Even though the cost of solar and wind is dropping, renewables might not be sufficient to meet our clean energy demand in the future. However, nuclear power can play a key role in the decarbonization of the energy sector.1 And I’m not talking about nuclear fission. Rather, quite the opposite. Yes, I’m talking about fusion, with it’s perpetual, 30-years-away target. But before you blow your fuse and start leaving your fusion jokes in the comments, there’s been a major fusion development we have to talk about and it’s kind of a nuclear bombshell … poor choice of words … it’s big news …

A catch up on nuclear power

I had a chance to speak to Dr. Martin Greenwald, a Deputy Director and Senior Research Scientist at MIT, who’s part of the team that achieved a pretty big fusion milestone. Before bursting out with the recent breakthrough on nuclear fusion though, it’s a good idea to take a step back and have a quick recap on nuclear power.2 Don’t worry, I’ll keep it high-level as I don’t want burn out your brain … or mine.

You can get nuclear energy through two processes: fission and fusion.3 Nuclear fission reactors are what we see used around the world today. In a fission reactor, you blast a neutron into an unstable Uranium-235 atom to split it into smaller fragments, including more neutrons. These new particles will hit other Uranium-235 atoms, which generates a chain reaction effect. The breakdown of the Uranium isotope releases energy in the form of heat, which is then used to vaporize water. The resulting steam can then be used to power a turbine to generate electricity.

What is fusion?

As the name suggests, the fusion process is basically the opposite of fission. Instead of splitting, we’re putting things together. A fusion reactor replicates what happens naturally within the suns core, where hydrogen isotopes split and then merge into helium nuclei under astronomical temperatures and pressures. In this case, the fusion reaction produces 4 times more energy than what’s obtained through the fission process.4

Instead of using uranium or plutonium, which both release long-lived radioactive particles, you feed hydrogen isotopes like Deuterium and Tritium into a fusion reactor. Deuterium is a stable element and Tritium radioactivity doesn’t last long.56 Besides being safer and more eco-friendly, the fusion fuel sources are more abundant and cheaper than fission fuels. That’s because you can extract Deuterium from seawater, while you can get Tritium during the fusion reaction itself when neutrons interact with elements like lithium. Or as Dr. Greenwald put it:

“It’s a potentially ideal source of energy. First of all, the fuel is essentially unlimited.”

“And it’s, it’s extremely energy, energy density form of fuel. So a tenth of a gram of deuterium and three tenths of a gram of lithium, if fused in a power plant would make enough electricity for an average American for a year, a full year. And those few tenths of a gram you wouldn’t need, if it was in your pocket, you wouldn’t even notice it. It’s like lint or something like that.” -Dr. Martin Greenwald

The benefits over fission

Fusions potential benefits over fission aren’t just about higher energy production and fuel energy density though. One of the biggest, is probably one you’ve thought of. The by-products of fission are highly radioactive and, if not appropriately controlled, can contaminate the planet for decades. On top of that, fission’s chain reaction can degenerate and can potentially get out of control causing a nuclear meltdown or explosion, which is what happened in Fukushima in 2011 after the tsunami hit the power plant and caused a series of failures.7

This type of incident wouldn’t happen in a tokamak, which is based on magnetic-confinement fusion (MCF). A tokamak is a doughnut-shaped chamber where you heat hydrogen isotopes up to 150 million degrees. I don’t know about you, but this isn’t the type of reactor I want Homer Simpson in charge of. At such a high temperature, the atoms are stripped of their electrons and turn into ions. You’re then left with a superheated ionized gas, which is plasma.8 Under these conditions the charged particles collide and fuse together … just like in the sun.

Another safety net for fusion is that you can stop the reaction just by cutting off the fuel supply.9 In nuclear fission, that’s not the case.

“It can’t melt down the way a fission plant can. It doesn’t have the same kind of waste materials. So, it has all these advantages. The other thing is it doesn’t use a lot of land, a lot of water. It’s a very good compliment to renewables.”

“…it could be used as a process heat for industry. It would be relatively straightforward in certain industries like making cement.” -Dr. Martin Greenwald

Fusion challenges

So based on all that, let’s go for fusion … we’ve got our winner. That’d be great, but that’s where the running joke of fusion always being 30 years away comes in. Nobody has produced a fully functional fusion power reactor yet. Why? Well, it takes an insane amount of energy to produce the heated plasma, so right now the power you put into a fusion reaction is always higher than the thermal power that you get out of it. To assess how well a reactor performs is referred to as the “fusion energy gain factor” or the symbol Q with a ratio.10 Basically, you want a Q value higher than 1, which is that thermal power breakeven point within the reactor. But we’re not even close to breakeven. The Joint European Torus (JET) held a record ratio at 0.67,11, but the National Ignition Facility (NIF) just recently broke that with a Q of 0.7.12 But it’s really important to note that Q isn’t accounting for the full power and electricity required to run the facility and how much electricity it can actually generate from the reaction. Q is just about the thermal power in versus thermal power out. For the full picture, that accounts for all of those additional energy costs and converting heat into electricity … basically, producing more electricity than it takes to run the facility … we’d most likely be looking at a Q somewhere between 10 and 25. There’s a lot of moving pieces. We have to learn to walk before we can run and hitting a Q of 1 or higher is us learning to walk. That’s why at this phase of fusion research, everyone focuses on the Q ratio just for the plasma reaction itself. Once we hit that, the focus will shift towards overall power gain.

