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