Harnessing the power of nuclear fusion has long been seen as the key to achieving virtually limitless energy on Earth. However, there are two major challenges that need to be overcome: ensuring that fusion power plants generate more power than they consume and securing enough fuel to sustain them.
Many fusion reactors rely on a combination of two hydrogen isotopes, deuterium and tritium, as fuel. While deuterium is abundant in seawater, tritium is extremely rare and needs to be manufactured. Currently, there is only 20 kilograms of tritium available worldwide, which is enough to start up a few commercial-scale power plants at most.
To address this issue, Marathon Fusion, a stealthy startup, believes it has a solution. The current tritium supply comes from a small number of nuclear plants that use fission, another type of nuclear power. Once fusion becomes a viable source of energy, the initial fusion plants will rely on this supply. However, future reactors will be designed to generate additional tritium as a byproduct.
This process involves using neutrons produced during fusion to strike a lithium blanket, which releases helium and tritium. The tritium is then filtered and injected back into the reactor as fuel or reserved for other reactors. Existing filtration systems are efficient but not suitable for commercial power plants due to their limited throughput. Marathon aims to refine a 40-year-old technology called superpermeation, which uses solid metal to filter impurities from hydrogen. This method allows hydrogen, including tritium, to pass through while blocking other substances.
Marathon has been working on this problem for several years and has received support from the Department of Energy’s ARPA-E program and the Breakthrough Energy Fellows program. Recently, the company raised $5.9 million in seed funding from investors including the 1517 Fund and Anglo American. Marathon has also secured letters of intent from Commonwealth Fusion Systems and Helion Energy, two prominent fusion startups.
While commercial fusion power is still years away and faces uncertainties, Marathon believes it is not too early to work on the fuel supply problem. The company has been impressed by the rapid progress made in fusion research over the past decade and believes that starting early will be beneficial if and when fusion reaches breakeven.