In 2025, the massive international fusion project known as ITER is supposed to start producing superhot plasma with a Q greater than 10 in France. Even though the project was born in the 1980s, construction of the tokamak only started in 2007.13 Once it’s complete, ITER will be the world’s largest fusion rig, which isn’t necessarily a good thing. Due to its size and scope it’s taking a long time and tens of billions of dollars to build.14 Plus, it’s designed to be a testing facility and not a working reactor … and won’t reach full operation until 2035.15 So even if it’s 100% successful, we still need to go through the process of then building out the final working reactor design. Now, I know that sounds a lot like we’re still 30 years away from having a fully operational fusion reactor. But there has been some electrifying breakthroughs recently from smaller and more nimble approaches, like what Dr. Greenwald has been working on.


One of the biggest challenges with MCF fusion reactors is the incredible magnetic field they have to generate to contain the plasma. Massive magnets ringing the rig, or the doughnut, create an intense magnetic field. This invisible bubble traps the blistering hot and electrically charged slurry in midair near center of the reactor. Being kept away from the rig walls, the plasma won’t melt them.16

And just this September we found out that 2021 is going out with a nuclear fusion bang. The Massachusetts Institute of Technology (MIT) along with the Commonwealth Fusion Systems start-up (CFS)17, designed one of the most powerful magnets ever created on Earth.18 This joint experiment hit on something extremely important. Managing to generate an incredible magnetic field with far less power. To achieve this milestone they used something called a high temperature superconductor (HTS).

The major innovation is actually not that new. Back in 2015, MIT proposed using this superconducting tape in their device design.19,20 I mean, a lot of it. The test magnet used 267 km (166 miles) of tape.21 This material retains superconductivity at high temperatures, which generates a more intense magnetic field. Martin gave me some really nice insights about this tape.

“The new material, the high temperature superconductor, which is really a ceramic like compound of rare earths and barium copper oxide, it’s a fairly fragile material, but people learned how to put it down as a thin film on a strong sub-structure” 

“It turns out there was a breakthrough in technology that we could take advantage of, that we weren’t responsible for. It was an invention discovery really by some IBM scientists working at a lab in Zurich in the ’80s and that was high temperature superconductors.”

“It didn’t really look like an engineering material, and a lot of people thought, well, this is really interesting scientifically but this will never be practical. You’d never be able to build a magnet or a wire out of this. But it had a lot of promise and we followed this very closely because we thought, well, this material could allow us to make a superconducting magnet that ran at high enough fields.” -Dr. Martin Greenwald

This is something I find fascinating about fusion development, and why it’s been taking so long. It’s taken decades to learn about new materials and techniques that can be applied to successfully controlling a fusion reaction at scale. Martin brought up a point that I hadn’t considered. The advantage of using this material wasn’t just making the magnet more powerful, but also more energy efficient.

“You can make great experiments and we’re able to get very high fields with copper magnets. But they consume an enormous amount of power.” -Dr. Martin Greenwald

So, that turned out to be a good deal as a stronger magnetic force translates into a 10 times greater power generated by the reactor. As a result, the MIT design is meant to achieve net energy gain in a much smaller unit.

“If you were able to go to higher fields, you can make the linear dimension smaller. You can shrink the size.” -Dr. Martin Greenwald

When you compare it to the ITER system, which uses low-temperature superconductors, the SPARC reactor MIT and CFS are designing is only 2% of its size. And that’s a significant reduction in construction cost and time. But does it work?

The big milestone that MIT and CFS just achieved in their recent test was putting together one full-sized magnet and running it through tests as if the full tokamak was built out. That test went extremely well … just how well?

“It reached a magnetic field of 20 tesla. That’s the unit we use. It’s not the highest field ever produced, or the highest field with HTS technology ever; those were produced in small magnets. But it’s the combination of the size and the field that really puts it in a class by itself.” -Dr. Martin Greenwald

The bottom line is that this test proved out the math and theory of Commonwealth Fusion Systems’ SPARC reactor design. This test was the final proof of concept they needed before moving on to the full build out.

“It worked very successfully and it really unlocked. It was the last piece of the puzzle to allow us to proceed. We’ve done work on the physics basis for this new experiment, and we published that about a year ago.” -Dr. Martin Greenwald

I don’t know about you, but I was…supercharged…when I heard all of this. And that’s not just based on Martin’s words. After 3 years of research, scientists nearly doubled the intensity of the field, which led to a tenfold increase in the power generation.22,23 That’s why the project leaders now herald this to be a key milestone for building a low-carbon24 energy-positive fusion reactor.25 MIT and CFS are now…aiming for the stars… In 2025 they will demonstrate SPARC, the world’s first demonstration fusion device that creates net energy output.

“Now we’ve just got to finalize the design and build the machine. And we hope that it’ll be operating by 2025, and producing fusion power shortly thereafter.” -Dr. Martin Greenwald

So, how much power are we talking about?

