China reaches energy milestone by "breeding" uranium from thorium
109 comments
·November 22, 2025credit_guy
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...
pdpi
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.
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jandrese
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.
JumpCrisscross
> 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
cyberax
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.
jgehring
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...
JumpCrisscross
Out of curioosity, do they forecast at what point it becomes cheaper to breed than mine?
wiz21c
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:-) )
JumpCrisscross
> 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.
HPsquared
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.
JumpCrisscross
> notable thing here is that it's a molten salt reactor design
Notable, but not unique. The unique bit is it burns thorium.
AtlasBarfed
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.
JumpCrisscross
> 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
rhoads
That's what you learn playing factorio
fmajid
Not really, the US bred several tons of U-233 from thorium in the 60s.
pfdietz
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.
cyberax
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.
bilsbie
What absorbs the neutrons then?
lazide
The thorium cycle is generally neutron negative.
JumpCrisscross
> 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.
T-A
A better explanation of the significance:
https://www.stdaily.com/web/English/2025-11/17/content_43298...
dang
Thanks! We've put that link in the toptext as well.
cubefox
> 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.
allenrb
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.
perihelions
This post is just an excerpt—it's the first 4 paragraphs of a 29-paragraph article,
https://archive.is/DQpXM ("China reaches energy independence milestone by ‘breeding’ uranium from thorium"–SCMP)
dang
Thanks! - since you've found a readable link, I've swapped https://humanprogress.org/china-reaches-energy-milestone-by-... out for the original source at the top, and put the archive link in the top text.
_trampeltier
This came up several times the last few weeks, but never stayed on the front for long. Also no comments.
I guess soon the west has to copy chinas tech.
JumpCrisscross
> soon the west has to copy chinas tech
Thorium MSRs don't make sense for the Americas, Europe or Australia. We have plenty of uranium.
Nuclear is receiving solid research backing in both America and China. (India is playing too. Austrlia is having an identity crisis.) Our different geologies mean there will probably be one solution for China, India and North Africa, on one hand, and the rest of the world, on the other hand.
pfdietz
Breeding is a technology looking for a business case.
It's more expensive than just using fresh uranium in current market conditions. It's a way from keeping future uranium shortages from making nuclear power more expensive; it's not a way to make nuclear cheaper than it currently is.
NewJazz
Emphasis on current market conditions. Relations with uranium mining countries and environmental opposition to uranium mining could shift conditions.
SirHumphrey
The truth is that nuclear power is not that financially attractive at the present and would the price of uranium rise enough that breeders would become economically viable most countries would just stop bothering with nuclear power altogether.
culi
China has more uranium reserves and less thorium reserves than the US though
Most thorium: India, Brazil, Australia, US, Turkey
Most uranium: Australia, Kazakhstan, Canada, Russia, Namibia
adrian_b
They highlight less the advantages from breeding, than other advantages of the molten salt design, like not needing a lot of cooling water, which allows this reactor to operate in the Gobi desert, the possibility of replacing the fuel without halting the reactor and various safety features.
JumpCrisscross
> other advantages of the molten salt design, like not needing a lot of cooling water
This advantage is conserved by all non-water moderated reactor designs.
littlestymaar
Nuclear reactors don't need a particularly big amount of cooling water.
The thermodynamic cycle needs a cold source though, and it's most commonly water. This doesn't depend on the reactor design and this is equally as true of coal plants.
As long as you are making electricity out of a thermodynamic cycle, you need a heat source (be it a flame or a nuclear reaction) and a cold source.
dmix
It also apparently provides a way to make reactors that don’t depend as much on water so they don’t all have to be near the coast.
This would allow Western China to also develop reactors to help underpin their renewable and coal energy.
> The interest in MSR technology and Thorium breeding did not disappear however. China's nuclear power production relies heavily on imported uranium,[10] a strategic vulnerability in the event of i.e. economic sanctions. Additionally, the relative lack of water available for cooling PWRs west of the Hu line is a limiting factor for siting them there.
JumpCrisscross
> also apparently provides a way to make reactors that don’t depend as much on water so they don’t all have to be near the coast
Non-water microreactors broadly fall into two categories: ones using a different moderator, most commonly sodium, a sodium salt or helium; and those using heat pipes. Most microreactor designs don’t use water.
littlestymaar
Nuclear plants don't need more water than a coal plant of the same power, they both use the same steam turbine with water as cold source.
lunar-whitey
There is no business case for basic research, but if you stop basic research long enough you will have no business. The United States and its allies seem to have completely forgotten this.
HPsquared
It makes sense for big monopolies like Bell, or the CCP. The investment can be justified if the ones investing are confident they will be able to capture the value and not some competitor.
littlestymaar
> in current market conditions.
That is, as long as we don't build more nuclear power plants.
If you want to increase nuclear power adoption, then you're not going to stay in “current market conditions” for long.
inglor_cz
Reducing the energy sector to pure business would probably work in the 1990s, but not now, when countries are afraid of strategic dependence on potentially hostile suppliers.
Uranium isn't as ubiquitous as, say, natural gas, and stockpiling it comes with a big heap of physical problems. I can definitely see countries spending on more expensive technology if it comes with more energy security.
culi
I mean we're already doing that in many avenues. Solar being the most obvious. The only functioning solar manufacturing plants in the US are Chinese-owned and are only here to take advantage of subsidies.
