alt.hn

4/21/2026 at 2:26:52 PM

Fusion Power Plant Simulator

 https://www.fusionenergybase.com/fusion-power-plant-simulator

by sam

4/21/2026 at 4:11:07 PM

A good addition would be the sales price per MWh, price for the power plant, and the loan interest rate.

Because IMO all that is extremely critical. I fully support the pursuit of fusion as a scientific endeavor, but given that we're probably at least 30 years away from having anything approaching commercial deployment (assuming ITER is built, works, is followed promptly by DEMO, it works, and is followed promptly by people building more reactors. That's a heck of an assumption), it's not at all a given that it'll ever make a profit. That's a lot of time to build a lot of very cheap renewables.

And there's also opportunity costs. I see a lot of hopes put on fusion and don't really understand this chasing of the perfect solution. Even best case, it's not happening in decades, and it'll take decades more to build fusion as anything more than one off multi-decade-long research projects. That's a lot of time for the world to get worse while waiting for fusion to happen, and we might as well just throw renewables at the problem now instead of waiting.

So opportunity costs would also make for an interesting thing to calculate. Given that fusion will likely not make a major difference climate/pollution-wise for half a century, what else could we build in that time, and how much and what effect would that have?

by dale_glass

4/21/2026 at 10:49:30 PM

> And there's also opportunity costs.

That's not really how it works. ITER has a budget measured in billions over multiple years, the global energy industry is trillions every year. The amount needed to do the research is such a small proportion that if there is even a tiny possibility that it could long-term provide a significant proportion of world energy, it's well worth doing the research. The scientific knowledge gain is just icing on the cake.

> That's a lot of time for the world to get worse while waiting for fusion to happen, and we might as well just throw renewables at the problem now instead of waiting.

We can do two things at once.

by AnthonyMouse

4/21/2026 at 7:58:37 PM

ITER is a many stakeholders project, with all it's advantages (the costs can be split among participants, international cooperation) and disadvantages (each government wants a piece of the pie - components are manufactured at many subcontractors, in multiple countries) and politics (for example the multi-year process for selecting a ITER location).

The bigger, principal problem of ITER is the used magnet technology (niobium–tin, niobium–titanium). This was safe and conservative choice in 1990s, but as consequence the tokamak has to be big and therefor expensive to build.

Commonwealth Fusion Systems is currently building a tokamak based on the same physics as ITER, but with modern magnet technology using rare-earth barium copper oxide (REBCO) high-temperature superconductors. Their ARC tokamak should be smaller and cheaper than ITER.

https://en.wikipedia.org/wiki/ARC_fusion_reactor https://en.wikipedia.org/wiki/Commonwealth_Fusion_Systems

Of all the fusion energy startups Commonwealth Fusion Systems is nearest to demonstrating a realistic fusion power plant.

by leonidasrup

4/21/2026 at 7:21:56 PM

ITER is not our best bet for commercial fusion. ITER was a peace project between the USA and the Soviet Union.

https://www.cfs.energy

by Gud

4/21/2026 at 7:39:48 PM

Side note, all fusion start ups have built upon decades of science research funded in the ITER program, so opposing ITER to fusion start ups is misleading

by alas44

4/21/2026 at 7:32:14 PM

ITER is definitely the best bet for a workable fusion concept. There are some unsolved issues left, but its nothing compared to the sci-fi solutions most US startups would require.

by tovej

4/21/2026 at 7:35:30 PM

CFS is ITER with better magnets.

by p1mrx

4/22/2026 at 5:15:19 AM

Did you click the link? Nothing “sci-fi” about commonwealth fusion systems..

by Gud

4/22/2026 at 10:29:23 AM

CFS is the most promising of the US startups. The reason being they have partially pivoted away from fusion towards superconducting magnets. Tbf their concept is also the most likely to succeed.

It is still more sci-fi than conventional fusion developments like ITER.

Source: I work in the field.

by tovej

4/21/2026 at 8:55:43 PM

Storing renewables for a whole season is an unsolved problem at the moment. Countries at higher latitudes might want fusion for baseload generation during winter. And later it'll help with climbing the Kardashev scale.

by the8472

4/21/2026 at 9:13:41 PM

But there's far easier solutions to that than fusion.

For example, HVDC. Interconnect and buy power from somebody with more sun. Or just overbuild solar by a lot. It's cheap, so chances are having too much of it still works out economically.

by dale_glass

4/22/2026 at 8:44:55 AM

> HVDC

Sorry, no. Our recent experiences during the energy crisis caused by the Russian invasion of Ukraine showed us that we cannot trust energy sources outside our own borders.

> overbuild solar

The effective sunlight in November in Finland is measured in single-digit hours per month. That's not a joke, or an exaggeration. Solar is completely out of the question.

Right now, the only carbon-free solution is fission. Fusion potentially adds another, but that's far off still.

by Tuna-Fish

4/22/2026 at 9:22:29 AM

> Sorry, no. Our recent experiences during the energy crisis caused by the Russian invasion of Ukraine showed us that we cannot trust energy sources outside our own borders.

You could trust Sweden, Estonia, etc. since they're all in the EU. Also Norway. But overall good point.

> Right now, the only carbon-free solution is fission. Fusion potentially adds another, but that's far off still.

I've never been to Finland, but I'm sure there's some wind there too.

