[Arodex]

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.

[mpweiher]

> Every SMR startup is failing.

https://news.ycombinator.com/item?id=48586648

[Arodex]

Have you read the comments?

[mpweiher]

Yes. Have you?

Are you of the opinion that the comments on that article are conclusive evidence for all SMR startups failing?

If so, how? Please try to be specific.

I don't see evidence of even one startup failing there, never mind all of them.

[Arodex]

>Please try to be specific.

https://www.rechargenews.com/analysis/smrs-v-renewables-mini...

"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...

https://www.pv-magazine.com/2026/05/06/firm-solar-and-storag...

"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.

[p2detar]

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.

0 - https://world-nuclear.org/information-library/nuclear-power-...

[Arodex]

>Yes. Have you?

I have a bridge to sell you...

[RealityVoid]

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.

[Arodex]

Thermodynamics are the reason why SMR aren't, and will never, be economical. A bigger nuclear reactor will always undercut your price per watt.

[Manuel_D]

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.

[crote]

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.

[0]: https://en.wikipedia.org/wiki/Akademik_Lomonosov

[chickenbig]

> Thermodynamics are the reason why SMR aren't, and will never, be economical.

And the link between thermodynamics and the price of electricity is what?

[Arodex]

Your small nuclear reactor is going to need almost as much engineering , plumbing, safety mechanism, personnel, maintenance, etc... as your big nuclear reactor.

[chickenbig]

> 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.

[0-_-0]

Not if it's mass produced

[crote]

Mass-produced reactors don't need operators or guards?

[palata]

Let's distribute the risk everywhere, what could go wrong?

[holoduke]

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

[dalyons]

This is just faith without evidence

[RealityVoid]

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.

[bakies]

What are the challenges they face?

[Manuel_D]

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.

[projektfu]

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.

https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/n...

[2muchcoffeeman]

Doesn’t China have SMRs?

[hangonhn]

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.

[lightedman]

"SMR make as much sense as space datacenters."

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.

[Manuel_D]

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.

[15155]

Naval reactors use HEU specifically so that humans can live and work in close proximity for long periods of time.

Land-based deployments don't have this constraint.

[Manuel_D]

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.

[15155]

HEU results in fewer actinide products and a substantially more-compact reactor.

[crote]

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?

[Arodex]

>the entire US Navy uses them

Is the business of the US Navy to sell electrity on the market?

You are the one conflating things that have absolutely no connections.

[lightedman]

"Is the business of the US Navy to sell electrity on the market?"

No but they do use those reactors to power areas in times of disaster relief.

[Arodex]

So, when cost is of no importance.

[RealityVoid]

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.

[lightedman]

"What is it computing up there."

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.

[crote]

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.

[lightedman]

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.

[marcosdumay]

Yes, SMRs probably have a small niche market on military-adjacent applications.

[john_strinlai]

>SMR make as much sense as space datacenters.

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?

[Arodex]

>commercially operating

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.

[TheDudeMan]

Efficiency is not the problem. We have plenty of nuclear fuel.

[Arodex]

Money doesn't grow on trees.

[jkman]

>'taylor-made' Says it all, doesn't it

[john_strinlai]

>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.

[Arodex]

>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.

[Jolter]

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…

[mpweiher]

The biggest risk for nuclear is the government.

That's why the government has to indemnify the companies against those risks.

Spot market prices are not total system costs.

[Scroll_Swe]

Base load generation.

Yes, we have hydro.

Wind is way too unpredictable, solar is too.

So, we can only have 2 powers to provide base load in Sweden.

https://www.svk.se/om-kraftsystemet/kontrollrummet/

[john_strinlai]

>All of these favor again bigger reactors.

how does having less available space favor a bigger reactor?

and how is constructing a bigger reactor faster than constructing a smaller one?

[bryanlarsen]

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.

[Arodex]

If you need 500 MW, you build one 500 MW reactor, not five 100 MW reactors. They will take more space.

As for speed, a 100 MW reactor is not commissioned in 1/5 of the time a 500 MW reactor is.

[cauch]

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.

(and same for the time)

[vablings]

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!

[Arodex]

>The problem with solar is that you need power 24/7 and solar will not make power in the night.

Ok, question: for the cost of one nuclear power plant, how many batteries can you have?

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?

[vablings]

> 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

[slibhb]

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.

The best energy strategies are all-of-the-above.

[Arodex]

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.

[p2detar]

> 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.

[Arodex]

>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.

[bryanlarsen]

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.

[crote]

> We also know SMRs work very well, considering the majority of the US Navy is powered entirely with SMRs

And what's their cost per MWh?

Considering they are fueled by highly-enriched uranium: are you okay with most of the world being handed the capability to build nukes?

[vablings]

> And what's their cost per MWh? We do not know but its likely expensive

>Considering they are fueled by highly-enriched uranium: are you okay with most of the world being handed the capability to build nukes?

There are SMR designs that do not use highly-enriched uranium.

https://assets.publishing.service.gov.uk/media/69b2f41497f6f...

" The RR SMR uses PWR technology and industry standard LEU fuel and builds on operational experience from existing PWR reactors."

I cite this as RR is the most advanced out of all the other companies working on this afaik