This company’s tech is crucial for the future of fusion power plants

Nuclear Fusion and Tritium: A Future Challenge in Power Generation

Advocates of nuclear fusion have long envisioned it as a source of nearly limitless power, replicating the sun's reaction on earth. The principal challenge is creating a fusion power plant that generates more energy than it consumes. Additionally, there is the issue of securing sufficient fuel, specifically a mix of hydrogen isotopes: deuterium and tritium. While deuterium is abundant in seawater, tritium is exceedingly scarce and essentially needs to be produced. Currently, there are only about 20 kilograms of tritium globally, enough to start merely a dozen commercial-scale power plants.

Today, tritium is a byproduct of fission reactions in a few nuclear plants. Initial fusion reactors will rely on this limited supply, but future reactors must generate additional tritium. This will be accomplished by breeding tritium using neutrons released during fusion to strike a lithium blanket, producing helium and tritium. The tritium will be extracted from the reactor core and some of it will be reinjected into the reactor, with the remainder reserved for fueling other reactors. However, existing equipment for this filtration process is suitable only for experimental reactors, requiring significant enhancement for commercial use.

Marathon, a startup led by CEO Kyle Schiller and CTO Adam Rutkowski, aims to address this with an improved version of a technology called superpermeation, which has been around for 40 years. This technology uses a solid metal membrane to filter impurities from hydrogen by converting the mixture into plasma and pressing it against the membrane. The membrane allows hydrogen, including tritium, to pass while blocking other impurities, and also compresses the hydrogen—a beneficial side effect. This enhancement could increase the filtration system's throughput by several magnitudes.

Marathon's development efforts have been supported by the Department of Energy’s ARPA-E program and the Breakthrough Energy Fellows program. Recently, the company secured a $5.9 million seed round led by the 1517 Fund and Anglo American, with additional backing from Übermorgen Ventures, Shared Future Fund, and individual investor Malcolm Handley. Furthermore, Marathon has tentative commitments from Commonwealth Fusion Systems and Helion Energy, two significant players in the fusion startup space.

Given that commercial fusion power remains years, if not decades away, some might argue that Marathon's focus is premature. So far, only one fusion experiment has achieved breakeven under scientific conditions, which does not account for operational overheads—a critical aspect for commercial viability. However, Schiller maintains that the rapid advancements in fusion technology over the past decade justify their early efforts. “We've been consistently amazed by the speed of progress in fusion,” he commented. “If we reach breakeven sooner than later, we’ll be grateful we started early.”