Every SMR startup is failing. The more they progress, the more they revise their costs upwards.
SMR make as much sense as space datacenters. You can gaslight investors, you can gaslight HN, you can gaslight a national parliament full of lobbyists, but you can't gaslight thermodynamics.
"What about the costs, both in terms of Capex to build them and the levelised cost of the power they produce?
Gadomski said: “We are very suspect of projections of costs from companies because they're inclined to be more favourable, as opposed to being more realistic. I think that getting a good cost estimate is something that is not possible right now because we haven't built any.”"
>I don't see evidence of even one startup failing there
"SMR developers will all want to avoid the fate of NuScale, the sector trailblazer that saw a pioneering US power deal cancelled when its estimated LCOE soared to $89/MWh from a previous $58/MWh."
Just a 100% cost mistake. Oops.
And even if they could have reached their 58$/MWh target, let's see what is the cost of competition...
"Firm wind-plus-storage costs in 2025 ranged from around $59/MWh in Inner Mongolia to $88/MWh to $94/MWh across Brazil, Germany, and Australia, with costs projected to fall to roughly $49/MWh to $75/MWh across those markets by 2030."
Oops oops.
"Construction timelines are also shortening, with projects typically built within one to two years of securing permits and grid connection."
Oops oops oops.
Renewable is running circles around nuclear. Every renewable technology is beating forecast. Every nuclear technology is breaking costs predictions and deadlines.
Not only that, but the landscape of SMRs research and development is becoming very rich [0]. I think we are going to see a renaissance of reactor technology in the coming decade, and it will be well deserved.
How are SMR's "gaslighting themodynamics"? I mean, sure, I can accept that they're not economical with current tech, but it's not a frigging' perpetuum mobile, it's feasible technology.
The value propositions of SMRs are logistics and re-use of existing infrastructure. The idea is that you could have easily transportable reactors that you can plop down in an existing coal plant, and then reuse the turbine, dynamo, etc. that are already in place.
The fact that we haven't seen more widespread use of SMRs suggests that you're right. But it's important to point out that there are cost saving opportunities that could potentially reduce the net price per watt despite worse thermodynamic efficiency.
But they'll never be small enough to be truly portable. It'll be closer to another Akademik Lomonosov [0] than a truck-sized diesel generator, which severely limits its deployment options.
The additional per-site engineering required to reuse things like turbines and dynamos is almost certainly going to kill any savings it would have. If you're already shipping a building-sized reactor, what's one more turbine? Realistically the main reusable component is the grid hookup itself - but that would incentivize building a large-scale reactor on the site.
As would reusing the turbines, for that matter: you can't exactly power the turbines of a 100MW coal plant with a 10MW reactor, and shipping ten inefficient 10MW reactors to the site just so you can reuse the existing ancient turbine isn't exactly an attractive option either.
Your small nuclear reactor is going to need almost as much engineering , plumbing, safety mechanism, personnel, maintenance, etc... as your big nuclear reactor.
Siting of an SMR is somewhat different (albeit related) to the SMR concept itself. You might cluster them together (like the plans for 3 RR SMR at Wylfa and 3 at Ringhals in Sweden).
> almost as much engineering , plumbing, safety mechanism, personnel, maintenance, etc
Sure, that is economics, not thermodynamics. I don't necessarily agree with the SMR manifesto, but it is conceivable that improved financing, construction, operation and oversight could make an SMR cheaper than a larger reactor.
The mindset that makes people stuck in time. Sorry but SMRs are potentially very cheap. Not at this point. ,but when operated on scale they will be. You need to start
I mean... you've got to have faith in your theory before testing it out. I am not having any opinion here about this, but the cycle in my mind is theory, belief, test, updated model of reality. I can imagine similar things said before we managed to have powered flight, "Pshhhsst! We'll never fly! The law of gravity forbids it."
