Waste in the form of long-lived nuclear fission products is fundamentally an unsolvable issue. Transmutation has been proposed but isn't really practicable, shooting it into the sun isn't really an option either, so the only choice is to confine it for geological timescales somehow.
Both options are really much better, in my opinion, than pumping more carbon dioxide into our biosphere.
This is a major fallacy that makes people think DT fusion is more promising than it actually is.
Engineering problems are perfectly capable of killing a technology. After all, fission after 1942 was "just an engineering problem". And DT fusion faces very serious engineering problems.
I include cost issues as engineering problems, as engineering cannot be divorced from economic considerations. Engineering involves cost optimization.
You also have the associated economic problems; the up-front cost of a launch loop would be so huge that you could never convince anybody to build it instead of using rockets. Fusion has the same problem; even if you can design a fusion power plant that produces net power, it needs to produce net power by a massive margin to have any chance of being economically competitive with fission let alone solar.
Fusion is only better insofar as the public don't yet understand how radioactive the reactor will become, but counting on that ignorance is a bad long term strategy.
Never mind what's required to deal with the fuel & waste products.
This work is related to actual genuine nuclear fusion, the kind that occurs at energy scales sufficient to overcome that Coulomb barrier. At those energy scales it becomes very hard to manage the plasma in which fusion occurs. This is a claimed advance in plasma management.
What happens is that thermal energies get high enough that the nuclei get close enough to have a significant rate of tunneling through the barrier. It's a quantum mechanical effect.
There is a nonzero rate of tunneling through the barrier even at room temperature -- just extremely low, far lower than putative cold fusion claims.
Worth noting that (while obviously not what is normally meant by "cold fusion") muon-catalyzed fusion is possible and is cold, so the above statement can't be quite right.
There is however Lattice Confinement Fusion [1] which claims to overcome the Coulomb barrier through some kind of "screening" from the electron cloud in the lattice. That seems more like it would work on at everyday scales, though I don't understand it nearly enough to offer any opinion on viability.
[1] https://www1.grc.nasa.gov/space/science/lattice-confinement-...
> First we deduce formally-exact non-perturbative guiding center equations of motion assuming a hidden symmetry with associated conserved quantity J. We refer to J as the non-perturbative adiabatic invariant.
Simply: this is not just some kind of unsupervised ML black-box magic. There is a formal mathematical solution to something, but it has a certain gap, namely precisely what quantity is conserved and how to calculate it.
> Then we describe a data-driven method for learning J from a dataset of full-orbit α-particle trajectories. [...] Our proposed method for learning J applies on a per-magnetic field basis; changing B requires re-training. This makes it well-suited to stellarator design assessment tasks, such as α-loss fraction uncertainty quantification.
With the formal simplification of the dynamics in hand, the researchers believe that a trained model can then give a useful approximation of the invariant, which allows the formal model, with its unknown parameters now filled in, to be used to model the dynamics.
In a crude way, I think I have a napkin-level sketch of what they're doing here. Suppose we are modeling a projectile, and we know nothing of kinematics. They have determined that the projectile has a parabolic trajectory (the formal part) and then they are using data analysis to find the g coefficient that represents gravitational acceleration (the data-driven part). Obviously, you would never need machine learning in such a very simple case as I have described, but I think it approximates the main idea.
for _ in 0..<1000000000000 { do_something_complicated() }
Finding simplified easy to solve solutions and using them to estimate solutions and using adjustments to get closer to the real solution is a baselime technique. That's the core of the pertubative approach in physics which uses : https://en.wikipedia.org/wiki/Perturbation_theory#:~:text=Pe...
However, now it's possible to train AI models to learn much more complex approximations that allow them to run much quicker and more accurately. A prime example is DeepMinds AlphaFold, IMHO.
I haven't read up on the research to much, but I'd place firm bets that AI models will be critical in controlling any viable fusion technology.
What does it mean? Beta radiation can cause structural damage? Is it really a problem?
1. High energy particles destroy the container. Alpha particles, which are just Helium nuclei, are quite small and can in between metal atoms. Neutrons too. High energy electrons too; and
2. It's an energy loss for the system to lose particles this way.
Magnetic confinement works for alpha and beta particles because they're electrically charged. Neutrons are a far bigger problem, such that you have fun phrases like "neutron embrittlement".
The paper introduces a new, data-driven method for simulating particle motion in fusion devices that is much more accurate than traditional models, especially for fast particles, and could significantly improve fusion reactor design.
The engineering challenges are so massive that even if they can be solved, which is far from certain, at what cost? With a dense high-energy plasma, you're dealing with a turbulent fluid where any imperfection in your magnetic confinement will likely dmaage the container.
