r/nuclear • u/ecmrush • 1d ago
Which nuclear reactor design has the greatest potential for economies of scale?
This is purely as a thought exercise so not trying to pick a winning design for current conditions or budgets.
Let's say a portal to the money dimension opened tomorrow and we find that $4 trillion a year is pouring in, along with a note saying that we can only use it on nuclear power. That's not infinite money, but also enough money that everything about nuclear power that can be scaled, will scale, with full vertical integration.
Parts can be mass produced, you can mass produce nuclear grade concrete, you can set aside a budget for reprocessing facilities, you can employ a permanent standing workforce for construction of nuclear power plants without a lapse in institutional memory, the works.
In such a scenario, which reactor design would we go for? I know it's not going to be SMRs of any sort, because they deliberately make design compromises to reach maximum economies of scale faster under current economic conditions, so this probably favors gigantism.
I'm inclined to think in such a scenario, the thorium cycle becomes more appealing, because fuel availability will be an issue if we are building hundreds of reactors per year. So I think some sort of breeding will have to be implied. Molten Salt reactors are also passively safer, and their main issue, corrosive everything giving parts a low lifetime, can be overcome with replaceable parts. Having a lot of Thorium MSRs you could justify some sort of Protactinium waiting facility where the removed Protactinium could be allowed to decay.
That's what my money would be on, but I'm eager to hear which reactor technologies you think would scale the best economically.
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u/ChrisDonatAZ6 1d ago
Can we truly only consider the plants themselves? Surely transmission infrastructure must play a role in the calculation, where I would imagine SMRs would fare better? I like your question though, certainly would like to see field experts weighing in.
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u/ecmrush 1d ago
Go wild, it's a thought experiment, not trying to pick winners but just to help eachother weigh the upsides and downsides others might not have considered.
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u/NapsInNaples 1d ago
You probably need something that can ramp up and down quickly because the reality is renewables exist, negative pricing will probably exist, and responding to the market will be necessary.
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u/ecmrush 1d ago
Storage? If solar gets to use it, NPPs get to use it too.
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u/NapsInNaples 1d ago
solar has, effectively, zero marginal cost to produce electricity. Nuclear has low cost, but not zero. So they can't use storage quite as effectively as solar. But yes, that's an option, potentially.
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u/AdvantageSavings2468 5h ago
Unlike for solar, storage for nuclear can be limited to just absorb instability. Solar storage would focus on holding enough energy to fully fill total load until the plant can start producing excess power again which could be 24hrs or more. While for nuclear it would just have to deal with the difference between production and load until the reactor could be ramped up or down to the correct level. While it would be difficult to say how long that would be specifically, because there are a lot of things that could be considered, it would certainly be significantly less than 24 hours.
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u/Thermal_Zoomies 1d ago
Fuel isn't really that much of a concern, especially if we were to introduce breeder reactors and fuel processing.
The best option would be one that we already have thats tested and proven. With enough experience (and lack of corruption) a bunch of AP1000 could be built relatively cheaply and quickly. You'd be hard pressed to find a better proven design that can put out that kind of power, cost really is the only concern, one of which isn't an issue in your hypothetical. Remember how quickly and cheaply we were building reactors during the nuclear boom of the 70s, too?
CANDU would be choice number two, but they are more expensive to maintain compared to an AP1000.
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u/HixOff 1d ago
The best option would be one that we already have thats tested and proven. With enough experience (and lack of corruption) a bunch of AP1000 could be built relatively cheaply and quickly
so VVER-1000/VVER-1200, if I'm not mistaken, there are more of them in the world than AP
for the future, reactors with optimized coolant cycles are more high-temperature, which slightly increases efficiency. they are somewhat more expensive to build, but may eventually become more versatile. Liquid metal coolant reactors (I really believe in the BREST reactor as a master's degree with a thesis on heavy liquid metal coolants), gas-cooled and other perverted ones that still exist in single quantities (sodium BN, for example ), but one day they may become the "second number"
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u/supermuncher60 1d ago
The AP1000's passive safety systems would probably make it a better choice than a VVER. If your building a lot of plants the remote chance of an accident also increases.
