One of my hobbyhorses. This page largely obsoletes both ITER etc and the problem with D-T but there is a lot going on. so you may like to look at those pages too for slightly different approaches.
Or see The Challenge of Fusion Power for a more recent attempt at the most important points (but not all of them by any means)
And it is probably equally unpopular. And while it's not part of the nuclear homework project, if you interested in either you will probably be interested in both.
I spend a lot of time on Quora, particularly discussing energy issues. A little less than I used to as one of the most prominent anti-nuclear campaigners there has now blocked me. He doesn't want to know, and he doesn't want you to know either. Which is interesting in itself, and I expect more of it and so should you.
One of the often-repeated questions there is whether or not fusion power is just around the corner and will solve all of our energy problems. Or sometimes that is asked in the negative, as in, why isn't it here already? There is often an expectation that it is almost with us. And that particular myth has been around for more than fifty years now, as is also pointed out from time to time at Quora, as have several other myths, some not for quite so long but all of them persistent and recurring.
So rather than repeating myself, I have set up this page and will link to it in future. It's hosted on a freemium site and will probably be deleted about 13 months after my death or incapacity to update it (which I hope is not to be soon but you never know), so if you'd like to archive it (with attribution please) then please do.
And watch this space, and maybe re-archive it whenever there's some more content. Or even when I correct any mistakes it may still contain. Yes, I do make mistakes.
In some ways this faith in fusion is very encouraging. Because, if only people would start asking the right questions, they would be (often reluctantly) forced to the conclusion that however good they think fusion is, fission is even better. You can lead a horse to water...
But of course not just any sort of fission reactor. Some nukes are better than others.
Or you could say it the other way around of course. However bad you think fission is, fusion is worse. I know that's not what you've been told.
So let us look at some of these specific myths. Such as
- The reaction... can fusion reactors use the reaction that makes the Sun hot?
- The easy problems... bombs, wastes, accidents, economics...
- The hard problem... those pesky neutrons.
- The little matter of fission products... yes, fusion does produce them!
- The puzzle... why are so many people so keen on it?
- The politics... the biggest lie of all, not surprisingly perhaps.
- The need... there isn't one, which is probably the biggest problem of all.
- The goals of ITER... now this is a real doozy...
The reaction
Myth: ITER and HL-2M and similar experiments will use the reaction that makes the Sun hot.
Reality: These reactors use Deuterium-Tritium_fusion, the reaction that is used in thermonuclear weapons.
The Sun uses the Proton - proton_chain_reaction. Larger stars use the CNO_cycle. Both of these are far too slow to use in a power station smaller than a star.
And we can't of course build a power station the size of a star. But this may give a hint as to why, even using D+T, the experiments are getting bigger and bigger.
But even these experiments are not trying to put the Sun into a box. They say they are just to piggy-back on the street cred of solar power. But what they are trying to put in the box is actually more like an H-bomb than the Sun. You can understand why they prefer not to say that.
To say or imply (as the HL-2M site has from time to time) that your tokamak is an artificial Sun or that D+T powers stars is a bit like saying that you've invented a diesel engine that can use water as fuel. And people have said that too from time to time, and others have fallen for it. Yes, really!
Don't be one of them.
The easy problems
Myth: Fusion reactors don't suffer the problems of fission reactors, or at least not so badly.
Reality: Fusion reactors suffer all of the problems of fission reactors, all of them just as badly, and most of them a bit more severely.
- Bombs. The "breeding blanket" modules of ITER could make excellent bomb grade Plutonium-239 or Uranium-233, while a PWR can't.
- Wastes. Every tokamak to date has created enormous quantities of radioactive waste compared to the tiny amount of energy released. And that's using Tritium produced in other reactors. If DEMO succeeds in breeding all of its own Tritium it will be even worse.
- Accidents. ITER will have an enormous and complex system to prevent an uncontrolled quench. The accident record of the PWR is excellent but even so it has been demonised by the politics. Just wait until they start linking to URLs of videos of little MRI quenches! See https://www.youtube.com/watch?v=1R7KsfosV-o and remember this machine is a tiny fraction of the size of ITER. Several other interesting videos too, just search for them. The accident "problems" of the PWR are purely political, but there is no reason to think that fusion reactors will be spared similar problems. ITER is most unlikely to suffer a major failure, but it is possible, and if it does I guess the antis will argue that this shows how dangerous a PWR is, just as they argue that Chernobyl and Fukushima show how dangerous PWRs are too. ITER will contain a significant amount of radioactive material (just not as fuel) and an enormous amount of stored energy (just not in the fuel). In fact the amount of energy stored just in the coils of ITER is about the same as that released by the nuclear weapon that destroyed Hiroshima, and it would all be released suddenly by an uncontrolled quench, as would other smaller but still significant additional amounts of energy.
