4 ms·

Tritium is only necessary because the magnetic confinement is poor. If we assume that it gets much better then it becomes economical to use deuterium fuel. Als

Tritium is only necessary because the magnetic confinement is poor. If we assume that it gets much better then it becomes economical to use deuterium fuel. Also, I question the explosion claim. Without confinement, the energy drops below the threshold necessary for fusion and the reaction stops. An explosion would require a self sustaining reaction of some kind and I'm just not sure where that would come from. It's not like there's much inertia in it. But you're right about the neutrons. Maybe you can get away with a rice maker sized reaction chamber, but you're going to want it shielded in something the size of a couch. Probably best to just put it in a deep hole and pump water down there. Then you can provide the neighborhood with steam for heating and electricity for everything else.

worik 2y ago
> Also, I question the explosion claim. Without confinement, the energy drops below the threshold necessary for fusion and the reaction stops I am not a physicist I expect the sudden failure of magnetic confinement would lead to a chemical explosion because of super heated plasma
- nine_k 2y ago
  The amount of plasma in such a reactor would likely be fractions of a milligram. What would scare me more is an asymmetric loss of the magnetic field, which would produce a huge and not-designed-for mechanical stress, potentially leading to pieces of the superstructure breaking off and flying at high speeds, pushed by the very strong magnetic field.
  - __MatrixMan__ 2y ago
    Also, a fraction of a milligram of plasma, suddenly free to roam about the entire to toroid rather than confined to a small part of it would lose temperature rapidly. But yeah, magnets throwing around chunks of each other, and chunks of radioactive shielding, would be an unpleasant thing.
andrewflnr 2y ago
Not to necessarily feed into fear mongering, but: an explosion only needs pressure. A can of compressed air can explode. And residual heat from the reaction helps, too. So the question is whether there's enough hot gas under pressure to push past the volume of the reaction chamber...
perihelions 2y ago
- "Tritium is only necessary because the magnetic confinement is poor." Startup hype notwithstanding, the other fusion reactions are only incremental improvements over D-T, in terms of emitting less neutron radiation. From the standpoint of radiation protection it's all utterly moot—you'll never have a fusion reactor in a "rice-maker" to "power homes and vehicles". The amounts of radiation are absurdly extreme, and of an exotic kind that's really, really, unshieldable. (Infamously, the whole point [0] of the neutron bomb was a Cold-War tactical antitank weapon. Something that heavy steel tanks, envisioned to be in a nuclear land war in the Fulda Gap or whereever, would have no chance of surviving—not even with all the efforts the superpowers threw at the military challenge). A sobering fact for those unfamiliar with nuclear physics. The point of less-neutronic nuclear fusion reactions isn't to render them mild enough not to disintegrate humans. It's to make them mild enough to not disintegrate steel [1]. [0] https://en.wikipedia.org/wiki/Neutron_bomb#Use https://en.wikipedia.org/wiki/Neutron_bomb#Use [1] https://www.nature.com/articles/nphys3735 https://www.nature.com/articles/nphys3735
spacephysics 2y ago
As much as a fallout nuclear energy world would be cool (with cars running on fusion), I think in our lifetime it’ll make more sense to just have the power plants run off fusion and delivery energy via the grid We’re already seeing very promising improvements in batteries (some without even needing lithium), so probably sooner we’ll get wildly high battery energy densities
- __MatrixMan__ 2y ago
  I agree, it's just not as practical as wind and solar and grid-connected energy storage for 95% of the things you'd want it for. But the reasons are that its complex and expensive, not that it's accidentally a bomb.

worik 2y ago

> Also, I question the explosion claim. Without confinement, the energy drops below the threshold necessary for fusion and the reaction stops I am not a physicist I expect the sudden failure of magnetic confinement would lead to a chemical explosion because of super heated plasma

nine_k 2y ago
The amount of plasma in such a reactor would likely be fractions of a milligram. What would scare me more is an asymmetric loss of the magnetic field, which would produce a huge and not-designed-for mechanical stress, potentially leading to pieces of the superstructure breaking off and flying at high speeds, pushed by the very strong magnetic field.
- __MatrixMan__ 2y ago
  Also, a fraction of a milligram of plasma, suddenly free to roam about the entire to toroid rather than confined to a small part of it would lose temperature rapidly. But yeah, magnets throwing around chunks of each other, and chunks of radioactive shielding, would be an unpleasant thing.

andrewflnr 2y ago

Not to necessarily feed into fear mongering, but: an explosion only needs pressure. A can of compressed air can explode. And residual heat from the reaction helps, too. So the question is whether there's enough hot gas under pressure to push past the volume of the reaction chamber...

perihelions 2y ago

- "Tritium is only necessary because the magnetic confinement is poor." Startup hype notwithstanding, the other fusion reactions are only incremental improvements over D-T, in terms of emitting less neutron radiation. From the standpoint of radiation protection it's all utterly moot—you'll never have a fusion reactor in a "rice-maker" to "power homes and vehicles". The amounts of radiation are absurdly extreme, and of an exotic kind that's really, really, unshieldable. (Infamously, the whole point [0] of the neutron bomb was a Cold-War tactical antitank weapon. Something that heavy steel tanks, envisioned to be in a nuclear land war in the Fulda Gap or whereever, would have no chance of surviving—not even with all the efforts the superpowers threw at the military challenge). A sobering fact for those unfamiliar with nuclear physics. The point of less-neutronic nuclear fusion reactions isn't to render them mild enough not to disintegrate humans. It's to make them mild enough to not disintegrate steel [1]. [0] https://en.wikipedia.org/wiki/Neutron_bomb#Use https://en.wikipedia.org/wiki/Neutron_bomb#Use [1] https://www.nature.com/articles/nphys3735 https://www.nature.com/articles/nphys3735

spacephysics 2y ago

As much as a fallout nuclear energy world would be cool (with cars running on fusion), I think in our lifetime it’ll make more sense to just have the power plants run off fusion and delivery energy via the grid We’re already seeing very promising improvements in batteries (some without even needing lithium), so probably sooner we’ll get wildly high battery energy densities

__MatrixMan__ 2y ago
I agree, it's just not as practical as wind and solar and grid-connected energy storage for 95% of the things you'd want it for. But the reasons are that its complex and expensive, not that it's accidentally a bomb.