Korean Fusion Program (KSTAR, K-DEMO)

Overview

The Korean fusion program represents South Korea's strategic, long-term investment in developing fusion as a sustainable and carbon-free energy source. Administered by the Korea Institute of Fusion Energy (KFE), the program is a significant contributor to global fusion research. Its activities are anchored by two principal pillars: the operation of the Korea Superconducting Tokamak Advanced Research (KSTAR) facility and the conceptual design and R&D for the Korean Demonstration Fusion Power Plant (K-DEMO).

KSTAR is a world-class experimental device notable for being one of the first tokamaks constructed with fully superconducting magnets, utilizing both Niobium-tin (Nb3Sn) and Niobium-titanium (NbTi) conductors. This design enables the exploration of long-pulse, high-performance plasma regimes, which are critical for the steady-state operation required by a future power plant. The program's focus on advanced tokamak physics, particularly the suppression of plasma instabilities and the management of plasma-wall interactions, positions it as a key research platform for the international fusion community and a vital contributor to the operational success of the ITER project, in which South Korea is a full member.

Physics / Mechanism

The technical foundation of the Korean fusion program is the advanced tokamak concept, which aims to improve upon the conventional tokamak design to achieve more efficient and commercially viable fusion energy. KSTAR embodies this approach through several key engineering and physics features.

Superconducting Magnet System: KSTAR's magnet system is its defining characteristic. The toroidal field (TF) coils, which generate the primary magnetic field to confine the plasma, are made of Nb3Sn, a superconductor capable of producing strong magnetic fields (up to 3.5 T on-axis) but which is notoriously brittle and difficult to manufacture. The poloidal field (PF) coils, which shape and position the plasma, are made of the more ductile NbTi. This fully superconducting system minimizes resistive power losses, allowing for extended plasma discharges far exceeding the capabilities of copper-magnet machines. This long-pulse capability is essential for studying plasma phenomena that evolve over long timescales, such as current profile evolution and plasma-wall interaction equilibrium.

Advanced Plasma Operation Modes: Research at KSTAR focuses on achieving and sustaining high-confinement modes (H-modes) of operation. A key area of investigation is the suppression of Edge Localized Modes (ELMs), which are intense, periodic bursts of energy from the plasma edge that can damage reactor walls. KSTAR has been a leading facility for testing ELM suppression techniques, such as applying non-axisymmetric magnetic perturbations using in-vessel control coils. The goal is to develop steady-state operational scenarios with high plasma pressure (high beta) and a high fraction of self-generated bootstrap current, which reduces the need for external current drive systems and improves the overall energy efficiency, a critical factor for meeting the Lawson criterion for net energy gain.

Plasma Facing Components and Divertor: Managing the intense heat and particle flux exhausted from the plasma is a central challenge for any fusion reactor. KSTAR's original divertor was composed of carbon tiles. An upgraded divertor using tungsten monoblocks, similar to the design planned for ITER, was installed in 2023. Tungsten is favored for its high melting point and low sputtering yield, but it presents challenges related to plasma contamination by high-Z impurities. The KSTAR program actively studies divertor physics, including heat load distribution, material erosion, and impurity transport, to develop robust solutions for K-DEMO and future reactors.

Historical development

The formalization of South Korea's fusion ambitions began with the National Fusion R&D Master Plan in 1995. This led to the establishment of the National Fusion Research Institute (NFRI) in 1996, which was later rebranded as the Korea Institute of Fusion Energy (KFE) in 2020.

1995-2007: KSTAR Construction: The KSTAR project was approved in 1995. The subsequent 12 years involved intensive R&D, design, and construction. This period was marked by significant domestic achievements in superconducting magnet technology, vacuum vessel fabrication, and high-power heating systems. The construction was completed in 2007, a major milestone for the Korean scientific and engineering community.
2008: First Plasma: KSTAR achieved its first plasma in July 2008, officially beginning its operational phase.
2010: First H-mode: The device successfully achieved H-mode, a high-performance operational regime, demonstrating the effectiveness of its heating and control systems.
2016: 1-minute Operation: KSTAR achieved a significant world record by sustaining a high-temperature plasma (over 50 million K) for 70 seconds, showcasing the advantages of its superconducting magnet system for long-pulse operation.
2018: 100 Million K: KSTAR reached an ion temperature of 100 million K, a critical threshold for efficient thermonuclear fusion reactions, for the first time.
2021: 30-second Operation at >100M K: The program set another world record by maintaining a plasma with an ion temperature exceeding 100 million K for 30 seconds. This achievement was enabled by improvements in the internal transport barrier (ITB) mode, a plasma confinement regime that reduces turbulent energy loss from the core.
2023-2024: Divertor Upgrade: KSTAR underwent a major upgrade, replacing its carbon-based divertor with a tungsten monoblock design. This was a critical step to enhance its heat-handling capabilities and align its research with the material choices for ITER and K-DEMO. The device resumed operations in late 2024 after the successful installation.

Throughout its history, the program has been deeply integrated with the international fusion effort, particularly through South Korea's membership in the ITER project since 2003. KFE is responsible for procuring key ITER components, including the thermal shields, some vacuum vessel ports, and superconducting conductors.

