https://www.iaea.org/bulletin/iter-the-worlds-largest-fusion-experiment

Building the World’s Largest Fusion Reactor

We’re here at ITER in the south of France, where construction crews are building the world’s largest fusion reactor. Building the world’s largest artificial sun has not gone smoothly. A series of setbacks has added years to the timeline and billions of dollars to the budget. These challenges explain why ITER costs so much and takes so long to complete.

Either Genius or Insane

At the same time, private fusion startups have multiplied as many companies hope to reach major milestones before ITER. China and Russia planned to collaborate with the United States and Europe, while Korea, India, and Japan also joined the effort. I ventured into the heart of this one-of-a-kind mega project, which aims to contain temperatures 10 times hotter than the core of the sun. I met the people working to bring this extraordinary power down to Earth.

ITER Is Already Changing the World

I discovered that ITER is already changing the world even though workers have not finished it yet. The sun inspired the dream behind ITER, and the sun proves that a self-sustaining fusion reaction can work under the right conditions.

Controlled fusion can release millions of times more energy than burning fossil fuels and four times more energy than the reactions that power traditional nuclear power plants. Fusion also avoids the risk of a meltdown and produces no long-lasting radioactive waste or carbon emissions during the fusion reaction.

Catch Lightning in a Bottle

However, recreating these conditions on Earth feels like trying to catch lightning in a bottle. Meet plasma, the fourth state of matter alongside solids, liquids, and gases. A substance becomes plasma when extreme heat separates the center of each atom from its electrons. This process creates a hot mixture of free electrons and charged ions.

The Only Way to Effectively Bottle It Is With Magnets

Because plasma contains charged particles, scientists can effectively contain it only with magnets. ITER combines magnetic fields from components made around the world. A central magnet comes from San Diego, D-shaped magnets around the vacuum vessel come from Italy and Japan, and circular magnets come from Russia, China, Europe, and other regions.

The Weave Has to Be Like Egyptian Cotton

To contain these microscopic particles, engineers must create an extremely tight magnetic field. Even if engineers make the machine 10 times larger, they still need to maintain millimeter-level precision.

The Largest Magnet in the World

ITER’s central solenoid magnet ranks as the largest magnet in the world. Once engineers install and fully assemble it, the magnet will stand five stories tall and weigh 1,000 tons. It will play an essential role in starting and maintaining ITER’s fusion reactions. ITER ultimately aims to study these reactions and reach a game-changing tipping point for fusion energy.

A Burning Plasma Heats Itself

We want to create something called a burning plasma. Fusion requires a large amount of energy to reach extremely high temperatures, but a burning plasma can heat itself. Fusion reactions create heat, and that heat can support additional fusion reactions.

Scientists have created burning plasmas in laboratories with lasers and in hydrogen bombs, but those reactions last only a very short time.

The World’s Largest Ever Tokamak

ITER aims to create a burning plasma with the same technology that commercial fusion companies will most likely use. To achieve this goal, ITER must build the world’s largest tokamak. This machine will control plasma heated to temperatures more than 10 times hotter than the core of the sun.

Why Even Hotter?

Why does ITER need to reach even higher temperatures? The sun has an advantage because its enormous gravity presses down on the particles inside its core. This pressure increases the particle density and allows fusion to occur at lower temperatures.

ITER will use less than one gram of fuel inside its comparatively huge vacuum chamber at any given time.

One of the Hottest Places in the Solar System

ITER must compensate for its low fuel density with extreme heat. The plasma inside ITER’s tokamak will reach 150 million °C, making it one of the hottest places in the solar system.

At the same time, superconducting magnets will surround the tokamak and contain the plasma. Engineers must keep these magnets at incredibly cold temperatures so they can work properly.

Some Very Small Cracks Created Some Very Big Problems

Engineers must maintain temperatures only a few degrees above absolute zero around the superconducting magnets. To make the system work, engineers must place one of the hottest environments next to one of the coldest environments and separate them with a very thin heat shield.

Engineers discovered several small cracks inside this heat shield, and those cracks created major problems.

We Want to Do It Right

Engineers found three leaks in the pipes during about 61 tests. As a result, they removed all 20 kilometers of piping and rebuilt or refabricated the shields.

