Progress toward fusion energy breakeven measured against Lawson criterion
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From the 60s to the 80s we got pretty good at tokamaks (stellarators have been catching up since we got computers) but Magnetic Confinement Fusion (MCF) triple product performance scales with major radius ^ 1.3 and confinement field strength ^ 3. Power density scales linearly with major radius and with the magnetic field strength ^ 4.
At some point increasing the major radius becomes extremely expensive, so pushing past the barrier of Q=1 has been a long, political process. At the same time a real burning plasma (Q>1) machine has a lot of added cost to operate a nuclear facility (tritium handling and neutron radiation).
So there has never been a physics barrier to Q>1, but an economic one. What's changed in the past year is that REBCO manufacturing and working matured to the point that confinement fields are now twice as strong as they used to be. Suddenly building a burning plasma machine isn't a 40 year international venture and economically viable MCF plants are in the crosshairs.
So could we have had a working fusion machine with infinite money and political will? Also what is your prognosis of the next 5 or 10 years?
My prognosis is that CFS is on a good track and that their state goals are achievable. There's going to be some big headlines in a few years. If other startups also hit their goals we'll likely see a race with private investment. Public interest and government funding will likely lag the private progress by a few years.
Defense uses only 3% of US steel production. That’s not the problem, and arguably, necessary.
https://www.commerce.gov/sites/default/files/department_of_d...
Looking at the graph in the tweet, I'd bet the strategy is patience. It seems clear that current research efforts will eventually produce net-positive-energy fusion, then the capitalists will start to swarm in. No need for anyone to take a big gambit.
what is the price target here?
If it is 2022 solar and wind LCOE cost, and you are targetting, say, 20 years to build a plant, then those aren't viable targets. Solar and wind will probably drop another 50% or more by then in LCOE cost.
It's worth research, sure. But the same issues of new-gen nuclear are shared with any fusion, except fusion is way further down the prototype stage. Solar/Wind/Battery is already near-price competitive with natural gas turbine unsubsidized (and they never seem to account for all the hidden fossil fuel subsidies), and the curves are still in prime economies of scale improvement.
> Small, modular & economically attractive fusion enabled by high-field superconductors
But I am just a robotics engineer who has watched a lot of the SPARC lectures, so I have no domain expertise here.
Lessons learned: make no assumptions on whether or not a magnet really is free to be released, do not place magnets loose on a workbench even if they are far away from your work area because when the friction unexpectedly disappears you are going to be in for a surprise.
Don't mess around with very large neos unless you know what you are doing, they can really hurt you. (And when you do know what you are doing: observe safety precautions religiously and always wear safety glasses until your whole rig is assembled and the magnets are safely enclosed).
Something like this just scares me:
https://www.apexmagnets.com/magnets/6-x-2-disc-neodymium-mag...
Let me give you one example of how hard it is to work with these: while building the windmill I had decided on an 'inside out' model where the rotor rotates around the stator, this has a bunch interesting properties, such as pushing the magnets onto the drump while they rotate instead of trying to eject them from the rotor in the normal designs. And because magnets get hot any kind of glue or other adhesive would be subject to all kinds of thermal stresses, might let go or melt. So that was a pretty neat solution. My rig for installing the drum was a half ton crane over a very heavy steel workbench that had the stator mounted to it.
As I lowered the rotor suddenly the whole assembly, table and all lifted off the ground and perfectly centered itself around the rotor. I swear I never ever saw that one coming and it really scared the crap out of me because only minutes before then I was still fiddling with pushing some wires in place inside the stator while the rotor was already floating above it. A bit earlier and I could have easily gotten pinched, in spite of all my precautions.
Also, beware that the head of MIT's fusion program (your source) is the head of SPARC. Since he siphoned a huge amount of money from gullible venture capitalists outside his field by now, you definitely shouldn't rely on him for an obective analysis of SPARC's fundamental design.
I will push back on your second paragraph though. The presentation I linked was from two years before the founding of CFS. It seems likely to me that Whyte founded CFS because he believed in the physics he presented, rather than the reverse.
I see this sort of causation reversal and associated accusations all the time in internet discussions. For example, yesterday someone told me that Musk only likes electric cars because he owns lithium mining rights. Tesla bought those rights in 2020, because they produce lithium batteries.
Don't get me wrong, I'd love for SPARC to be a success. I just haven't seen any objective, external review that would confirm (or at least try to show) how they solved the problem of controlling turbulent plasma in a high gradient field. It's not even fully clear that ITER will be able to do that, and they'll have a much easier time due to the larger reactor radius.
At this point, as a woefully ignorant layman, I'm forced to weigh two contrary claims. One is by the head of MIT's fusion program. The other is by a commenter on HN, helpfully linking an impressive-looking paper I don't understand, which does not appear to say with layman-friendly clarity that higher magnetic fields make fusion plasmas less stable.
Personally, the claim that stronger fields make plasma more stable doesn't seem all that extraordinary to me, and certainly not one that's contrary to simple common sense. And when it comes to evaluating sources, Dennis Whyte seems like a fairly reputable one.
https://aip.scitation.org/na101/home/literatum/publisher/aip...