Current status

As of 2026, the Korean fusion program is focused on pushing the operational boundaries of KSTAR and advancing the design of K-DEMO. Following the successful installation of the new tungsten divertor, the primary experimental goal for KSTAR is to extend the duration of high-temperature, high-performance plasma operation. The near-term target is to achieve a 300-second H-mode operation with an ion temperature exceeding 100 million K by 2026–2027. This objective serves as a crucial integrated test of steady-state physics and the performance of the new plasma-facing components.

Research campaigns are centered on optimizing plasma scenarios that are directly relevant to ITER and K-DEMO. This includes refining ELM suppression techniques, developing reliable plasma start-up and ramp-down procedures, and studying the physics of tungsten-plasma interactions. The data gathered from KSTAR operations directly informs the physics basis and engineering design for K-DEMO.

The K-DEMO project is in its conceptual design phase. The current reference design, K-DEMO-2, envisions a two-stage development. Stage 1 aims for electricity generation (hundreds of MWe) with a modest tritium breeding ratio (TBR) below 1.0, requiring an external tritium supply. Stage 2 targets a fully self-sufficient fuel cycle with a TBR greater than 1.0 and an increased net electrical output of over 500 MWe. The KFE is conducting extensive R&D on key technologies required for K-DEMO, including high-temperature superconducting (HTS) magnets, advanced breeding blanket concepts, and remote handling systems.

Notable implementations

Korea Institute of Fusion Energy (KFE): The central government-funded institute responsible for executing the national fusion roadmap. KFE operates KSTAR and leads the K-DEMO design and associated R&D.
KSTAR (Korea Superconducting Tokamak Advanced Research): The flagship experimental device of the program. Located in Daejeon, it is a medium-sized tokamak (1.8 m major radius) with a fully superconducting magnet system. Its primary mission is to explore advanced, steady-state operational modes for future fusion reactors.
K-DEMO (Korean Demonstration Fusion Power Plant): The long-term objective of the program. It is a conceptual power plant designed to follow ITER and demonstrate the commercial viability of fusion energy. The design is continuously evolving based on results from KSTAR and progress in the global fusion community.
Industrial Collaboration: The program involves significant collaboration with South Korean industrial partners. Companies like Hyundai Heavy Industries and SK Hynix have been involved in the fabrication of major components for KSTAR and ITER, building a domestic supply chain for critical fusion technologies.

Open challenges

Despite its significant progress, the Korean fusion program faces several scientific and engineering challenges.

Steady-State Plasma Control: While KSTAR has achieved record pulse lengths, maintaining a perfectly stable, high-performance plasma for hundreds of seconds—and eventually for hours in K-DEMO—remains a formidable challenge. This requires integrated control of the plasma density, temperature, current profile, and impurity content with unprecedented precision.
Divertor Heat and Particle Loads: The new tungsten divertor must prove its ability to handle the extreme heat fluxes (projected at 10-20 MW/m²) expected in long-pulse, high-power scenarios without excessive erosion or plasma contamination. Managing transient events like disruptions, which can deposit enormous amounts of energy onto the divertor plates in milliseconds, is a critical area of ongoing research.
Tritium Breeding and Fuel Cycle: The development of a reliable tritium breeding blanket is a universal challenge for fusion energy and a key focus for the K-DEMO design. The program must develop and test blanket modules that can achieve a tritium breeding ratio greater than 1.0, operate reliably in a harsh neutron environment, and allow for efficient tritium extraction. This is a major technological leap from current experimental devices.
High-Temperature Superconductor (HTS) Magnets: While KSTAR uses low-temperature superconductors, the K-DEMO design relies on HTS magnets to achieve higher magnetic fields and greater operational efficiency. The maturation of HTS magnet technology, including manufacturing long-length, high-quality conductors and managing quench protection, is a critical R&D path for the program.

Outlook

The credible 5- to 15-year trajectory for the Korean fusion program is ambitious and methodical. In the near term (2026-2030), the primary focus will be on exploiting the upgraded KSTAR to achieve its ultimate goal of 300-second operation at ion temperatures above 100 million K. Success in this phase would provide the world's first integrated demonstration of the core physics required for a steady-state fusion reactor and would solidify the operational basis for ITER.

In the medium term (2030-2035), the program will pivot towards technology maturation for K-DEMO. This will involve the construction and testing of prototype components, such as HTS magnets and tritium breeding blanket modules, in dedicated test facilities. The conceptual design of K-DEMO will be refined based on the final results from KSTAR's long-pulse campaigns and initial operational data from ITER. A government decision on the construction of K-DEMO is anticipated in the mid-2030s, contingent on continued technical progress and favorable policy conditions.

By 2040, if the roadmap proceeds as planned, South Korea could begin construction of K-DEMO. The program's strategy of concurrently operating a world-class experimental facility while pursuing a focused, long-term power plant design positions South Korea to be a leader in the eventual commercialization of fusion energy.

References

KSTAR research progress and future plans — Nuclear Fusion (2022)
Overview of the K-DEMO Program in Korea — Fusion Engineering and Design (2019)
KSTAR: The key steps to the first plasma — Fusion Engineering and Design (2009)
A sustained high-temperature plasma regime in the KSTAR tokamak — Nature (2022)
South Korea's KSTAR fusion reactor sets new record — ITER Organization Newsline (2021)
KSTAR resumes operation after divertor upgrade — World Nuclear News (2024)
Design concept of the K-DEMO for near-term implementation — Nuclear Fusion (2015)
Korea's KSTAR aces test of new tungsten divertor — Korea Institute of Fusion Energy (KFE) (2024)

Korean fusion program (KSTAR, K-DEMO)