But on the subject of war, fission turns out to be a huge vulnerability for Ukraine. Fusion would be better but it'd still be extremely expensive infrastructure that could be very easily disabled. So from the war standpoint what's probably most beneficial is a very distributed usage of wind/solar.

by dale_glass

4/22/2026 at 9:34:19 AM

> You could trust Sweden, Estonia, etc. since they're all in the EU. Also Norway. But overall good point.

Your neighbors have winter at the same time as you. HVDC only solves this problem if it goes very far.

by Dylan16807

4/22/2026 at 10:12:14 AM

> You could trust Sweden, Estonia, etc. since they're all in the EU. Also Norway. But overall good point.

No. I wasn't just referring to loss of supply from Russia. What I was referring to was that when supply from Russia was lost, every country in the EU scrambled to secure their own supply, essentially competing on who could fuck over their neighbors the most. (It was Germany. Germany wins that prize.) No supply outside our borders can be trusted.

> I've never been to Finland, but I'm sure there's some wind there too.

Finland is subject to a weather phenomena where a stable anticyclone forms over the country, resulting in a high-pressure system that's essentially still. In winter, this can result in weeks of dead calm during the coldest temperatures experienced in the country. We already have a lot of wind capacity, and whenever this happens the electricity prices spike sky high.

> But on the subject of war, fission turns out to be a huge vulnerability for Ukraine. Fusion would be better but it'd still be extremely expensive infrastructure that could be very easily disabled.

We are a NATO member, and we have our own long range strike capability. If Russia directly attacks, Moscow will burn, which is why they likely won't. But Putin likes to play these hybrid games, where he tries his best to fuck over everyone without directly attacking.

by Tuna-Fish

4/21/2026 at 11:29:31 PM

> For example, HVDC. Interconnect and buy power from somebody with more sun.

Who is Japan interconnecting with, or any other country that doesn't trust its neighbors? What is Canada supposed to do when it's ~6000 km from the equator and might not want to rely on the US for electricity regardless?

> Or just overbuild solar by a lot. It's cheap, so chances are having too much of it still works out economically.

Solar is cheap per kWh but those kWh come disproportionately in the sunnier months of the year at any non-equatorial latitude. To build enough for January you'd then have oversupply and a price of zero for the nine months out of the year when you have the most output, requiring you to make back the entire cost in the three months when solar output is lowest. Then you're only getting paid anything for e.g. 12.5% of the kWh you generate (the 25% of the months that have 50% of the average output) which means you need the price during those months to be 8x the average price you need to break even, but then you're not cheaper than existing alternatives. And that's before you even deal with nights or cloudy winter days.

It obviously makes sense to use solar to reduce the need for natural gas plants during hot summer days with a lot of air conditioning demand, or for charging electric cars that can hold off a couple days if it's cloudy. It equally obviously doesn't make sense to try to generate 100% of electricity from the same intermittent source whose output is regionally correlated by season and weather systems.

by AnthonyMouse

4/22/2026 at 12:08:20 AM

> What is Canada supposed to do when it's ~6000 km from the equator and might not want to rely on the US for electricity regardless?

Most Canadians live quite far south. Toronto is on the same latitude as France’s Mediterranean coast and they of course have plentiful hydropower. Solar is surprisingly useful even in more northerly places like the UK or Denmark since it is anti-correlated with wind power.

by laurencerowe

4/22/2026 at 8:43:19 AM

> Most Canadians live quite far south.

"South" in Canada is still north. Calgary (third largest city) is almost 6000 km from the equator. Toronto is the major city furthest south and it's still almost 5000 km.

> Toronto is on the same latitude as France’s Mediterranean coast

Europe is also quite far north. The Mediterranean has warmer temperatures because of ocean currents carrying warm water from the south, not because of its latitude. Toronto is at the same latitude as Wisconsin.

> and they of course have plentiful hydropower.

They get a little over half from that. You still need something to do the other half.

by AnthonyMouse

4/22/2026 at 7:22:17 AM

> Who is Japan interconnecting with, or any other country that doesn't trust its neighbors? What is Canada supposed to do when it's ~6000 km from the equator and might not want to rely on the US for electricity regardless?

With space. By space-based solar power instead of HVDC.

by LargoLasskhyfv

4/22/2026 at 8:39:39 AM

We have currently only one long term, scalable, low-carbon, low material requirements energy storage technology: nuclear fission power plants.

In 50-100 year we will have another energy storage technology: nuclear fusion power plants.

by leonidasrup

4/22/2026 at 12:46:29 AM

Let's be fair here, we're trading one megaproject for another.

by willis936

4/22/2026 at 8:35:46 AM

Yes, but we're trading a research megaproject that might not ever live up to its promises when it's done in 30 years, for a boring megaproject we can start right now and that will very quickly start producing power.

by dale_glass

4/22/2026 at 11:25:02 AM

Pumped hydro is a great storage solution, as long as geography allows it.

by ForHackernews

4/22/2026 at 12:31:20 PM

I wonder if it will one day be practical to emulate photosynthesis and use renewable power, captured CO2 and water to produce biofuel that could then be used at a later time.

by nisegami

4/21/2026 at 6:54:45 PM

I think it's impossible to calculate at this stage since there're no fusion power plants which actually produce net power.

by mono442

4/21/2026 at 7:04:45 PM

True, but we've built tokamaks and we're building ITER, which so far has an estimated price of between $45 billion and $65 billion.

