just last year the Bulletin of the Atomic Scientists asked if fusion might be “forever the energy of tomorrow.”
But Banerjee was hopeful. “Despite the incredible challenges, fusion is too big of a prize to give up on,” he said. “The transformative potential has been clear but there have been critical gaps in engineering designs, materials science for extreme environments, and understanding of the complexity of plasma processes to enumerate just a few gaps. There is an intensifying global competition and billions of dollars in private and public investments—while still not imminent, there are promising signs of realistic fusion energy in about two or three decades.”
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