[tsimionescu]

Fusion is still at the phase of fundamental research in some areas, while others are in a sort of "engineering research".

Either way, it's actually hard to imagine fusion will ever be a promising power source, at least with any tech resembling what we know today. It is extremely complex technology living in proximity to extreme radiation bombardment and extreme temperature differences. A fusion reactor will need basically complete replacing every 20 years in the best possible conditions, assuming nothing goes wrong. Re-building the most expensive power plant in the world every decade or two is not likely to be a great way of powering your country.

Also, despite the common narrative, it requires an extremely rare fuel: tritium. Basically the only way to create tritium is to run a fission reactor, which negates the safety promises of fusion.

I think overall wind+solar+fission are a much better and safer investment in the future. Fusion is fine as an experiment progressing along in the background, but nowhere near as promising as it's made out to be.

[baryphonic]

Not an expert at all in this area, but my understanding was that CFS' design addresses the neutron bombardment problems and the tritium breeding problems by making the reactor smaller and enveloping it in some sort of molten salt. Because the wall is smaller, they plan on being able to replace the inner wall yearly via 3D printing.

Wind & solar are fine where they make sense (i.e. windy or particularly sunny places), though solar panel production depends on rare earth metals, and wind + solar at scale require huge land areas covered with panels or turbines. Fission is fine, but is expensive and has a serious regulatory hurdle to getting safer, modern designs up and running, and produces long-lived radioactive isotopes.

Anyway, I'm interested in all of the above. Any of them are better than fossil fuels, and some scale better than others.

[tsimionescu]

> CFS' design addresses the neutron bombardment problems and the tritium breeding problems by making the reactor smaller and enveloping it in some sort of molten salt. Because the wall is smaller, they plan on being able to replace the inner wall yearly via 3D printing.

My understanding is that even these molten salt or molten lithium blankets can only catch some of the neutrons - so the magnets and other outer structures will still get neutron bombardment, and the tritium you can produce will not fully replace the tritium you put in. The once a decade or two replacement of the entire reactor number I heard was predicated on a shield like this - without a shield IT would probably be once every few years.

Note that I am not claiming wind, solar and fission don't have problems. It's just that they all seem to be much simpler problems than fusion has, fundamentally, even in the long run.

I'm not suggesting we shouldn't keep researching fusion technology, but I also don't think it can or should he treated as a priority, or as if once it's done it will solve all of our energy woes. It will take a huge amount of time even after the first actual plant is operational until fusion becomes in any way economical and widespread, with initial fixed costs that will make fission seem like chump change.

[AtlasBarfed]

The LCOE of wind/solar is under natural gas, and sodium ion batteries will hit the market this year or next according to CATL press releases (always a grain of salt until you see the product on the market).

They are supposed to be half the cost of LFP.

And let's face it, nat gas / coal are effectively subsidized by ingrained government policy while they SHOULD be subject to a ten year escalating carbon tax.

Nuclear is still ... ok, it's on the high end of solar/wind deployments.

Perovskites may solve even more problems, but that hasn't really panned out like hoped, probably a ten year project.

Wind and solar don't require "huge areas of land". Well, not new land or land we need. There's a LOT of roofs everywhere. Residential power can be almost completely addressed with rooftop solar + storage, I haven't seen single family homes that need "more than the roof", and the excess can go to multifamily buildings.

Windmills can be offshore, or sticking out of farmland or nature preserves.

Utility solar can use deserts, there's plenty of that. I hate the hype about "green hydrogen" since it is a shadow play by oil companies to keep other "color" hydrogen sources which are invariably oil/gas.

Fusion should continue to get research dollars. We should be pursuing LFTR and other new gen fission.

But let's be real, no fission or fusion project initiated now will be ready in ten years, and no one can predict the price of solar/wind/storage in ten years. It won't drop like the previous ten years, but there is enough in the works that it will likely drop ... 50%?

I don't think new fission/fusion can be commercially planned until wind/solar/storage prices stabilize. It doesn't matter how cool a fusion reactor is if the energy it produces is 3x the cost of wind/solar.

I think the hardest thing to say about fusion is that the "it's always 20/30/40 years in the future" was always a technological commentary.

But now the new challenge even if they get a working plant in 20/30/40 years is "is it cheaper?"

Constant 3D printing reactor walls sounds like an expensive proposition. Granted I think the same strategies are in LFTR designs since the materials is hard there too. Liquid metal fusion and molten salts has all the materials engineering and endurance issues LFTR had. I guess fusion fuel is effectively liquid though, so they could just move the liquid to another generator while they "overhaul" the one that has neutron degradation. I figured if LFTR hit mainstream they would do the same: mass produce the reactors and then just move the fuel between them as they wear out, and then recondition the "spent reactor".

Can a LFTR expert comment on whether it can "burn"/breed/transmute/process most nuclear waste as usable fuel, or at least move the isotopes to other better isotope decay paths? LFTR is supposed to be able to use 99% of its thorium fuel without nuclear waste.

[tsimionescu]

I think you're a bit too optimistic on solar deployment for residential areas. Sure, you're probably right in California, but Norway won't be powering their homes through roof-top panels.

Also, most people don't live in single family homes, they live in 30-100 family apartment blocs, where even at the equator there won't be enough roof space to power the whole building through solar.

Wind does have a massive land use problem as well (as does hydro). In most of the world outside the USA, there aren't huge swaths of unused land anywhere near residential or industrial areas.

Which is why for example France has green-lit 6 new fission reactors, and the EU in general is looking at declaring fission green energy to get the required subsidies. This is also why Germany, that went all in on wind and solar and even has a few days each year where the entire grid is running on wind+solar+hydro, still produces about twice the GHG as France (both total and per capita).