Chinese research institute confirms success of fission-based innovation that is poised to reshape clean, sustainable nuclear power.
The achievement makes the 2 megawatt liquid-fuelled thorium-based molten salt reactor (TMSR) the only operating example of the technology in the world to have successfully loaded and used thorium fuel.
According to the academy, the experiment has provided initial proof of the technical feasibility of using thorium resources in molten salt reactor systems and represents a major leap forward for the technology.
It is the first time in the world that scientists have been able to acquire experimental data on thorium operations from inside a molten salt reactor, according to a report by Science and Technology Daily.
The article, published on Saturday, was China’s first official confirmation of its success in the development of TMSR technology, an innovation that is poised to reshape the future of clean sustainable nuclear energy.
02:37
Trump orders US military to resume nuclear weapons tests for first time in 33 years
Li Qingnuan, Communist Party secretary and deputy director at the Shanghai Institute of Applied Physics, told the newspaper that “since achieving first criticality on October 11, 2023, the thorium molten salt reactor has been steadily generating heat through nuclear fission”.
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By credit_guy 2025-11-2220:377 reply Before anybody gets too excited, it's better to understand what exactly happened.
China ran an experimental reactor that achieved some conversion of thorium into uranium. More precisely, the conversion ratio was 0.1 [1]. This means that for each new fissile atom generated from thorium (i.e. uranium-233) 10 atoms have been burned from the original fissile inventory.
Now, conversion happens in every nuclear reactor. Some new fissile material (generally Pu-239) is generated out of "fertile material" (generally U-238). And, surprisingly, that conversion ratio is quite high: 0.6 for pressurized light water reactors and 0.8 for pressurized heavy water reactors [2].
What China has achieved therefore is well below what is business as usual in regular reactors. The only novelty is that the breeding used thorium, rather than uranium.
Is this useless? No, it is not. In principle increasing the conversion ratio from 0.1 to something higher than 1.0 should be doable. But then, going from 0.8 in heavy water reactors to more than 1.0 should be even easier. Why don't people do it already? Because the investment needed to do all the research is quite significant, and the profits that can be derived from that are quite uncertain and overall the risk adjusted return on investment is not justified. If you are a state, you can ignore that. If China continues the research in thorium breeding, and eventually an economically profitable thorium breeder reactor comes out of that, the entire world will benefit. But the best case scenario is that this would be three decades in the future.
[1] https://www.world-nuclear-news.org/articles/chinese-msr-achi...
[2] https://en.wikipedia.org/wiki/Breeder_reactor#Conversion_rat...
By keepamovin 2025-11-237:193 reply The real killer feature isn’t "more thorium than uranium" (thorium is already 4× more abundant). The real win is that thorium MSRs can eat the existing mountain of "spent" fuel rods from regular reactors and turn what we currently call high-level waste into electricity while leaving waste that’s safe in a few hundred years instead of tens of thousands. That’s hundreds of thousands of tons of "waste" suddnely becoming centuries of clean fuel. That alone flips the economics on its head.
Also: passive safety (the thing just drains and freezes if anything goes wrong), no pressure vessel, tiny physical footprint, way less long-lived actinides, and U-233 is basically proliferation-proof because of the hard gamma from U-232. Uranium feels cheap and plentiful right now exactly the way oil felt infinite in the 1950s. China is playing the long game, and this little 2 MW rig lighting up and breeding U-233 last month is the “Sputnik moment” for the thorium cycle.
So...Three decades? Maybe if the West keeps sitting on its hands. China says 10 MW by 2030 and 100 MW demo by 2035. I wouldn’t bet against them.
So yeah, exciting as hell actually.
By nandomrumber 2025-11-239:555 reply 1. There is no mountain of nuclear waste.
Literally almost all the waste that’s ever been generated is stored on site at the nuclear power plants where it was created. That’s how little of it there is.
Talking about “thousands of tonnes” of nuclear waste is comically misleading when you realise how tiny the volume is.
2. There is no high level waste that is both very dangerous right now, and will remain so for tens of thousands of years. It’s either highly radioactive for not very long, or not very radioactive for very long, but never both.
How do these myths persist in otherwise educated people.
By tonyarkles 2025-11-2313:45 > Talking about “thousands of tonnes” of nuclear waste is comically misleading when you realise how tiny the volume is.
Yeah, it’s really easy to forget how dense these materials are. A jug of milk (4L/1gal) weighs 4kg/8.8lb. Milk has about the same density as water, 1g/cm^3. Uranium has a density around 19g/cm^3, making that same gallon jug weigh 76kg/167lb. A metric ton of uranium (1000kg) is about 13 gallons.
By interestica 2025-11-2321:00 > Talking about “thousands of tonnes” of nuclear waste is comically misleading when you realise how tiny the volume is.