Now of course that's a research reactor full of experiments and instrumentation that wouldn't be part of a normal power plant, but given current experience that I think we can expect we won't suddenly knock down the cost to $100M. It's going to be somewhere in the billions. And we have expectations of that DEMO is going to make 750MWe.

We can then plug those estimates into the calculator and basically figure out how cheap and how powerful a fusion reactor has to be for it to make economical sense.

by dale_glass

4/21/2026 at 9:35:41 PM

Part of that cost is from ITER being so huge, which is because they use obsolete superconductors. CFS is doing the same thing in a reactor a tenth as big, using newer superconductors that support stronger magnetic fields.

The size and also the complicated governance have made ITER very slow to build, which also increases expense. The JET tokamak is about the size of the reactor CFS is building, and JET was built in a year for the reactor itself, plus three years before that for the building they put it in.

by DennisP

4/21/2026 at 7:33:28 PM

I think a lot of the cost is custom parts. Standardization and economy of scale would bring the price down quite a bit.

by tovej

4/21/2026 at 7:48:00 PM

If that happens it will still take decades.

It took us a lot of time to standardize computers. We made lots of weird architectures before things settled down.

by dale_glass

4/21/2026 at 10:49:50 PM

The market never went that way with fission (except France?). What would be the difference with fusion?

by nomel

4/21/2026 at 11:43:07 PM

"and we might as well just throw renewables at the problem now instead of waiting."

We have spent about $10T on renewables over the last 20 years. We use more FF today than 20 years ago because renewables don't provide enough power to compensate for the normal yearly increase in energy demand (which is pathetic). The solution is nuclear (fission). It was the solution before we were born. It will be the solution after we die. No amount of politics and propaganda will ever change that. The laws of physics care nothing about what you think.

by hunterpayne

4/21/2026 at 7:06:38 PM

And outputs for how much power would be generated by an equivalent-cost conventional fission or solar facility.

by sandworm101

4/21/2026 at 3:16:30 PM

For those interested not only in simplified energy balance of a fusion power plant as shown in Fusion Power Plant Simulator, but in more realistic engineering of heat extraction from a tokamak I recommend the following lecture by Dr. Dennis Whyte from MIT Plasma Science & Fusion Center.

Fusion Reactor First Wall Cooling

https://www.youtube.com/watch?v=bHJyoqDO0zw

One of the designs uses 3D printed silicon carbide vacuum vessel cooled by a layer of molten lead and a layer of FLiBe (a molten salt made from a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2)).

https://en.wikipedia.org/wiki/FLiBe

The lithium component of FLiBe is used for breeding of the radioactive isotope tritium, which will be extracted from the salt and used for making the deuterium-tritium fuel of the tokamak.

by leonidasrup

4/21/2026 at 5:06:14 PM

My favorite video that walks through fusion energy design/sizing/cost equations is also a lecture by Dennis Whyte: https://youtu.be/KkpqA8yG9T4?si=U8xaAAvjdnt6yqr8 It’s a really engaging lecture - I’m normally pretty put off by 100-minute lectures on YouTube but this one was both very easy to follow and perfectly scoped. Can highly recommend it - the learnings from it are timeless fundamentals that really make fusion power design and economics accessible.

The big takeaway is that better magnets reduce reactor size by the 4th power, and energy output and cost by the cubed power. Finding a material for the magnets which doubles their strength would reduce the size of the reactor by 94% and the cost by 88%.

A possible conclusion one could make is that with regular advancements in magnets it’s very possible that the first operational commercial fusion reactors will be relatively low-cost compared to current and planned fusion reactors, and even though they may begin construction after the next generation of super-sized fusion reactors - they might be finished and operational before their “predecessors” with inferior magnets have completed being built.

by nerdsniper

4/21/2026 at 11:53:36 PM

Some Sci Fi authors have made the point that the first interstellar space ship is likely to be greeted at their destination star by human immigration control officers boggling at their long superseded sublight ship.

This is also one of the reasons ITER is such as bad project. It's so big, slow, and had to be planned so far ahead that it "locked in" older superconducting tape technology that has been superseded.

by jiggawatts

4/21/2026 at 6:59:49 PM

The wildcard for our civilization that I pay a lot of attention to:

will AI help us get through blockers like this?

I'm out of the prediction business but my guess is: absolutely, but iff we don't collapse in some way first.

Wild to be alive as the centuries-long horse race of industrialization between doom, or the stars, approaches its finish line.

by aaroninsf

4/22/2026 at 12:58:31 AM

How would AI help achieve commercial fusion? You first need to identify the blockers. These almost all entirely boil down to "how do we precision machine large pieces of hard metal?", "how do we assemble facilities with untold process channels?", "how do we capture neutrons without making a prohibitively massive machine?", and "how do we make metal that doesn't melt?".

Now, AI might have a chance at supercharging material research and making miracle materials that help address the blanket and first wall challenges, but honestly those are roadblocks we're not even running into yet. AI can not and will not fix issues related to organizing labor and supply chains and suddenly make megaprojects have a 100% success rate for on-time and on-budget. It's just not going to happen.

So are these problems intractable? Of course not. It's just not what the chatbot is well suited for. Anyone saying otherwise is selling something.

by willis936

4/21/2026 at 11:48:49 PM

This is the science fiction fan's version of hopes and prayers.

by hunterpayne

4/21/2026 at 5:09:27 PM

>realistic engineering of heat extraction from a tokamak

This is why I love the idea of Helion so much.