Plenty has been learned by the US/West from copying their approach to agriculture, robotics in factories, mining, drones, etc. Have you seen their electromagnetic catapult technology?? That stuff seems like its from the space-age! There's even plenty of tech that we can't really explain like the all-moving wingtips on the new J-50s. (and yes, I'm avoiding talking about their supersonic cruise missiles)
jonplackett
I think I read recently that this was a US idea that was abandoned that China took up and made it work. Is that accurate?
lunar-whitey
No country has seriously invested in the thorium fuel cycle because it cannot be used to create weapons. Unfortunately, the technology also began to look most promising as an energy source around the same time the Three Mile Island nuclear accident effectively ended all interest in nuclear energy in the United States.
retrac
India has shown some of the most interest to date, due to their lack of domestic uranium reserves. But it's been slow going their fast breeder reactor plans were delayed by like two decades. But it is built and it was loaded with fuel last month [0]
The French interest in breeder reactors and nuclear reprocessing also originates from a similar concern about lack of domestic access to raw uranium. Though Super-phoenix [0] was a more traditional uranium -> plutonium approach and not thorium. They gave up because just using uranium is way, way cheaper than synthesizing your own fissile materials.
[0] https://www.world-nuclear-news.org/articles/indias-prototype...
datadrivenangel
Thorium can be used to make weapons via the breeding cycle. It's much less convenient and straightforward than uranium/plutonium, but it is possible.
lunar-whitey
Theoretically, perhaps, but I don’t think anyone with a serious interest in weapons would pursue it. From a nonproliferation perspective, I’d guess the infrastructure necessary to remove contaminants from uranium bred through the thorium cycle would be costly and difficult to conceal.
lazide
Also, it’s only energy positive under some specific carefully managed conditions, and is a real pain to make work.
If you have easy access to uranium, you just use it directly instead.
jbverschoor
Well, fible energy is trying to do lots. Gates invested in MSTR (molten salt thorium reactor).
But regulation, while it has its purposes, stifles many things. At the same time time it’s not even doing what they were meant for.
There are a number of countries being run far better than the US or the EU
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dmix
> There are a number of countries being run far better than the US or the EU
It will be funny if China is what convinces the US to be more open to free industry. Opposite day vs the 1970s
bilbo0s
To be fair, these advances are not being made in China due to "free industry". They have something of a command economy for their critical sectors. So it's unfair not to point out that it's easy to make advances if a nation as a whole points to a hill and says, "take that hill". Of course you can do it under those circumstances.
If it's just your company or some trifling consortium trying to develop nuclear energy advances in a "free industry" environment, the guy who is just slapping up windmills, [T Boone Pickens RIP], is just gonna mop the floor with you. There's just no way to compete on moonshots like that.
impossiblefork
Historical experiments with alternative fuel cycles, not serious development attempts. A serious development attempt happened in India though.
hit8run
Meanwhile Germany just decommissioned its last nuclear reactors. Given the challenges of baseload renewable generation, it's frustrating to watch working infrastructure being dismantled while we're still heavily dependent on fossil fuels.
littlecranky67
Comparing those old conventional reactors to MSR is not suitable at all. And they were not fully functional past their expiry date.
JumpCrisscross
> Comparing those old conventional reactors to MSR is not suitable at all
It is given we're talking about perceptions. I see no evidence Germany's Greens are suddently rational when it comes to modern reactor designs, of which MSRs are one.
AngryData
To be fair, a lot of nuclear reactors around the world should be shut down just due to age and outdated designs. However they should also be being replaced with modern reactors, which few people have, which makes shutting them down while we are still largely utilizing fossil fuel power and chemical plants really dumb.
BoredPositron
By all the doomerism about German and nuclear there is at least Wendelstein 7-x doing frontier work. It's fine to get rid of legacy nuclear if there is a feasible bridge ahead.
p2detar
Not sure what the point of this comment is. China has its equivalent EAST, France has ITER. Countries can do both fission and fusion research. To me the problem isn't that Germany closed some legacy reactors, but that too little is done into looking into alternative designs.
Hikikomori
There's a danish company building modular container sized molten salt reactors.
SilverElfin
This type of progress shows China is capable of moving from an economy that’s build on labor arbitrage or copying others to genuine innovation. It’s also further evidence of the extreme competence of the CCP in governance, which I feel should be acknowledged despite their authoritarian negatives.
JumpCrisscross
> This type of progress shows China is capable of moving from an economy that’s build on labor arbitrage or copying others to genuine innovation
China has been genuinely innovating in manufacturing techniques for decades. If anything, that ingenunuity peaked when Xi began his term, and has been degrading as his dictatorial tendencies needlessly hamstrung Chinese industry.
inglor_cz
"extreme competence of the CCP in governance"
I don't think it makes sense to extrapolate from one particular technical field to governance in general.
The US managed to defeat both Nazi Germany and Japan plus develop nuclear weapons, all in 1941-5. Was it a proof of extreme competence of the US government in general? The some government tolerated abuse of blacks and forced segregation in the South, I would call it a serious governance failure.
inshard
Thorium is abundant in Sri Lanka’s mineral sands. Mined with dredgers at shallow depths 10-100m off the western coast.
jmyeet
A detailed explanation of the Thorium Fuel Cycle [1].
I'm glad China is doing this even though I'm skeptical about nuclear power ever being commercially viable. At least they're trying different things.
DeathArrow
I wonder if people would think China copied this from the West.
https://archive.is/DQpXM
https://www.stdaily.com/web/English/2025-11/17/content_43298...