People get caught up on cheap or free fuel and the fact that stars do this. The fuel cost is irrelevant if the capital cost of a plant is billions and billions of dollars. That has to be amortized over the life of the plant. Producing 1GW of power for $100 billion (made up numbers) is not commercially viable.
And stars solve the confinement problem with gravity and by being really, really large.
Neutron loss remains one of the biggest problems. Not only does this damage the container (ie "neutron embrittlement") but it's a significant energy loss for the system and so-called aneutronic fusion tends to rely on rare fuels like Helium-3.
And all of this to heat water to create steam and turn a turbine.
I see solar as the future. No moving parts. The only form of direct power generation. Cheap and getting cheaper and there are solutions to no power generation at night (eg batteries, long-distance power transmission).
Another reason is that ̶t̶r̶a̶n̶s̶m̶i̶s̶s̶i̶o̶n̶ distribution costs are half of your energy bill... so even if you could theoretically get fusion energy generation for "free" (which is impossible) you've still only cut your power bill in half.
Edit: I meant to say distribution costs not transmission. Looking at last months bill I paid $66.60 to deliver $51.76 of energy (about 56% of my total bill was delivery). The raw distribution charge was $49.32 or 42% of the bill. I'm not alone in these numbers, but your mileage may vary.
So if you build loads of wind & solar & battery all over - either (1) you've got to build so much battery capacity, all over, that you'll never need the grid, or (2) you've still got to build the grid to get you through occasional "calm & dark" periods.
Either way, you're looking at vastly higher capital expenses.
- moderately overbuild solar
- batteries for short term storage
- natural gas for seasonal storage
One wonders if this is why Lockheed-Martin dropped their effort:
https://www.lockheedmartin.com/en-us/products/compact-fusion...
(that page is still up, but news reporting indicates it has been dropped)
Say a house uses 10,000kWh per year at $0.10/kWH so $1000/year electrcitiy bill. Now say you get a solar system that produces 5,000kWh per year, focused in the summer months (where your power bill tends to be higher anyway). You may even export some of that power back to the grid. Have you cut your power bill in half? No. It's probably down ~20-25%.
Why? Because regardless of how much power you use (within limits) you still need a connection to the power grid and that needs to be maintained. You'll often even see this on the electricity bill: fixed charges like "access charge" per month.
We benefit from being on a connected grid. Your own power generation might be insufficient or need maintenance. It's inefficient if everyone is storing their own power. So it's unclaer what the future of the power grid is. Should there be large grids, small grids or no grid?
Renewables and something like Iron-Salt battery containers, would be pretty efficient over all. Easy to roll-out, very safe.
We'll still need some sort of base load somewhere and backup to restart everything obviously. But the big giant power plants (with the huge capital costs, delays and NIMBY headaches) might become less necessary.
This depends on where you live!
Wait, what?
Wikipedia[0] seems to disagree:
> Long-distance transmission (hundreds of kilometers) is cheap and efficient, with costs of US$0.005–0.02 per kWh, compared to annual averaged large producer costs of US$0.01–0.025 per kWh
Do you maybe mean that half electrical energy dissipate between production plant and consummer? But that figure seems quite large compared to what I can find online, and this would not be a problem with "free fusion".
Care to explain?
[0]: https://en.wikipedia.org/wiki/Electric_power_transmission
My point is that the infrastructure related to the delivery of energy to a physical location is a non trivial part of an energy bill, and that this part doesn't go away magically because "fusion".
Distributing tiny fractions of all that energy to each of millions of individual residences, then maintaining all the short/complex/low-capacity wiring needed to do that - that part ain't the least bit efficient.
We're not at that point yet with natural gas because a combined cycle turbine is more efficient than a steam turbine.
Yeah, next 50 years you might not see coal/nat gas being replaced by fusion. But you will see fusion displacing chunks of what those powerplants will be powering
There is no chance that early fusion plants will be small enough to justify building them in the same building as a factory. They will start large.
> For example, aluminum requires ~14-17MWh to produce 1 ton
The Hall–Héroult process runs at 950 C, just below the melting point of copper. It is close to twice the temperature of steam entering the turbines. It is not something that can be piped around casually- as a gas it will always be at very high pressure because lowering the pressure cools it down. Molten salt or similar is required to transport that much heat as a liquid. Every pipe glows orange. Any industrial process will effectively be a part of the power plant because of how difficult it is to transport that heat away.
Also NB that the Hall–Héroult process is for creating aluminum from ore, and recycling aluminum is the primary way we make aluminum.
Industrial parks centered around power plants might become a thing in the future, being looked at as essential infrastructure investment.
