[rladd]

You left out d) how long will it last?

Fusion reactions produce lots of neutrons, and neutrons weaken metal, in many cases within a few hours.

It may be that a "successful" fusion reactor is still a failure because it can run for only a few hours, days, or weeks before it has to be scrapped and completely rebuilt.

[DennisP]

I watched a presentation by the article's author, about MIT's ARC reactor design. He said they would replace the inner wall of the reactor once per year. In operation that would be surrounded by molten FLiBe salt, which would absorb the neutrons and breed tritium fuel. The inner wall would be 3D-printed, and the superconducting coils would be hinged so the reactor could easily open up; MIT has already tested joints in modern superconducting tape.

MIT spun off the company Commonwealth to commercialize the idea.