Comment by cyberax

4 hours ago

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

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).

> 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.

  • 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.

    • > 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?

      4 replies →

  • 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.

    • 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

  • What's the effect of this in a populated area in a certain radius? Compared to nuclear power plants...

    • > 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.

    • 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.