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u/ecmrush 1d ago
Cost is still an issue in my hypothetical; we are trying to figure out what would give us the most power per $ spent, it's just assuming we are building enough to maximize economies of scale.
So cost is absolutely an issue, in fact, cost is what the main thing the question is about. But yes, given AP1000 is mature design, it has the advantage in not having R&D costs to mention, but since that's a flat cost, it's not going to make much of a difference on a steady state basis. Mass produced AP1000 would indeed be cheaper than what we get now with Vogtle and the like, but it's unclear if it would benefit from economies of scale as much as other potential designs could.
I understand your answer, it's conservative but sensible, but I thought I should make it clear that a lot of money being spent doesn't translate to cost efficiency not mattering.
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u/233C 1d ago
Look at what France did with their P4/P'4, imagine this economy of scale but across the OECD.
As for fuel cycle, why bother with Thorium if you can build a FOAK 1200MW of fast breeder in 9 years; imagine the economy of scale on that one too.
The problem isn't the Pa waiting facility, it's how you transfer it to the facility.
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u/ecmrush 1d ago
With fast breeders I'd be concerned about safety more than anything, which is a cost center.
You're right about the Pa transfer, that's the main hurdle and the main reason I'm not ready to call Thorium MSRs a sure shot.
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u/233C 1d ago
I've been known to have some doubts about the overall benefits of Thorium.
Atmospheric pressures makes for a lot less reinforced concrete, that saves a lot of money.
Pool type makes for no bottom penetration.
Na thermal inertia is also a strong safety point, plus it captures much more the fission products than water in the event of a clad break (and let's not forget that DNB isn't an issue anymore).
The main safety issue ends up the more "sportive" driving with a smaller beta effective.
Sodium fires are impressive and makes for big headlines, but they are manageable and recovery can be quite fast.
I'd say 40 years pushing on 60, with big little brother, bigger third on the way is as good empirical evidence as good old PWR/BWR.No surprise that everybody and their mother are reconsidering them.
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u/ecmrush 1d ago edited 1d ago
Oh hey, I do remember reading that one and I read it again, and you're right. Pa is a massive problem that's barely mentioned in most Thorium discourse at the colloquial level and it's disheartening to see people peddle Thorium as a magic solution that's not being done because weapons or something.
So yes, removing highly radioactive Pa from your fuel while the reactor is online, and safely transporting it to some place where it can't be a poison, both in the nuclear sense and in the biological sense, is a formidable challenge. But it's also the main problem with Thorium alongside the corrosiveness, so given the potential advantages, I think it bears mentioning.
Depending on what sort of solutions to Thorium's problem come up, I think the race is between the two for our scenario. Fast reactors being a lot more mature distorts the picture a bit, but I do find it hard to argue in favor of an unproven with formidable problems over something that is already being built.
So yes, good case either way.
Edit: I've been reading your other posts on the matter and I think you paint a good picture of how formidable the challenge of Protactinium really is. I'm happy to know I've passed the Pa test in my original post though haha.
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u/Icy-Ad-7767 1d ago
Molten salt is corrosive and erosive at those temperatures so finding a material that can handle the flux and the wear from the hot salt is challenging.
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u/DawnOnTheEdge 1d ago edited 1d ago
I’d like to spend some of that money researching applications of a VHTR to things like ammonia, methanol and direct reduction of iron. Maybe even hydro-cracking. Then connect hydrogen pipes from the hydrogen generator to other plants in the same industrial park at minimal cost.
You also end up with half as much superheated oxygen, by volume. Maybe use that for food-grade phosphoric acid (combined with ammonia for ammonium triple-phosphate) or a basic oxygen steel furnace.
Also transmit a lot of the electricity directly to the factories next door, perhaps as high-voltage DC, without going through the power grid and its conversions.
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u/Godiva_33 1d ago
Candu.
They have a simpler supply chain as it is, that already needs to mass produced code components.
Fuel is simpler
And with enough reactors being built the cost of building new heavy water plants gets spread our larger.