Who knows if it will ever work, but skipping the thermal transport and doing direct current generation from EMF in the reactor seems like it has tremendous potential for simplifying (and eventually downsizing)

by jcims

4/21/2026 at 7:15:52 PM

It would be quite outstanding if MIT Plasma Science & Fusion Center released their core courses on OpenCourseWare. Considering the potential impact of this technology and how much it's needed, humanity doesn't seem to be trying that hard to make it work.

by TheAceOfHearts

4/21/2026 at 7:33:05 PM

> cooled by a layer of molten lead

Really gives a perspective on the range of temperatures handled.

by ASalazarMX

4/21/2026 at 7:36:41 PM

I actually like the recirculation simulation. Although all kinds of cyclical engines have recirculation of power as part of their function, in fusion there is an important difference from what people are used to. In an internal combustion engine, the crankshaft and flywheel in a car recirculate power from the power stroke to the compression stroke, doing the same thing as the recirculated energy does in this simulation. But in fusion, this 'crankshaft' is very lossy. I suspect if you have a model in your head of how an internal combustion engine works, crankshaft losses are not a big thing. Teaching people that when they model fusion reactors that they need to include this because it's important, I think would help people develop better physical intuition. The 'lossy crankshaft' model was an important part of why I opted for partial direct conversion with the design I built back in the '90s. Set both eff sliders high to see how much this helps.

That said, one big missing thing (other than the economic stuff, mentioned by others) which would add a lot to this simulation would be more about 'where does Q come from?'. Obviously this could be too complicated for a little sim, but perhaps a few simple things could be added like showing how increasing the volume/surface ratio for tokomaks/sphereomaks can help, or how getting rid of certain types of instabilities can improve say mirror or pinch designs. This might help people to understand why certain design decisions (like building ITER so big) were made.

by FiatLuxDave

4/21/2026 at 7:49:44 PM

Well said about the “lossy crankshaft”. As for what determines Q, that’s up next, stay tuned :)

by sam

4/21/2026 at 8:04:46 PM

I will quote Prof. Dennis Whyte

"The limitations of 20+ year-old Nb3Sn superconductor magnet technology forces ITER to be so large it is taking the entire world to build a single device"

https://youtu.be/KkpqA8yG9T4?t=1471

by leonidasrup

4/21/2026 at 3:19:24 PM

No melt down? This game sucks.

On a serious note: I wonder how practical and safe it would be to build fusion pants close to city centers in order to harvest the excess heat for district heating. Would be a boon in e.g. NYC which already has a large district steam system. You can do cooling too, look up "steam absorption chiller."

by MisterTea

4/21/2026 at 5:35:22 PM

It already exists in many countries. They transport it through pipelines .

E.g. Temelín Nuclear Power Plant, Paks Nuclear Power Plant And many more

by ExpertAdvisor01

4/21/2026 at 8:59:37 PM

My question is more about the safety of locating one smack in the middle of a city. There is radiation to shield but no radioactive fuel waste. HOWEVER, worn reactor parts that need to be replaced will be piping hot when measured with a Geiger counter. So is it safe to build and operate in the middle of e.g. NYC?

And further, if they are safe, what is the public's perception of fusion? Do people hear "nuclear fusion" and immediately think nuclear disaster imagery brought about by incidents like Three Mile Island and Chernobyl?

by MisterTea

4/21/2026 at 11:55:06 PM

"My question is more about the safety of locating one smack in the middle of a city. "

We don't put any other type of powerplant in a city, so why would we do it for fusion? That being said, fusion won't happen in our lifetimes and even when we do get it, we probably will never really use it. Fission is just better in almost every way. It makes 5x the power per amount of fuel, it makes far less neutrons, and the temperature generated is far more usable. Oh, and fusion absolutely makes radioactive waste and a fusion failure makes a meltdown (which doesn't have to be a failure case for fission) look like a Sunday picnic.

by hunterpayne

4/21/2026 at 9:53:34 PM

Judging by the comments I see most places, the general public's perception of fusion is "magical scifi tech that will never happen."

by DennisP

4/21/2026 at 11:55:55 PM

That's because it almost certainly is. Don't hate on the messengers.

by hunterpayne

4/22/2026 at 1:54:54 AM

My point is, that's a pretty positive view of fusion. They think it's too good to be true, but if it actually happens then I doubt many people will suddenly switch into thinking it's a dirty old explodey thing like fission's public image.

by DennisP

4/21/2026 at 3:55:16 PM

> I wonder how practical and safe it would be to build fusion pants close to city centers in order to harvest the excess heat for district heating

The cost/benefit for doing this seems pretty similar between fusion as gas power. We don't usually do this with gas, so I guess it's probably not viable for fusion.

by advisedwang

4/22/2026 at 12:45:19 PM

Look at where the Barmen gas power plant is in Wuppertal, Germany to see....

by namibj

4/21/2026 at 9:19:38 PM

Many cities/towns in the USA have small power plants in them (typically associated with a University, large hospital system, or central business district) which "sell" not just power, but also hot water, and steam. The steam is typically used to heat buildings. Google for "$CITY steam tunnels" or "$CITY CHP plant" to find these in your area.

