4 ms·

Fusion power plants can't "melt down". The amount of plasma inside the vacuum chamber is just around a gram.

by cyberax 6mo ago

JumpCrisscross 6mo ago
> Fusion power plants can't "melt down" Eh, a core-containment failure (in any magnetically-contained system) would involve superheated hydrogen getting friendly with oxygen. That, in turn, would give neutron-impregnated barrier materials a free ride on propellant. It's not strictly a melt down. But it's in the same practical category of failure.
- Aardwolf 6mo ago
  What's the effect of this in a populated area in a certain radius? Compared to nuclear power plants...
  - JumpCrisscross 6mo ago
    > What's the effect of this in a populated area in a certain radius? I'd imagine this is, like with fission plants, deeply dependent on the specific design.
  - cyberax 6mo ago
    Radiologically? Pretty much nothing. The regular industrial safety concerns will matter more. The plant will have some tritium, and the material in reactor walls will get activated by the neutron flux. Some of the activated materials can disperse in case of a catastrophic explosion (e.g. a couple of large airplanes being flown the reactor building). But the material of the walls is not volatile, so it'll stay on the site. And tritium is very volatile, so it'll quickly disperse to safe levels. You'll be able to detect them with sensitive equipment, but it won't be dangerous.
- gmueckl 6mo ago
  Ths is a massive misunderstanding of the technology. First of all, the amount of hydrogen in the reactor is tiny. The magnetic confinement severely limits the density of the plasma. The inner containment vessel is a ultra high vacuum chamber. The chemical energy that would be released by a reaction between the hydrogen in the reactor amd oxygen from the air would be less than what is released by popping a hydrogen filled balloon with a lighter. The truly concerning failure modes would be related to release of radiation or activated materials. But that would require damaging the reactor in ways that the reactor is incapable of imparting on itself. Overall, the technology is remarkably safe.
  - JumpCrisscross 6mo ago
    > chemical energy that would be released by a reaction between the hydrogen in the reactor amd oxygen from the air would be less than what is released by popping a hydrogen filled balloon with a lighter Thanks for the correction. If you're breeding lithium in the walls, might that be an incendiary concern?
    - rnhmjoj 6mo ago
      The breeding blanket is entirely contained inside a vacuum vessel, so there isn't any oxygen to react with. Also, the are many blanket designs, but the lithium is never present in its elemental form (precisely because it would be very reactive), but in a stable chemical bond with some neutron multiplier (like lithium-lead alloys or beryllium ceramics). In some design the lithium is even immersed in the coolant itself, which is high pressure helium, so it's not going to ignite in any reasonable way.
      - JumpCrisscross 6mo ago
        > breeding blanket is entirely contained inside a vacuum vessel, so there isn't any oxygen to react with When the vessel works. If the vessel breaches, that lithium could ignite. Note a showstopper. But I suppose a risk to be thought about by the engineers (probably not by policymakers).
        leonidasrup 6mo ago
        Commonwealth Fusion Systems plan to use lithium in salt form FLiBe, a molten salt made from a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2). It does not violently react with air or water. https://en.wikipedia.org/wiki/FLiBe https://en.wikipedia.org/wiki/FLiBe
    - pixl97 6mo ago
      There seems to be a number of different prototypes of blankets, but the average operating temperature seems to be 300-700C. Adding oxygen to some of these designs while that hot may cause metal burning. This said, many of them are ceramic designs and would likely resist combustion. With all that said, it seems to be way less 'dangerous' material than would be in your average nuclear reactor, making it more of an industrial accident versus a planet contaminating mess.
- Symmetry 6mo ago
  There's only a few grams of hydrogen in the reactor's plasma, it's reaction with oxygen wouldn't be much more exciting than just losing containment. There are engineering challenges that have to be addressed but no worse than the 6 MW research reactor I used to walk by every day to my college classes in the middle of a dense city. The proliferation risk of someone using the neutron flux to produce an atomic or dirty bomb are real but that exists no matter where it is.
  - leonidasrup 6mo ago
    I think the proliferation risks will be in future the reason, independent of technological obstacles or costs, why US will not allow to build fusion power plants in all countries around the world. Hybrid nuclear fusion–fission power plants have been already proposed and studied in theory. "In general terms, the hybrid is very similar in concept to the fast breeder reactor, which uses a compact high-energy fission core in place of the hybrid's fusion core. Another similar concept is the accelerator-driven subcritical reactor, which uses a particle accelerator to provide the neutrons instead of nuclear reactions." https://en.wikipedia.org/wiki/Nuclear_fusion–fission_hybrid https://en.wikipedia.org/wiki/Nuclear_fusion–fission_hybrid
    - bleepblap 6mo ago
      > Hybrid nuclear fusion–fission power plants have been already proposed and studied in theory. I have a hand-wavy hard sci-fi universe I've been rolling around my head for years and I eventually came to the conclusion that fission-fusion drives would be really handy for spacecraft, since it would be much easier to start a fission reaction in a cold/dark ship than fusion because of the power requirements. Otherwise you need some other way to generate 10s or 100s of MW to start the fusion reaction.
      - leonidasrup 6mo ago
        Using the energy of fission for spacecraft propulsion has been studied and some prototypes have been already constructed. Most of these nuclear engines should be used only outside of Earths atmosphere. https://en.wikipedia.org/wiki/Nuclear_propulsion https://en.wikipedia.org/wiki/Nuclear_propulsion https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA Most interesting and promising are direct nuclear propulsions, like fission-fragment rockets. https://en.wikipedia.org/wiki/Fission_fragment_rocket https://en.wikipedia.org/wiki/Fission_fragment_rocket
PunchyHamster 6mo ago
Might not be similar to nuclear meltdown but still enough to need a lot of money to fix
adrianmonk 6mo ago
That's the joke, isn't it? A fission power plant simulator lets you have fun playing through a meltdown disaster scenario. A fusion power plant simulator is "worse" because it takes away the "fun" of meltdowns. The humor is in reacting to the simulator as if it were a game (some are, but this one isn't).
- Dylan16807 6mo ago
  The first line reads as a joke, but then they actually ask if it's safe later in the comment.
  - MisterTea 6mo ago
    I probably could have worded it better but while I understand the process and the inherent safety vs fission, I am no expert in the nuclear field. I suppose what I should have asked is what are the risks of e.g retrofitting a fusion reactor into an existing Con Edison facility in the middle of Manhattn, e.g. the historic IRT Powerhouse on 59th st.

