Somewhat relevant, folks here might also be interested in a whitepaper we recently put up on arXiv that describes what we are doing at Pacific Fusion: https://arxiv.org/abs/2504.10680
Section 1 in particular gives some extra high-level context that might be useful to have while reading Sam and Scott's update, and the rest of the paper should also be a good introduction to the various subsystems that make up a high-yield fusion demonstration system (albeit focused on pulser-driven inertial fusion).
Any truth to that?
Bear in mind that I wasn't directly involved, and this my impression picked up from conversations during my time in fusion research, which was about 10 years ago.
Modern lasers can also repeat shots much more quickly. Power gain on the capsules appears to scale faster than linear with the input power, so getting to practical gain might not be as far off as it appears at first glance.
These are some of the reasons that various fusion startups are pursuing laser fusion for power plants.
Btw, NIF achieved those recent results by adding strong magnetic field around the target (penny-shrinkers knew that tech for 20+ years :). There are other things like this around that can potentially be similarly useful. Only if somebody had money and interest ...
https://lasers.llnl.gov/about/what-is-nif
>NIF is a key element of the National Nuclear Security Administration’s science-based Stockpile Stewardship Program to maintain the reliability, security, and safety of the U.S. nuclear deterrent without full-scale testing.
So it seems more likely to me that some physicists figured out how to get their fusion power research funded under the guise of weapons research, since that's where the money is. NIF's original intent was mostly weapons research but it's turned out to be really useful for both, and these days, various companies are attempting to commercialize the technology for power plants.[3]
[1] https://theaviationist.com/2025/04/26/us-nuclear-weapons-wil...
[2] https://www.fusionindustryassociation.org/congress-provides-...
[3] NYTimes: https://archive.is/BCsf5
The purpose of it is to show that the USA is still capable of producing advanced hydrogen bombs. More advanced then anybody else.
The '2.05 megajoules' is only a estimation of the laser energy actually used to trigger the reaction. It ignores how much power it took to actually run the lasers or reactor. Even if they update the lasers with modern ones there is zero chance of it ever actually breaking even. It is a technological dead end as far as power generation goes.
The point of the 'breakthrough' is really more about ensuring continued Congressional approval for funding then anything else. They are being paid to impress and certainly they succeeded in that.
However I suspect this is true of almost all 'fusion breakthroughs'. They publish updates to ensure continued funding from their respective governments.
People will argue that this is a good thing since it helps ensure that scientists continue to be employed and publishing research papers. That sentiment is likely true in that it does help keep people employed, but if your goal is to have a working and economically viable fusion power plant within your lifetime it isn't a good way to go about things.
If the governments actually cared about CO2 and man-made global warming they would be investing in fusion technology and helping to develop ways to recycle nuclear waste usefully. Got to walk before you can run.
The idea of using literal guns (gunpowder, then light gas gun, then coil gun) to impact projectiles against each other seemed like it was probably ludicrous, but I haven't seen any critical media or numbers yet.
There's "breakeven" as in "the reaction produces more energy than put into it", and there's breakeven as in "the entire reactor system produces more energy than put into it", which isn't quite the same thing.
On the other side of the coin, if you put 10kWh in and get 10kWh of fusion out, that's 20kWh to run a steam turbine, which nets you about 8kWh. So really you need to be producing 15kWh of heat from fusion for every 10kWh you put in to break even.
Availability (reliability engineering) https://en.wikipedia.org/wiki/Availability
Terms from other types of work: kilowatt/hour (kWh), Weight per rep, number of reps, Total Time Under Tension
Additionally the final plot of scientific gain (Qsci) vs time effectively requires the use of deuterium-tritium fuel to generate the amounts of fusion energy needed for an appreciable level of Qsci. The number of tokamak experiments utilizing deuterium tritium is small.
Here was my completely layman attempt to forecast fusion viability a few months ago. https://news.ycombinator.com/item?id=42791997 (in short: 2037)
Is there some semblance of realism there you think?
> The design operating current of the feeders is 68Ka. High temperature superconductor (HTS) current leads transmit the high-power currents from the room-temperature power supplies to the low-temperature superconducting coils 4K (-269°C) with minimum heat load.
Much of the interesting tokamak engineering ideas were on small (so low-power) machines or just concepts using high-temperature superconducting magnets.
There's the common joke that fusion is always 30 years away, but now with the help of ITER, it's always 10 years away instead.
This is why much of the fusion research community feel disillusioned with ITER, and so are more interested in these smaller (and supposedly more "agile") machines with high-temperature superconductors instead.
Mind you, it's not useless! It produced a TON of very useful fusion research: neutral beam injectors, divertors, construction techniques for complex vacuum chambers, etc. At this point, I don't think it's going to be complete by the time its competitors arrive.