“What we use for our estimates of how it will perform is the same set of physics rules that are used for the ITER experiment.” -Dr. Martin Greenwald

Remember that ITER is predicted to have a Q greater than 10 and so does SPARC. To develop this…stellar…prototype, CFS has raised over $250 million.26

Next steps

You may see why this may…spark…a revolution in nuclear fusion that could drastically shrink the infamous 30-year window. This sounds amazing, right? But is there anything…bursting…the magnetic fusion bubble? Because of the compact SPARC design, you’ll have a greater power density, which means a higher heat load generated in the reactor core during the fusion process. That higher heat load makes managing the high temperatures a challenge.27 The structure surrounding the magnet needs to be kept cold enough to absorb the thermal stresses. But we won’t have to wait long to find out how well it handles that because in 4 years the SPARC test plant may be able to verify these technical features. In the meantime, the project leaders are planning a lot of work behind the scenes.

“Milestones now, they’re maybe less flashy: the completion of the first building, the completion of the test cell, arrivals of some major components. So they’re not going to be big flashy things, but very important for the project.” -Dr. Martin Greenwald

And there’s one thing I have to address. If you’ve been following fusion research, you’ll know that all of these fusion reactor tests are typical running for a few seconds at a time. That’s not necessarily an issue with fusion reactors in general, but it’s how these test devices are built to save on cost while they prove out key concepts.

“Those experiments often have very, very short pulse lengths. Due to the physics of the experiment.”

“I mean, the machines are not designed to be long pulsed. They would have to be considerably more expensive. There would be much more costs up front.” -Dr. Martin Greenwald

I can hear you already. Is fusion going to happen in our lifetime? It’s a tricky question but Martin’s words sound really encouraging.

“If we produce net power in a device which can demonstrably scale up, that will attract funding. It’ll basically change the narrative from fusion in 30 years always to, okay, this is real, and it would attract the kind of investment to start building out as an industry. ”

“So, that’s our hypothesis. We’re testing it. We have fairly audacious goals, but you kind of have to have audacious goals if you want to play in this particular arena.” -Dr. Martin Greenwald

The end of the fusion jokes?

I don’t know if we’re still going to be 30 years away from fusion in 4 years. Jokes aside, I believe a cheaper and safer nuclear power will be essential for the future of green energy. While there are still plenty of hurdles to overcome, this recent breakthrough proves that getting unlimited power from fusion may be a realistic and achievable goal sooner than you think.

  1. “Nuclear Power and the Clean Energy Transition: Scientific Forum ….” 22 Sept. 2020 ↩︎
  2. “The truth about nuclear fusion power – it’s coming – Undecided with ….” 28 Apr. 2020 ↩︎
  3. “Fission vs. Fusion – What’s the Difference? | Duke Energy.” 27 May. 2021 ↩︎
  4. “Advantages of fusion – ITER.” ↩︎
  5. “DOE Explains…Deuterium-Tritium Fusion Reactor Fuel.” ↩︎
  6. “Fuelling the Fusion Reaction – ITER.” ↩︎
  7. “Fukushima Daiichi Accident – World Nuclear Association.” ↩︎
  8. “Ionized Gas – an overview | ScienceDirect Topics.” ↩︎
  9. “Safety and Environment – ITER.” ↩︎
  10. “About: Fusion energy gain factor – DBpedia.” ↩︎
  11. “Milestones around the world – ITER.” ↩︎
  12. “National Lab Achieves Big Step in Fusion Research – EE Times.” 8 Aug. 2021 ↩︎
  13. “A Dream of Clean Energy at a Very High Price – The New York Times.” 27 Mar. 2017 ↩︎
  14. “A commercial path to fusion – Physics World.” 5 Aug. 2019 ↩︎
  15. “What is ITER?.” ↩︎
  16. “Why Nuclear Fusion Is Always 30 Years Away | Discover Magazine.” 23 Mar. 2016 ↩︎
  17. “Commonwealth Fusion Systems: Home.” ↩︎
  18. “MIT-designed project achieves major advance toward fusion energy.” ↩︎
  19. “A small, modular, efficient fusion plant | MIT News.” 10 Aug. 2015 ↩︎
  20. “A commercial path to fusion – Physics World.” 5 Aug. 2019 ↩︎
  21. “World’s strongest fusion magnet brings new power to … – New Atlas.” 8 Sept. 2021 ↩︎
  22. “A small, modular, efficient fusion plant | MIT News.” 10 Aug. 2015 ↩︎
  23. “A Star in a Bottle: The Quest for Commercial Fusion – YouTube.” 8 Sept. 2021 ↩︎
  24. “Is nuclear power zero-emission? No, but it isn’t high-emission either.” 20 May. 2015 ↩︎
  25. “A Star in a Bottle: The Quest for Commercial Fusion – YouTube.” 8 Sept. 2021 ↩︎
  26. “Fusion gets closer with successful test of new kind of magnet – CNBC.” 8 Sept. 2021 ↩︎
  27. “A commercial path to fusion – Physics World.” 5 Aug. 2019 ↩︎

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