DEMO

DEMO
Name	DEMO
Type	Fusion reactor demonstration plant
Purpose	To demonstrate net electricity production from nuclear fusion
Status	Conceptual design phase

DEMO. The DEMOnstration Power Plant, often styled DEMO, is a proposed tokamak facility intended to be the successor to the ITER project. Its primary mission is to demonstrate the feasibility of generating net electrical power from nuclear fusion on a sustained, commercially relevant scale. The project represents a critical bridge between experimental fusion research and the first generation of commercial fusion power plants, integrating reactor technologies and materials necessary for continuous operation.

Overview

The concept for DEMO emerged from the global fusion energy roadmap, which positions it as the step following the ITER experiment, currently under construction in Cadarache, France. While ITER aims to achieve a tenfold gain in fusion power (Q≥10), DEMO is designed to deliver electricity to the electrical grid and prove the integrated operation of all essential reactor systems. Key international bodies, including the European Union's EUROfusion consortium, have developed detailed conceptual designs, with other major players like China, Japan, and the United States pursuing parallel studies. The project's success is seen as pivotal for validating fusion as a viable, large-scale, and low-carbon energy source for the latter half of the 21st century, influencing energy policies worldwide.

Design and objectives

The baseline design for DEMO is a tokamak configuration, building upon the physics and engineering lessons from ITER and preceding devices like JET and JT-60SA. Its core objectives are to achieve a fusion power output significantly higher than its auxiliary heating input, demonstrating a net gain in electrical production after accounting for all plant systems. A primary goal is the continuous generation of several hundred megawatts of electricity for grid injection over extended pulses. Furthermore, the design must incorporate a closed tritium fuel cycle to ensure self-sufficiency, advanced breeding blanket modules for tritium breeding, and systems for efficient heat extraction and conversion to electricity via a conventional turbine and generator setup.

Technical specifications

While final parameters are under definition, current European studies envision a machine larger than ITER, with a major radius exceeding 9 meters and a plasma volume over twice as large. The target fusion power is in the range of 300 to 500 megawatts, aiming for an electrical output of a few hundred megawatts. The machine will require advanced divertor designs to handle intense heat fluxes and employ reduced-activation ferritic martensitic steel or similar materials for in-vessel components to minimize long-lived radioactive waste. The breeding blanket will utilize lithium-based ceramics or liquid metals like lead-lithium to produce tritium. Superconducting magnets, based on niobium-tin or high-temperature superconductor technology, will generate the necessary magnetic field confinement.

Development timeline

The development path for DEMO is intrinsically linked to the results from ITER, with its construction not expected to begin until after ITER achieves full-power operation, currently projected for the late 2030s. The EUROfusion roadmap targets a decision to construct DEMO around 2030, with construction lasting approximately 10-15 years. First plasma operations are thus envisaged for the 2040s, followed by a phased commissioning of systems leading to integrated electricity production demonstrations by the 2050s. Parallel programs in other nations, such as China's CFETR project, follow similar, though not identical, timelines, reflecting a global race to realize practical fusion energy.

Challenges and research

Significant scientific and engineering hurdles must be overcome for DEMO. These include developing materials capable of withstanding extreme neutron irradiation from the deuterium-tritium reaction for the lifetime of the plant, which drives extensive research in facilities like the IFMIF-DONES neutron source. Achieving reliable plasma scenarios for steady-state operation, beyond the pulsed operation of ITER, is a major physics challenge. Integrating all plant systems—from the tokamak itself to the balance of plant, tritium processing, and remote maintenance systems—into a reliable and economically plausible whole presents a monumental engineering endeavor, requiring advances in fields like robotics and materials science.

International collaboration

Like ITER, DEMO is envisioned as a major international scientific undertaking, though its precise governance model remains under discussion. The ITER Agreement between members including the European Union, India, Japan, China, Russia, South Korea, and the United States provides a framework for potential future collaboration. Bilateral and multilateral agreements, such as those coordinated through the International Atomic Energy Agency (IAEA), facilitate joint research on critical technologies like breeding blanket testing. National agencies, including the U.S. Department of Energy and the Japan Atomic Energy Agency, are conducting foundational research that will inform the global DEMO design effort, aiming to pool resources and expertise to tackle this grand challenge.

Category:Proposed nuclear fusion reactors Category:Energy development Category:Experimental nuclear reactors