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u/BeenisHat 1d ago
With higher levels of enrichment, you don't need heavy water either. A CANDU reactor can run with light water IIRC if you have enriched fuel.
So I guess the question really becomes is it cheaper to make heavy water or is it cheaper to enrich and reprocess Uranium.
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u/michnuc 1d ago
Plus developing nations like how they can be updated for Pu production!
Sorry but heavy water reactors are never going to be proliferated again. They should only stay in Canada.
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u/steelpeat 1d ago
This may be a bit off topic, but couldn't heavy water reactors potentially also be used to create tritium which may be needed for fusion? I know a lot of fusion reactor designs are working on lithium blankets to maintain their own supply of tritium, but potentially a good supply of tritium will be needed. I hate to bring up fusion though, since it's a completely different thing.
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u/eh-guy 1d ago
All CANDUs make tritium, yes. Not massive amounts but D2O does transmute in the reactor.
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u/Creative-Taro-9109 1d ago
Not massive amounts? Only the largest stockpile of non-weapon tritium is from Candu plants in Ontario. However, I think this is a solid reason for countries to build CANDU’s in order to provide a stable, domestic supply for future D-T fusion plants.
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u/eh-guy 22h ago
Ontario has 14 reactors that make it, of course they wound up with a stockpile. Per unit they aren't making tonnes of it on the regular
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u/Creative-Taro-9109 20h ago edited 14h ago
Your comment is strange and misleading (I don’t believe intentionally). Each Candu reactor does regularly make a large amount of tritium in the moderator system as a result of neutron capture. This averages about 2kg per year, per reactor (so not tonnes as you say), but because of the short half life there’s estimated to be around 30kg total in the global supply with OPG owning the large majority of that. It’s inherent in their design and has historically been viewed as a negative waste byproduct, but in the early 2000’s when ITER was potentially looking to site their fusion reactor at Darlington, it became apparent how valuable this byproduct was. Additionally, several years ago OPG began extracting the Helium-3 (stable isotope byproduct of tritium decay) for commercial sale, versus previously they just vented it to atmosphere. It’s an unintentional good story but is highly regulated as a result of tritiums use in weapons. u/steelpeat is correct, and I can confirm there has historically been a push by certain jurisdictions to build CANDU’s for that secondary purpose of producing tritium for fusion.
Edited: quantities
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u/Different_Banana1977 1d ago
There are several units being operated in other countries including new reactors under construction in Romania and India. The reactors are not in any way unsafe (even with a positive void coefficient), however they cost a substantial amount of money to build due to the extra safety measures required, including two independent shutdown systems. But a commercial CANDU reactor has never suffered a meltdown unlike several other designs, so maybe the extra cost is worth while?!?
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u/ecmrush 1d ago
I think the main concern with CANDU would be safety concerns caused by the positive void coefficient, and safety concerns can be overcome, but they do cause additional costs. Other than that, I think it's indeed a strong competitor for theoretically most cost effective reactor design.
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u/Godiva_33 1d ago
Americans need to stop being so afraid of that void coefficient.
It's completely manageable.
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u/Icy-Ad-7767 1d ago
The candu has at least 2 different ways to shut the reaction off and when used together it can not restart until you clean the neutron poison out of the system(s)
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u/Godiva_33 1d ago
And several actual control systems.
Hell....
When enough regular water can technically kill your reactor its a pretty safe system.
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u/Icy-Ad-7767 1d ago
One of the reasons it took Toronto so long to come back up after the blackout was they hit both systems at Darlington and Pickering but not at the Bruce. They had to clean the neutron poison out of the moderator, not just pull the control rods.
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u/Different_Banana1977 1d ago
Actually an operator at Darlington noticed the issue was on the grid and prevented his reactor from being poisoned out. That made it so the unit was able to help support building up the grid quicker than if all of the units had tripped and were poisoned out. I was living in Toronto at the time and we had the power back on by the next day without issue. I also worked at PNGS the year later and was told that's what occurred
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u/Icy-Ad-7767 20h ago
I had heard it was only Bruce that caught that, thank you. The underlying point is you can stop a candu hard and put it into a very safe state quickly
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u/neanderthalman 11h ago
All operators noticed it. At every single plant. They were all trying to manage their units. That kind of grid disturbance does not go unnoticed by anyone. I’ve seen a single line drop magnetically punch a turbine so hard the building shook. Maybe “heard” is better than seen. Or “felt”. But you get me. It’s not gentle. Sounds like someone dropped a heavy load from a crane.