It helps my layman's eyes clearly relate the trajectories of the various developmental processes of each approach. I wonder why SPARC and ITER are the only projected ones. Do the other reactors being built not have estimated yields? My favourite has long been the wendelstein, because of they way it looks and how it feels like its pathway to success might be software based. I like the way Tokamak Energy markets itself, and would have loved to see the ST25 and the ST40 in that image, but maybe they're not complete enough projects to be on there?
So you need a high enough density of those that stay hot enough for long enough (the triple product, vertical axis) at a high enough temperature (horizontal axis) for enough atoms to fuse.
At the boundary, enough energy will start being released from fusion reactions to keep the reaction going. at Q=1 you have theoretical break-even. Somewhere between Q=5 and Q=10 you could extract more heat than you put in. The heat produced by the reactions should be enough to sustain the reaction. At Q=inf it just keeps burning like a fancy camp fire. Just throw in fuel, remove ashes and enjoy the heat. Commercial fusion can only start being viable probably somewhere between Q=10 and Q=20.
Do note that the projected future in OP's gif should contain way more attempts from various companies to reach that limit. Just mentioning sparc is a bit selective.
In my opinion, it is a bit misleading to add this to the plot, because for this laser-based fusion, the theoretical breakeven lies really far from the practical, commercial breakeven. But as shown there on the gif, the NIF did manage to cross the Q=1 for inertial confinement fusion last year!
The Q_sci^MCF contours correspond to scientific energy gain (ratio of fusion power to heating power crossing the vacuum vessel boundary) for a magnetic confinement experiment.
For ICF we can't draw simillar Q_sci^ICF contours because the total fusion energy released depends on the degree to which the ignited hot-spot propagates a burn in the surrounding cold fuel. And this depends on other variables like the symmetry of the implosion which are not captured in this plot.
If you're curious to read more about this check out Section III.F of the linked paper (pp.10-11).
At Q=infinity, you get out as much energy as you want compared to what you put in initially, but it keeps burning (as long as you add fuel and remove ashes, that is). At that point you pay an initial start-up cost and can fuse as much as you want.
In practice, no such plant will ever exist, because there is no plausible prospect of the power being competitively priced.
Once you start to get enough neutron kinetic energy out, those neutrons have to be captured and their kinetic energy degraded to heat in thousands of tons of molten lithium pumped in big pipes snaking around inside your magnets, which you must then use to boil water and drive a turbine.
The cost of operating such a plant would be at least 10x the equivalent fission plant. But fission is already not competitive, and gets less so every day.
Part of operation would need to be purifying grams of tritium, daily, out of those thousands of tons of radioactive molten lithium, for the fuel needed to continue operating. That might not be possible. No one is even trying it yet.
The power density of your D-T plasma would be much less than fissioning uranium (Th, Pu, etc.), which means you need a great deal of it, and a huge plant. If superconducting magnets squeeze it smaller, you have the problem that all this neutron flux has to come through a wall of limited area, destroying it in short order. Magnets so strong would need thousands of tons of steel to hold them in place, which would weaken rapidly under heavy hot neutron bombardment.
So, the D-T fusion chased is a series of fascinatingly hard technical problems, but there is no plausible prospect of ever getting any commercially valuable power out. And, they are not even safer than a regular nuke; the thousand tons of molten radioactive lithium is hugely inflammable, even explosive, and the smoke turns into radioactive drain opener on contact with anything damp, e.g. lungs.
However, that's unfashionable to talk about, so they are touted as a potential source of energy. Given that a single shot costs many tens of millions of dollars (because of the incredibly precisely machined piece of gold, called a target, that gets heated up by lasers until it emits X rays that cause the fuel pellet to implode in a perfectly symmetrical fashion), and is over in nanoseconds. So, a continously operating plant would literally spend millions of dollars per minute even with optimistic improvements in the cost of the targets - not exactly a promising new "free energy" generation technology.
> A volcano, earthquake, or hurricane releases many TWh of energy, but not usefully so, for reasons.
People keep repeating this (fission is not competitive) like it's a law of nature, but the reason they are not competitive are entirely human-made.
Personally, I believe an advancement in construction productivity is quite possible, but that it will take an entirely new generation of bright, ambitious, and innovative individuals entering the field, as well as compensation to attract them from other fields that currently outpay construction by quite a bit. But that's a loooong and expensive change of economies.
For a quick overview, skip down to figure 12, which shows a plot of overnight construction costs across time and countries. Note that the bulk of them are below $3000/kW, quite a bit less than the most expensive reactors in the US.
So here's an optimizer that finds the lowest overall grid cost, based on various assumptions you can modify: https://model.energy/
Pick a country. "Show advanced assumption settings." Check the box for "dispatchable technology 2." Set the overnight cost down to $3000. The lifetime of 25 years is unrealistic, given that the average age of US reactors is 40 years. Set that to a more accurate value, like 60 years. Finally, give it the same discount rate as everything else.