One spinoff of this is high-temperature superconductor research that is now close to producing actually usable high-TC flexible tapes. This might make it possible to have cheaper MRI and NMR machines, and probably a lot of other innovations.
I'm sure there'll be plenty of fascinating applications of high-Tc tape, however I'm not sure MRI/NMR machines will be one of those. There would still be a lot of thermal noise due to the high temperature. Which is why MRI/NMR machines tend to use liquid helium cooling, not because superconductors capable of operating at higher temperatures don't exist.
ITER has been criticized since early days as a dead end, for example because of its enormous size relative to the power produced. A commercial follow-on would not be much better by that power density metric, certainly far worse than a fission reactor.
There is basically no chance than a fusion reactor operating in a regime similar to ITER could ever become an economical energy source. And this has been known since the beginning.
I call things like ITER "Blazing Saddles" projects. "We have to protect our phony baloney jobs, gentlemen!"
I think this is overly harsh and somewhat unfair. You could make the same argument that anything operating in a regime similar to the Chicago Pile 1 could never be an economical reactor nor a bomb, but that does not mean skipping that particular development step is viable.
As far as fusion reporting goes, articles are at least somewhat consistent on the fact that ITER is a pure research project/reactor, while every 10-man fusion startup is being hyped up beyond all reason even if there is not even a credible roadmap towards an actual reactor in the 100MW range at all.
Personally I don't see fusion being a mainstream energy source (or helpful against climate change) in this century at all and maybe never, but ITER (even with all the delays) is at least an honest attempt at a credible size, and being stuck on older technology is an unfortunate side-effect of that.
I looked hopefully at the HR report https://www.iter.org/sites/default/files/media/2024-11/rh-20... to see if there was some sort of job categorisation - scientist, engineer, management. Disappointingly scant. PhD heavy. Perhaps the budget would be more insightful.
"Execution not ideas" is a common refrain for startups.
I wonder how much of the real engineering for ITER is occurring in subcontractors?
It does, for high-current buses that interface with regular resistive power distribution. They are also planned for some auxiliary components (like the neutral beam injectors).
> ITER has been criticized since early days as a dead end, for example because of its enormous size relative to the power produced.
ITER is NOT designed for power generation. It's essentially a lab experiment to see how plasma behaves in magnetic confinement and test various technologies.
That's why ITER was designed with a very conservative approach to reduce the technical risk. We don't need it to be compact, this can come later. We just need it to work.
And yes, it is necessary. Plasma behavior can't be simulated numerically or analytically. It always provides surprises, sometimes even good ones: https://en.wikipedia.org/wiki/High-confinement_mode
That's the go-to excuse. But if you look at DEMO, it's power density is not enormously greater. ITER is so far out of the running that DEMO (or PROTO, etc.) will be too.
We're learning a great deal about something that's largely irrelevant.
They're based on the state-of-the art from about 2005. Since then, a lot of improvements happened. A more realistic power plant design is going to use a thinner center column (because of better superconducting magnets), resulting in a smaller cryostat volume. Possibly high-TC magnets.
It can also be made more compact, if neutral beams can be used to suppress some plasma instabilities.
(it's been 30 years away for 50 years already, but as long as I'm not dead 30 years from now, it's still a good investment...)
https://www.metaculus.com/questions/9464/nuclear-fusion-powe...
I want to believe, but this does not make that easier.
(I work for one startup in the field, Commonwealth Fusion Systems. We're building our SPARC tokamak now to demonstrate net energy gain in a commercially relevant design.)
High density is actively bad, you want to maximize strength and minimize density for flywheel designs, and this makes you much more likely to end up with low density composites (rather than high density tungsten alloys or somesuch).
fission has relatively low temperature heat, i.e. no metal reduction, no "concrete" production. you can cook hot dogs with it. also electrification of heat can provide lower losses stemming from regulation or lack thereof. with electricity you can say i need 293.5 degrees C and you just type it somewhere and you get it for almost free (regulation).
There are any problems with fission that are all related to the extraordinary danger of handling the fuel, byproducts, and the sites themselves.
The cost of them is huge, some people are hoping that modularity will help with construction, but it is still astonishingly expensive.
The problems of handling the fuel has been solved, in theory and practise. Except when commerce is involved. When the money people get involved corners will get cut, and we are back to incredible danger. Technically solvable, but I would not go near it. I have known too many business people.
The problem of the long-term waste is entirely beyond us. There has been no practical progress on this front. Long term waste (including some parts of the assemblies themselves) are very dangerous for hundreds of thousands of years.
This is, with current technology that can be bought to bear, unsolvable.