ITER will need about 5 billion euros more to complete this work. That amount represents a huge expense, but the team wants to do the job correctly.

Quite Normal, Quite Expected

Quality problems can increase costs. According to the project team, these kinds of setbacks are normal and expected in a project of this scale. However, explaining those setbacks to politicians who control the funding presents a much greater challenge.

More Than 30 Countries Collaborating on ITER

More than 30 countries collaborate on ITER. Each member contributes a specified share. Europe contributes 45%, while each of the other members contributes 9%. The members provide their contributions mainly through components rather than simply through cash.

So Many Cooks in the Kitchen

Because so many countries participate and so many resources remain at stake, ITER uses a consensus-based decision-making model similar to systems used by the Antarctic Treaty, the World Trade Organization, and NATO.

The project has also created a de facto global supply chain.

The ITER Tokamak Hall

That global supply chain leads to the ITER Tokamak Hall, where scientists and engineers from around the world follow a precise construction process.

Here, you can see sections of the vacuum chamber. Once engineers assemble these sections, giant yellow cranes will lift them over the wall and place them inside the tokamak pit, which will become our next stop.

The Most Sensitive and Sacred Part

The tokamak pit serves as one of the most sensitive and important areas of the sprawling ITER complex. ITER rarely allows outsiders to visit this part of the facility.

This Is Where the Magic Happens

Before entering, visitors receive a simple warning: they must make sure they carry nothing that could fall. If something drops, they will never get it back, and the machine will not work properly.

This area contains the heart of the fusion process. ITER will use deuterium and tritium as its fusion fuels. These two forms of hydrogen contain one and two neutrons respectively.

The Same Fuel Mix

Commercial fusion reactors will most likely use the same fuel mixture that ITER plans to use for its research.

When deuterium and tritium fuse, they produce helium and a high-energy neutron. The neutron carries a great deal of energy and has no electric charge, so the surrounding magnets cannot control it like they control the charged plasma.

A Component That Will Stop the Neutrons

During fusion, these high-energy particles will strike the tokamak walls. Engineers must therefore design those walls and components to withstand these impacts.

Engineers will place shield blocks inside four of the yellow openings. These components will help stop the neutrons.

The Ability for a Reactor to Make Its Own Fuel

Some shield blocks will contain special materials that could unlock another major fusion-energy capability: allowing a reactor to produce its own fuel.

Deuterium exists abundantly in nature, but tritium remains extremely scarce. Scientists can produce tritium by placing lithium in some form inside the tokamak walls.

Scientists have already demonstrated this process, but they still need to demonstrate it at a larger scale.

ITER will not provide electricity to the power grid because it serves as a research tokamak. That was never its purpose. Instead, ITER will serve as a bridge between research facilities and future commercial fusion machines.

One Less Problem to Confront

Every problem that ITER solves will remove one challenge that commercial fusion companies will have to face. Many new tokamaks already resemble ITER because researchers continue to build on the project’s knowledge.

Scientists are also developing software that can predict plasma behavior, and they are working to release this software as open source.

Treated Like an Open Book

One of the things that impressed me most about ITER was the project’s open approach. The team is writing an ITER engineering handbook and openly discussing mistakes.

They explain what they learned and what they did wrong so future projects can avoid the same problems.

Access to All the Science

Every member state in the ITER agreement receives access to the scientific knowledge that ITER produces. A non-member state can also request access to the research if all member states agree to share it.

A Model for How Countries of Unlike Persuasion Can Work

ITER has become a model for how countries with different interests and viewpoints can work together over several decades.

These countries have experienced trade wars and other disagreements, but they continue to cooperate around a shared vision of creating a better world for future generations.

This Is the Knowledge of the World

Collaboration between public and private organizations has already produced world-changing technologies such as the internet, GPS, space travel, and modern consumer technologies such as Siri, touchscreens, and Google Search.

ITER represents a publicly funded project that brings together knowledge from around the world.

Always a Decade Away

People often describe fusion as a technology that always seems to remain a decade away. But seeing the future that ITER is building with my own eyes gave me hope that we may actually live in the final decade when people describe fusion as a distant dream.

This is the ITER control center. Workers are still building it, but the facility will become a busy hub of activity when ITER produces its first plasma.

ITER currently schedules its first plasma for 2034.

What do you think about fusion power?