You'll find that in many countries, nuclear does quite well. In countries without good wind/solar resources, even a higher capital cost can result in a 100% nuclear grid.
Saying 60 years is "more accurate" is kind of putting one's thumb on the scale, as is putting an overnight cost at $3000/kW. These sorts of overly rosy and unrealistically optimistic assumptions are how we get into such terrible estimates for nuclear.
Even though MIT has been one of the sources of inaccurate nuclear optimism in the past, I think that this is perhaps the best assessment of how to make nuclear competitive again:
https://energy.mit.edu/research/future-nuclear-power/
I still thinks it's somewhat overly optimistic, but it at least tried to address the real and deep issues within the industry instead of hand waving them away.
Until nuclear proponents both acknowledge the full reality of construction, in the 2020s, and the errors of the past, they will never be able to get to $10k/kW or even $5k/kW. A future at $3k/kW in the US is not worth even contemplating until we could reliably even hit $5k/kW, and a world with $5k/kW is currently not worth contemplating because we are so far away from that.
We see this cost disease in all sorts of large construction projects, not just nuclear. Though nuclear seems to be particularly bad. And that's why we need breakthrough in productivity. Personally I think that such a construction productivity breakthrough would have its greatest impact on decarbonization through cheaper subway construction, high speed rail construction, and through increased urban density with cheaper big buildings. These type of construction projects have few realistic alternatives, whereas renewables plus storage are already a great way to power an energy system.
So if we can fix companies like Bechtel, we will see lots of improvement throughout our society far beyond nuclear construction.
High cost of large projects is certainly a general problem in the US, but it may not be due to labor costs alone. Here's a Bloomberg article that attributes it to "over-design, inefficient project management and misaligned politics." https://www.bloomberg.com/news/articles/2021-12-08/why-build...
I think it's entirely possible that in the US, where we have copious wind and solar resources and we've gotten bad at doing large projects economically, nuclear is not the best option. That says little about the rest of the world, though. And it's possible that small modular reactors would help even in the US, because while we suck at big infrastructure projects, we're not too bad at high-volume production in factories.
And that brings us back to fusion, because a lot of modern fusion designs would be more like factory-produced modular devices rather than large site-built infrastructure projects.
By the time any new nukes could be brought online, capex and opex for renewables will have fallen far, far below even their most aspirational projections.
Lack of those is not the cause of construction cost overruns, so increasing their supply would not help. Cost overruns are a deliberate consequence of wholly-legal institutional corruption, which no one shows any appetite for rooting out. Ingesting exemplary individuals just generates disillusioned individuals out the other end.
I don't quite follow your point here. Presumably the issue with earthquakes and hurricanes is that they aren't dispatchable and the work environment for operating a plant is quite hazardous. The issue with volcanoes (although I'd bet we already do use volcanoes for power) could very easily be as simple as that they tend to be in difficult to reach locations because of the plate tectonics (ie, mountains) & the hot parts take a lot of drilling to get to.
If there is energy, we can find a use for it.
The barriers are entirely practical in that these power sources don't scale well and aren't easy to get on demand. None of the problems there are similar to having a tokamak - it isn't like we are going to struggle to find the tokamak (it will be marked on the map with something like "tokamak here") and it will likely have a big on/off switch.
[0] https://www.science.org/content/article/could-volcanoes-powe...
We also never, ever drill into magma chambers. Drilling into a magma chamber is a good way to get a new, vitrified surface, several feet deep, for miles around what was once your drilling rig.
I'm just going to nitpick this part. In ARC, the magnets go outside the blanket, which is a molten salt, fully surrounding the inner wall. The salt has to absorb almost all the neutrons, to generate enough tritium. The steel outside of that shouldn't be getting many neutrons.
No optimistic projections for cost of extraction are better than idle speculation. Practicality of extracting diffuse 3H from a molten metal blanket, needed for fuel, is as previously noted purely speculative.
Renewables are driving cost per kWh well below any plausible, or even aspirational, figures.
The only fusion technology that has any chance of competitive extraction cost is Helion's, which does not depend on a round trip through heat. But it depends on a regular supply of 3He, a decay product of 3H which must be produced via operation, filtered from the working plasma, and then held for its 12y decay half life. It is anyway not clear if its process can be achieved at all.
SMRs depend on the round trip through heat and incur all the other costs of traditional nukes, so offer no prospect of keeping up with plummeting cost of renewables.
Fission's fuel rod meltdown is not the only catastrophic failure mode available. Fukushima demonstrated hydrogen detonation. Breached containment of thousand-ton inflammable, caustic, radioactive molten metal neutron absorption blanket would be adequately catastrophic.
I wonder the same about SpaceX and the other rocket companies… does US manufacturing mean you really have no choice but to operate in obsolete units, or are these things so “custom” that they get to be done in metric anyway?
That is a common but very limited evaluation of what happened. The contractor ignored the specifications, no proper testing was done to make sure their component would do what it was supposed to before launch, and when someone noticed the issue in-flight they were ignored due to the bureaucratic process until it was too late. The exact same issue would have happened entirely in metric units if one side used CGS and the other used MKS.