You’re mixing mass and volume here. From what I can tell, their numbers were essentially right. Are you saying we don’t have thousands of tonnes of nuclear waste produced?
> Talking about “thousands of tonnes” of nuclear waste is comically misleading when you realise how tiny the volume is.
What is the actual volume?
Long life, high activity nuclear waste represents less than 3500m3 (one Olympic swimming pool), and this, since the start of civil nuclear electrical production in the 50's. World wide.
By keepamovin 2025-11-2310:292 reply Global waste is 400,000+ tons (https://www.stimson.org/2020/spent-nuclear-fuel-storage-and-...). Even 1 pool full is ~28,000 tons (UO2 package 8tons/m3). Urainium is dense.
20 swimming pools of total waste isn't that impressive. I don't want to live near that, but I'm sure I'd we can find a place to put that in that will have minimal impact on people's lives.
By keepamovin 2025-11-2312:59 Exactly. The waste isn't really a problem. But it doesn't have to be waste. That's the point. All that U235 in 'spent' silos? You can get 60x - 100x its OG power feeding it to nextgen reactors. So cool
I wrote about the high energy, long life waste. The part really causing issues.
By keepamovin 2025-11-2311:14 I guess you mean the "super hot for centuries" minor actinides (Np-237, Am-241/243, Cm-242/244/245 etc..)? These are less than 1% global waste, but next gen reactors can still eat them. The majority of waste (95%+) is U-235, then Pu, which nextgen also eats.
By nandomrumber 2025-11-2310:201 reply Many magnitudes of order less than any of: all the steel, glass, aluminium, wood, or plastic, ever produced, and we aren’t yet drowning in cubic miles of any of those.
By aitchnyu 2025-11-245:25 But a disposed sachet from Australia isnt going to enter my cranium here in India... oh wait
By franktankbank 2025-11-2316:30 You sound butthurt by what the person youre responding to is saying. There's no liability in their statement, its severe optimism.
By credit_guy 2025-11-2321:00 > The real win is that thorium MSRs can eat the existing mountain of "spent" fuel rods from regular reactors
That's not true.
The spent fuel can burn in fast reactors. There are hundreds of molten salt reactor designs (see for example [1]), and some of them are fast reactors.
But thorium MSR are not fast. That's the attraction of thorium, it can undergo transmutation (into protactinium, which then decays into fissile uranium-233) using thermal neutrons. Nobody is proposing thorium MSR as a solution to burn spent nuclear fuel.
> So...Three decades? Maybe if the West keeps sitting on its hands.
The West does not keep sitting on its hands. There are dozens, maybe hundreds of nuclear startups in the West, and they are actually making progress.
However, thorium is hard. Very hard. Breeding plutonium from uranium is much easier than breeding uranium-233 from thorium.
Here's a good post [2] about the thorium myths written by a former active HN forum member, Nick Touran. It's a good read. But, now, for an even better understanding, you can just ask ChatGPT, or any other LLM, how thorium breeder reactors compare to plutonium breeder reactors, and which technology is closer to reality.
[1] https://www-pub.iaea.org/MTCD/Publications/PDF/STI-DOC-010-4...
This can be done in usual breeders like superphenix or bn800. What china wants to experiment with is continuous filtration instead of using breeding+purex/pyroprocessing. Still, it's nothing more than an experiment, china is rather slow with nuclear compared to french messmer and sweden in the past
By keepamovin 2025-11-239:58 Well I'm just an interested outsider. I will defer to the true experts here.
Fundamentally the problem is that Uranium is so damn energy dense and abundant enough that there's little need to set up these complicated recycling systems. If we start to run out of Uranium then this technology starts to look appealing, but in the modern day it just doesn't make economic sense.
By JumpCrisscross 2025-11-2222:011 reply > Uranium is so damn energy dense and abundant enough that there's little need to set up these complicated recycling systems
Uranium is abundant, but not homogenously so [1]. (China has some. But not a lot. And it's bound up expensively. And it's by their population centres.)
For the Americas, Europe, Australia, southern Africa and Eastern Mediterranean, burning uranium makes sense. For China, it trades the Strait of Malacca for dependence on Russia and Central Asia.
[1] https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1800.pdf
Uranium can be stockpiled for years in advance, relatively easily. Enough to tide over a small war while you're setting up domestic production. And China should have enough low-grade ores for that.
Also, they can bring it in by rail from Russia. So they can avoid the seaward path.
By branko_d 2025-11-235:49 China imports substantially all of its uranium from Kazakhstan and Namibia, and a tiny bit from US. Russia is insignificant.
https://wits.worldbank.org/trade/comtrade/en/country/CHN/yea...