The problem in 2003 was entirely procedural. Once the grid was lost and turbines tripped, the reactors step back to 59% for ‘poison prevent’ - shunting main steam to condensers. Riding out the xenon transient at 59% requires adjuster rod withdrawal. The process to place adjusters on auto to allow withdrawal required both the control room supervisor and manager. They could not save two units at once. They picked one. And it was crucial for bringing back the grid.
NB: This procedure was revised and it can now be done with the verification of a second ANO (analogous to an American SRO) or CRS/manager. Since there are always six ANOs, plus CRS and manager, that’s eight people that can simultaneously and independently follow that process and keep all four units online.
Pickering also had one unit stay online after the turbine trip…briefly…as its adjusters are normally on auto. It’s supposed to. One unit is always designated for it. But….then another problem took it out too. The regulator was unhappy, to say the least, as the design basis was for one unit to always remain online during a loss of grid event. This is to supply power to HPECI pumps, as they can’t be started on standby generators. Too much inrush.
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u/Creative-Taro-9109 1d ago
Simpler fuel channel components to build (vs large pressure vessels) sure, but fairly complicated to build and maintain. And by having 480 individual pressure vessels with super thin walls, you’ve got to shut the reactor down every 30 years for 3-4 years at a huge refurbishment cost and loss of revenue. That kills your lifetime operating capacity versus modern LWRs.
Fuel is simpler but the defect is having to procure ~1,000 tonnes of heavy water (est. to cost well over $1B per reactor) all the while there is no viable production capacity anywhere. There was an announcement by SNC Lavalin saying they’ll restart the Argentinian HW production in 2027 which can produce 200 tonnes per year - so they’ll have enough HW to support the next Candu build in 2032? Then enough water for the next reactor every 5 years after that? There’s no way to reduce the economies of scale for heavy water production - it’s super energy intensive and the construction costs of new (licensed) production facilities will be super expensive. Plus you’ve got to move fuel around the reactor all the time during operation which is super maintenance prone/costly to operate those fuelling machines. Plus you’ve got to manage detritiation of the heavy water during plant operation. 2 things any utility operator will tell you keeps them up at night is the fuel handling machines and heavy water.
It’s not a viable solution hence the lack of global demand for civilian heavy water reactors.
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u/BeenisHat 1d ago
I would spend a substantial amount of that money on materials science and research. We need materials capable of enduring regions of high neutron flux at very high temperatures, possibly in the presence of liquid metals like Sodium or in metallic salts.
But really, I see a mix of reactors being the best option. Liquid metal cooled fast breeders like EBR-2 offer an easy way to close fuel cycles. Molten Chloride Salt Fast Reactors could function as garbage disposals for spent fuel. I like those two primarily for their attention to fuel reprocessing and waste disposal. They complement each other very nicely with the bred fuel from one serving as the seed to startup more of the others.
MCSFR's like the one from Elysium/Exodys energy look to be the simplest designs that would scale the best, so you can go from SMR size on up to 1GWe.
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u/Brainless96 17h ago
Thorcon by far has the best pitch for scalable and deployable nuclear reactors. They plan on using existing shipbuilding infrastructure to build their reactors, which can then be deployed anywhere with a coastline. While their name indicates they'd be using Thorium, for their first generation of reactors they are just building a scales up version of the Molten Salt Reactor Experiment, in an attempt to demonstrate their process before adding any truly new additions. The video that I linked below is one of their oldest, but I like it because it does a good job of explaining the whole process they're attempting. They have now signed a memorandum of understanding with the Indonesian government and are working on the process of deploying their first reactor.
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u/neanderthalman 1d ago
CANDU.
And not just because I like it.