Fusion power plants can't "melt down". The amount of plasma inside the vacuum chamber is just around a gram.

by cyberax 6mo ago

Fusion power plants can't "melt down". The amount of plasma inside the vacuum chamber is just around a gram.

> Fusion power plants can't "melt down" Eh, a core-containment failure (in any magnetically-contained system) would involve superheated hydrogen getting friendly with oxygen. That, in turn, would give neutron-impregnated barrier materials a free ride on propellant. It's not strictly a melt down. But it's in the same practical category of failure.

Aardwolf 6mo ago
What's the effect of this in a populated area in a certain radius? Compared to nuclear power plants...
- JumpCrisscross 6mo ago
  > What's the effect of this in a populated area in a certain radius? I'd imagine this is, like with fission plants, deeply dependent on the specific design.
- cyberax 6mo ago
  Radiologically? Pretty much nothing. The regular industrial safety concerns will matter more. The plant will have some tritium, and the material in reactor walls will get activated by the neutron flux. Some of the activated materials can disperse in case of a catastrophic explosion (e.g. a couple of large airplanes being flown the reactor building). But the material of the walls is not volatile, so it'll stay on the site. And tritium is very volatile, so it'll quickly disperse to safe levels. You'll be able to detect them with sensitive equipment, but it won't be dangerous.
gmueckl 6mo ago
Ths is a massive misunderstanding of the technology. First of all, the amount of hydrogen in the reactor is tiny. The magnetic confinement severely limits the density of the plasma. The inner containment vessel is a ultra high vacuum chamber. The chemical energy that would be released by a reaction between the hydrogen in the reactor amd oxygen from the air would be less than what is released by popping a hydrogen filled balloon with a lighter. The truly concerning failure modes would be related to release of radiation or activated materials. But that would require damaging the reactor in ways that the reactor is incapable of imparting on itself. Overall, the technology is remarkably safe.
- JumpCrisscross 6mo ago
  > chemical energy that would be released by a reaction between the hydrogen in the reactor amd oxygen from the air would be less than what is released by popping a hydrogen filled balloon with a lighter Thanks for the correction. If you're breeding lithium in the walls, might that be an incendiary concern?
  - rnhmjoj 6mo ago
    The breeding blanket is entirely contained inside a vacuum vessel, so there isn't any oxygen to react with. Also, the are many blanket designs, but the lithium is never present in its elemental form (precisely because it would be very reactive), but in a stable chemical bond with some neutron multiplier (like lithium-lead alloys or beryllium ceramics). In some design the lithium is even immersed in the coolant itself, which is high pressure helium, so it's not going to ignite in any reasonable way.
    - JumpCrisscross 6mo ago
      > breeding blanket is entirely contained inside a vacuum vessel, so there isn't any oxygen to react with When the vessel works. If the vessel breaches, that lithium could ignite. Note a showstopper. But I suppose a risk to be thought about by the engineers (probably not by policymakers).
      - leonidasrup 6mo ago
        Commonwealth Fusion Systems plan to use lithium in salt form FLiBe, a molten salt made from a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2). It does not violently react with air or water. https://en.wikipedia.org/wiki/FLiBe https://en.wikipedia.org/wiki/FLiBe
  - pixl97 6mo ago
