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ITER’s ‘burning plasma’: One giant step toward fusion energy

Construction is advancing steadily on the ITER tokamak complex and supporting facilities in France, while components are in fabrication around the globe. Image credit: ITER Organization

A December 2018 report by the National Academies ushered in the new year by re-affirming strong support for U.S. participation in the ITER Project and “increased attention to engineering and technology-based development.”

The doughnut-shaped ITER will, for the first time on Earth, create a burning (self-heating) plasma and contain it with a magnetic field. The plasma itself will be heated and sustained primarily by its own fusion reactions—literally the same energy source that powers the sun and the stars. 

So, what does the ITER experiment provide that makes this leap forward possible? ITER will be the first fusion device to produce net thermal energy, meaning the total thermal power produced by a fusion plasma pulse is greater than the thermal power injected to heat the plasma. It is expected to generate 500 megawatts of thermal power for every 50 megawatts of thermal power injected to heat the plasma. 

The experiment will also be the first to maintain a fusion reaction for minutes at a time, rather than seconds. And finally, ITER will be a proving ground for many systems, materials and technologies needed to develop commercial-scale fusion reactors. When ITER succeeds in producing a burning (self-heating) plasma, commercial-scale fusion energy will move firmly into the realm of the possible. 

Why fusion?

The prospect of harnessing fusion is compelling for a number of reasons. First, the primary fuel, deuterium, can be extracted from ordinary seawater. The other main ingredient, tritium, can be produced from lithium, which is also widely available. Moreover, fusion reactors will not produce carbon emissions or greenhouse gases and will recycle most of their fuel. Finally, the low-level, short-lived radioactive waste generated by fusion reactions is mainly in the form of activated structures (reactor components that become radioactive); these require only a human lifetime to decay to safe levels.

When asked to describe one idea that would transform our society, the late Stephen Hawking said, "I would like to see the development of fusion power that gives an unlimited supply of clean energy and a switch to electric cars. Nuclear fusion would become a practical power source that would provide us with an inexhaustible supply of energy without pollution or global warming.”

When ITER reaches "first plasma" in 2025, the international ITER project will begin to address Hawking’s vision of inexhaustible energy, but it will be more than just the culmination of decades of fusion science and engineering. It will embody the confluence of technological advances from across the scientific spectrum that are necessary before scientists and engineers can tackle the challenge of constructing the first fusion power station.

Broader impact

As in previous "big science" projects such as the International Space Station or the Large Hadron Collider, knowledge gained through the ITER experiment will expand not only the boundaries of its own field of plasma physics but those of science in general. Because of the project’s sheer scale and complexity, ITER has already led to advances in an array of industrial technologies, including superconducting magnets, vacuum technologies, cryogenics, and robotic systems for handling materials. 

Global game changer

Once ITER is completed, experiments will begin to provide answers to questions that are critical to the construction of a fusion power station, including:

  • How does a reactor-scale burning plasma behave? What are the implications of producing fusion power at a mass scale for electricity?
  • Does burning plasma behave differently when it is being sustained by its own fusion reactions rather than heated by external sources?
  • How does a burning plasma affect the performance of components and systems needed for a fusion reactor?

Based on knowledge and experience acquired through research conducted on ITER and other fusion research devices, most experts expect commercial fusion power generation to become a reality in the mid- to late 21st century.

Energy Secretary Rick Perry recently characterized the ITER experiment and fusion energy as global game changers. 

“If we can deliver fusion energy to the world,” he said, “we’ve changed the world forever."