KSTAR upgrades divertor to enhance performance

[Courtesy of KFE]

The South Korean artificial sun, Korea Superconducting Tokamak Advanced Research (KSTAR)’s replacement of its divertor now allows it to successfully maintain a plasma of 100 million degrees Celsius for 48 seconds.

“This achievement, which is considered a world record, brings us one step closer to realizing an artificial sun,” Korea Institute of Fusion Energy head of research Yoon Si-woo said.

Yoon explained on Thursday that the divertor acts as a heat-resistant device that protects the inner vessel from intense heat while serving as an outlet for various impurities generated during the fusion process.

“The installation of the new divertor on KSTAR, which set a new record, marks a significant milestone in the realization of fusion power,” he said.

Nuclear fusion is a phenomenon where the nuclei of light elements such as hydrogen and deuterium combine to form heavier atomic nuclei, releasing energy in the process.

As the process is similar to how the sun produces heat, it is referred to as an artificial sun and is gaining attention as a clean energy source as it does not produce carbon emissions.

It is theoretically possible to produce energy equivalent to that of 10 million tons of fossil fuels with just 1 kilogram of fusion fuel.

For nuclear fusion reactions to occur, plasma, or a state of matter where atomic nuclei and electrons are separated, and temperatures exceeding 100 million degrees Celsius are required.

While the sun naturally creates this high-temperature plasma via its mass and gravity, it needs to be artificially generated on Earth.

KSTAR is a fusion experimental facility that produces these plasmas and has achieved remarkable results since its completion in 2007. It achieved its first 100-million-degree plasma in 2018 and has been increasing the duration each year, while also recently succeeding in maintaining it for 48 seconds to set a new world record.

This was achieved by replacing the old divertor with a new one that only increases the surface temperature by a quarter of the previous level. The new divertor is made of tungsten, a metal whose melting point is 3,422 degrees Celsius. The metal is also known for its excellent mechanical and tensile strength as well as its efficient heat dissipation.

“KSTAR is undergoing refurbishment to sustain higher temperatures for longer periods,” Yoon said. “We plan to sequentially improve the performance of heating and current drive systems.”

The ultimate goal is to achieve 300 seconds by 2026.

“To accomplish this, the KSTAR research team plans to focus on research and device performance improvement, including securing real-time feedback control technology based on artificial intelligence,” Yoon said. “Achieving 300 seconds means that plasma technology for fusion power plants will have completed laboratory validation.”

Fusion energy is one of the most advanced scientific fields in which Korea is a global leader. The government is mulling fusion energy for practical application and aims to begin the conceptual design for a demonstration reactor by 2026, with engineering design to begin by 2035.

“Fusion energy is no longer a dream,” Yoon said. “A commercial fusion power plant will be in operation by the mid-2030s, following the demonstration reactor within the 2030s.”