alt Hacker Newsthe PBS Space Time episode suggests to me the housing walls might be the biggest problem
it consumes itself or makes molecules that are destructive to the walls or insanely toxic so can never risk leaks
whatever solution they come up with I suspect it will require a lot of constant maintenance on the first generation
Then they are wrong. The biggest problem is efficiently gathering energy from the fusion reaction. Right now, we can only get a tiny fraction (less than 1%) of the energy out. If that can't be raised to 50% or so, fusion will never happen.