Nuclear Fusion Illusion. Is it time to park the pipe dream?

Nuclear fusion promises to provide unlimited, cheap, safe energy for the future of humankind. It's a lofty goal and it's easy to see why so much research funding has been ploughed into the endeavour over the last three decades. But are the latest "breakthroughs" really as good as they're made out to be, or are we deluding ourselves if we think this technology will have any impact on our global energy challenge?

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Research Links

Original Research by Steven Krivit

Sabine Hossenfelder's video based on Steven Krivit's research

ITER

JET

EAST

NIF

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[NotJustBikes]

Great video. I actually studied this stuff in university, and I have been frustrated for years at how poor the reporting has been from science journalists around the efficiency of fusion. I am very fed up with articles quoting Q-fusion numbers, when literally the only thing that matters is Q-total.

I get that fusion researchers are focusing on Q-fusion, because that's their line of research, and they don't have much control around Q-total, because it involves systems that they don't necessarily build. Maybe somebody else can come up with huge efficiencies in lasers, superconducting magnets, or heat-to-electricity conversion, and these would reduce Q-total without the fusion researchers needing to do anything differently.

But I think at this point, any time a science journalist reports on fusion and quotes Q-fusion instead of Q-total it should be considered journalistic malpractice. It's really not acceptable to keep repeating this misleading term.

Now, I'll leave you with one fun fact about fusion: our sun is not actually hot enough to fuse hydrogen into helium. The only reason it does is because quantum physics is "fuzzy", and there are outliers in any reaction at a quantum level. Just as an electron can "tunnel" through a solid "wall", nuclear fusion can happen at lower temperatures if there is such an insane number of atoms available that even a very low percentage of outliers can fuse. So these reactors on Earth need to be _hotter_ than the sun, because the only reason the sun can fuse elements is because there's a sun's worth of atoms in there.

[brett]

We've made progress. When I was young, the joke was, "Nuclear fusion is only FIFTY years away." (Not "twenty")

[kentw.england]

As an expensively trained nuclear physicist who teaches others at great expense to be nuclear physicists, I support fusion research because I can't make a latte to save my life.

[apoema]

As an economist, I feel that the economy aspect of fusion is often forgotten. Fusion not only have to be technically viable but economically viable. If we are struggling to make it break even in terms of energy it is incredibly hard to imagine that it will eventually be more economical than just getting energy from the sun, wind and water.

[Scrogan]

I would also mention the response video to Sabine’s nuclear fusion video. One of the main points presented in the response is that most efforts have been solely towards improving Q plasma because it’s much more unknown then the rest of it. Once Q plasma is significantly over 1, the rest of the system can be refined. Like using high efficiency lasers for the inertial confinement fusion.

Magnetic confinement fusion is also mainly an issue of scale. By doubling the size of a tokamak you multiply the amount of plasma (and hence its power) by a factor of 8, but the required cooling and confinement powers scale only by 4. So once we understand how a unity gain plasma acts (the express intention of ITER), we can design a fusion reactor that will definitely have overunity wall plug efficiency. Science is an iterative process.

Though personally I’m more of a mind to follow the high-temperature superconducting magnets of MIT’s SPARC reactor, as the magnetic field can be a lot stronger and make the required tokamak a lot smaller. As we’ve seen with ITER, the logistics of making such a large tokamak are very challenging. But the materials science of making a high temperature superconductor into a durable wire is also challenging. Either way, it will be a while before anything is built that can easily pay for itself, even with overunity, but it will almost certainly happen. I’d give it 50 years max.

[mute]

A minor nitpick, but what we aim to achieve is not replicating processes going on in the Sun. Nuclear fusion in stars is very slow, with only one pair of atoms out of many many billions accidentally fusing and releasing a bit of energy. Any human fusion reactor, on the other hand, would have to achieve conditions far more extreme than those in the middle of the sun, to force a significant amount of atoms to undergo fusion.

[jamesasimmons]

The reason fusion was out of reach for so long is that the material technology didn't exist to make it possible. The most important factor to achieve fusion is the strength of the magnet field. The power output is to the fourth power which means if you double the field strength you get 16 times the output. The reason I have little hope for ITER is it used 400 ton 11.8 telsa strength super conduction magnets made from Nb3Sn / NiTi that require cooling to 4 K (-269 C). Compare this to the SPARC reactor at MIT which with it 10 ton YBCO cooled to 77 K produced a 20 telsa field this January. This means the SPARC reactor can achieve 16 times the output of power output with 2.5% the material and the far cheaper cooling cost of liquid nitrogen verses helium. Their are other good design elements of the SPARC reactor like its modular design, use of lithium salts, etc that I can't go over due to space limitations here.

[AdrianJamesEllis]

Another interesting problem I heard from a postgrad student at JET was that the high energy particles tended to pulverise the steel framework of the tokomac. It does make me wonder why so little effort is made with thorium salt reactors, when so much is spent on fusion.

[jbjefe]

Couldn't help but notice you chose a picture of windmills, but I can't help but think we need to focus on nuclear reactors, and the addition of thorium looks like a great solution.

We now have small modular nuclear reactors in production, and several new designs. We could have dozens of those up and running in 10 years. Granted not as fast as wind and solar, but more reliable less destructive, and way more bang for the buck.

