What is nuclear fusion and why it shouldn’t, for now, help the climate crisis


The next leap in human civilization could be in the stars. More specifically in the field of stellar energy: nuclear fusion.

Fusion, due to its potential to generate huge amounts of clean energy, brings hope that, in the future, nations will no longer depend on fossil fuels for energy generation.

The problem in the previous paragraph is in one word: future. Humanity cannot count immediately — and considering the current technological stage, even in the medium term — on this energy source to deal with the ongoing climate crisis on Earth.

Nuclear fusion occurs when two hydrogen nuclei fuse and form a helium atom. It’s worth a caveat here: don’t confuse fusion with nuclear fission, which is used in nuclear power plants and consists of, as the name says, bumping two atoms together so that they “break”.

If the human being can “break”, then the way to merge must already be known, right?

Right. The problem is to put into practice and control, on Earth, the reactions that take place in the stars.

Fusion is only possible when the particles are at extremely high temperatures — to the point of forming plasma, the fourth state of matter, an ionized gas — under high pressure. This is because the protons (present in the nuclei that one wants to collide) exert repulsion among themselves. To bring them together and fuse them together, only under extreme conditions, like the millions of degrees Celsius inside a fusion reactor.

But when the union works and helium forms, large amounts of energy are produced, which in turn could serve humanity’s energy thirst.

Currently, we are able to produce fusion, but there are a number of problems that prevent its use for commercial energy production.

“The biggest problem is that you don’t generate more energy than you consume”, says Vinícius Njaim Duarte, a researcher at the Plasma Physics Laboratory at Princeton University, in the United States. In other words, the energy used to put the fusion reactors into operation is greater than the energy generated in the reaction.

In August of this year, from fusion, scientists managed to produce 10 quadrillion watts, in a point the size of a human hair, per 100 trillionths of a second. To do this, they bombarded a hydrogen plate with more than a hundred lasers.

This specific initiative, however, has no energy purpose, warns Njaim Duarte. The purpose of the Lawrence Livermore National Laboratory’s program at the National Ignition Facility in the US is military, in search of new weapons.

But, back to peaceful applications, another problem is how little time researchers are able to maintain the reaction. For large-scale power generation, of course, it would be necessary for the process to be more durable.

In June of this year, the Chinese reactor East (Experimental Advanced Superconducting Tokamak) announced that it had set a record: maintaining the plasma flow for 101 seconds at 120 million degrees Celsius.

Besides the issue of time, there is also the problem of the raw material of the plasma. Two isotopes of hydrogen are needed, deuterium and tritium.

Deuterium is an isotope widely available in Earth’s oceans. According to the Princeton researcher, the reservoir is virtually inexhaustible. But tritium is practically non-existent.

“There is no longer tritium in nature, anywhere in the Universe”, says Gustavo Canal, a researcher at USP at the plasma physics laboratory. The element is radioactive and has a half-life (generally, the time it takes for the amount of the substance to decay by half) of only 12 years.

For the production of tritium, it is necessary to bombard lithium with neutrons, an extra step in the production of energy from fusion.

“Very high”, “huge”, “millions”, “quadillions”, substances that don’t exist. The descriptions already give an idea of ​​the level of complexity of the process. And, with nuclear accidents that have marked the last few decades, grandiloquent descriptions can also sound like a warning of risk.

But in addition to the promise of clean energy, fusion brings with it a guarantee of safety, experts say.

Any problem in the process, contrary to what one might imagine from an experiment with so many superlatives, would only result in the complex reaction being interrupted.


Fusion is now typically developed in machinery known as a tokamak. It is where, in a vacuum, heat and magnetic fields conduct the deuterium and lithium soup, preventing the particles from colliding with the walls.

When the fusion takes place, neutrons break free and, yes, they have to collide with the walls. The energy contained in this shock is transformed into heat, which heats water, which in turn evaporates and turns turbines, which then generate electrical energy —mechanisms already used in thermoelectric plants.

There are other machines with different tokamak settings, but the essence is the same.

The test, perhaps definitive, of the viability of fusion for energy production is almost ready in France, thanks to a group of more than 30 countries that are looking for the way. “The way”, in Latin: Iter.

The colossal tokamak Iter, at a cost of around US$20 billion, has big ambitions: to be the first in which the fusion produces more energy than it consumes and the first to run for long periods, two of the problems mentioned above.

The joint international work to carry out the project, which began in Cold War plans for collaboration between the US and the Soviet Union, ends up, in the current scenario, finding an echo in the universal efforts of nations —which at least should happen— to contain the crisis climate.

Logically, the structure of a tokamak also needs to withstand the hurdle of nuclear fusion. And that’s where another issue comes in: the development of sufficiently resistant materials.

The hostility inside a fusion reactor is compared, by Duarte, to a spacecraft reentering the atmosphere. “The shuttle’s nose is small and it only needs to withstand the bombardment of particles for a few seconds. The ITER has to withstand twice as much bombardment per hour, for years.”

It does not stop there. During fusion, instabilities occur that generate filaments at the edges of the plasma, the ELMs (Edge-Localized Mode). Something comparable would be solar eruptions, says Canal, who studies exactly this phenomenon and is looking for answers to the problem with a tokamak at USP.

If in a normal fusion process the bombardment inside the tokamak is already extreme, ELMs can take the situation to unimaginable levels.

“We are working at the limit of the materials we know,” says Canal. “During an ELM, the bombing value goes up exorbitantly, it’s an order of magnitude above what the materials support.”

ITER is already about 75% ready, and the first plasma should run through the device as early as 2025, if the projections hold up.

Although all this technology seems to be a distant future, the Princeton researcher points out that there is already enough private money being invested in the merger, which would suggest that stronger results may be closer than imagined. Among the merger’s investors are Google, Bill Gates and Jeff Bezos.

“Developed countries have realized that the future is fusion”, completes the scientist from USP, pointing out the state investments in the area. Canal also says it is seeking, within Brazil, partnerships with companies to support the national merger project.

“The domain of fusion will be a milestone of civilization”, sums up Duarte, although clean energy, he ponders, will not be enough to solve all the world’s problems.


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