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Before anybody gets too excited, it's better to understand what exactly happened. China ran an experimental reactor that achieved some conversion of thorium in

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-achieves-conversion-of-thorium-uranium-fuel https://www.world-nuclear-news.org/articles/chinese-msr-achi... [2] https://en.wikipedia.org/wiki/Breeder_reactor#Conversion_ratio https://en.wikipedia.org/wiki/Breeder_reactor#Conversion_rat...

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jandrese 11mo ago
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 11mo ago
  > 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 https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1800.pdf
  - cyberax 11mo ago
    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.
    - JumpCrisscross 11mo ago
      > 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.
      - Ericson2314 11mo ago
        Uranium is far, far energy denser than any fossil fuel, and thus much easier to stockpile.
        JumpCrisscross 11mo ago
        > 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.
pdpi 11mo ago
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.
- mnw21cam 11mo ago
  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.
anal_reactor 11mo ago
I'm getting impression that China is trying to position itself as scientific powerhouse before its massive industrial production scheme stops working. Smart move.
- comeonbro 11mo ago
  > 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.
keepamovin 11mo ago
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.
- Moldoteck 11mo ago
  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
  - keepamovin 11mo ago
    Well I'm just an interested outsider. I will defer to the true experts here.
- nandomrumber 11mo ago
  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.
lbruder 11mo ago
CTRL+F protactinium Once again, nothing.
tremon 11mo ago
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?

deleted 11mo ago

[deleted]

jandrese 11mo ago

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 11mo ago
> 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 https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1800.pdf
- cyberax 11mo ago
  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.
  - JumpCrisscross 11mo ago
    > 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.
    - Ericson2314 11mo ago
      Uranium is far, far energy denser than any fossil fuel, and thus much easier to stockpile.
      - JumpCrisscross 11mo ago
        > 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.

pdpi 11mo ago

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.

mnw21cam 11mo ago
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.

anal_reactor 11mo ago

I'm getting impression that China is trying to position itself as scientific powerhouse before its massive industrial production scheme stops working. Smart move.

comeonbro 11mo ago
> 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.

keepamovin 11mo ago

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.

Moldoteck 11mo ago
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
- keepamovin 11mo ago
  Well I'm just an interested outsider. I will defer to the true experts here.
nandomrumber 11mo ago
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.

lbruder 11mo ago

CTRL+F protactinium Once again, nothing.

tremon 11mo ago

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?