Comment by cubefox
5 days ago
Commercially viable likely also means: cost competitive with nuclear fission. Which might well never happen, since the reactor designs for fusion are orders of magnitude more complex (and therefore more expensive).
They also need a lot of ignition energy which requires a powerful separate power source, which limits where the fusion reactor can be built.
Moreover, there is the issue of the reactor core being degraded by the heavy neutron radiation which is produced by the fusion reaction. So the chamber has to be replaced regularly. Which may also be quite expensive.
>the issue of the reactor core being degraded by the heavy neutron radiation which is produced by the fusion reaction.
There are some reactor designs that use aneutronic fusion, which eliminate this particular issue.
https://en.wikipedia.org/wiki/Aneutronic_fusion
Does the commercial viability change when one considers regulatory constraints on building new fission plants? People may be more inclined to allow fusion reactors than fission reactors, since the former doesn't require uranium. (I'm sure there are dangerous failure modes for fusion, like there are for everything else, but Chernobyl continues to haunt the nuclear industry in the popular imagination.)
I guess the existing regulations apply to all reactors which handle radioactive materials, not just to fission reactors which produce radioactive uranium isotopes with long half-life, and which include the risk of a nuclear meltdown. Though it would make sense if the safety requirements are significantly lower for fusion reactors because of their higher innate safety.
My understanding as well is that fusion could take care of base load, but it can't be scaled up or down based on grid demand to the same degree that fission reactors can. So fusion and renewables alone would not be capable of a carbon-free future grid.