South Korea's proposed DEMO-class reactor — leveraging KSTAR's superconducting tokamak expertise to build a fusion power plant by mid-century.
K-DEMO is South Korea’s conceptual design for a demonstration fusion power plant, developed primarily by the Korea Institute of Fusion Energy (KFE, formerly NFRI) and the Korean national fusion community. Building on decades of experience with the KSTAR superconducting tokamak, K-DEMO is intended to be the machine that takes Korean fusion science from experimental physics to electricity production. It represents one of the most detailed national DEMO concepts outside Europe and China.[1]
K-DEMO has been studied in multiple design iterations since the early 2010s. The most widely cited configuration describes a conventional-aspect-ratio tokamak with a major radius of approximately 6.8 m, a toroidal field of 7.4 T on axis, and a plasma current around 12 MA. The device targets fusion power of approximately 2.6–3.0 GW with net electrical output of roughly 500 MW — ambitious parameters that would place K-DEMO among the largest fusion devices ever proposed.[2]
The design assumes high-temperature superconducting magnets, steady-state or long-pulse operation, and a full tritium breeding blanket. Multiple blanket concepts have been evaluated, including helium-cooled ceramic breeder and helium-cooled lithium-lead configurations. The choice of blanket technology remains one of the most consequential unresolved design decisions.[3]
K-DEMO draws directly on the experience accumulated through KSTAR, South Korea’s flagship tokamak at the KFE campus in Daejeon. KSTAR — which achieved first plasma in 2008 — is a fully superconducting tokamak with Nb3Sn toroidal field coils and NbTi poloidal field coils. It has set multiple records for sustained high-performance plasma operation, including maintaining H-mode plasmas for extended durations. KSTAR’s operational expertise in superconducting magnet systems, real-time plasma control, and long-pulse scenarios feeds directly into K-DEMO’s design basis.[4]
Korean planning documents have described a two-phase approach. Phase I would build a reduced-power version of K-DEMO — sometimes referred to as K-DEMO-1 — operating at lower fusion power to validate tritium breeding, materials performance, and plasma control in a reactor environment. Phase II would upgrade or rebuild the device for full-power electricity production. This staged strategy reflects the enormous technical uncertainty inherent in any DEMO project and mirrors the phased approaches adopted by CFETR and early EU-DEMO studies.
K-DEMO faces the same fundamental challenges as every DEMO concept: unproven tritium breeding at scale, materials that can survive decades of neutron damage, divertor solutions for extreme heat exhaust, and an economic case that can compete with incumbent energy sources. South Korea’s fusion budget, while substantial by national standards, is modest compared with the estimated multi-billion-dollar cost of a DEMO-class device. International collaboration — particularly with ITER partners and the US fusion program — is expected to be essential.[5]
The Korean roadmap envisions a construction decision in the early 2030s, with first operations of a Phase I device around 2040–2042 and full DEMO-level operations by mid-century. These dates depend heavily on ITER’s operational results, the maturation of HTS magnet technology, and sustained government funding commitments that extend well beyond any single political cycle.