By JumpCrisscross 2025-11-231:34 > they can bring it in by rail from Russia
Uranium is better for Chinese energy security than oil. But this still leaves China at Moscow's mercy. That's not too differet, energywise, than the situation is now.
By JumpCrisscross 2025-11-2223:032 reply > Uranium can be stockpiled for years in advance, relatively easily
So can oil. Energy security is an important priority for a global power.
Stockpiles are good. Own supply chains are better.
By Ericson2314 2025-11-2223:092 reply Uranium is far, far energy denser than any fossil fuel, and thus much easier to stockpile.
By JumpCrisscross 2025-11-231:332 reply > Uranium is far, far energy denser than any fossil fuel, and thus much easier to stockpile
Sure. That doesn't remove stockpiles' inherent disadvantages: finiteness and vulnerability. Relying on uranium stockpiles would immediately put China at a known limit in a war of attrition that wouldn't constrain their adversaries.
By Qwertious 2025-11-233:25 A sufficiently large stockpile of uranium gives China time to simply pivot away from depending on imported Uranium (either by building new mines locally or building out solar or such). An equivalent stockpile of oil simply isn't feasible, if only because oil is usually used directly and not via a source-agnostic electrical grid.
By Ericson2314 2025-11-2317:421 reply Is 150 vs 250 years of energy reserves a disadvantage in practice?
By JumpCrisscross 2025-11-2319:531 reply > Is 150 vs 250 years of energy reserves a disadvantage in practice?
Reserves != stockpiles.
By Ericson2314 2025-11-2323:05 I know. I am not saying I got the order of magnitude exactly right, just pointing out beyond a certain threshold the size of the stockpile doesn't matter. I suspect that if a nation state puts its mind to it, stockpiles great enough to last a war are totally possible.
By ViewTrick1002 2025-11-2311:09 Which is why renewables are even better. Zero fuel input.
By realusername 2025-11-237:441 reply Well no, no country on earth has 5 years worth of oil stockpile, logistically it's impossible.
Nothing can compete with the energy density of uranium.
By dotancohen 2025-11-238:431 reply Arguably Qatar does, as do most other nations who produce it locally. That is exactly GP's point.
Oil is relatively easily, inexpensively, and quickly mined and refined. Compared to, say, uranium.
By realusername 2025-11-239:231 reply That's not a stockpile, they have to extract and refine it to use it. Russia understood it the hard way with the refineries attacks.
And no, oil is more expensive (especially nowadays) to extract than uranium.
There's a reason nobody ever became rich with a uranium mine, all the value is in the plant and the market price barely covers extracting it, some mines even closed because of the price being too low.
By dotancohen 2025-11-244:47 We're not talking about ore, rather fuel. Uranium ore might be inexpensive, I don't know, but converting that ore into fuel is not an easy task. I'm guessing that the reason it's not profitable is that so little of it is actually needed, relative to oil.
There's not that much Uranium actually that's economically sensible to extract. The NEA says in their 2024 report on Uranium [1]:
> Considering both the low and high nuclear capacity scenarios to 2050 presented in this edition, and assuming their 2050 capacity is maintained for the rest of the century, the quantities of uranium required by the global fleet – based on the current once-through fuel cycle – would likely surpass the currently identified uranium resource base in the highest cost category before the 2110s.
Their "high" scenario assumes having a bit more than double of today's capacity by 2050; today we have about 4-5% supply from nuclear energy worldwide.
[1] https://www.oecd-nea.org/jcms/pl_103179/uranium-2024-resourc...
By Moldoteck 2025-11-239:48 It's a bit different. Higher demand will lead to higher price, opening more options to mine. Now uranium is too cheap to open new mines and exploration
By JumpCrisscross 2025-11-2222:301 reply Out of curioosity, do they forecast at what point it becomes cheaper to breed than mine?
There are tons of mines which were shut down a long time ago, but could be reopened if there was much of a uranium market again.
The actual efficiency of breeding thorium is so low, it would take a HUGE scarcity to actual make any sense.
By dotancohen 2025-11-238:491 reply Local scarcity, not necessarily global scarcity. Especially during times of conflict. China has no uranium, so this may make sense for them.
Also, currently all transport channels for uranium are oil dependent, which is becoming a scarce resource in the relevant timeline - decades.
By lazide 2025-11-2310:50 China has massive Uranium reserves [https://www.nucnet.org/news/chinese-state-media-announces-di...].
By dotancohen 2025-11-238:47 And I hate to pollute this thread with more AI fear-mongering, but AI inference is already showing its effects on the energy sector and it is expected to grow very rapidly. Energy demands may likely grow at a stronger rate than initially expected.