- Scale. ITER is enormous. Its successors are planned to be even bigger, and unlike a fission reactor, it requires enormous electrical input at startup. So in practice, a fusion power station will need to have multiple units, probably needing to have a fission unit operational at all times.
- Economics. Fission reactors have suffered escalating costs, and there is no reason to expect fusion reactors to be any different in this regard. Just the opposite, if ITER is any guide.
There is every reason to hope that all of these problems can be solved, for both fission reactors and fusion reactors. For fission reactors some of them already are. And eventually they will probably be solved for fusion too.
But there's no reason to hope that any of them will ever be less of a problem for fusion than for fission.
The hard problem
Myth: All we need to do to make fusion power happen is to make the plant big or efficient enough to release much more energy than it takes to run it.
Reality: All serious work focusses on Deuterium-Tritium_fusion which releases 80% of its energy in the speed of a very fast neutron. Converting this energy into electricity is problematic. ITER will not even try to.
Fusion and fission differ radically in this regard.
When a fissile nucleus absorbs a neutron and splits, the two fragments are propelled apart releasing energy. But these fragments are of about the same mass as each other, and of similar or greater mass to the surrounding material, so this energy is divided between them and then quickly spread as heat that can be used to boil water, turn a turbine, and generate electricity. These fragments do themselves emit neutrons, some very quickly (prompt neutrons) and some delayed and these are very important but none of these neutron emissions release anywhere near as much energy as was given to the fission product nuclei immediately on fission occurring. The neutrons are still fast neutrons but not nearly so fast as those from D+T fusion. The fission product nuclei don't get far, they are too big and electrically charged to be very penetrating. Few of them even escape the fuel (that's what the cladding is there for).
And most important, none of the fission products produce any further, unwanted nuclear reactions in the things they hit. They just don't have enough speed or energy to do that.
The neutrons are far more of a problem than the fission fragments. In a fast reactor, where there is no moderator and the coolant is chosen specifically to be transparent to neutrons, they are a severe problem. Even in other reactors, unwanted neutrons, and their disastrous effects on the materials around them, are the reason that the AGR was an economic failure, and what set Windscale #1 on fire. In some classes of fission reactor, the problem has been successfully solved in various ways. But neutrons are not to be taken lightly!
When Tritium and Deuterium fuse the result is Helium-5, a highly unstable nucleus, in a highly stressed state. This nucleus also quickly emits a neutron, becoming stable Helium-4. And nearly all of the energy released in fusion is released in propelling these two fragments apart. And conservation of momentun means that it must be the neutron, being by far the lighter fragment, that picks up most of the speed and energy. About 80% of the energy in fact. They are far faster than any neutron from a fission reaction.
And then our problems begin. The near-vacuum of the fusion reactor and the powerful magnetic fields that confine the plasma (both the fuel and the Helium product) are both completely transparent to neutrons. So they don't give up any energy until they strike something, like the reactor vessel walls. Even then many of them go straight through the first wall. Neutrons are the most penetrating and deadly and destructive form of nuclear radiation. (I hope the magnitude of the problem is starting to dawn on the reader at this stage. And we are only just beginning.)
These are the most penetrating and deadly and destructive neutrons ever produced for peaceful purposes. ITER will be the first opportunity to study them except in bomb tests (and will thus give bomb programs some very valuable data just BTW) unless the International_Fusion_Materials_Irradiation_Facility (part of the ITER program) gets there first which looks doubtful, see below. As pointed out above, unexpected neutron damage to materials was what doomed the AGR to failure, and set Windscale #1 on fire. Unexpected fast neutron reactions also caused the Castle Bravo test to fatally contaminate some Japanese fishermen. Neutrons are not to be taken lightly.
Even in a bomb these neutrons can be a problem, as Castle Bravo demonstrated. But in a bomb, you're not concerned about what happens to the equipment once it has done its one-time job. Neutron damage to the electronics, for example, is irrelevant. Once the explosion has started, they've done their thing, and are about to be vaporized anyway. In a fusion reactor, on the other hand, you want the equipment to last for more than a few milliseconds.
But the bigger problem is, it's not obvious how to convert their energy into electricity. When they do strike an atom and bounce off, they don't give up very much energy because they are relatively light. But worse is to come. When they do eventually strike another atom and are absorbed, they do cause a nuclear reaction. Typically, the atom becomes radioactive. It is now nuclear waste. This is how most of the nuclear waste generated by fusion originates.
