A New Method of Supplying Lithium Can Make Fusion Fuels Greener

Infinite power from nuclear fusion can be brought one step closer following the accidental discovery of a new process to supply isotope lithium-6, essential to providing fuel to sustainable fusion reactors.

The most challenging fusion process combines two isotopes of hydrogen, deuterium and tritium to produce helium, neutrons and many more energy. Tritium, a rare radioisotope of hydrogen, is difficult to procure and expensive. The “Breeder” reactor aims to produce tritium by bombarding lithium with neutrons.

Lithium atoms exist as two stable isotopes. Lithium-7 accounts for 92.5% of natural elements, with the remainder being lithium 6. The more rare isotopes react with neutrons much more efficiently and produce tritium in fusion reactions.

However, separating the two lithium isotopes is extremely difficult. Until now, this has been achieved on a large scale using highly toxic processes that depend on mercury. Environmental impacts have forced the process to be unemployed in Western countries since the 1960s, forcing researchers to rely on a decline in the stockpile of lithium-6 produced before the ban.

Sarbajit Banerjee Eth Zurich and his colleagues in Switzerland happened to discover alternatives while considering ways to clean water contaminated by oil drilling.

Researchers noticed that cement membranes containing lab-made compounds called Zeta vanadium oxide collect large quantities of lithium and appear to separate lithium-6 disproportionately.

Zetavanadium oxide contains tunnels surrounded by oxygen atoms, Banerjee says. “Lithium ions pass through these tunnels, which just happens to be the right size. [to bind lithium-6]”We found that lithium-6 ions bond more strongly and are retained within the tunnel.”

Researchers don’t fully understand why lithium-6 is preferentially retained, but based on simulations they believe it is related to the interaction between ions and atoms at the edge of the tunnel, says Banerjee.

He says he has not separated less than six grams of lithium to date, but he wants to expand the process to produce tens of kilograms of isotopes. Commercial fusion reactors are expected to require large amounts of elements every day.

“But these challenges become pale compared to the major challenges with laser ignition for plasma reactors and fusion,” says Banerjee.