San Francisco has[0][1][2][3] at least five combined heat and power plants that generate electricity and also sell steam to neighboring buildings via 72,000 feet of pipes.

I worked at a privately-owned for-profit "factory" in Santa Monica whose primary product was chilled water (their other product was warm water). They built pipelines to nearby large buildings and sold chilled water to them.

0: https://cordiaenergy.com/locations/san-francisco-3/ (2 for-profit CHP plants)

1: Skanska (for-profit)

2: San Francisco General Hospital

3: Apparently there are some "Muni" CHP plants scattered about SF as well (publicly-owned)

by nerdsniper

4/21/2026 at 5:45:00 PM

Combined heat and electricity production is uncommon in the US, but much more so in Europe. Especially in the Baltics, Scandinavia and the Netherlands, non-CHP generation is rare. Related: higher energy cost, and elaborate local heat distribution networks.

by markvdb

4/22/2026 at 7:23:17 AM

> The cost/benefit for doing this seems pretty similar between fusion as gas power.

The real problem is stupid capitalism reprices everything good to the price of the non-good thing. Solar was supposed to be almost-free clean electricity, but the price of panels has been repriced to make them the same as dirty electricity.

by dheera

4/21/2026 at 4:31:37 PM

Fusion power plants can't "melt down". The amount of plasma inside the vacuum chamber is just around a gram.

by cyberax

4/21/2026 at 6:49:07 PM

That's the joke, isn't it?

A fission power plant simulator lets you have fun playing through a meltdown disaster scenario. A fusion power plant simulator is "worse" because it takes away the "fun" of meltdowns. The humor is in reacting to the simulator as if it were a game (some are, but this one isn't).

by adrianmonk

4/22/2026 at 9:41:28 AM

The first line reads as a joke, but then they actually ask if it's safe later in the comment.

by Dylan16807

4/21/2026 at 6:43:58 PM

Might not be similar to nuclear meltdown but still enough to need a lot of money to fix

by PunchyHamster

4/21/2026 at 4:55:07 PM

> Fusion power plants can't "melt down"

Eh, a core-containment failure (in any magnetically-contained system) would involve superheated hydrogen getting friendly with oxygen. That, in turn, would give neutron-impregnated barrier materials a free ride on propellant. It's not strictly a melt down. But it's in the same practical category of failure.

by JumpCrisscross

4/21/2026 at 5:28:20 PM

Ths is a massive misunderstanding of the technology. First of all, the amount of hydrogen in the reactor is tiny. The magnetic confinement severely limits the density of the plasma. The inner containment vessel is a ultra high vacuum chamber. The chemical energy that would be released by a reaction between the hydrogen in the reactor amd oxygen from the air would be less than what is released by popping a hydrogen filled balloon with a lighter.

The truly concerning failure modes would be related to release of radiation or activated materials. But that would require damaging the reactor in ways that the reactor is incapable of imparting on itself.

Overall, the technology is remarkably safe.

by gmueckl

4/21/2026 at 5:39:33 PM

> chemical energy that would be released by a reaction between the hydrogen in the reactor amd oxygen from the air would be less than what is released by popping a hydrogen filled balloon with a lighter

Thanks for the correction. If you're breeding lithium in the walls, might that be an incendiary concern?

by JumpCrisscross

4/21/2026 at 6:09:35 PM

The breeding blanket is entirely contained inside a vacuum vessel, so there isn't any oxygen to react with. Also, the are many blanket designs, but the lithium is never present in its elemental form (precisely because it would be very reactive), but in a stable chemical bond with some neutron multiplier (like lithium-lead alloys or beryllium ceramics). In some design the lithium is even immersed in the coolant itself, which is high pressure helium, so it's not going to ignite in any reasonable way.

by rnhmjoj

4/21/2026 at 6:55:33 PM

> breeding blanket is entirely contained inside a vacuum vessel, so there isn't any oxygen to react with

When the vessel works. If the vessel breaches, that lithium could ignite. Note a showstopper. But I suppose a risk to be thought about by the engineers (probably not by policymakers).

by JumpCrisscross

4/21/2026 at 8:13:51 PM

Commonwealth Fusion Systems plan to use lithium in salt form FLiBe, a molten salt made from a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2). It does not violently react with air or water.

https://en.wikipedia.org/wiki/FLiBe

by leonidasrup

4/21/2026 at 6:29:25 PM

There seems to be a number of different prototypes of blankets, but the average operating temperature seems to be 300-700C. Adding oxygen to some of these designs while that hot may cause metal burning. This said, many of them are ceramic designs and would likely resist combustion.

With all that said, it seems to be way less 'dangerous' material than would be in your average nuclear reactor, making it more of an industrial accident versus a planet contaminating mess.

by pixl97

4/21/2026 at 11:59:43 PM

You are ignoring that the plasma would ignite the O2 in the air. You are also ignoring what happens when several hundred MW of energy (at about 1,000,000C) under pressure is released instantly. Anytime you have a powerplant with enough energy to be economically viable, releasing that energy at once will be a problem. Even FF PPs can explode quite violently.

by hunterpayne

4/22/2026 at 9:52:47 AM

> You are ignoring that the plasma would ignite the O2 in the air.

What does this even mean?

> You are also ignoring what happens when several hundred MW of energy (at about 1,000,000C) under pressure is released instantly.