Heat transport could be seen as an entire sub-industry unto itself, adding efficiency and cost-savings for conglamorates that choose to partner with companies that invest in and build power plants.
Fusion would use a conventional turbine with boiling water. Is this a better source of mechanical inertia than hydropower or fission?
Is there a better way to solve the problem of frequency instability?
Why is this fact downvoted? This article mentions "synthetic inertia;" what are its drawbacks?
https://www.bloomberg.com/news/articles/2025-05-09/spain-bla...
Obviously, this configuration of solar and battery banks will work more optimally when they are closer to the equator.
Will different types of power grids be required for areas further away, or is it practical to ship power long distances to far Northern/Southern areas?
Could you point to the outage conclusion report?
That “3X” figure assumes a high‐insolation region (CF ~25 %). In Central Europe, where solar CF is only ~12 %, you’d need about 5x the PV capacity to equal a 1 GW coal plant’s annual generation. How does scaling up to 5 GW of PV change the cost comparison vs a coal plant?
You're making the obvious mistake here of equating 1 GW solar with 1 GW of any other source with a 95-99% baseload capacity. To achieve the equivalent result, you'll need to have at least >2 GW actual solar power to equally compare the two.
Granted, in most developed places, solar still beats coal, but this is why in many developing economies with ample coal resources, it makes more sense economically to go with the coal plants.
Take any other resource, say hydel or geothermal - solar and wind quickly go down in economic efficiency terms compared to these, in most cases almost doubling or tripling in costs.
Which is why I compared 1GW of coal power to 3GW of solar power.
https://www.energy.gov/energysaver/solar-water-heaters
I recall hearing that they are 80% efficient while photovoltaics tend to be around 20% efficient.
As a peer post noted (without back it up but seems reasonable):
> Only 20% of our energy needs are supplied by electricity.
It is a fair viewpoint to talk about energy instead of only electricity. For exemple the current EV are build using charcoal (steel and cement for the infrastructure) and parts/final product are moved around continent with oil (ships). Same for solar panels and their underlying steel structure. Same for the road were using those EV, etc… there’s technical solutions for those, but they didn’t prove to be economically competitive yet. So I’ll happily take that 80% efficiency when we need relatively low heat : domestic and commercial AC and water heating. Those are by far the most energy intensive usage in the residential sector when there isn’t an electric vehicle and are most needs in pick time (mornings, evening at winter). We better take that +60%.
The most economical solution for reducing our carbon emissions by 95% is doing these two steps in parallel:
1. Use electricity instead of fossil fuel 2. Generate electricity in carbon free manner
Yes, there are some use cases this doesn't work well at yet: steel & ocean transport are two you listed. But it does cover the 4 biggest sources of carbon emissions: ground transport, heating, electricity generation and agriculture. The big 4 are 95% of our carbon emissions.
The photovoltaic panels have the added bonus that the energy can be used for other purposes (e.g. transport, HVAC, computers, cooking, laundry, A/V equipment) should my hot water needs be low compared to what the system is designed to produce. However, from a pure efficiency standpoint, it is unclear to me which approach is better. They seem to be a rough tie, with losses for both approaches making the real world worse than ideal conditions. I am not sure if one is better than the other in the actual real world and if anyone who knows the answer is kind enough to share it, I would find the answer enlightening.
We can live with huge land areas converted to power generation, but more space efficient alternatives will be a big improvement.
Conclusion, land isn't really a constraint in the US.
Anyway, the area issue seems not too bad. In the US as least, we have places like the Dakotas which we could turn like 70% of into a solar farm and nobody would really notice.
I see it similarly to the difference between a car with a combustion engine and an electric one. Combustion engines are fully developed. We're reaching the maximum possible performance and utilisation. It's a dead end. However, with electric cars, for example, new battery development is far from over. E.g sodium batteries.
And just off the top of my head, in fusion, the discovery of better electromagnets, as happened a while back, can quadruple energy output.It's not a dead end, and writing it off would be short-sighted.
But so long as there is a boatload of prestige and funding to be harnessed via fusion research, it'll be a Really Big Thing.
Centuries ago, an ambitious and clever alchemist could harness a fair quantity of those things via transmutation research. Vs. these days, we have repeatedly demonstrated the ability to transmute lead into gold. But somehow, there's no big talk about, or prestige in, or funding for scaling that process up to commercial viability.
But another more nefarious factor is the nexus of fusion energy research and nuclear weapons research [1]. To build and maintain a stockpile of nuclear weapons (specificially thermonuclear weapons) you need appropriate trained nuclear energy physicists.
