A major breakthrough in nuclear fusion research


So this is the holy grail of nuclear fusion?

Not enough. Last week, scientists from the Joint European Torus (JET), a nuclear fusion research project based near Oxford, set a new world record for the most energy ever generated by a fusion experiment. The team of researchers from the 30-nation Eurofusion consortium, based at the Culham Center for Fusion Energy, produced 59 megajoules from a sustained reaction lasting five seconds.

That in itself isn’t a lot of energy: it’s about enough to boil 60 kettles full of water or to power a 60-watt light bulb for 11 days. Nor is it the long-awaited breakthrough in the history of nuclear fusion when, for the first time, fusion generates more energy than has been put in place. But what happened in Oxfordshire is still a major breakthrough, scientists say.

Why is this a breakthrough?

First, because it more than doubles the previous record, set in 1997. Second, because five seconds is “on a nuclear time scale, a very, very long time indeed,” says Dr Arthur Turrell, fusion expert. Maintaining this energy level and demonstrating the stability of the experimental plasma for five seconds is a big problem. According to the JET scientists, scaling up to five minutes or five hours should prove relatively easy. More importantly, however, the JET result is significant as a kind of proof of concept.

The method used by the JET team – including the hydrogen isotopes used and the materials used to build the doughnut-shaped experimental chamber (or “tokamak”) – validates the design choices and method for a reactor massively larger experimental one under construction in southern France.

This ITER project involves an international team of scientists from China, Russia and the United States, as well as Europe. If all goes well, scientists believe JET’s success means it’s likely that France’s reactor, ITER, could achieve that holy grail: nuclear fusion that releases more energy (ten times more, some say) than what is set up.

What exactly is nuclear fusion?

It’s the process of squeezing two forms of hydrogen together – under great pressure and incredibly high temperatures – to release excess energy from their nuclei.

Nuclear fusion should not be confused with nuclear fission, which involves splitting the unstable nucleus of a single atom into two, releasing large amounts of energy. Fission is the basis of all nuclear energy hitherto existing, as well as the bombs dropped on Hiroshima and Nagasaki.

Fusion is different. It involves the fusion of two nuclei of two separate lighter atoms (two isotopes of hydrogen) to create a new single nucleus of a heavier atom (helium) – a process which releases a large amount of energy.

Scientists realized about 100 years ago that this is the process that powers the Sun (and all stars) and is therefore ultimately responsible for the existence of our solar system and life on Earth. If it can be replicated on Earth, it could provide a clean, inexhaustible source of energy.

So why hasn’t it already been done?

The challenge is threefold. To achieve fusion, you need a very high temperature to give the hydrogen atoms enough energy to overcome the repulsion between the protons. This allows the electrons to be separated from the nuclei and the gas to become a plasma, potentially allowing fusion. In the Sun, this occurs at 15 million degrees Celsius. But on Earth, because it is not possible to replicate the extreme pressures of the Sun, it must be even higher, over 100 million.

Second, you need high enough plasma particle pressure and density for many collisions to actually occur.

Third, you need a way to hold the plasma in place long enough for fusion to occur. Scientists must solve all three problems simultaneously, while efficiently capturing the energy released.

What is the solution ?

Since the 1950s, nearly every effort to achieve this has involved a tokamak, a Soviet invention which is a doughnut-shaped vessel in which two isotopes of hydrogen (deuterium and tritium) are superheated in a plasma held in place by a magnetic magnet. cage inside a vacuum. JET is currently the largest tokamak in the world; ITER will be ten times larger.

But this so-called “magnetic confinement fusion” (MCF) method is not the only possibility. The other main option being investigated is “inertial confinement fusion” (ICF), which uses powerful lasers to implode pellets containing hydrogen atoms and then compress that fuel (to much higher pressures than is possible with tokamaks) to the melting point.

Last August, the US National Ignition Facility, a laser-based inertial confinement research institute in Livermore, California, came closest to achieving a net energy gain (it released 70 units of energy for 100 entries). A third possible method being investigated is “magnetized target fusion” (MTF), which would use electrical pulses to create plasma and then steam pistons to compress it.

Which companies to watch?

The vast sums and decades-long timelines involved in fusion research mean that large projects are supported by the state. But there are plenty of exciting private companies working on fusion – mostly in the laser and MTF fields – and attracted around $4 billion in investment funding last year. I

n December, the American start-up Commonwealth Fusion Systems secured $1.8 billion from backers such as Bill Gates and George Soros; a few weeks earlier, rival Helion had raised $500 million from the investment vehicle of Peter Thiel, among others. Other companies in the sector include TAE Technologies in California, Zap Energy and General Fusion in Canada.

In the UK, First Light Fusion and Tokamak Energy are both based near Culham, where the Culham Center for Fusion Energy’s own reactor, due to open in 2040, is set to demonstrate the business side of fusion.

In Germany, Marvel Fusion has attracted investment from Siemens and Thales, among others.


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