By keepamovin 2025-11-2314:19 Hm, is that really the case? Nextgen reactors are not just about lowering the cost of U. Or "saving the environment" from waste. Bonuses, sure. Real strength is increasing efficiency, which means: 1) lower buildout costs, 2) faster time to first iphone charged, 3) smaller, safer designs. They're a way around the giganto-plants of the past, on the way to making nuclear power the ubiquitous reliable utility it should be.
I also like to think of U/nuclear as "Civilizational thinking" - it's the only solid power we can trust to stay by us through 10,000s of years, through cataclysims, and planet migrations, and it's ideal (before we find something more abundant, dense, and reliable) to take us from Earth, to a multi-planet, local-cluster exploring species, I think.
By cryptonector 2025-11-236:301 reply The reason TMSR is appealing is that U-233 is hard to use for weapons purposes because it produces a lot of gamma radiation, which makes it hard to work with. There is also the claim that TMSRs are much safer designs than is possible with Uranium. It's possible that if TMSRs were mass produced that we could see them installed in many countries where we don't want to see Uranium or Plutonium reactors for proliferation reasons.
At this point few care about this topic. It's not like it's easy to make a bomb with classic pwr
By cryptonector 2025-11-2316:541 reply With a Uranium-based reactor you need a) a source of enriched Uranium (see proliferation risks), b) inspectors to check that you're not post-processing fuel rods to extract Plutonium.
With Thorium if the operator country wants to extract the U-233 you think "maybe let them, they won't like it".
By Moldoteck 2025-11-2321:58 With classic pwr rods can't be used for weapons because of parasitic isotopes. At best you need to run the reactor in a specific way that would trigger global attention looking at power fluctuations. And still it'll not be easy afterwards. You can buy enriched uranium from others. With th- I'm not sure but don't you need enriched material anyway to kickstart it?
> abundant enough
It's not uniformly distributed. Countries like India, for ezample, has an abundance of Thorium but they have to buy Uranium for use in any large scale application.
By hunterpayne 2025-11-230:344 reply Sorry, but there are quite a few things you are missing. Nuclear engineering is well, nuclear engineering. The first big difference is that you can use the Thorium in a liquid fueled reactor instead of a solid fueled one. This allows you to burn far more of the fuel. For example, 2-4% of a solid fuel rod would fission, while in a liquid fueled reactor you can get to 90+%. This is good economically for 2 reasons: 1) more energy per unit of fuel and 2) the waste lasts far less time.
There are also other advantages of a liquid fueled reactor. The big one is that it is far easier to run because it self regulates. When a liquid heats up it expands (slowing the reaction) and when it cools it contracts (speeding up the reaction). So its safer to run, makes less waste and gets 20+X more power per unit of fuel.
There is one final thing to know about this stuff. A nuclear reactor is several billion in infrastructure supporting reactors that cost 10s of millions using a fuel load that costs less than your car. The way we scale and handle nuclear reactors just makes no sense economically. Each NPP is custom and they are built so rarely that everything has to be custom made. When you start building stock reactor designs with consistent supply chains, the cost goes way down. And most of the cost is lawsuits, lobbyists and PR. For developed countries, using or not using nuclear power is a political choice. One that we have been making badly. When you realize that the only real choices for baseload are FF and nuclear, the real political situation makes sense. Once again, the cause is just the excuse, not the real issue.
By laurencerowe 2025-11-2320:07 > When you realize that the only real choices for baseload are FF and nuclear, the real political situation makes sense.
That’s not really accurate. Many countries already meet a substantial portion of their baseload power requirements with renewables and are building out more and more renewable generation because it is cheap and fast to build.
This requires dispatchable backup generation to cover low wind periods, but that may only need to run a few weeks a year. This is by far the cheapest and fastest way to get to 90% carbon free power since most of the cost in gas generation is the fuel itself rather than the capital for the plant.
Nuclear is the opposite so cannot economically fill that role so it seems little is likely to be built.
By Moldoteck 2025-11-239:50 You can get +- same efficiency with classic breeding and purex/pyroprocessing
By credit_guy 2025-11-231:58 > Nuclear engineering is well, nuclear engineering.
Not sure I get what you are trying to say. Are you saying that you are a nuclear engineer and I am not? Because, frankly, the rest of your comment does not read as one written by a nuclear engineer.
There's also the choice to match our energy consumption dynamically to intermittent power sources (e.g. solar), reducing the baseload demand. This is entirely orthogonal to decisions about where the baseload generation should come from.
By hunterpayne 2025-11-233:023 reply That's called load following. That's also a thing a liquid fueled reactor can do that a solid fueled reactor can't.
By dalyons 2025-11-235:21 doesnt make a difference to the economics of a nuke plant. Fuel consumption is a tiny fraction of the cost of nuke power, its almost all fixed cost - amortized construction costs, operations, etc. You need to run it at as close to 100% always to have any chance at payback & economical $/kw. Thats why they arent getting built.
