A superconducting tokamak at the National Fusion Research Institute (NFRI) in South Korea has achieved a world record of more than 70 seconds in high-performance plasma operation. Researchers hailed the achievement as a “huge step forward for the realization of fusion power.”
According to NFRI, researchers used a fully non-inductive operation mode—a “high poloidal beta scenario”—to achieve the long and steady-state operation at the experimental KSTAR tokamak (Figure 4). They also used a high-power neutral beam and various other techniques to alleviate the accumulated heat fluxes on plasma-facing components.
While research to harness fusion power—energy that is generated by the fusion of two lighter atomic nuclei (typically hydrogen) to form a heavier nucleus—was revived in the 1970s following a breakthrough at a Soviet tokamak, the cost and complexity of projects has tempered advancements.
Foremost among technical challenges is controlling plasma, a fourth state of matter that is produced by heating a gas to several million degrees. As some researchers describe it, plasma can be compared to a “soup,” where nuclei and electrons are no longer linked and move around freely. When two “light” nuclei collide at high speed, they can fuse, forming a heavier nucleus and releasing energy as a result of the fusion. But controlling plasma operation in a steady state has proven challenging. That’s why KSTAR’s steady-state plasma operation for more than a minute is significant.
According to NFRI, about 15 fusion devices exist around the world, with research underway in the European Union, the U.S., Russia, Japan, China, and South Korea. Most are conventional tokamaks, though much research has been carried out on stellarators, similar devices that use a different approach to plasma containment. At the end of 2015, for example, Germany switched on the Wendelstein 7-X stellerator, a device that is producing three-dimensional magnetic fields as predicted. The most-watched project, however, is ITER in southern France, a large tokamak experiment led by an international effort that seeks to produce roughly 500 MW of thermal energy using deuterium and tritium fusion fuels. In November, the ITER Council endorsed a schedule that projects first plasma will be achieved in 2025 and deuterium-tritium operation by 2035.
—Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)