What is nuclear fusion and could it be the answer to all our clean energy needs?

Scientists in California have achieved a significant breakthrough but there is still a long road ahead before could power our homes

I hear we’re getting nuclear fusion, but what is it?

Put simply, it is the process that gives the sun and other stars their energy. And from there on it really gets as complicated as you like. Essentially, pairs of atoms are heated and smashed together to form a single heavier one. When you can do that, you release a huge amount of energy. Fusion reactions have proved difficult to sustain over long periods because of the sheer amount of pressure and temperature required to join the nuclei together.

Oh, I thought we already had that.

No, we have nuclear fission, which is kind of the opposite. That is where heavy atoms are split apart, the process by which the nuclear power stations we are so used to today generate electricity. Both yield millions of times more energy than other sources through nuclear reactions but fusion would be much “cleaner” than fission in terms of the waste products it generates. In nuclear power plants, uranium and plutonium are most commonly used because they are easy to initiate and control.

Well, if fusion trumps fission, then why not go for fusion?

Why not, indeed? Researchers have been attempting to do this for a long time, about 70 years, with some sporadic progress, but it is an immense engineering and scientific challenge.

So what has changed?

A major breakthrough. Earlier this month, scientists at the Lawrence Livermore National Laboratory in California briefly achieved a net energy gain in a fusion experiment using lasers, for the very first time. Through a complicated process, they focused a laser on a target of fuel to fuse two light atoms into a denser one, releasing energy.


You say fusion, I say fission – what does it all really mean anyway?

It could potentially mean a lot. While different parts of the scientific community have different views on its actual significance, it is no doubt significant. It is a scientific proof, the first important step in showing the world that a clean, endless supply of energy is obtainable. That would have massive implications for a planet in the throes of global warming, desperate to be rid of fossil fuels.

So how far away are we from that?

That is now the question, and one that divides scientific opinion, but in short, a very long time. Decades. Reacting to the news this week, Professor Ronan McNulty, a physicist at University College Dublin, said that while it was encouraging, expectations should remain reasonable.

“Fusion as a viable energy source will not be available tomorrow or even in five years’ time. However, in the long-term, I think it is the ultimate solution to obtaining clean and limitless energy.”

Jeremy Chittenden, professor of plasma physics at Imperial College London, said anyone in the field “would be quick to point out that there is still a long way to go from demonstrating energy gain to getting to wall-plug efficiency where the energy coming from a fusion reactor exceeds its electrical energy input required to run the reactor”.

Why so long?

Engineering and investment, basically. Now we know we can do it, it needs to be done, but that will take time. The good news, though, is that this month’s breakthrough is expected to kickstart investment in the technology.

According to Bloomberg, investors are on track to put in more than $1 billion this year. That is down on the more than $2.6 billion last year but almost three times the 2020 level. Given that this crucial research step has demonstrated it may eventually be possible to build a commercial fusion power plant, that investment is likely to gain momentum.

Mark Hilliard

Mark Hilliard

Mark Hilliard is a reporter with The Irish Times