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That fusion reactions are so difficult to get started makes the reactors very safe because failure makes them stop. So, if you lose magnetic confinement the reaction stops. The reactor may be damaged but that's it.

This is unlike fission reactors, where a failure causes reactivity to increase. That causes meltdown and the possibility of explosion and all the nasty radioactive contamination.

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My understanding is that more recent fission reactor designs are done in such a way that they fail in ways which cause the reaction to diminish rather than build up further, which puts you in a better place than, say, Chernobyl.

You still have a very hot very radioactive lump of death in the middle of your busted reactor when it's all done though, and that's definitely not fun. Fusion failure modes - in current designs anyway - are far more appealing to anybody who happens to be in the area at the time.

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