You need to go tell the French that what they've been doing for decades isn't possible, then.
By thinkcontext 2025-11-2317:19 EPR has shown that the French have lost the ability to build reactors rapidly and on budget.
By wizzwizz4 2025-11-236:40 No, it's the opposite: https://en.wikipedia.org/wiki/Demand_side_management. Load-following is a good property for a power plant to have, though, especially if the plant is suitable for baseload generation.
and we still don't know where to store the trash. Thorium seems better (but my knowledge is close to zero here, I must admit:-) )
By JumpCrisscross 2025-11-2222:301 reply > we still don't know where to store the trash
We really do. Nuclear waste is less toxic than plenty of trash we just bury. And calling it "waste" is a bit reductive, given it almost certainly becomes valuable to reprocess within another century or two.
No, you really do not.
Long term storage is still up in the air in the US. Yucca mountain was the plan but didn't happen
Correct me if I'm with m wrong
Radioactive waste is decidedly nasty stuff, but the total volume of it is tiny. There are plenty of chemicals that are just as nasty that were simply buried in the ground in much larger quantities over the years with nary a peep from the population. Nuclear waste is a political problem not a technological one.
The crazy part is that people want to insist that the sites need to be absolutely safe even if they aren't maintained for 1,000 years, but by that point the radioactivity would be no more than the base ore anyway so demanding these extended timelines doesn't make anybody safer. They're just red tape.
It's a political problem, maybe.
It's peculiar that it's a political problem in pretty much every country though? I know Finland is well on its way for long term storage but that's the only example I know of.
There's also quite a few cases where it is a technical problem. Gorleben in Germany for example.
By JumpCrisscross 2025-11-2319:51 > peculiar that it's a political problem in pretty much every country
It's a political problem in every country that shares its nuclear heritage from the ashes of WWII.
By nandomrumber 2025-11-2310:35 What trash? Where’s the waste?
Point to the nuclear waste.
If there’s so much of it somebody must be able to point it out to me.
By unethical_ban 2025-11-230:30 That's a political problem, not a technical one.
We also know that we could re-cycle nuclear waste with other nuclear plant designs, but the US chooses not to.
By Moldoteck 2025-11-239:51 You know. In US it's yucca mnt, similar to onkalo. Its just not politically pursued as a priority. Recycling is banned
By piskov 2025-11-235:30 Russians recycle it
By skinkestek 2025-11-238:571 reply Joking here since it would be impractical, but I guess you can bury it under my house. I'd not be bothered at all to live on top of a modern nuclear waste deposit like Finlands.
Waste from modern nuclear power plants seems to be a giant nothingburger. And yes, I came from the other side but flipped as I learned more about the technicalities, how Finland has solved it and how near you need to get hurt.
By nandomrumber 2025-11-2310:42 Have you come across the ‘coke can of thorium’ vs ‘800 elephants of coal’ guy yet?
Dr Barry Brook. Reading his stuff 15 years ago flipped me.
My understanding is that reactors will use that plutonium just fine, so the energy you get from a fresh fuel rod is almost exclusively from uranium fission but, as time goes on, an increasingly large share is from plutonium fission.
In principle, using Thorium would give you the energy from Thorium fission, then Uranium fission, then plutonium fission, which is pretty cool. However, I suspect you might hit an issue here where such a low conversion rate would make the reactor go sub-critical.
By mnw21cam 2025-11-2313:06 No, this is a misunderstanding of how fission works.
When a nuclear reactor is run with mildly-enriched Uranium, which is a mixture of Uranium 235 and Uranium 238, it forms a self-sustaining chain reaction with the Uranium 235 (which is fissile) and a load of the spare neutrons get absorbed by the Uranium 238 (which is fertile), converting it into Plutonium 239, which is also fissile. But most Uranium 235 reactors use a moderator which slows down the neutrons, which makes them more likely to cause fission in Uranium 235 but less likely to transmute Uranium 238 to Plutonium 239. So most modern reactors don't produce much Plutonium. In any case, the fission you get from Uranium and the fission you get from Plutonium is from different source materials. Once an atom is fissioned, it is split into smaller atoms and can no longer be fissioned.
Thorium isn't fissile, it's fertile. That is, if you fire a neutron at Thorium 232, you get Thorium 233, which decays to Protactinium 233, which then decays into Uranium 233, which is fissile. You then fire another neutron at Uranium 233, which then fissions into much smaller nuclei, giving you energy and the neutrons to do the above. The Uranium is no longer around after that to form Plutonium. There is no way to get any significant amount of Plutonium 239 from this, because that would require adding 7 more neutrons to the original Thorium 232 and having none of them trigger a fission event. The fissions that do occur don't provide 7 neutrons anyway, so it wouldn't be possible to get a self-sustaining conversion of a significant amount of Thorium into Plutonium for final fission even if the previous sentence weren't true - it would have to be enhanced with some other provider of lots of neutrons.
