Nuclear fusion has long been the Holy Grail of energy production. It has, for some people, been seen as an impossible dream, and one that will never be achieved.
Now a team of scientists at a laboratory in the UK has something to say about that.
First, what is fusion?
Fusion powers the Sun and stars as hydrogen atoms fuse together to form helium, and matter is converted into energy. Hydrogen, heated to very high temperatures changes from a gas to a plasma in which the negatively-charged electrons are separated from the positively-charged atomic nuclei (ions). Normally, fusion is not possible because the strongly repulsive electrostatic forces between the positively charged nuclei prevent them from getting close enough together to collide and for fusion to occur. However, if the conditions are such that the nuclei can overcome the electrostatic forces to the extent that they can come within a very close range of each other, then the attractive nuclear force (which binds protons and neutrons together in atomic nuclei) between the nuclei will outweigh the repulsive (electrostatic) force, allowing the nuclei to fuse together. Such conditions can occur when the temperature increases, causing the ions to move faster and eventually reach speeds high enough to bring the ions close enough together. The nuclei can then fuse, causing a release of energy.
The sun is able to produce the right conditions due to the massive gravitational forces involved, but this is somewhat harder to achieve on Earth, for we are just a tiny blue dot in comparison.
But if it can be achieved, the potential is huge.
Where the sun, with the gravitational forces it has, can achieve fusion at a mere 10 million degrees Celsius, on Earth the temperatures need to be much higher—around 100 million degrees Celsius:
Fusion fuel – different isotopes of hydrogen – must be heated to extreme temperatures of the order of 50 million degrees Celsius, and must be kept stable under intense pressure, hence dense enough and confined for long enough to allow the nuclei to fuse. The aim of the controlled fusion research program is to achieve ‘ignition’, which occurs when enough fusion reactions take place for the process to become self-sustaining, with fresh fuel then being added to continue it. Once ignition is achieved, there is net energy yield – about four times as much as with nuclear fission. According to the Massachusetts Institute of Technology (MIT), the amount of power produced increases with the square of the pressure, so doubling the pressure leads to a fourfold increase in energy production.
Different laboratories, teams, and scientists have been working incredibly hard to make the breakthroughs hoped for in getting the ball rolling. But successes have been few and far between.
JET laboratory (Joint European Torus), however, has just smashed its own world record for the amount of energy extracted by fusing two forms of hydrogen (deuterium and tritium). They have just been able to produce 59 megajoules of energy over five seconds (11 megawatts of power), which is the equivalent of boiling 60 kettles at once.
This may sound like small fry, but it represents a massive leap for the science of nuclear fusion and hints that large-scale fusion reactors might not be just a pipe dream.
And whilst 5 seconds doesn’t sound long, this is something to shout about. As Dr. Arthur Turrell, the author of The Star Builders: Nuclear Fusion And The Race To Power The Planet, told the BBC:
“It’s a landmark because they demonstrated stability of the plasma over five seconds. That doesn’t sound very long, but on a nuclear timescale, it’s a very, very long time indeed. And it’s very easy then to go from five seconds to five minutes, or five hours, or even longer.”
Indeed, JET can only run the experiments for that long because the electromagnets get too hot.
Traditionally, a further issue has been that the pay-off has not justified the amount of energy required to start the fusion process. JET has been using two 500-megawatt flywheels to run their experiments. There is good evidence to suggest, though, that when the plasma is scaled up, the deficit can be overcome.
Other than the sheer volume of energy output that could be achieved, the benefits of fusion are that it produces no greenhouse gases and only tiny amounts of very short-lived radioactive waste. That’s a win-win in comparative terms.
The head of operations at JET, Dr. Joe Milnes, admitted, “The JET experiments put us a step closer to fusion power. We’ve demonstrated that we can create a mini star inside of our machine and hold it there for five seconds and get high performance, which really takes us into a new realm.”
Another reason that this new achievement has a lot of significance is that a big fusion reactor is now being built in France. The EU, the US, China, and Russia are pooling resources to support the construction of the ITER facility in southern France. If this experiment hadn’t worked, then the project would probably have been doomed to failure.
“These experiments we’ve just completed had to work. If they hadn’t then we’d have real concerns about whether ITER could meet its goals,” said JET CEO Prof Ian Chapman. “This was high stakes and the fact that we achieved what we did was down to the brilliance of people and their trust in the scientific endeavor.”
ITER have special internally cooled electromagnets that can operate longer than the 5 seconds involved with the JET experiments. But even then, after scaling up, the thought is that ITER will break even in terms of input and output energy. After this, as is often the way, the commercial sector will come in and stand on the shoulders of the research and development of the previous century to produce a net gain.
Due to the fact that no material exists that can withstand such high temperatures, the solution involves super-heated gas (plasma) being held inside a donut-shaped magnetic field.
Although this sort of work gives us great hope for combatting climate change, the reality is that commercialization would be at least 20 years away, and even then it would need to be scaled up. The results of this would then only come about further decades into the future. But for the long run, this is looking good. It could well solve our power problems in the latter half of this century, even if it won’t solve our climate challenges before then.