And then our problems really begin. Whatever this material was, we probably didn't want it changed. If it was any part of the machine, whether pressure vessel, coils, instrumentation, whatever it was, it has been degraded. Even if the material irradiated was the PFM of the first wall, any damage to that risks contaminating the plasma. The resulting radioisotopes are going to go somewhere! Even if they stay in the PFM for now, when they decay they will again likely move, and further degrade both the PFM and the plasma.
So even if we knew how to waste and dispose of these neutrons and their energy, that would be progress. To harness their energy is problematic. The hope often expressed is that they can be used to generate Tritium (which otherwise needs to be provided by a fission reactor, as it will be for ITER). But this isn't as simple as it might sound.
It was and still is hoped that work on what to do with these neutrons could start when the International_Fusion_Materials_Irradiation_Facility became operational, but it is suffering even worse delays and cost overruns than ITER. Both it and ITER will have as key objectives to work out what to do with these neutrons.
Such high energy neutrons have only been available in thermonuclear weapons up until now. That's what many bomb tests were about. And some of these, notably of course Castle_Bravo (mentioned above), gave highly unexpected results, and this was because the behaviour of the materials that these high energy neutrons hit was not as predicted.
Our models of the nucleus are incomplete and inconsistent. ITER will help to complete and unify them.
So by all means propose a new scheme to harness this energy. Ideas are precious at all times, even if most good ideas don't work (ask any successful inventor). If your idea for converting the energy of these very fast neutrons to electricity works, you will be very, very popular.
See also the problem with D-T
Fission products
Myth: Fusion power won't produce fission products.
Reality: All current proposals do and will, one way or another. This is part of the waste problem.
ITER will use Tritium "from stockpile". This means, produced in a fission reactor, which produced fission products for disposal.
DEMO will produce all of its own Tritium, or so it is hoped, using the neutrons from D+T fusion to generate it from Lithium. But hold on... every neutron D+T produces consumes one Tritium nucleus. Every Tritium nucleus that Li+n produces consumes one neutron. 100% efficiency? No neutron losses at all? And pigs might fly.
So DEMO will use a "neutron multiplier" to overcome this. The fission of this neutron multiplier will produce more neutrons than it consumes, just as in a fission reactor, and will also produce fission products, just as in a fission reactor, and they will be just as radioactive. You're not supposed to ask that.
The puzzle
Myth: If fusion wasn't a real prospect for carbon-free electricity generation, people wouldn't be putting so much time and money into it.
Would they? This is a very good question! Because the above looks like a very reasonable conclusion to those who don't know how the funding of nuclear research works.
Reality: No researcher is going to knock the money back. ITER and similar projects are useful for all sorts of reasons, providing for example opportunities for awesome and often well-funded research into both neutron irradiation and superconductivity.
And the decision to provide this money is of course political. Spin, and FOMO, and of course widely believed myths influence such decisions, both the above myths and this one itself. That's how FOMO works. See Thurber's The Fairly Intelligent Fly.
There's even a distinct possibility that the information gained will help to build better H-bombs. They are the existing use of D+T, and testing them is now banned. The US National_Ignition_Facility is funded by the US military. So is that another reason for funding ITER too? You're definitely not supposed to ask that question.
But it's not even that simple.
Let us put it into context. Australia similarly spent a great deal of money on research into Beryllium-moderated fission reactors. This wasn't because we thought it would necessarily work. It was because this gave us information to share with others, information nobody else had, and this gave us credibility and access to other information internationally. And at the same time, it provided opportunities to develop our own nuclear experts to receive this information, and interpret it and advise policy makers. That's how nuclear research used to work and often still does. See my father's book Australia's Uranium Opportunities for more on this.
So none of that proves that any of these people believe that a fusion power station will ever be the result. But some of them probably do! As Paul Simon said, a man hears what he wants to hear, and disregards the rest.
What it proves is that all of them think that the program will get them money, or work or business, or academic status, or promotion, or votes, or access to information from this and other nuclear programs, or a feeling of self-worth, or whatever else they care about. See pollies and participants and maybe the green nuclear backdown.
The politics
Myth: Fusion will soon make fission obsolete.
Reality: Fusion has an enormous amount of catching up to do, and there is no reason to hope that it will ever do so.
While nuclear (fission) power is not in theory renewable in the way that wind, solar and hydro are, there is plenty of fuel using established and proven technology to allow fission to power humanity until the Sun makes the Earth uninhabitable anyway.
And neither is fusion renewable, just BTW. But both fission and fusion appear to be sustainable.