By tremon 2025-11-2315:26 In principle increasing the conversion ratio from 0.1 to something higher than 1.0 should be doable
Is this a typo? I can understand increasing the yield to a number slightly below 1, but how do you get more than 1mol Uranium from 1mol Thorium?
By anal_reactor 2025-11-2223:261 reply I'm getting impression that China is trying to position itself as scientific powerhouse before its massive industrial production scheme stops working. Smart move.
By comeonbro 2025-11-2223:30 > trying to position itself as scientific powerhouse before its massive industrial production scheme stops working
Holy shit what a perspective. Put it in a museum. If this is representative, put it on our grave.
By lbruder 2025-11-2310:40 CTRL+F protactinium
Once again, nothing.
The notable thing here is that it's a molten salt reactor design, where the fuel is dissolved in a molten salt (FLiBe). This allows online continuous processing of the fuel, unlike with solid fuel rods sealed inside a pressure vessel.
This unlocks a lot of options for the fuel cycle, including the use of thorium.
This work builds on a previous molten salt reactor experiment at Oak Ridge, decades ago. There's a whole lore about MSRs.
By JumpCrisscross 2025-11-2219:572 reply > notable thing here is that it's a molten salt reactor design
Notable, but not unique. The unique bit is it burns thorium.
By AtlasBarfed 2025-11-2220:143 reply It breeds thorium to fissionable uranium from a starting fissionable uranium starter fuel. It doesn't directly use thorium for fuel.
What people need to understand about the cycle efficiency is that when you mine uranium, the fissionable part of uranium (U-235) is only 1% of that uranium, the rest is nonfissionable U-238.
Thorium is about twice as abundant as Uranium (all isotopes). The MSR uses Thorium to create U-233, a fissionable but not naturally occurring Uranium isotope.
So the "unlimited energy aspect" is that about 200-300x more breedable Thorium exists than fissionable U-235.
A MSR nation could also try to breed U-238 into plutonium, which would provide another 100x more breeding stock, although LFTR never talked about U-238 breeding. IIRC the plutonium may be difficult to handle because of gamma rays, but I don't recall exactly.
While I don't have confidence that even LFTR/MSR reactors can get economical enough to challenge gas peakers, it may be possible to make truly price-competitive MSR electricity with the right modular design. I wish the Chinese the best of luck, because if they do it will spur the rest of the world to adopt this about-as-clean-and-safe-as-it-gets nuclear design.
By JumpCrisscross 2025-11-2220:321 reply > Thorium is about twice as abundant as Uranium
China has thorium, and while less than others [1], it’s better than they do with uranium [2].
> it may be possible to make truly price-competitive MSR electricity with the right modular design
Yes. But probably not in the near term with thorium. This isn’t designed to be cheaper. It’s designed to be more available to China than being dependent on Russian deposits.
[1] https://www.nature.com/articles/492031a
[2] https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1800.pdf
By mikhailfranco 2025-11-246:45 Geoneutrino surveys show the Tibetan plateau and western China are full of uranium and thorium:
https://en.wikipedia.org/wiki/Geoneutrino
Economic recoverable reserves are another matter, but there's plenty there.
By rhoads 2025-11-2220:24 That's what you learn playing factorio
By cryptonector 2025-11-236:34 Eh, U-235 is .7%, not 1%, but also U-238 can be bred into Plutonium. What makes Thorium interesting -besides its abundance- is that U-233 is very difficult to work with, so proliferation concerns are mitigated.
By fmajid 2025-11-2222:29 Not really, the US bred several tons of U-233 from thorium in the 60s.
MSRs have some attractive features, but they also have significant drawbacks.
The most pressing is that fissionable material is spread throughout the fluid, so fission and decay of fission products is occurring right up to the edge of the fluid. The walls and pipes containing the molten salt, and anything dipped into the salt, are exposed to unmoderated neutrons. One can shield using (say) graphite, but then damage to that (and soaking up of radioactive materials) become issues.
The Molten Salt Reactor Experiment at Oak Ridge was near the end of its radiation exposure lifetime when the program ended.
Contrast this to light water reactors. These are designed so that no lifetime component sees unmoderated neutrons. There's a thick barrier of water between the fissioning fuel and the reactor vessel wall and the support structures for the fuel bundles. The bundles themselves are exposed, but they are replaced for refueling and are not lifetime components.
By nateglims 2025-11-233:44 I think it has a key advantage for China specifically though which is it consumes significantly less water and they have a lot of water poor territory.
The oakridge experiment ended and not a lot of R&D has been done on salt reactors. It makes sense that China is still basically in research and testing phases for molten salts.
