A fusion reactor vacuum vessel will be bigger than the
core of a fission reactor of equivalent power, certainly. But I wonder if a better metric is containment vessel size: there's a lot of very radioactive, very contaminated equipment inside a PWR containment vessel that isn't the core itself.
>orders of magnitude more
Really? Wikipedia says "a typical large 1000 MWe nuclear reactor produces 25–30 tons of spent fuel per year". I don't see a commercial fusion reactor being quite that bad, unless reactor lifetime ends up being very short.
Helion's promotional images keep showing the reactor vessel in a shipping container, which is narrowly true, but doesn't show the support equipment on the other side of a five meter thick concrete radiation shield. No vacuum pump near a running fusion reactor will survive long.
There are all sorts of fascinating engineering problems for a commercial reactor. Photos of the Wendelstein 7-X show it covered with ports for sensors, which you couldn't do with a power reactor, because anything you attach directly to the vacuum vessel will be destroyed. It'll probably end up terribly ugly, the usual intestinal tangle of any industrial plant, a big spiky sausage with pressure sensors at the ends of long tubes to reduce their neutron flux. If you have to mount any sensor directly to the vessel then you use ten or twenty fold redundancy, since replacement is impossible.
After five years of operation, if you go to replace a sensor on the vessel and the threaded fitting crumbles away when you apply the wrench, what do you do? Weld on another one? What's the weld heat-affected zone look like inside the steel after it's spent five years soaked in hot hydrogen, helium, and is richly marbled with transmutation products, dozens of odd elements you don't ordinarily choose to alloy steel with?