[1]: https://thebulletin.org/premium/2024-11/the-entanglement-of-...
There are interesting small fusion reactors that skip the steam step. They compress plasma magnetically, and when the fusion happens, the expanding plasma in turn expands the magnetic field, and the energy is harvested directly from the field. No steam and turbines.
Here is the video where I learned about it: https://www.youtube.com/watch?v=_bDXXWQxK38
Maybe any physicists in this thread could share insight on how feasible this is?
Your main point stands of course: this is a moonshot project, and solar works TODAY!
This is true of Tokamak type designs based around continuous confinement, but perhaps less so with something like Helion's design which is based on magnetically firing plasma blobs at each other and achieving fusion through inertial confinement (cf NIF laser-based fusion), with repeated/pulsed operation rather rather than continuous confinement.
No doubt the containment vessel will still suffer damage, but I guess it's a matter of degree - is it still economically viable to operate or not, which I guess needs to be verified experimentally by scaling up and operating for a sufficiently long period of time. Presumably they at least believe the approach is viable or they'd not be pursuing it (and have an agreement in place with Microsoft to power one of their data centers with one of the early units).
Have you seen the videos of Helion's reactor - hardly a basement project. Sam Altman (OpenAI) also has personally invested hundreds of millions of dollars into Helion, presumably after some due diligence!
Kinda. The main catalyst of stellar fusion is quantum tunneling. Temperature and gravity together are not enough to overcome the Coulomb barrier.
So what is the difference between those two places? Temperature and pressure. In the Sun those arise from gravity. On the Earth, we need to create them mechanically.
First, actually getting fusion to positive energy ROI. That's step zero and we're not even close.
Second, scaling the production of fusion in an safe and economical way. Given the utter economic failure of fission nuclear power (there has never been a profitable one), my priors are that the fusion advocates are vastly underestimating, if not willfully ignoring, this part.
Finally, even if we do get to "too cheap to meter" energy, what then? Limitless electricity is not the same thing as limitless stored energy. Only 20% of our energy needs are supplied by electricity. To wit, the crucial industrial processes required to build the nuclear power plant in the first place can only be accomplished with combustible carbon. A power plant cannot generate the energy to build another power plant. Please let that sink in.
We're already seeing countries with photovoltaic and wind hitting $0/kW on sunny windy days - the grid is nearly saturated for daytime load. There isn't enough demand! This makes the economic feasibility of fusion even less attractive. No one is going to make money from it.
I would expect that there have been multiple nuclear power plants that provide a net positive return, specially on countries like France where 70% of their energy is nuclear.
However a reasonable argument can be made the public benefited from externalities like lower pollution and subsidized electricity prices even if it was a money pit and much of the benefit was exported to other countries via cheap off peak prices while France was forced to import at peak rates.
So while regulations may be overkill it’s not arbitrary only hydro is really comparable but hydro also stores water and reduces flood risks most years. Fusion sill had real risks, but there’s no concern around $500+ Billion cleanup efforts.
Most reactors are old and in need of repair, most of these earlier than planned afaik.
There is also the bigger issue that some reactors are shut down in the summer because cooling water would leave the reactor so hot that it would be a danger to the animals living in the river.
I mean sure, waste disposal is a serious issue that deserves serious consideration. But fission waste contaminates a discrete area. Fossil fuels at scale cause climate change that contaminates the entire freaking planet. It's a travesty we haven't had a nuclearized grid for 20-30 years at this point.
The problem(s) of scale are not only those of scaling up, but also scaling down.
One of the best and most unsung benefits of solar is that it is profoundly easy and intuitive to build a very small (ie, vehicle- or house-sized) grid.
In an increasingly decentralized and stateless world, it makes sense to look for these qualities in an energy source.
And before someone chimes in and says Nuclear doesn't make sense - it made sense at plenty of times and in different places.
It doesn't make sense in Western countries that are hell bent on making it as expensive as possible, strictly to ensure it doesn't get built, so we stick on fossil fuels as long as possible.
I’m also skeptical, but I think the emphasis of my skepticism is on “commercially viable” as opposed to an available energy source. That is, I think fusion development will (and should) proceed anyway.
There’s a good argument that nuclear fission is not really commercially viable in its current form. Yet it provides quite a lot of commercially available electricity. And it also powers aircraft carriers and submarines. And similar technology produces plutonium for weapons. In other words, I don’t think fission’s continued availability as a power source is a strictly commercial decision.
I think there’s a quite a lot of technology that is not directly commercially viable, like high energy physics, or the space program. But they remain popular and funded. And they throw off a lot of commercial side benefits.