If you have a gram of hydrogen at a million degrees, it can continue putting out several hundred MW for about a fiftieth of a second.

Even if it somehow gets outside the machine with no heat loss to the structure, by the time it mixes with a few cubic meters of air it'll be down to 1000C or less.

by Dylan16807

4/21/2026 at 5:29:55 PM

There's only a few grams of hydrogen in the reactor's plasma, it's reaction with oxygen wouldn't be much more exciting than just losing containment. There are engineering challenges that have to be addressed but no worse than the 6 MW research reactor I used to walk by every day to my college classes in the middle of a dense city.

The proliferation risk of someone using the neutron flux to produce an atomic or dirty bomb are real but that exists no matter where it is.

by Symmetry

4/21/2026 at 8:25:10 PM

I think the proliferation risks will be in future the reason, independent of technological obstacles or costs, why US will not allow to build fusion power plants in all countries around the world.

Hybrid nuclear fusion–fission power plants have been already proposed and studied in theory.

"In general terms, the hybrid is very similar in concept to the fast breeder reactor, which uses a compact high-energy fission core in place of the hybrid's fusion core. Another similar concept is the accelerator-driven subcritical reactor, which uses a particle accelerator to provide the neutrons instead of nuclear reactions."

https://en.wikipedia.org/wiki/Nuclear_fusion–fission_hybrid

by leonidasrup

4/21/2026 at 9:31:17 PM

> Hybrid nuclear fusion–fission power plants have been already proposed and studied in theory.

I have a hand-wavy hard sci-fi universe I've been rolling around my head for years and I eventually came to the conclusion that fission-fusion drives would be really handy for spacecraft, since it would be much easier to start a fission reaction in a cold/dark ship than fusion because of the power requirements. Otherwise you need some other way to generate 10s or 100s of MW to start the fusion reaction.

by bleepblap

4/21/2026 at 10:01:25 PM

Probably not all countries, but any NPT signatory has the right to build nuclear power plants, they just have to submit to inspections.

by DennisP

4/22/2026 at 8:14:38 AM

This is the basic promise behind the "Treaty on the Non-Proliferation of Nuclear Weapons" (NPT).

https://en.wikipedia.org/wiki/Treaty_on_the_Non-Proliferatio...

In the text of the treaty there are promises to NPT signatories, such as:

Article IV "1. Nothing in this Treaty shall be interpreted as affecting the inalienable right of all the Parties to the Treaty to develop research, production and use of nuclear energy for peaceful purposes without discrimination and in conformity with articles I and II of this Treaty."

https://en.wikisource.org/wiki/Nuclear_Non-Proliferation_Tre...

But the hard reality of U.S. nuclear politics in regard to other countries can be read here:

"The Nuclear Fuel Cycle and The Bush Nonproliferation Initiative"

https://www.iaea.org/sites/default/files/neff.pdf

"The world’s leading nuclear exporters should ensure that states have reliable access at reasonable cost to fuel for civilian reactors, so long as those states renounce enrichment and reprocessing."

"The 40 nations of the Nuclear Suppliers Group should refuse to sell enrichment and reprocessing equipment and technologies to any state that does not already possess full-scale, functioning enrichment and reprocessing plants."

For example when United Arab Emirates wanted to build the Barakah nuclear power plant, (supplied by Korea Electric Power Corporation, not by an U.S. company), it had to sign an the Section 123 Agreement with United States of America. As part of the agreement, the UAE committed to forgo domestic uranium enrichment and reprocessing of spent fuel.

https://en.wikipedia.org/wiki/U.S.%E2%80%93UAE_123_Agreement...

To be fair, it's not only U.S. who want's the control access to nuclear technology and nuclear materials. For example India wanted to become a member of Nuclear Suppliers Group for a long time. As of 2019, China has thwarted every attempt of India's inclusion into NSG and has made it clear that status quo will remain citing "lack of consensus" among NSG members.

https://en.wikipedia.org/wiki/Nuclear_Suppliers_Group#India

Another example is South Korea. South Korea is constrained in its nuclear power policy by the 1974 Korea-US Atomic Energy Agreement. Only in November 2025 did the USA formally affirmed support for South Korea’s civil uranium enrichment and spent fuel reprocessing for peaceful uses.

https://www.armscontrol.org/act/2025-12/news/us-supports-sou...

https://world-nuclear.org/information-library/country-profil...

by leonidasrup

4/22/2026 at 12:25:57 PM

Good points, but in all of that they are specifically targeting enrichment and reprocessing, while allowing nuclear power plants.

A fusion reactor is a power plant. It produces neutrons but so does fission; in fact, conventional fission plants get a third of their power from plutonium that they breed from U238, and plutonium accounts for most of the long-term radioactivity in the waste.

By comparison, a fusion plant would have no uranium present for any legitimate reason, and assuming it's D-T it would need those neutrons to breed tritium. Tritium has a use in thermonuclear weapons but not without highly enriched fissiles, and tritium is also a byproduct of fission plants.

by DennisP

4/21/2026 at 10:23:37 PM

Fission-fusion or accelerator-driven fission is pure BS. It combines the disadvantages of _both_ and none of the advantages.

Modern fission power plants are designed with a reactor vessel to last a century and to withstand high pressures and temperatures. It's built and emplaced permanently in a large concrete shielding structure.

