There definitely trendy since some high profile YouTubers were invited to tour! I sincerely hope they can succeed. I believe a limiting factor is going to be fuel unfortunately, as well as I’m not entirely sure it’ll be radiation free.
The original fuel is deuterium, which is absurdly abundant on Earth. Pure deuterium fusion results in half helium-3, and half tritium which decays to helium-3 with a 12 year half-life. Then their main reaction is D-He3.
The D-D reaction is less energetic and produces a neutron, and the D-He3 reaction doesn't produce a neutron. The combined reaction would release about five percent of its total energy as neutron radiation. The neutrons from D-D are about as energetic as fission neutrons, rather than the extremely high energy of D-T fusion neutrons.
They'll never run out of fuel; there's enough deuterium in your morning shower to provide all your energy needs for a year. But the need to breed He3 will put a limit on how fast they can possibly scale up. It could be that manufacturing will be slower than that anyway though.
