The global fusion energy community eagerly awaits the International Thermonuclear Experimental Reactor (ITER)’s momentous first plasma, expected in 2025. While ITER takes center stage, smaller reactors worldwide are making groundbreaking strides in preparation for the next-generation energy project. Among these pioneering reactors stands the Korea Superconducting Tokamak Advanced Research reactor (KSTAR) in Daejeon, South Korea.

Since its inception in 2008, KSTAR has been a bastion of research into the fundamental principles of fusion energy, the same process that powers our Sun. By generating plasma temperatures exceeding a scorching 100 million degrees Celsius, KSTAR compels specific hydrogen isotopes to fuse, producing colossal amounts of energy.

Creating plasma hotter than the Sun itself is just one facet of the challenge. The reactor, shaped like a torus (or donut), must also confine this searing plasma for extended durations—an immensely complex endeavor. In September 2022, KSTAR achieved a significant milestone by sustaining a 100 million-degree Celsius plasma for a full 30 seconds. While promising, this duration falls short of producing more energy than is consumed to heat the plasma initially.

However, a recent announcement by the Korea Institute of Fusion Energy has kindled new hope. KSTAR is set to undergo an upgrade that will enable it to contain plasma for durations ten times longer than its previous record, with this capability expected to be realized by 2026. This development aligns perfectly with the ambitions of the internationally supported ITER project, as data gleaned from KSTAR will undoubtedly contribute to ITER’s success.

KSTAR’s extended plasma confinement will be made possible through the implementation of a new tungsten divertor, designed to withstand the immense heat flux inherent in tokamak reactors. Divertors, located at the vacuum vessel’s base, play a pivotal role in managing exhaust and impurities while enduring extreme surface heat loads. Previously, KSTAR employed a carbon-based divertor, prized for its high melting point. Nonetheless, this material posed a challenge as plasma particles tended to adhere to its surface, limiting reaction durations. Tungsten, with its similarly high melting point but greater atomic mass, circumvents this issue, allowing KSTAR to sustain reactions for minutes rather than mere seconds.

Phil Ferguson, the director of the Material Plasma Exposure eXperiment (MPEX) Project at Oak Ridge National Laboratory, emphasized the critical role of materials in the fusion process. “For fusion, you have to do three things—you have to get enough particles together, you have to get them hot enough, and you need to hold them long enough for the reaction to take place,” explained Ferguson. He added, “You need a material solution. Give me the materials that can hold this thing together, at temperature, to be efficient.”

As we approach an era where our understanding of fusion science reaches its zenith, the pursuit of harnessing this ultimate energy source emerges as one of the most formidable engineering challenges in human history. KSTAR’s progress signifies a significant stride towards unlocking the potential of fusion energy and shaping a sustainable future.

By Impact Lab