The growth of solar for domestic consumer power will certainly continue and that is a good thing. But I bet we’ll have fusion too in the long run. There’s no lack of ideas for interesting things to do with extreme amounts of heat and power. For example I’m hopeful that humanity eventually figures out space propulsion powered by fusion.
Depleted uranium is one example but that has terrible implications due to radioactive pollution that would result, disposal costs and risks, etc.
Surprised theres not more research into meta-materials and alloys that are neutron-resistant, neutron-slowing, or neutron-absorbing.
The LHC uses ~86 megawatts, about the same power as a 747's engine at full throttle. It's about the same as a small natural gas powered turbine. GE builds gas turbines that produce 800+ MW.
The LHC is just a controlled environment to study the kind of particle collisions that are happening all over the earth every day. We live next to a giant fusion reaction, and freak particles come in from outer space all the time. We have detected many particles with millions of times more energy than the particles in the LHC- the Oh-My-God particle had 20 million times more energy.
> Can someone tell me what the likelihood of a humongous explosion from nuclear fusion could be?
Fission self-sustains. Each reaction produces 3 neutrons that can start another reaction. It explodes because the neutrons grow like 3, 9, 27 etc.
Fusion does not. You have a number of atoms, and 2 of those atoms have to find each other to fuse. One reaction does not make any other reactions more likely. Unlike fossil fuels or fission reactions, the fuel cannot be lit. It can only burn when carefully confined. You can only build up enough flame to break the containment vessel, at which point it goes out. Since the inside of the vessel is basically a vacuum, it will implode instead of exploding.
Unfortunately, sentences like this are going to be way less common soon.
The beginning is nearly always federal R&D funding. Much of it won't work, sure, and that's fine. It's not wasted, because when it works, it creates such a massive everlasting surplus and opportunity machine that it overcomes all past failures by orders of magnitude. Such as, computers, and all they enabled over the last 100-ish years.
The myth of the lone inventor in the garage should have been updated even in the pre-WW2 era.
I have at least one friend who runs a biomedical research lab.
From conversations, here is what it going on:
- incoming students and researchers have been retracting their applications because of fear of ending up in detention for having something the regime doesn't like on their phone or on social media, or having their photo snapped at a protest about something the regime doesn't like, or their research being on a subject the regime doesn't like...or even something as stupid as the letters "trans" appearing as part of a word like "transgenic." (That's actually happened.)
- the schools have had to retract offers for others because there's no money to pay their stipends or for their lab/office space
- meeting with their administrations to discuss how long their schools can float salaries for lab staff. Admin assistants, scientific support staff like lab and animal technicians, and so on.
- planning phases of the euthanization of their organism / animal models
- planning phasing of the liquidation of lab equipment (in a market being flooded with such equipment)
My friends are talking about not being able to bear making their techs or researchers mass-euthanize research animal populations (typically rodents) and doing it themselves, in tears. Many of them justify the normal 'sacrifice' of research animals because their deaths help us advance science - but in this case, it's just because some transactional dickhead can't directly draw a crayon line between their research and GDP. But it's also because it's a visceral representation of scientific progress being destroyed. All to "own the libs" (but really to give billionaires tax cuts.)
One said they are trying to figure out what to do now that their career, which they have spent two decades of 60+ hour weeks on, is basically over - what little positions are left will see hundreds if not thousands of applicants. Salaries will plunge both out of necessity and a saturated labor supply.
The damage that has been done in less than 6 months to scientific research is immesurable and the consequences will be generational.
If you don't believe me, go through your list of friends, coworkers, family, etc and see who works in research and see what they're posting on social media or talk with them.
Got any friends who work in companies that make scientific equipment, reagents, etc? They might not have a job already, or soon.
Kids get into science in part because their parents or a family member is in science. Or they see a cool show on PBS about science. All that's going away. We're going to see a precipitous drop in the number of people pursuing scientific educations and careers.
Billionaires are about to find out that it doesn't matter how much money you have if your kid has cancer and there's nobody to treat them, no drugs being researched or manufactured, no diagnostic equipment (that was in part funded by research project grants), and o on.
perihelions•6h ago
RhysU•5h ago
> Then we describe a data-driven method for learning from a dataset of full-orbit α-particle trajectories. We apply this method to the α-particle dynamics shown in Fig. 1 and find the learned non-perturbative guiding center model significantly outperforms the standard guiding center expansion. Our proposed method for learning applies on a per-magnetic field basis; changing requires re-training.
Is this interpolation at its heart? A variable transformation then a data fit?
Anyone know which functionals of these orbits are important? I don't know the space. I am wondering why the orbits with such nuance should be materially important when accessed via lower-order models.