In a hybrid design this just won't work. Fuel will need to be right next to a high-vacuum chamber that will need periodic maintenance.

by cyberax

4/21/2026 at 5:09:53 PM

What's the effect of this in a populated area in a certain radius? Compared to nuclear power plants...

by Aardwolf

4/21/2026 at 5:12:28 PM

> What's the effect of this in a populated area in a certain radius?

I'd imagine this is, like with fission plants, deeply dependent on the specific design.

by JumpCrisscross

4/21/2026 at 6:17:04 PM

Radiologically? Pretty much nothing. The regular industrial safety concerns will matter more.

The plant will have some tritium, and the material in reactor walls will get activated by the neutron flux. Some of the activated materials can disperse in case of a catastrophic explosion (e.g. a couple of large airplanes being flown the reactor building).

But the material of the walls is not volatile, so it'll stay on the site. And tritium is very volatile, so it'll quickly disperse to safe levels. You'll be able to detect them with sensitive equipment, but it won't be dangerous.

by cyberax

4/21/2026 at 7:16:37 PM

Don't they already do this for existing types of power plants (gas, coal) that produce waste heat?

by grishka

4/21/2026 at 8:22:39 PM

When people get excited about fusion as a source of energy, I’m always reminded of Henry Ford’s famous quote: “If I had asked people what they wanted, they would have said faster horses.” although apparently he probably never said that.

Fusion is that faster horse - promising a cheaper to operate firebox which when attached to a stream engine attached to an alternator can produce electricity.

This approach to generating electricity has been superseded by new technologies - first by gas turbines which removed the steam engine and then by wind turbines which removed heat from the process and now by solar PV which has removed all the mechanics.

I just can’t see any circumstances under which steam engines are “coming back” and becoming competitive for electricity no matter how cheap the firebox fuel is.

by derriz

4/22/2026 at 12:17:09 AM

"I just can’t see any circumstances under which steam engines are “coming back” and becoming competitive for electricity no matter how cheap the firebox fuel is."

Industrial grade steam is still widely used and that probably won't ever change except to move from steam to supercritical CO2 and then only for power production. Most steam is used to do other things that are critically important to modern society. The biggest one is to make fertilizer without which we can't feed most of the planet. Your understanding of how industry works is fundamentally flawed.

by hunterpayne

4/21/2026 at 8:34:35 PM

Some fusion reactions release their energy almost entirely as fast moving charged particles.

You can slow down those particles against an electric field and harvest the energy as electricity directly. No steam turbine. No Carnot limit.

by minihat

4/22/2026 at 6:55:17 AM

There are many kinds of nuclear fusion reactions

https://en.wikipedia.org/wiki/Nuclear_fusion#Important_react...

The lowest-threshold nuclear fusion reactions (deuterium–tritium (D–T) fusion, used by ITER, Commonwealth Fusion Systems) release up to 80% of their energy in the form of neutrons. These designs have to convert energy of the neutrons to electricity, indirectly using heat.

Since it is simpler to convert the energy of charged particles into electrical power than it is to convert energy from uncharged particles, an aneutronic reaction would be attractive for power systems. However, the conditions required to harness aneutronic fusion are much more extreme than those required for deuterium–tritium (D–T) fusion.

https://en.wikipedia.org/wiki/Aneutronic_fusion

by leonidasrup

4/21/2026 at 6:06:41 PM

Does anyone have a collection of these little simulator systems? I love playing with them.

by 0cf8612b2e1e

4/21/2026 at 6:54:13 PM

Apologies if I've missed something, but isn't this all just a fantasy? None of the current methods for getting fusion power are even close to being practical -- even the theoretical net output experiments require extensive and sensitive measurement setups just to establish whether or not they are positive energy.

We are not in a place where we expect fusion power to be incrementally achieved by the current systems. We need major breakthroughs that are both impossible to predict and may not even exist outside of stars or thermonuclear devices.

The idea that we'll get massive improvements in Qsci, while maintaining the same basic structure as existing fusion systems, is in the end a bit silly. What would we estimate our confidence to be that when someone invents the Fromboculator, that the Fromboculator will even have a heating system or "vacuum vessel" or a plasma system.

In the end, this looks like it's a steam engine simulator more than anything else, but with some fancy words thrown in.

by andrewla

4/21/2026 at 10:07:10 PM

That wildly overstates how far off we are. To take the most conservative example, tokamaks have very well-known scaling laws and based on those, CFS is generally expected to exceed breakeven with SPARC and get to practical power levels with ARC, over the next several years.

by DennisP

4/22/2026 at 12:04:36 AM

> over the next several years.

More like decades. The earliest time any planned fusion reactor will make net electrical output -- but not yet an economically useful amount -- is the mid 2030s, a decade from now.

Commercially relevant amounts of electrical generation is uncertain, but most plans start around 2045 and then would take decades to replace fossil fuel plants at scale.

by jiggawatts

4/22/2026 at 1:58:00 AM

There's a big difference between "it will be decades before we've replaced fossil plants at scale" and "we won't have net power until we invent magical new technologies that we have no clue about today."

by DennisP

4/21/2026 at 5:41:16 PM

The recirculating power for the magnetics should be included (at least for pulsed), as the RTE there tends to drive the design.

by chris_va

4/21/2026 at 5:51:58 PM

Power to magnets (at least those not contributing to heating) are assumed to be included in the house load.

by sam

4/21/2026 at 6:04:35 PM

For pulsed power, with an optimistic beta of 1, the magnetic field energy is going to be comparable to the heat energy. The house load here seems tied to a static superconducting coil, not a pulsed field.