    There seems to be a number of different prototypes of blankets, but the average operating temperature seems to be 300-700C. Adding oxygen to some of these designs while that hot may cause metal burning. This said, many of them are ceramic designs and would likely resist combustion. With all that said, it seems to be way less 'dangerous' material than would be in your average nuclear reactor, making it more of an industrial accident versus a planet contaminating mess.
Symmetry 6mo ago
There's only a few grams of hydrogen in the reactor's plasma, it's reaction with oxygen wouldn't be much more exciting than just losing containment. There are engineering challenges that have to be addressed but no worse than the 6 MW research reactor I used to walk by every day to my college classes in the middle of a dense city. The proliferation risk of someone using the neutron flux to produce an atomic or dirty bomb are real but that exists no matter where it is.
- leonidasrup 6mo ago
  I think the proliferation risks will be in future the reason, independent of technological obstacles or costs, why US will not allow to build fusion power plants in all countries around the world. Hybrid nuclear fusion–fission power plants have been already proposed and studied in theory. "In general terms, the hybrid is very similar in concept to the fast breeder reactor, which uses a compact high-energy fission core in place of the hybrid's fusion core. Another similar concept is the accelerator-driven subcritical reactor, which uses a particle accelerator to provide the neutrons instead of nuclear reactions." https://en.wikipedia.org/wiki/Nuclear_fusion–fission_hybrid https://en.wikipedia.org/wiki/Nuclear_fusion–fission_hybrid
  - bleepblap 6mo ago
    > Hybrid nuclear fusion–fission power plants have been already proposed and studied in theory. I have a hand-wavy hard sci-fi universe I've been rolling around my head for years and I eventually came to the conclusion that fission-fusion drives would be really handy for spacecraft, since it would be much easier to start a fission reaction in a cold/dark ship than fusion because of the power requirements. Otherwise you need some other way to generate 10s or 100s of MW to start the fusion reaction.
    - leonidasrup 6mo ago
      Using the energy of fission for spacecraft propulsion has been studied and some prototypes have been already constructed. Most of these nuclear engines should be used only outside of Earths atmosphere. https://en.wikipedia.org/wiki/Nuclear_propulsion https://en.wikipedia.org/wiki/Nuclear_propulsion https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA Most interesting and promising are direct nuclear propulsions, like fission-fragment rockets. https://en.wikipedia.org/wiki/Fission_fragment_rocket https://en.wikipedia.org/wiki/Fission_fragment_rocket

PunchyHamster 6mo ago

Might not be similar to nuclear meltdown but still enough to need a lot of money to fix

adrianmonk 6mo ago

That's the joke, isn't it? A fission power plant simulator lets you have fun playing through a meltdown disaster scenario. A fusion power plant simulator is "worse" because it takes away the "fun" of meltdowns. The humor is in reacting to the simulator as if it were a game (some are, but this one isn't).

Dylan16807 6mo ago
The first line reads as a joke, but then they actually ask if it's safe later in the comment.
- MisterTea 6mo ago
  I probably could have worded it better but while I understand the process and the inherent safety vs fission, I am no expert in the nuclear field. I suppose what I should have asked is what are the risks of e.g retrofitting a fusion reactor into an existing Con Edison facility in the middle of Manhattn, e.g. the historic IRT Powerhouse on 59th st.