If we could get really small with these designs, I think that would be great, let's decentralize the grid as much as possible. It makes us extremely vulnerable.

[davidf]

I think the current approach looks broadly correct: society has essentially stuck fusion development on a background thread and is getting on with other stuff in the meantime. The billions spent so far look to me almost nothing over the timescales we're talking about.

[sclemmen]

There might be a misunderstanding here. The current reactors (ITER as most obvious example) are simply not meant to have a large total Q yet. I think increasing the "out-of-plasma-Q" is supposed to be less demanding. Eventually, the energy lost at various places (say the heating of a laser for instance) can eventually serve as heat to warm up water, create steam, --> electricity. It remains to be seen to what degree this can indeed be fixed. 
Tritium is certainly a problem.
The scale (and time for deployment) of a project like ITER is also a problem.

[gbulmer]

A very good, unusually realistic, balanced presentation. Well done, Sir. However, you didn't mention another issue which fusion reactor proponents omit. *Neutron Embrittlement.* Nuclear fusion creates enormous quantities of neutrons, which are unaffected by magnetic containment. Those neutrons smash into the walls of the vacuum vessel†, actively destroying the material. Published estimates posit refurbishment every two years of the vacuum vessel.

Remember, the vacuum vessel is the 'core' of the fusion reactor, so removing it is not trivial. The now radio-active vacuum vessel will have to be safely disassembled, and removed. Then a new vacuum vessel installed, tested and commissioned, before it can go back to generating electricity. The suggestion I read was that process might be measured in months. Plus, there is the issue of safely 'disposing' of the radio active vacuum vessel material
.
I don't think this is a 'nit pick', though I think you did a much better analysis than any fusion reactor proponent I've seen, and I've been following fusion research since the mid/late '80s.

Again, very good, worthwhile video. Plus your balanced analysis is, sadly, rare in these highly polarised times.
Best Wishes to 'You and Yours' for 2022. ☮️

[davesutherland]

For the commenters that think we are getting close to a real breakthrough, ITER is going to start plasma testing in 2035, 50 years after planning started. If successful it will point to the next generation reactor, but you can only start planning that after ITER data reviews the critical design parameters. I can’t see that happening before 5 to 10 years of operation. Then you build the high Q reactor where the Q-total has to be high enough to make the excess power commercially viable. How long will that be - the elusive 20 years (but start counting in 2045) or, like ITER, another 50 years? Now you have to build a prototype reactor that generates power to show it really works - I think you will have a tough time raising 10’s to 100’s of billions of dollars for commercial reactors before proving the technology will work for power generation. So optimistically you are talking two 30 year cycles (20 years design, 10 years operational testing) and 20 years to get the first commercial reactors up and going. Starting at 2045, that brings you to 2135. If there the next generation cycles take longer or requires extra design iterations, you will be into 2200’s or 2300’s. In that time there are a multitude of currently existing technologies that will have made huge advancements.

As many commenters have pointed out there are other fusion options beyond magnetic confinement and laser inertial confinement. But, these are all relatively early in development. While a breakthrough is possible, any one who has worked in advance science or engineering knows that the timing of breakthroughs can not be predicted, and there are more breakdowns than breakthroughs.

[LKemp-lrky]

BRAVO!! Some 50 years ago--whilst in school--our science instructor excitedly burst into the room and excitedly announced that fusion had been accomplished! I knew it was baloney at the time, however supercalifragic it would have been. We are all, understandably, emotionally sitting on edge.😒

[certhass]

something a lot of ppl always seem to forget when they talk about ITER or almost any other _research_ fusion reactor is the fact that they are designed for fundamental reasearch and finetune the fusion process. they are not ment to produce more power than they need to be run.

[asgerms]

I wish people would not judge fusion based on a list of single points and then doing some kind of "layman's sum" in their head. Perhaps only consider the reluctance to spend ~$20B on ITER (over decades) while society will happily spend ~$14B on 3 weeks of Tokyo olympics. The thing is, the whole success matrix is so complicated that you just cannot hold it in your head. Human brains are worthless in taking exponential factors into account. Such as improved superconductors influence on Qtotal, ability to do fast low-bureaucracy single-site solutions, etc. My 2 cents. Forget fusion saving us from greenhouse effect but also keep encouraging + funding them (they are a bargain).

[TroggyPB]

For info. Way before Moby used the Stardust reference it was made by Joni Mitchell in her classic song Woodstock made famous by Crosby Stills Nash. 1969

[Mr_Stone]

I agree that both energy research and renewable energy production are underfunded, but I would rather they reroute current fossil subsidies than cannibalise either. We need both.

[Natabus]

Having to maintain staggeringly hot plasma in such close proximity to staggeringly cold superconducting magnets, and then having to insert yourself between the two to utilize the heat, has always struck me as being stuck in a cage fight with Maxwell's Demon.

[JonMartinYXD]

This video perfectly expresses my frustration with the fusion power movement. It allows people to avoid any change because fusion is just over the horizon and is going to solve all our problems. Why invest in renewables, fusion is just around the corner! Why change our lifestyles to reduce carbon emissions, fusion will come to the rescue! Why build small modular fission reactors, fusion will make them obsolete any day now! I fear that one day we will look back on our fusion efforts and see a tragic misprioritization of funding and talent.