And can in many cases be much higher than the heat energy (e.g. theta pinch).

by chris_va

4/21/2026 at 3:04:47 PM

Something I've been asking my AIs to do when modelling with them is to ask for the algebra for the model so I may recreate it by hand. Including such a PDF with these links would be helpful because it succintly presents the logic in a denser form than an explainer article.

by JumpCrisscross

4/21/2026 at 3:31:58 PM

For whatever reason the game doesn't load until I switch to the dark mode

If I enable advanced mode, the "exiting" in Heating Power (exiting) gets overlapped with corresponding numbers

Display menu doesn't allow switching to Energy mode

by NooneAtAll3

4/21/2026 at 3:33:33 PM

Thanks - what browser?

by sam

4/22/2026 at 5:56:16 AM

technically LibreWolf, but it should be just latest Firefox with some privacy options preselected (like blocking your requests to cloudflare insights)

other that said cloudflare, I see no other errors/warnings in f12

the "load only on lighting theme switch" has fixed itself, the other 2 problems are still there for me

by NooneAtAll3

4/21/2026 at 3:45:07 PM

I think the first thing I thought when every man opened this project was: how to make this thing explode.

by caldis_chen

4/21/2026 at 3:26:11 PM

This would sell on Steam with a light Godot reskin

by rao-v

4/21/2026 at 3:15:08 PM

fantastic PBS Space Time on what the last steps are going to be to finally make fusion possible

https://www.youtube.com/watch?v=nAJN1CrJsVE

(fusion is -always- just a decade away, perpetually, lol)

by ck2

4/21/2026 at 6:46:16 PM

It's a nice video, but a striking thing about it is that it ends with "I just want my infinite free energy". Where on earth is that supposed to come from?

Fusion is ultimately a fancy way to boil water. The tokamak (or stellarator) heats a given amount of water per second, which after losses to power the plant itself and the losses in the steam turbine, makes some finite amount of MWh to output to the grid. This contraption is as the video says very non-trivial to design and build and so it costs some very non-zero amount of money, and lasts a finite time (walls are damaged)

Big $$$ / finite_amount_of_mwh / life_expectancy = min_cost_per_mwh, if we want to pay this thing off. Very possibly more than existing methods.

I'm extremely on the side of doing scientific research, but I'm baffled by constantly bumping into people who suggest somehow fusion is going to mean infinite free power, or anything even close to that.

So far the tech seems headed towards just being an alternate form of a fission plant -- complex, expensive, slow to build, possibly won't ever make a profit. Likely worse, since fission is a known, mature tech.

by dale_glass

4/21/2026 at 11:02:51 PM

I had the same thought recently, that if a new power source was created that was like, a perpetual superheated cube or something with no input costs, it still might actually be beaten by solar + batteries. If not right now, then in just a few years.

Since you'd still end up having to build a gigantic heat exchange setup with steam turbines, pipes/ducts/pumps, generators, valves, gauges, vents, maybe even a cooling tower, etc. Plus a labyrinth of catwalks, ladders, access tunnels for workers in hard hats servicing/inspecting/replacing stuff who are on-site 24/7 and exposed to non-trivial occupational hazards dealing with superheated liquids at high pressure every day.

The entire concept of a steam turbine is just fundamentally a big hassle compared to an inexpensive solid state slab + batteries that are modular and basically plug-and-play by comparison.

by toraway

4/21/2026 at 3:17:57 PM

> fusion is -always- just a decade away, perpetually

Wasn't it perpetually 20 to 50 years away? I'm not an expert on the space. But new computational methods and magnets seem to be genuine steps forward.

by JumpCrisscross

4/21/2026 at 6:09:20 PM

IIRC the one of the first times a group put timelines to a fusion reactor they had time vs funding level of something like 20 years/50 years/never, and the funding level that actually materialised was below the 'never' amount and yet it started the 'always 20 years away' joke. Now I think the timeline was probably still optimistic but fusion is also obviously a very expensive thing to develop and while it's gotten a lot of funding it's still at the 'in the background' level.

by rcxdude

4/21/2026 at 4:33:18 PM

the PBS Space Time episode suggests to me the housing walls might be the biggest problem

it consumes itself or makes molecules that are destructive to the walls or insanely toxic so can never risk leaks

whatever solution they come up with I suspect it will require a lot of constant maintenance on the first generation

by ck2

4/22/2026 at 12:19:38 AM

Then they are wrong. The biggest problem is efficiently gathering energy from the fusion reaction. Right now, we can only get a tiny fraction (less than 1%) of the energy out. If that can't be raised to 50% or so, fusion will never happen.

by hunterpayne

4/21/2026 at 8:32:44 PM

Great... Decades, and probably trillions of dollars later, we have a really cool fusion simulator.

That's awesome. Maybe we can fly it around the moon and take selfies with it!

Might as well roll all the high cost pseudo-science into one big instagram package...

p.s. Of course this is in contrast to using the giant fusion reaction that we have running, literally over our heads...

by johnea

4/21/2026 at 11:54:58 PM

[dead]

by stefantalpalaru

4/21/2026 at 4:08:20 PM

[flagged]

by Lapsa