72 Scientific American, December 2020Humans are an energy-Hungry species, and our
current sources of power are not cutting it. Nucle-
ar fusion, the process that fuels the sun, might
offer the kind of clean, abundant energy we need—
if only scientists can figure it out. The Internation-
al Thermonuclear Experimental Reactor (ITER)
is the biggest and most ambitious attempt yet to
harness the energy produced by forcing two
atoms to become one. The $25-billion experiment
in Saint-Paul-lez-Durance, France, is a joint proj-
ect of the European Union, China, India, Japan,
South Korea, Russia and the U.S. Its ultimate goal
is to do what no fusion experiment has done
before: produce more heat than it consumes.
The project has been stymied by delays and ballooning costs, and
a critical independent assessment forced out the top leadership sev-
eral years ago. In some skeptics’ eyes, it will always be a boondog-
gle, a waste of too much time and money for an experiment that is
aiming to be not even a working power plant but merely a proof of
concept. But ITER finally reached a long-sought milestone in July
2020 with the official start of machine assembly—when scientists
began joining the various components provided by the partner coun-
tries. “We have the same feeling as somebody who is supposed to
run successive marathons, and you achieve the first one, but still
you know there are many more to do,” says Bernard Bigot, who took
over as ITER director general in 2015. “It gives us more confidence
in the future, but we know that nothing is [taken] for granted.”
The challenge is to essentially build a miniature star inside a lab-
oratory—and then control it. The heart of the experiment is a
23,000-ton cylinder where intense superconducting magnets will
try to keep a 150-million-degree-Celsius plasma contained long
enough for fusion to occur. Making the physics work out will be a
huge challenge, but so will conquering the construction. “It is a lar ge-
scale international project where parts are made all across the world,
and it has to fit together like a puzzle, and it has to work,” says plas-
ma physicist Saskia Mordijck of William & Mary, who is not part of
the ITER team.
Scientists hope to press the proverbial red button and turn on
the reactor in 2025, with the ultimate goal of running it at full pow-
er by 2035. If it succeeds, the payoff would be gigantic. Fusion has
the potential to release much more energy than burning coal or oil
or even nuclear fission, which fuels traditional nuclear power plants.
Fusion produces no greenhouse gases or radioactive waste. “Fusion
from my point of view is really the one option that complements
reusable energy and could be the solution for climate change,” Bi got
says. “The next three or four years will be absolutely critical.”
Clara Moskowitz is a senior editor at Scientific American,
where she covers space and physics.