The proposed demonstration fusion power plant intended to follow ITER — bridging the gap between experimental reactor and commercial electricity generation.
DEMO (DEMOnstration Power Plant) represents the next major step in the international fusion energy roadmap after ITER. Unlike ITER, which is designed to demonstrate net energy gain from fusion plasma but will not generate electricity, DEMO is intended to be the first fusion device that produces net electrical power and feeds it into the grid. The concept has been studied by multiple programmes worldwide, with the European Union's EUROfusion consortium maintaining the most advanced design effort.[1]
DEMO must solve engineering challenges that ITER deliberately defers. These include tritium self-sufficiency through breeding blankets, materials capable of withstanding 14.1 MeV neutron fluences over years of operation, remote maintenance systems for highly activated components, and a complete balance-of-plant for electricity conversion. The European design targets a fusion power of 1,500–2,000 MW thermal and net electrical output of 300–500 MW.[2]
Under EUROfusion's revised roadmap, the conceptual design phase runs through the late 2020s, with engineering design anticipated in the early 2030s. Construction could begin in the mid-2030s, targeting first plasma in the 2040s and electricity production by approximately 2050. However, DEMO's schedule is closely linked to ITER's success in achieving Q≥10 burning-plasma operation.[3]
The principal challenges for DEMO include qualifying structural materials (such as reduced-activation ferritic-martensitic steels or advanced alloys) to withstand neutron damage exceeding 50 displacements per atom, demonstrating a tritium breeding ratio greater than unity with margin, achieving high plant availability (>30%) despite the need for regular blanket replacement, and designing divertor systems that can handle steady-state heat fluxes of 10–20 MW/m².
While EUROfusion's design is the most publicly documented, several nations have their own DEMO-class concepts. Japan's SlimCS and successive designs target a compact, high-beta tokamak approach. South Korea's K-DEMO aims for a staged programme with early electricity production. China's pathway runs through CFETR before reaching its own DEMO-scale plant. Each variant reflects national priorities in timeline, technology readiness, and industrial capability.