By hunterpayne 2025-11-230:412 reply > One can shield using (say) graphite
Oh dear god, no. Graphite is a very good moderator, it is in no way a shield. Those two properties are (sort of) opposites of each other. Lead makes the cheapest and best shield. Also, those parts that are exposed to neutron flux stay radioactive for about 10 years. So it shortens their lifetime in the reactor but the waste isn't a big issue.
> Oh dear god, no [...] Lead makes the cheapest and best shield.
Oh my, definitely no :-) Do not use lead for neutron shielding. You're thinking gamma radiation but then we're talking apples vs oranges then. You want atoms comparable in size to neutrons, so something with plenty of hydrogen. Think water or PET (plastic) when you don't want water to "leak" when transporting a source. For thermal neutrons maybe PET impregnated with boron. Now neutrons may generate gamma when captured by hydrogen, then you may want some lead for secondary effects like that but I am not sure how strong those are.
Lead is fine for shielding of sufficiently energetic neutrons, which can lose energy to lead by inelastic nuclear collisions. But below the threshold for that lead does very little.
By rdtsc 2025-11-238:07 Maybe as a special case then as a thin layer before following up with water or PET, or PET impregnated with boron. But would also need an extra layer following it for secondary gamma emission from neutron capture.
Lead is essentially useless as a shield for neutrons that are below the minimum excitation energy of a lead nucleus. Elastic neutron collisions with lead leave the neutron energy essentially unchanged.
By hunterpayne 2025-11-234:071 reply I assume this is why an alloy of lead is used in practice. Still doesn't change the fact that graphite is a moderator not a shielding material. Also, structural materials in reactors are usually invisible to neutrons and a sandwich of materials is often used. Different layers do different things. Usually, one layer of shielding and one layer of a material that isn't impacted (much) by neutron flux for structural strength.
There is a rabbithole for almost all of these material choices, especially in nuclear. Not going down that rabbithole in a discussion targeted at folks who don't spend their lives working in nuclear doesn't make that person wrong. It makes them an effective communicator.
PS Lead is a very very common shielding material in nuclear.
By pfdietz 2025-11-234:26 A moderator is a neutron shielding material, since it removes energy from the neutrons. That's what moderation is all about. Water is a much better moderator, but graphite still performs the function.
To add to this, even with the shielding provided by water in light water reactors, the neutron exposure is _the_ limiting factor for the reactor vessel.
The metric to look for is called "DPA" (displacements per atom), the number of neutron collisions that a material can tolerate before losing enough structural integrity to fall below the acceptable limits. The best modern reactor steels are at 150-180 DPA.
And a lot of potentially cool reactors like TWR (travelling wave reactor) end up being logistically impossible because lifetime-limited components will be exposed to multiple hundreds of DPAs.
Many old LWR's have had their reactor vessels heat treated during a maintenance break to undo some of that neutron radiation damage and extend the life of the reactor.
Not sure whether it would be possible to do something similar to a liquid fueled reactor, including all the hot pipework. Maybe, but yet another cost. Notably some of the recent MSR projects propose replacing the entire reactor every now and then (Terrestrial or whatever they were called, not sure if they are still around).
I wonder if it's possible to run it hot enough for the radiation damage (basically a bunch of dislocations, right?) to just anneal itself out continuously, like how Wigner energy is dissipated in graphite when it's hot enough.
By cyberax 2025-11-2320:34 No, this is fundamentally impossible with steel. Annealing works by making the material more "plastic", and this necessarily reduces its tensile strength. Which is the limiting factor for the vessel.
You can make the vessel thicker to compensate, but then you can just make it thicker in the first place and skip annealing.
By cyberax 2025-11-2320:32 Yes, it's called "annealing". Basically, the core is de-fueled and a huge electric resistive heater is put inside it. Then the entire vessel is heated to something like 600C, and kept there for several days.
It helps the atoms displaced by neutron collisions to "snap back" into the correct places in the crystalline structure. But it can never restore the material completely, and over time the annealing breaks will have to be more and more frequent.
It also can't be used for everything. Some pipes will experience large thermal stresses if annealed, and some components can't be heated properly due to complex geometry.
As with everything in engineering, all problems can be solved with additional complexity. It's possible to design LFTR reactors to be more annealable, but it will likely make them impractically complex.
There are also other issues with LFTRs. A significant part of the energy production will happen _inside_ the pipework carrying the molten salt, as delayed fission happens and daughter products decay. This will cause inevitable problems with the reactor power control.
Modern light water reactors are engineering marvels. They are incredibly compact for the amount of power that they generate, and they are now designed with the anticipated 70-100 year operating lifetime. Getting LFTRs to the same level of maturity might be possible, but it'll require literally hundreds of billions (if not trillions) invested, just like with the classic nuclear.