You do need to have unreasonable goals for things once in a while. In this case, I don't have a particularly fixed stance about SMR's, but the claim that "Thermodynamics are the reason why SMR aren't, and will never, be economical" feels a bit stronger than it is warranted. Never is a damn' looooong time. And I can easily imagine things being less efficient, but having other advantages that make them more economical. Claiming it's impossible is just stretching.
One is regulatory. At least in the US, every nuclear reactor that produces at least 100 MW needs to carry a 375 million dollar insurance policy at minimum. Under 100 MW there is an alternate schedule that ranges from 5 million to 75 million scaling based on output. But the net result is that it's still more profitable to built a single large reactor, since a 1 GW reactor is less to insure than 10 100 MW reactors. This is written into law, it would require Congress to change it.
Second is that nuclear reactor efficiency tends to improve with size. The ratio of thermal watts to electric watts tends to be better with large reactors. I'm not super well versed on the engineering tradeoffs here by my rough understanding is that waste heat scales with surface area while useful energy extraction scales with volume.
In the grand scheme of things, that doesn't seem to be too expensive. According to the NRC, insurance is per site, and additional reactors on a site don't increase the insurance nearly as much as the first. The example they give is $1.1 million annual premium for a $500 million policy, with multi-reactor sites going up to $1.5 million. They also mention property insurance ($1.06 billion policy) and they didn't discuss the premiums on that, but as it's not liability insurance it's probably cheaper.
The big costs are still going to be the cost of siting and building the reactor, the fuel, and the ongoing cost of running it. They pay off over a very long time horizon, so it's also the opportunity cost.
Just one so far and it's not particularly small compared to a more conventional reactor.
Russia actually does have a smallish SMR but it wasn't terribly cheap to build nor operate. IIRC it is in the form of a ship and used to power a city somewhere in the north.
SMR has a place for sure but no one has demonstrated the unit costs savings of making a lot of them yet.
You can actually get some, if not most, of the economy of scale by doing a fleet build of one specific design. The US seems to be working on that and picked the Westinghouse AP-1000. I think that initiative has a decent chance of succeeding. The first few will be slow and expensive to build (even China has had delays with their nuclear roll out) but the subsequent ones will get cheaper and faster to build. This is how some countries did it during the first nuclear power expansion era.
you are in this thread a lot, so i am guessing you must be very familiar with the industry. maybe you can help me understand:
is the wikipedia on SMRs incorrect/lying when they say that there are commercially operating SMRs since 2020?
and how have so many smart people and companies been duped into seriously considering SMR technology if SMRs apparently break the laws of thermodynamics?
And struggling, propped up by taylor-made laws and public money.
>how have so many smart people and companies been duped into seriously considering SMR technology if SMRs apparently break the laws of thermodynamics?
Never said they break the laws of thermodynamics. They are just inefficient and will never be more efficient than alternatives such as... Bigger nuclear reactors.
Or solar.
And how long have you been out there? Have you never seen investors dumping and wasting billions in dead-ends? Never seen a mania before?
Nuclear attracts clever people, but it isn't smart nor wise.
>Never said they break the laws of thermodynamics.
true, you said "gaslight thermodynamics", which i have no idea what that means, so i took a guess at what you were implying.
>never be more efficient than alternatives such as... Bigger nuclear reactors.
is efficiency really the only metric to be considered? i feel like available space, availability of alternatives, time to complete construction, etc. are worthwhile to consider.
>And how long have you been out there? Have you never seen investors dumping and wasting billions in dead-ends? Never seen a mania before?
considering the length of time and sheer number of people, companies, and governments worldwide considering/investing in SMR tech it seems unlikely to be a mania. but i am not an expert. you are talking like you are one, which is why i am asking questions.
>i feel like available space, time to complete construction
All of these favor again bigger reactors.
>considering the length of time and sheer number of people, companies, and governments considering/investing in SMR tech it seems unlikely to be a mania.
All of the Swiss energy companies are asking to be bailed out in advance of the investment in nuclear.