Well, it's a bit hard to tell with fusion until we know more about how it will work, if it does. But if D+T can be made to work somehow, there is no likely shortage of Deuterium. Lithium may be another story. Unlike Uranium, Lithium does have other uses, notably batteries of course. But maybe there's plenty of it too. Fusion advocates prefer to talk about Deuterium and seawater only, and just leave Tritium and Lithium out of the discussion. Making it another question you're not supposed to ask.
So in that sense, fusion is a solution seeking a problem. And it's not obvious what problem it might ever solve.
MSRE achieved in the 1960s what ITER hopes to achieve for fusion by the end of experiments that will start in 2035 at best. But there are still no commercial power reactors using the molten salt fuel technology of MSRE. Fusion has even further to go.
It may happen that fusion will one day obsolete fission. But it's a very, very big maybe, and most unlikely to be soon. My personal guess is AD2200 at best, and AD3000 far more likely. If ever.
The need for fusion
Myth: A new energy source is needed.
Reality: Solar, wind and nuclear (fission) can provide all of the energy humankind needs until the Sun roasts the Earth anyway. Actually nuclear fission could probably do it all on its own, but it's best to diversify. Solar, wind, nuclear, geothermal and biomass are all parts of any rational energy policy.
The goals of ITER
Myth: ITER is a power station or will become one.
Reality: ITER will produce no electricity at all. Not even to partly satisfy its own enormous consumption of electricity. Not even a little to light a few light globes as a demonstration that it can, as EBR-1 did in 1951. None at all.
And there has never been a plan for it to ever generate even a little electricity. It is generally agreed that it will be far cheaper to start again, making full use of everything that has been learned since ITER was designed. ITER is just a research reactor.
And it is not hard to see why. ITER hopes to achieve Q>1, which means that more energy is being released than is being input. This will probably be a world first for a tokamak if they manage to do it, but the smart money is that they will do it, and that they will be the first to do so. (Others are also trying. And NIF achieved it in 2022 by vaporising a little hohlraum in exactly the same way that a bomb achieves it with a much bigger hohlraum.) And they even hope to do this for up to ten minutes at a time. But ten minutes isn't a great deal of time. There's not much point in running a turbine for ten minutes. It will barely be up to speed by the time you need to shut it down again.
Well. the point would be to show that it can be done, as was done when EBR-1 lit four light globes in 1951, and as X-10 did previously. But ITER will not even do that. Not even for ten minutes.
So the hope is instead to follow ITER with a reactor about 15% larger (in linear dimensions... they quote that of course because the figure is bigger of you measure instead the volume which is probably a better one to consider), or perhaps even several of these in different countries. This class of reactor is called DEMO, and this reactor or reactors will still produce no electricity. Not even a little bit. But some or all of these DEMO reactors may later be converted to power stations, called PROTO class reactors. Or again it may be cheaper to start again, and build PROTO reactors from scratch. The need for that decision is still a good way off, as is just how much electricity PROTO will actually produce. But it will at least light a few light globes.
So frankly to think that ITER will produce electricity is so out of left field that... well, read on. Perhaps the source of the confusion is just that DEMO may be upgradable to PROTO. But ITER won't be, and that has always been the intention.
From a recent Quora conversation... Dear Andrew Alder, what shall they do with that energy as soon as they “produce net energy gain”? - Boiling eggs? And it got worse, with appeals to Conservation of Energy to somehow prove that ITER would need to generate electricity in order to get rid of the fusion energy it produces. This person firmly believes that ITER will be a power station and feed power back to the grid, even after being referred to the ITER website that clearly says it won't, and apparently having read the page in question at the ITER website. See https://www.iter.org/mach/CoolingWater and https://www.usiter.org/us-hardware/tokamak-cooling-water-system for where the heat... and there is a lot of it!.. will go.
IBM Australia (under the awesome Allan Moyes) used to work on the principle that for every person who tells you of a problem, nine others know they have the problem but don't tell you, and for every person who knows that they have the problem, nine others do have the problem but don't know it. So that's a hundred problems for just one report. I'm guessing that here the ratio is even more severe. So I've decided to list it here as a myth, despite my being aware that just how popular this myth is I do not yet know. It might hopefully be just this one person but I doubt it.
And my mind is still boggling at the profound and disturbing ignorance it shows. But where matters nuclear are concerned, perhaps I should not be surprised by this any more. It's not just that people have not done their homework. The problem is more that some people see no need for it.
But it does make some sort of sense, in that these people also assume that you are as happy to remain ignorant as they are, and so you won't do your homework either. See how to reveal yourself and books they do not want you to read for more on this. And as I say in the second of those pages, I invite you to prove them wrong.
See also
Probably more to follow. It is a fascinating subject. But you probably get the idea, and hopefully will now start asking some of the right questions.
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