This Fusion Fuel Experiment Will Bring Us One Step Closer to Ignition

Den W. Den W. 17 May
This Fusion Fuel Experiment Will Bring Us One Step Closer to Ignition

If you hear the word ITER and think food, well...you’re not exactly wrong. ITER actually refers to the International Thermonuclear Experimental Reactor, but where you’d be right about the food part is a long-awaited experiment. This is currently testing the fuel that ITER needs to gobble up to hopefully get us that one step closer to the ever-elusive temptress of fusion ignition.

If you’re new to the world of nuclear fusion, welcome to the decades-long waiting party. See, nuclear fission is what most of us are more familiar with: it’s when atoms are split apart to create huge amounts of energy. But fusion is the fusing of two atoms, which releases an energy yield several times greater than fission.

Almost all fusion experiments work specifically on fusing hydrogen atoms to form helium. We’ve actually achieved fusion several times in a lab setting, using the most energetic lasers on Earth or alternatively, some of the world’s strongest magnets. But the key thing, the thing we’ve been chasing since fusion’s inception, is ignition. That’s the tipping point at which a fusion reaction starts to sustain itself, and we get more energy out of it than we put into creating it.

That’s the big dream of fusion ignition—it would produce a limitless supply of clean energy. But as you can imagine, heating hydrogen plasmas to 150 million degrees Celsius and then compressing and confining them down into states of matter even more extreme than what’s at the center of the Sun is...kinda hard.

There are private and nationally-funded facilities all over the world working toward this...and that’s where ITER comes in. It’s an international collaboration between its member states, and it will be the world’s largest-ever tokamak when it’s completed and begins experimenting around 2025. And if you’re wondering what a tokamak is, it’s a very specific donut-shaped set-up of magnetic and vacuum fields that can create the extreme conditions necessary for nuclear fusion.

So, how do you test the most advanced facility of its kind...before it opens for experiments? Well, JET to the rescue! The Joint European Torus is a EUROfusion research facility that opened in 1983.

Being a tokamak itself, JET has been the proving ground for all things tokamak fusion. It’s the perfectly scaled-down version of ITER, 1/10th the size— essentially, JET walked so that ITER can fly.

JET will prove useful once again by testing out ITER’s fuel— kinda like a bodyguard tasting a royal’s food to make sure it’s not poisoned.

The fuel mix is deuterium and tritium, two heavy versions of hydrogen that are typically used as the ingredients that get smashed together to produce helium — and all that energy. And I say ITER is the royal in that relationship because it’s the facility many experts around the world think has the best shot of actually achieving fusion ignition.

It’s the culmination of many, many decades of fine-tuning all this complex science. But JET needs to test-run ITER’s fuel mix because tritium decays super freaking fast, so it’s both really rare in nature and is more difficult to work with than deuterium. In fact, tritium is so rare that the world's supply is just 20 kilograms, produced as a byproduct of nuclear reactors. So, many experiments don’t use it at all, and instead only use deuterium smashed into deuterium. Plus, tritium has that extra neutron — that means it produces more neutrons during a reaction than just deuterium does. So, when used by itself or in a 50:50 mix...we get a heck of a lot of neutrons to contend with. These can interfere with or damage the tools that help scientists see what’s actually going on.

The newest generation of scientists who are working on this experiment...have probably never worked with tritium before this. But that tricky extra neutron also means a high potential energy yield, much higher than just deuterium and deuterium. In fact, tritium is so rare that the world's supply to work with in experiments like this is just 20 kilograms, produced as a byproduct of nuclear reactors. So, many experiments don’t use it at all, and instead only use deuterium smashed into deuterium. Plus, tritium has that extra neutron — that means it produces more neutrons during a reaction than just deuterium does. So, when used by itself or in a 50:50 mix...we get a heck of a lot of neutrons to contend with. These can interfere with or damage the tools that help scientists see what’s actually going on inside a fusion reaction.

The newest generation of scientists who are working on this experiment...have probably never worked with tritium before. But that tricky extra neutron also means a high potential energy yield, much higher than just deuterium and deuterium. So, one key goal of these experiments at JET is to understand how adding tritium to the mix will affect the plasma dynamics of a D&T reaction when it’s actually happening inside ITER. And also, this is just a fun fac t— but when experiments with tritium start at ITER, all those extra neutrons that are produced will actually be used to make more tritium for future experiments, which I think is so cool.

All of this exciting work at JET means that we’ll be able to make the most of ITER’s capabilities as soon as it’s ready and make sure the new experiments don’t wreck any of that specialist equipment we spent so long getting right as soon as it comes online. Because who knows? Maybe this is the decade that the dream of fusion ignition comes to fruition. 

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