Sweden recently did the same: in order for companies to agree to make new reactors, the government had to promise them a price floor for the electricity they produce. The price floor suggested is more than twice the current price on the spot market. That means that, for the lifetime of those reactors, Swedish taxpayers will be subsidizing production of nuclear power. I thought the idea was that they would be profitable? What happened to the political right’s love of the free market? When politicians go fixing prices with this kind of ”advance bailout”, it just makes it look like they are trying to get a nice retirement job in the nuclear power sector…
You’re right, the total system costs include a lot of things, including disposal of spent fuel. Which is apparently so expensive, nuclear can’t compete with renewables fairly.
That's not true. Disposal of spent fuel was always included in the price of electricity (for example in Germany, but many/most others as well) and is negligible in cost.
Finland just built a spent-fuel repository for ~ € 1 billion. For the entire country. Just the single EPR at Olkiluoto 3 will produce electricity worth €100 billion over its lifetime if you assume a price of 10 cents/kWh.
So at 10 cents, it would be 1% of the price of electricity if Olkiluoto 3 had to finance the whole thing by itself.
What part isn’t true? That disposal of fuel is part of the total systems cost?
Or that the new nuclear can’t compete without subsidies? I think both are evident truths.
I see I implied that the disposal was a major part of the the total cost. Sorry for that, I was being facetious when answering your statement that spot market prices are not total system costs.
Clearly there are many other costs than disposal, which are contributing to its none-competitiveness.
Regarding cost competitiveness: if new nuclear is cost competitive in Sweden, how come it needs to be so heavily subsidized?
1. Once again, when you take full system cost into account and not just spot prices (marginal costs), nuclear is absolutely competitive, even compelling.
2. Nuclear is not heavily subsidized. In fact, it is intermittent renewables that are and must be heavily subsidized pretty much everywhere. In Germany, for example, just the EEG is more than €20 billion per year. And that's not the only subsidy by far.
Within these non-competitive markets that feature heavily subsidized intermittent renewables, other sources may need guarantees, though last I checked the biggest guarantee in Sweden is the one protecting from the risks of government action.
What do you mean by 2), ”it’s not heavily subsidized”?
Remember we’re talking specifically about Sweden now, so I’ll discard any arguments about Germany or elsewhere. I don’t know the background there at all.
The Swedish authorities are right now processing requests for subsidies from prospective owners of future nuclear plants. You can read their announcements here for instance. See the little summary fact box at the bottom. https://www.regeringen.se/pressmeddelanden/2026/06/ansokan-o...
The aforementioned subsidies aren't just for the electricity it produces, it is also for the electricity it could produce. The nuclear plant has a right to sell electricity to the grid at a certain price. Market price too low? The government pays the difference. No demand? The government buys the unused production capacity.
In practice this means that during periods of excess you are shutting down dirt-cheap solar and wind just so you can run a heavily-subsidized nuclear power plant. Nuclear doesn't pick up the gaps left by solar and wind, solar and wind pick up the gaps left by nuclear!
It’s literally the definition of a straw man argument. You state a proposition that nobody proposed, because it’s easy for you to tear it down. While others are arguing about your straw man, nobody is looking at or following up on the proposals *actually* on offer.
Nobody in the thread has proposed turning off all nuclear, hence you were building a straw man. Please don’t do that on HN.
There are two ways of achieving economies of scale: making things bigger or making more of them.
For small quantities, the former is usually more effective -- making things bigger lets you make fewer of them, reducing costs.
For large quantities, a factory can enable insane economies of scale.
SMR proponents are talking about building dozens of reactors. That fits very firmly in the "small quantity" column where economies of scale almost always favor building things bigger.
I think the promise of SMR is that the 1/5th reactor can be built in 1/2 the time. And you build five of them in parallell. And you have your power sources gradually online over about the same time as one ”big bang” build would take.
I don’t think it’s going to work out that way, but that’s how it’s being sold.
Even like that, it is not clear-cut.
