How to make nuclear fusion the Holy Grail of clean energy?

The way scientists think about fusion changed forever in 2022, when what some have called the experiment of the century demonstrated for the first time that fusion can be a viable source of clean energy.

The experiment, carried out at Lawrence Livermore National Laboratory, demonstrated ignition: .

Furthermore, recent years have been marked by private investment of several billion dollars in this field, mainly in the USA.

As engineers who have worked on the fundamental science and engineering applied to nuclear fusion for decades, we have seen much of the science and physics of fusion come of age in the last 10 years.

But, as , to make fusion a viable source there are now a whole series of engineering challenges that have to be resolved before fusion can be scaled up to become a safe and economical source of virtually unlimited clean energy. In other words, it’s engineering time.

Build a fusion reactor

Fusion occurs when two types of hydrogen atoms, the deuterio and the tritiumcollide in extreme conditions.

The two atoms literally fuse into a single atom, heating up to 180 million degrees Fahrenheit (100 million degrees Celsius), 10 times hotter than the core of the Sun. For these reactions to happen, the fusion energy infrastructure will have to withstand these extreme conditions.

There are two approaches to achieving fusion in the laboratory:

• a inertial confinement fusionwhich uses powerful lasers;
• ea magnetic confinement fusionwhich uses powerful magnets.

While inertial confinement fusion has been used, magnetic confinement fusion has not yet demonstrated that it can break even in energy production.

What remains to be done?

Both mentioned fusion approaches share a number of challenges that will not be easy to overcome.

For example, researchers have to develop new materials that withstand extreme temperatures and irradiation conditions.

Fusion reactor materials also become radioactive when they are bombarded with highly energetic particles. Researchers have to design new materials that can decay in a few years to levels of radioactivity that can be disposed of safely and more easily.

Produce enough fueland doing so in a sustainable way, is also an important challenge.

For one, deuterium is abundant and can be extracted from ordinary water.

However, increase tritium productionwhich is normally produced from lithium, it will be much more difficult. A single fusion reactor will need hundreds of grams to a kilogram of tritium per day to function.

Currently, conventional nuclear reactors produce tritium as a byproduct of fission, but cannot provide enough to support a fleet of fusion reactors.

So engineers will have to develop the ability to produce tritium within the fusion device itself. This may involve surrounding the fusion reactor with lithium-containing material, which the reaction will convert to tritium.

To scale up inertial fusionengineers will need to develop lasers capable of repeatedly hitting a fusion fuel target, made of frozen deuterium and tritium, several times per second.

However, no laser is powerful enough to do it at this speed – yet. Engineers will also have to develop control systems and algorithms that guide these lasers with extreme precision to the target.

Furthermore, engineers will have to increase target production in orders of magnitude: from a few hundred handmade every year, priced at hundreds of thousands of euros each, to millions costing just a few euros each.

For magnetic confinement, materials engineers will have to develop more effective methods for heating and controlling plasma and more heat- and radiation-resistant materials for reactor walls.

The technology used to heat and confine the plasma until the atoms fuse should work reliably for years.

All of these are challenges that, although difficult, are not insurmountable.

And after that, the financing

Investments from private companies around the world have increased – likely to continue to be an important factor in advancing fusion research. Private companies have attracted around €7 billion in private investment over the past five years.

Several startup companies are developing different technologies and reactor designs with the aim of adding fusion to the power grid in the coming decades. Most are based in the US, with some in Europe and Asia.

It was the US Department of Energy that invested around $3 billion to build the National Ignition Facility at Lawrence Livermore National Laboratory in the mid-2000s, where the “experiment of the century” took place 12 years later.

In 2023, the Department of Energy announced a four-year, $42 million program to develop fusion centers for the technology. While this funding is important, it likely will not be enough to resolve the most important challenges that remain for the United States to emerge as a global leader in practical fusion energy.