By JumpCrisscross 2025-11-2220:121 reply > thorium cycle is generally neutron negative
Source for the fuel cycle?
Thorium 232 -> 233 is neutron negative. But after that you get all kinds of nonsense.
Thorium 232 is the thorium in the cycle yes. And all kinds of nonsense is correct for the daughter products. But in general, to actually use do anything with thorium you need excess neutrons.
Even the daughter uranium 233 only produces on average 2.48 neutrons per fission, so it’s very difficult even in a combined lifecycle process to have enough - thorium doesn’t produce uranium 233 immediately (takes almost 30 days), neutron capture with that low a ratio requires a LOT of thorium, which is going to mostly just suck up all neutrons and you won’t have any extra for addition uranium 233 fissions, etc.
It’s quite difficult (impossible?)to have actually work without a source of a large amount of additional neutrons.
By JumpCrisscross 2025-11-2222:021 reply > to actually use do anything with thorium you need excess neutrons
Unless 100% of those neutrons is being absorbed by the thorium, this means you'll have neutron flux at the boundary. Which, for a liquid moderator, means all the pipes and tanks and pumps.
It’s almost like there is a reason why it’s not commonly used despite all the hype.
By hunterpayne 2025-11-230:553 reply Sure, if you ignore all the parts of the neutron economy that make it possible to work. The part everyone missed in this discussion is that all of the numbers of neutrons (and their barns) aren't constants. Since the fuel is a fluid, you can use density and shape to improve the neutron economy in the reactor core. Basically, when the atoms are closer together, the economy improves. You can also use a better moderator like graphite since the basic design is safer and the rate of fission is just easier to control.
And considering that people made these things work 60 years ago without modern computers, the idea that its impossible or needs 40 years of research seems pretty far fetched. What is left of the nuclear industry wants to build current designs like the AP1400. That is a great idea, but there are things you can do with a LFTR that you can't do with an AP1400. The biggest of them is making synthetic fuel. The other advantages are the amount of waste produced and the fact that you can make a LFTR into a waste burner consuming the spent fuel rods from a AP1400. The downside is you actually have to fix nuclear regulations to do this and getting politicians to do that has proved impossible.
There are no technological barriers, this is entirely political.
By JumpCrisscross 2025-11-231:37 > What is left of the nuclear industry wants to build current designs like the AP1400
That's just Westinghouse. There is a lot of research happening in small and medium-sized reactors.
> There are no technological barriers, this is entirely political
To thorium MSRs? The main barrier is economic.
Nah, it’s just hard and silly - without a lot of payoff. When there are plenty of easier options for most nations.
That you’re even discussing graphite moderated (?!!) makes this pretty clear.
By hunterpayne 2025-11-233:011 reply > That you’re even discussing graphite moderated (?!!) makes this pretty clear.
And why would this be? Is graphite expensive? No it isn't. Also, we created a working one of these designed in the 1960's without computers. You seriously think this is hard compared to other types of engineering we do today?
A LFTR can also do things that a PWR or BWR can't and has several major advantages. But since it uses pencil lead apparently we can't even try it.
Because it has dangerous behavior in real reactors due to the void co-efficient behavior, to the point of… being the cause of the largest nuclear disaster in recorded history?
Not OP but he maybe referring to the new gas cooled gen 4 reactors not Soviet RBMKs. The ones I heard are working with sealed beads of uranium, encased in porous carbon, then some other layers, including some carbide (silicon?). The porosity of carbon absorbs gases but they ultimately stay sealed. The whole thing is helium cooled.
The issue with those is the pellets end up not as well sealed as thought or promised (many, many leaks historically), so then you have other problems.
By rdtsc 2025-11-2317:10 Yeah. I was listening to David Ruzic's video [1] about them getting one of those reactors on campus and when he showed the structure of beads, that's the first thing that popped in my head - at that size how are they going to ensure every single bead has an intact surface.
A better explanation of the significance:
https://www.stdaily.com/web/English/2025-11/17/content_43298...
By dang 2025-11-2221:25 Thanks! We've put that link in the toptext as well.
> Now, the research team is conducting systematic studies on the key scientific issues related to adding thorium, and aims to completethe construction of a 100-megawatt TMSR demonstration project, and begin operation by 2035.
For comparison: A commercial nuclear power plant is 1 gigawatt, a 10x difference. I assume this would be the next step.
By allenrb 2025-11-2222:40 The typical 1 gigawatt rating for a nuclear power reactor is measuring electrical output. Given the various inefficiencies, the actual reactor output (as heat) is something like 3x that amount. Whereas a research reactor will be quoted as thermal output.
That to say, a typical commercial reactor might be 30x the power of a 100 MW research device.