1/5 in 1/2 the time is still 2.5 shorter per worker, and building in parallel require multiplying expert builders, which is not easy (as it takes time to acquire the expertise and you don't want to learn a trade to build one project and have nothing to do next).
But, yes, I get it is how it is sold. Just that even sold like that, people with common sense should say "wait a minute, that's obviously not that simple".
Just a guess (I'm not the previous user), but I guess you need to look at the space _per GWh_?
If a big nuclear reactor takes 10x more space but has 20x more capacity, then it means not having much space favors the big nuclear reactor rather than building 10 small ones that will take twice more space.
its probably my fault for not making myself clear. i mean when the available space is constrained to a specific amount of space that cannot be exceeded.
just picking random numbers:
i have 1 square mile available. a big reactor takes 4 square miles. i cannot fit a big reactor, despite the bigger reactor being more efficient.
well, I don't think that there is a real problem of "1 square mile is available but not 4 square miles" (this is a different sentence than "there is not enough space"). Especially as small reactor also need to be placed very specifically. So even then, it is still possible that the advantage is for big nuclear plant, as they are still more compact per GWh.
>"1 square mile is available but not 4 square miles" (this is a different sentence than "there is not enough space").
how are these different? one is an example, one is general, but they communicate the exact same point. if you have something that requires 4 sq. miles, you cannot fit it into a place that is 1 sq. mile in size because there is not enough space to fit it.
>as they are still more compact per GWh.
i am really struggling here... if i cannot fit something large, whether the large thing is "more compact per GWh" does not matter. i only have so much physical space to work with. if its too big, its too big.
for a more easily visualized example, you cannot fit a reactor from three mile island into a submarine. efficiency doesnt come into the equation, because physical space constraints get in the way first.
Well, if you have 1000 places of 1 square mile and 0 space of 4 square miles, the available space is 1000 square miles.
If you have 100 places of 4 square miles, the available space is 400 square miles.
You cannot say that the first sentence means the same thing that the second sentence, and you cannot say that "there is not enough space" is only something you can say in the first-sentence situation and not in the second-sentence situation.
Maybe what you meant to say is not "there is not enough space", but "there is plenty of small space but not a lot of large space" (which I doubt is true in the real world: space occupancy is usually regrouped in dense areas, leaving non-dense areas).
> if i cannot fit something large ... i only have so much physical space to work with
First, the idea that, for a domestic power plant, you only have limited space, seems very unrealistic. The real world is not a submarine or a 7/11: you want your power plant at the periphery of cities, not squeezed between 2 buildings in the middle. There is only disadvantage of doing so: you cannot distribute high power lines from the middle of the city safely, you probably need facilities to deal with the fuel, probably need water for cooling, probably need a security perimeter as you have around any typical factory, the cost of the square meter is more expensive, ...
But secondly, you need the power plant to produce some power. If your country needs X GWh, and you need either 1 large power plant of 4 square miles or 10 SMR of 1 square mile and you just have few places where you can put a power plant, the "the unit itself is more compact" does not matter . I only have so much physical space to work with. If the surface needed to get X GWh using SMR is too big, it's too big.
> you cannot fit a reactor from three mile island into a submarine
Yep. Similarly, you cannot fit a SMR in a bicycle. But how is that relevant? In real life, domestic power plant do not have the constraints of being in thigh places (on the opposite, it is better for a power plant to be in regions that also happen to not have thigh places).
>Maybe what you meant to say is not "there is not enough space", but "there is plenty of small space but not a lot of large space"
my bad, i forgot i was on HN where this type of pedantry is the national sport. it sure sucks any tiny little bit of enjoyment one might get out of having a conversation. it's evident from the rest of your comment you knew exactly what i meant.
>First, the idea that, for a domestic power plant, you only have limited space, seems very unrealistic [...] But how is that relevant? In real life, domestic power plant do not have the constraints of being in thigh places
part of the point of SMRs is to be able to have them in space-constrained places where you otherwise cannot build a large facility. that's the appeal! google and meta aren't looking at them so they can power san fransisco or the country with multiple GW. they want to power a datacenter. i can think of other examples of space-constrained places where an SMR is appealing and a traditional facility is impossible, but you've managed to kill any interest i had in having a conversation.
