Fusion would necessarily be a lot more expensive than fission. But fission is itself not competitive, and gets less so with each passing day. So, the longer it takes before fusion is actually, technically possible, the less value there is in it.
Plus, they have much more parasitic power loss (running the superconducting magnets and cooling them to keep them superconducting, plus keeping the vaccum in the reactor chamber all require massive power, and they scale with the size of the reactor). You need some extra power to produce hydrogen through electrolysis as well, though that is probably lower. Note that making the magnets stronger to keep the vessel lower (so that everything is more easily cooled) will not get you much more, since we are already nearing the limits of material resistance for the supporting steel structures in the presence of the extreme magnetic forces trying to crush the reactor together - especially given embrittlement.
Not to mention, you will always need at least a small fission reactor to breed some tritium, since the fusion reactor will always have some losses.
Finally, the much much higher neutron flux that fusion expels (32x or more neutrons, and much higher energy per neutron as well) means that everything close to the reactor becomes brittle in 2-4 years. This means that things like support beams and the magnets themselves need to be constantly replaced. Even worse, they become medium level radioactive waste, which needs to be stored.
These are all intrinsic limitations of fusion that fission reactors just don't have.
So if something is complex we shouldn't or can't build it? OK. I hope you aren't an engineer.
Energy is needed to perform electrolysis to create hydrogen. What about the energy needed to mine uranium? I think it might require quite a lot of effort, particularly once supplies get harder to reach and extract.
The parts get radioactive and need maintenance and storage. The radioactivity is much more short term than fission. Fission fuel needs stored away from all life for 100,000 years. It will be a miracle if we manage to achieve that.
I think small scale modular fission is a good option, but your arguements against fusion aren't good.
We were discussing why fusion plants are necessarily more expensive than fission plants - not whether they can (or even should) in principle be built.
> Energy is needed to perform electrolysis to create hydrogen. What about the energy needed to mine uranium? I think it might require quite a lot of effort, particularly once supplies get harder to reach and extract.
I listed many other energy costs - including some uranium to breed tritium.
> The radioactivity is much more short term than fission.
Sure, but that still means decades for tritium and centuries for the neutron-bombarded materials - more than enough to make it as big of a problem in our lifetimes per kg, just with many more kg of waste from fusion.
Fusion's going to have to go with advanced fuels to have a chance. For that and various related reasons, I consider Helion the least dubious of the fusion efforts.
All that could make that tolerable is that a 2MW package just produces a lot less of everything than a 2GW (or 20GW) monstrosity.
The idea for future designs is to breed Tritium in the blanket surrounding the vessel. This obviates the need for external sources.
> everything close to the reactor becomes brittle in 2-4 years
I'm no expert on solid state physics, but that seems a little short? JET is more than ten times as old, and as we speak it's in its second run of D-T experiments.
> These are all intrinsic limitations of fusion that fission reactors just don't have
To be clear these are limitations of a specific kinds of fusion reaction and/or reactor design, primarily that of Deuterium-Tritium in a solid-walled tokamak. This may be a nitpick as it's currently far and away the most promising for energy production, and the alternatives are much further from any sort of workable prototype, but I have heard of them undergoing active research: tri-alpha (aneutronic reaction, meaning no activation or embrittlement of reactor components), liquid metal for the walls and divertor (in effect, continuously replacing neutron-bombarded material), etc.
The problem is that, at best, you can create as much Tritium in the blanket as you put in as fuel (since every emitted neutron is coming from a Tritium atom). So, to be self-sustaining, every emitted neutron would have to be caught by the blanket to form a Tritium atom, and you would have to be able to extract every single atom of Tritium from the blanket back as usable fuel - and this is assuming 100% of the tritium you put in actually fuses, which is unlikely given how hard tritium is to contain (essentially every material is porous to Tritium). So, since there are losses at each of these levels, you need to inject new tritium into the cycle.
Also note that this entire blanket design is entirely theoretical at the moment: no fusion experiment has ever attempted to do anything with the fusion products other then measure the amount of heat generated.
> I'm no expert on solid state physics, but that seems a little short? JET is more than ten times as old, and as we speak it's in its second run of D-T experiments.
I'm no expert either, but these are the estimates I have read everywhere. JET is not in any way representative, as they do a handful of fusion events per year, for a few seconds - while a DEMO plant would be running continuously, 24/7. The amount of irradiation is incomparable.
> To be clear these are limitations of a specific kinds of fusion reaction and/or reactor design, primarily that of Deuterium-Tritium in a solid-walled tokamak.
These are all limitations of the only fusion electrical power-producing technology that is anywhere close to realistic.
All other fusion reactions require much, much higher temperatures and pressures to ignite, so they are many more decades away (regardless of what some snake oil start-ups are claiming).
All other magnetic confinement D-T fusion reactions have the same problems I discussed.
And inertial-confinement fusion approaches are much less likely to ever be economical given the huge costs of the actual fuel.
CFS for example uses beryllium in a FLiBe salt. General Fusion and Zap Energy use lead.
It is conceivable that fusion could be made to work in outer solar system spaceship propulsion, where the constraints are very different. It will never generate commercial power on Earth. The billionaires pumping cash into fusion startups are being taken for a ride. They can afford it.
By contrast, Bill Gates got US taxpayers to pony up fully half of the scratch on his pet SMR project, without giving up any ownership. So, we are the ones taken for a ride, instead.