The plasma hits the wall, cools rapidly and you have to deal with hydrogen gas and a slightly warmed wall. The thing about fusion reactors is, that the energy densities at any given moment are actually not that high at any given moment, it is just that the fuel cycles are quite rapid and consequently you can get a lot of energy out.

It's actually an incredibly small amount of material that is heated to millions of degrees. It is a drop in the bucket compared to the amount of matter in the immediate surrounding environment, so the energy can be soaked up relativity easily.

I think I remember hearing something like that anyone more than 50 feet away would be completely unaffected (but don't quote me on that).

"relativity easily" is my favorite typo of the week.

From what I understand I think don't know and it hasn't been extensively modeled because we are still trying to just get the process to start. Having said that I think that if the reactions containment breaks the actual fusion process breaks down super fast and cools much faster then something like a meltdown at a fission reactor. If any more qualified wants to refute any of this please do.

I think that, without the magnet, there is no such thing as a containment vessel for a 100 million degree plasma.

The reactor is ruined. No damage to larger area. Possible smaller radiation in the structure, since the reactor inside is possibly radioactive.

Basically natural gas explosion, with a radioactive metal torus.

It would explode, but for any reactor we’re likely to build in our lifetimes, it wouldn’t be anything like a nuclear bomb. We’ve had nastier explosions in natural gas refineries. There would be radiological contamination from the Tritium and any neutron-activated material, but it would be more of an expensive cleanup than an environmental disaster. It would be dirty though, especially if the reactor had been running for a while, building up dust. What wasn’t radioactive would still likely be stuff you don’t want to breathe or ingest.

TL;DR Boom lots of dead people in the containment structure, expensive cleanup, but nothing like a fission disaster. It would be an uninspiring explosion, but it would be dirty.

This is wrong in every possible way. There isn't enough mass of hot material in any plausible fusion reactor to even breach the vacuum chamber.

Or for better context: research facilities today regularly lose plasma containment. It's why we don't have practical fusion reactors, but they're already at the plasma densities we would run at (which is an order of magnitude or so better then the Sun achieves).

Yeah. There's even a clue in what it's called: a vacuum chamber.

Densities are extremely low, so you only have a few grams of material in the reactor, even at large volumes anticipated for a commercial design.

Furthermore, the reaction is extremely finicky, as demonstrated by what an incredibly hard time we are having creating and more importantly sustaining it. Any deviation from the ideal and it just goes out. So no runaway chain reactions.

https://en.wikipedia.org/wiki/Fusion_power#Accident_potentia...