You seems to be the pedantic one here: ask anyone in the street "what does it mean to not have much space in a room", they will never answer "having a big room surface but the stuffs in the room are spread so that there is not much space between each things".
Pretending that saying "we don't have much space" and crying like a baby when someone say "well you may not have plenty of 10 miles squares areas, but you can put a 4 miles square large reactor in one of them, and it will be better than having to build 10 1 miles square small reactors", that's being the pedantic one: you cannot complain that normal people understand normally what "we dn't have much space" means.
> part of the point of SMRs is to be able to have them in space-constrained places
Yes, but this is not a problem that exists in real life. It helps in some scenarios, but it is not the main practical issues that people have.
> that's the appeal! google and meta aren't looking at them
Google and Meta are not looking at SMR _because they don't have enough space_. This is not true at all: if you look at their projects, they have plenty of space.
They are looking at them because they want to generate a small quantity of electricity for their own usage. They want their own small reactor. But it does not invalidate that these small reactors are less efficient than big reactors: they are just happy to pay 2X dollars for a reactor they fully own than to pay X dollars for the same quantity of energy for a share of a big reactor, because it is more difficult to manage if you have to find partners and make sure everyone is agreeing.
I think you have a misunderstanding of what a SMR is supposed to be.
Nuclear power plants are eye watering levels of expensive. The require massive scale and cost with lengthy approvals and requirements, the fundamental idea of SMRs is to move that cost and approvals into a smaller scale so that multiple standard units can be produced and deployed in a turnkey situation, they still will be expensive but the time to deploy and cost will be significantly reduced.
We also know SMRs work very well, considering the majority of the US Navy is powered entirely with SMRs and have been for a very long time. Off the top of my head ship power has been exported to local areas for disaster relief
Solar is absolutely fantastic and your average person should not be hawking at solar for your home to offset your power bill. The problem with solar is that you need power 24/7 and solar will not make power in the night.
I don't think the likes of Westinghouse, Siemens, Rolls Royce and GE are duped. They are trying to solve a very hard problem!
This is such a silly argument. Battery and solar technologies are progressing regardless of people building nuclear. It's simply not the case that we can stop investing in nuclear and use that money to accelerate battery/solar.
This isn't a silly argument, this is a problem of allocation of resources.
We could have had mass solar deployment since the 70s. We chose not to, and allocate the money elsewhere. Nuclear will take away billions in public money, put it into the hands of nuclear industries, to get electricity at twice the going rate, maybe, in twenty years. A white elephant and a waste of effort.
All the R&D and industrial capacity building we have done since the 70s could have been accelerated if we had invested in it as much as we invested in nuclear, or oil, or gas, or coal. With public money.
> Ok, question: for the cost of one nuclear power plant, how many batteries can you have?
Not that many. Sizewell C the latest nuclear project in the UK is projected to cost around 50 billion and expected to last for 60 years. We can cut that estimate short to say oh well, About a billion a year for the next 50 years.
Assuming that you can purchase storage at $70/kwh with 50 billion you could purchase around 715GWh of battery storage, at the same output of Sizewell C that means you could output 3.2GW for 200+ hours! wow.
One problem. The batteries will realistically only last somewhere between 10-20 years. A moderate 15-year estimate would be more realistic. Now obviously it's very hard to calculate and account for a reduction in pricing increase in capacity etc... But with today's technology you would have to buy the pack 3.33 times over
So now you go into 0.300 * 715GWh gives you 214.5 GWh and now with that 3.2GWh load it could run for just shy of 3 days. This is like the entire capacity storage of China right now.