The only thing we can do is put it in a stable site, be ready to move it when the site becomes unstable (nowhere on Earth is known to be stable on such time scales), and find a way of communication, across thousands of generations, just how poisonous this stuff is.
Maybe our ancestors will get lucky and find a way to safely dispose of it....
So fission power is making future generations pay for today's consumption.
Fortunately for us it is moot. The costs of renewables is dropped to the point that the only reason for fission is to build the capacity for nuclear weapons.
reprocess the dirty fuel and bury the actual waste deep underground like Finland is doing at the Onkalo spent nuclear fuel repository.
https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repo...
And there is still very much a need for zero-carbon DISPATCHABLE electricity of witch nuclear is the ONLY choice. You simply cannot have 100% of your electricity from only solar and wind because it is far too variable and we simply don't have the technology to store electricity cheaply enough.
Your attitude towards nuclear energy is as irrational as the average antivaxer towards vaccines.
How deep, to stay put thousands of generations?
Lithium ion batteries are light with a high energy density, so are great for cars.
Flow batteries have a low energy density, but increasing the duration means a bigger tank, and the cost of bigger tanks increases as a function of the cube root (?) of their volume Flow batteries are well over a century old, but I have been reading about improvements over the last two decades. Where are they?
It is the good old: Good enough beats theoretically perfect.
Presumably your comment is either to persuade or to inform; it does neither. I'm very curious about this field and its future, do you care to try again?
ITER began building in 2013, first plasma is expected for 2034. DEMO is expected to start in 2040.
So, ITER is taking an estimated 20 years. It's being built for a reason, so I imagine follow-ups want to wait to see how that shakes out. So certainly, DEMO needs to start a few years after ITER is finally done.
Then DEMO isn't a production setup either, it's going to be the first attempt at a working reactor. So let's say optimistically 20 years is enough to build DEMO, run it for a few years, see how it shakes out, design the follow-ups with the lessons learned.
That means the first real, post-DEMO plant starts building somewhere in 2060. Yeah, fair to say a lot of the here present will be dead by then, and that'll only be the slow start of grid fusion if it sticks at all. Nobody is going to just go and build a hundred reactors at once. They'll be built slowly at first unless we somehow manage to start making them amazingly quickly and cheaply.
So that's what, half a century? By the time fusion gets all the kinks worked out, chances are it'll never be commercially viable. Renewables are far faster to build, many problems are solvable by brute force, and half a century is a lot of time to invent something new in the area.
ARC, which uses those high temperature superconductors, is just 40x lower power density.
Neither promises to be competitive with fission, never mind the things beating fission.
This is the reality. It’s not happening. It’s a welfare program for bullshit artists that depends on a credulous public.
The issue right now is cracking the code. Once that is done, performance gains and miniaturization can take place.
Fusion can work on lots of things. Its possible that a fusion system the size of a car could be made within 25 years of the code being cracked that would power a house, or the size of a small building that could power a city block.
The waste product of hydrogen fusion is helium, a valuable resource that will always be in high demand, and it will not be radioactive.
And yes, it will need coolant as with hot fusion the system uses the heat to turn a turbine, but that coolant isn't fancy, it's just water.
Fusion has the potential to solve more problems than it causes by every metric as long as it is doable without extremely limited source materials, and this is what these big expensive reactors are trying to solve.
Quote:
A fusion power plant produces radioactive waste because the high-energy neutrons produced by fusion activate the walls of the plasma vessel. The intensity and duration of this activation depend on the material impinged on by the neutrons.
The walls of the plasma vessel must be temporarily stored after the end of operation. This waste quantity is initially larger than that from nuclear fission plants. However, these are mainly low- and medium-level radioactive materials that pose a much lower risk to the environment and human health than high-level radioactive materials from fission power plants. The radiation from this fusion waste decreases significantly faster than that of high-level radioactive waste from fission power plants. Scientists are researching materials for wall components that allow for further reduction of activation. They are also developing recycling technologies through which all activated components of a fusion reactor can be released after some time or reused in new power plants. Currently, it can be assumed that recycling by remote handling could be started as early as one year after switching off a fusion power plant. Unlike nuclear fission reactors, the long term storage should not be required.
https://www.ipp.mpg.de/2769068/faq9
Basically, whatever containment vessel becomes standard for the whole fusion industry would need probably an annual cycle of vessel replacements, which would be recycled indefinitely and possibly mined for other useful radioactive byproducts in the process.
We are also very bad at anything very long term. We've hardly pulled off any physical project to last more than one generation recently. We barely invest in any.
The winning energy tech of the future better have as little negative externalities as possible, especially long term ones.
Unironically: you’re the first person I’ve come across to openly acknowledge this issue. Thank you.