The Korea Institute of Fusion Energy (KFE) has equipped its KSTAR tokamak with a cutting-edge tungsten diverter, designed to withstand the immense heat generated during fusion experiments and pave the way for sustained high-ion temperatures exceeding 100 million degrees Celsius. This upgrade represents a significant step towards achieving longer plasma operation times, a crucial milestone in fusion energy research.
KSTAR, often referred to as an “artificial sun” due to its ability to replicate the nuclear fusion process that powers our star, has been operational since 2008. Roughly one-third the size of the ITER tokamak under construction in France, KSTAR offers valuable insights into fusion technology. Both reactors are tokamaks: doughnut-shaped devices utilizing powerful magnetic fields to contain superheated plasma, the state of matter required for nuclear fusion.
A key component in a tokamak is the diverter, situated at the bottom of the device. The diverter handles the exhaust of waste gas and impurities produced during the fusion reaction. As a plasma-facing component, the diverter endures extreme heat and particle bombardment. KSTAR’s previous carbon diverter limited plasma operations to around 30 seconds. With the new tungsten diverter, KFE scientists aim to achieve 300-second plasma operations by the end of 2026, a tenfold increase.
The KSTAR tokamak in Daejeon, South Korea.The KSTAR tokamak, located in Daejeon, South Korea, is playing a key role in advancing nuclear fusion research. Photo: Korea Institute of Fusion Energy (KFE)
The shift from carbon to tungsten stems from tungsten’s superior heat resistance. Its higher melting point significantly improves the reactor’s heat flux limit, essentially doubling its capacity to handle extreme temperatures, according to Korea’s National Research Council of Science and Technology. The development of the tungsten diverter began in 2018, with a prototype completed in 2021 and final installation concluding last year.
A Step Towards ITER and the Future of Fusion
“KSTAR’s adoption of a tungsten diverter, the same material chosen for ITER, underscores our commitment to contributing valuable data and insights to the international fusion community,” stated KFE president Suk Jae Yoo. This collaboration aims to accelerate the development of fusion as a viable energy source.
Progress in Fusion Research
The journey toward controlled nuclear fusion has witnessed notable advancements. In 2022, scientists at Lawrence Livermore National Laboratory achieved net energy gain in a fusion reaction, a historic first. While significant challenges remain in realizing a practical and sustainable fusion power plant, this achievement demonstrates the progress being made in the field.
Close-up view of the KSTAR's tungsten diverter.The tungsten diverter, a critical component in the KSTAR tokamak, is designed to handle the extreme heat generated during fusion experiments. Photo: Korea Institute of Fusion Energy (KFE)
ITER, the world’s largest fusion project, is expected to achieve its first plasma in 2025, with the first fusion reaction anticipated in 2035. However, the project has faced delays and cost overruns, pushing back the timeline for realizing its full potential.
A Global Effort in Fusion Energy
Despite these challenges, momentum in fusion research continues to build. The recent inauguration of the JT-60SA tokamak in Japan and the operation of over 50 tokamaks worldwide, as reported by the International Atomic Energy Agency, highlight the global commitment to this promising energy technology.
KSTAR’s Next Steps
Plasma experiments using KSTAR’s new tungsten diverter will continue through February. These tests aim to validate the diverter’s performance, ensure a stable operating environment, and confirm the reproducibility of 100-million-degree plasmas. The data gathered from these experiments will be instrumental in refining fusion technology and contributing to the global pursuit of clean energy.
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