So yeah, to answer your question 214.5 GWh of storage
> For the cost of the R&D of one next generation nuclear reactor design, how many next generation battery and solar panels technologies can you develop
This is a horrible argument. Yeah, let’s not spend money improving technology. We wouldn’t have increased Solar panel efficiency if we followed such ill advice.
>We wouldn’t have increased Solar panel efficiency if we followed such ill advice.
We didn't for decades. The photoelectric effect is known since the XIXth century. Solar panel research could have had far more money behind it since the 70s and the first oil crisis. It was a choice not to. And the current US and Swiss governments are choosing to prop up some industries -coal, nuclear- at the expense of others, with public money that don't grow on trees.
I think you have a misunderstanding of economies of scale.
There are two ways of achieving economies of scale:
1. make things bigger
2. make more of them
Making things bigger generally is more effective when n is small. You need fewer sites, fewer approvals, each of the steps in the process is done fewer times.
When n is large, you can build and optimize a factory for them and achieve economies of scale that way.
Nuclear plants got large to take advantage of economies of scale because n is small. Nobody's building millions or even thousands of SMR's.
So a whole lot of sense given the entire US Navy uses them and I already have one datacenter operating up in space (small test unit that over 3 months has provided ZERO issues) and a bigger one heading up into orbit next year when it's done being made.
"but you can't gaslight thermodynamics"
No but you can certainly conflate them like you're doing right now.
The Navy uses highly enriched uranium for its reactors, something like 70-80% enrichment. This is a non starter for civilian use, on account of proliferation concerns. That, and the enrichment requirements drive up fuel costs.
What does the enrichment of uranium have to do with humans working in proximity? In both low-enriched land based plants and in marine nuclear power plants, the radioactive materials are contained in the pressure vessel and inner cooling loop.
So in other words: a non-naval SMR which doesn't use HEU is going to be substantially larger - which would make it substantially more expensive, and therefore not representative of civilian SMRs?
Who said anything about expense? Why does "bigger" equal "more expensive?" Lead, concrete, etc. are cheap on land, but volume is a precious resource on a ship. HEU isn't the only reactor fuel out there, either.
And of course, all non-naval reactors are naturally going to be larger: they aren't surrounded by a practically-infinite fluid heatsink.
Ok, this is interesting. I am skeptic about DC's in space, but I do appreciate people actually doing stuff. What is it computing up there. How did you get it up? How does one usually talk with their satellite. I guess you don't merely have a dish since it's probably not geostationary.
Hyperspectral satellite imagery - think ASTER/LANDSAT/MODIS but more modern, for surficial minerals study.
"How did you get it up?"
How else? Paid a rocket company to launch it into orbit after proving various flightworthiness tests and getting various certifications and permissions from relevant gov't authorities.
"How does one usually talk with their satellite. I guess you don't merely have a dish since it's probably not geostationary."
K-band. Don't need tons of power, just a good LoS from ground on your target. And yea, not Geostat, I'm in LEO.
Right, so a regular satellite. That's indeed as relevant to the multi-100kW-scale "space datacenter" idiots like Musk are proposing as naval SMRs are to commercial power plants.
All satellites are regular satellites, there is literally nothing special about anything in orbit outside of what it carries - it's still just a falling body in space.
100kw is literally nothing to generate in space. At typical silicon efficiencies that's football field in size, and about 70% that if you jump to more expensive multi-junction cells. I can make a folding panel the size of a compact car that'd unfurl out to cover that. That's maybe 4 hours in NX just retooling my current design. The only limitation is the capabilities of the launch vehicle.
I've already got one small (single 4U) datacenter in orbit. It works. It works GREAT. It can scale up to constellation quantity.
And I don't have to waste any water for cooling or constantly pollute the air for power generation or throw extra waste heat into our atmosphere, as a side bonus.
It makes plenty of sense to those with the education. What's hilarious is I'm doing all this on a GED.
SMR make as much sense as space datacenters. You can gaslight investors, you can gaslight HN, you can gaslight a national parliament full of lobbyists, but you can't gaslight thermodynamics.