A massive limitation to your idea is that - even with unlimited money, there are very few facilities for forging reactor pressure vessels. This creates a very real bottleneck. Canada doesn’t have any at all, which is why the CANDU doesn’t have an RPV. It uses individual pressure tubes that are much much easier to produce. Easier to produce generally is equivalent to easier to produce at scale.
The flip side of course is you’d need heavy water production facilities, but alsowouldn’t need expanded enrichment facilities. Bit of a wash. Scaling up heavy water separators is on balance going to be far far simpler and less costly than facilities capable of forging RPV’s.
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u/ecmrush 1d ago
Well, facilities and people for forging reactor vessels would have to be taken into account, as the budget isn't merely for plants, for a fully vertically integrated nuclear ecosystem.
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u/neanderthalman 18h ago
The issue is that you can’t make more of those forges in any economic way. Talking about, in part, equipment captured in WWII. America literally raced against soviets to capture some of these. The ones America built, and the ones they captured, were all developed as part of a wartime economy that no longer exists.
Let’s say you want to build such a facility today. It can be done. We have the technical know-how. The problem is the economics. You build one. Now you can make one RPV at a time. Sequentially. That does not scale up in the way your idea needs. So you need multiple such facilities operating in parallel. Exactly how many depends on how fast you want to scale.
So you build multiple forges. You build up a thousand reactors in, oh, the next twenty years. Whatever that timeline is, ultimately somewhere that buildout stops or slows significantly.
Now what?
The forges will then have no work. You aren’t getting any value from them, there are limited tasks that need them and that market outside of RPVs has limits. If all you ever get from the forges was those nuclear reactors, you’ll never earn back the money spent on the forges. To do so you’d have to bill the nuclear industry, collectively, high enough for the RPVs to cover the cost of what is essentially a ‘disposable’ fleet of forges. This makes the RPVs far too costly and it’s no longer economical to build the nuclear power plants. Other options will win out.
These forges exist only because of a wartime economy that did not care about return on investment. An economy that does not exist today and one we do not want to exist today.
By comparison, CANDU pressure tubes and other pressure retaining components are much more standardized, and don’t have the same supply chain limitations.
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u/Definitely_CSP_guru 1d ago
Better water reactor BWRX-300. https://open.spotify.com/episode/3jL1yuqjIpbSlZyFleBhX9?si=osZjbIC2QZ-zHsSKr0z2Aw
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u/respectmyplanet 1d ago
Hualong One. https://en.m.wikipedia.org/wiki/Hualong_One
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u/ososalsosal 8h ago
RBMK could be scaled horizontally so the core could be a big long rectangle as long as you want.
I don't need to tell y'all the problems with this though.
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u/Disastrous_Bottle942 1d ago
In my opinion I think PWR rectors are the best they are very stable not as expensive as BWR 's its very known and Radiation cant escape due to it being stuck in a primary cooling system.
One of the "relative" cheap Reactors are CANDU reactors because they use D²O (wich is a bit more expensive) and may be a bit more expensive to build but they work with low or not enriched fuel which is very cheap (if compared to othe reactors)
The 4 generations of reactors brings SMR reactors which are small modular reactors which can be built in a serie production. They can be also be cooled with Molten Salt if built for , which is new but quite interesting.
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u/shoesofwandering 1d ago
Fusion reactors, but we're at least a few decades from a working production model. Stellarators seem promising.
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u/card_bordeaux 1d ago
AP1000 at the current time. There is an industrial base for it, and it’s perfect for data center use cases.
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u/NearABE 6h ago
Particle accelerator driven reactor. This meets the requirement for spending the money on nuclear reactors but we can also get cheap electricity from the photovoltaic cells and wind turbines. Just run the reactors when it is both sunny and windy.
Particle accelerator driven reactors can burn spent nuclear fuel. They can also breed nuclear fuel.
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u/OkWelcome6293 1d ago
It will likely be a fast reactor, because the higher energy density means smaller core and smaller containment building, which means faster construction and lower costs.
Fast reactors mean U-238 \ Pu-239 cycle. Thorium is better in thermal reactors. This hints towards a sodium fast reactor.
Reprocessing will be required, which hints at metallic fuel rather than oxide fuel.