[apendleton]

> It would require a technological breakthrough that we have not yet imagined.

Maybe, but not necessarily. The necessary breakthrough might have been high-temperature superconducting magnets, in which case not only has it been imagined, but it has already occurred, and we're just waiting for the engineering atop that breakthrough to progress enough to demonstrate a working prototype (the magnets have been demonstrated but a complete reactor using them hasn't yet).

Or it might be that the attempts at building such a prototype don't pan out, and some other breakthrough is indeed needed. It'll probably be a couple of years until we know for sure, but at this point I don't think there's enough data to say one way or the other.

> And already, solar plus storage is cheaper than new nuclear.

It depends how much storage you mean. If you're only worried about sub-24h load-shifting (like, enough to handle a day/night cycle on a sunny day), this is certainly true. If you care about having enough to cover for extended bad weather, or worse yet, for seasonal load-shifting (banking power in the summer to cover the winter), the economics of solar plus storage remain abysmal: the additional batteries you need cost just as much as the ones you needed for daily coverage, but get cycled way less and so are much harder to pay for. If the plan is to use solar and storage for _all generation_, though, that's the number that matters. Comparing LCoE of solar plus daily storage with the LCoE of fixed-firm or on-demand generation is apples-and-oranges.

I think solar plus storage absolutely has the potential to get there, but that too will likely require fundamental breakthroughs (probably in the form of much cheaper storage: perhaps something like Form Energy's iron-air batteries).

[bruce511]

One can discuss base load and season shifting all day long. But ultimately fusion will fail for two simple reasons; time and money.

If we started building a fusion commercial scale plant today (ie started by planning, permits, environmental assessments, public consultation, inevitable lawsuits, never mind actual construction and provisioning) it'd come online in what? 10 years? 15 years? 20 years?

Want to deploy more batteries? It can be online in months. And needs no more construction than a warehouse.

Financially fusion requires hundreds of billions, committed now, with revenue (not returns) projected at 10 years away (which will slide.) Whereas solar + storage (lots and lots of storage) requires anything from thousands to billions depending on how much you want to spend. We can start tomorrow, it'll be online in less than 2 years (probably a lot less) and since running costs are basically 0, immediate revenue means immediate returns.

Of course I'm not even allowing for fusion being "10 years" from "ready". It's been 10 years from ready for 50 years. By the time it is ready, much less the time before it comes online, it'll be redundant. And no one will be putting up the cash to build one.

[pfdietz]

High temperature superconducting magnets are not a panacea for the problems with DT fusion. Those issues follow from limits on power/area at the first wall, and the needed thickness of the first wall; these ensure DT reactors will have low volumetric power density, regardless of the confinement scheme used.

With HTSC magnets, a tokamak much smaller than ITER could be built, but ITER is so horrifically bad that one can be much better than it and still be impractical.

[epistasis]

And these are not new issues, they've been known for more than 40 years, but never addressed. From the 1983 Led

> But even though radiation damage rates and heat transfer requirements are much more severe in a fusion reactor, the power density is only one-tenth as large. This is a strong indication that fusion would be substantially more expensive than fission because, to put it simply, greater effort would be required to produce less power.

https://orcutt.net/weblog/wp-content/uploads/2015/08/The-Tro...

[apendleton]

In terms of cost of materials to build a reactor, sure, that seems right. But most of the cost of fission is dealing with its regulatory burden, and fusion seems on track to largely avoid the worst of that. It seems conceivable that it ends up being cheaper for entirely political/bureaucratic reasons.

[pfdietz]

Relaxed regulatory burden doesn't seem to be making fission competitive in China; renewables are greatly overwhelming it now, particularly solar.

We might ask why regulations are so putatively damaging to nuclear, when they aren't to civil aviation. One possibility is that aircraft are simply easier to retrofit when design flaws are found. If there's a problem with welding in a nuclear plant (for example) it's extremely difficult to repair. Witness the fiasco of Flamanville 3 in France, the EPR plant that went many times over budget.

What would this imply for fusion? Nothing good. A fusion reactor is very complex, and any design flaw in the hot part will be extremely difficult to fix, as no hands on access will be allowed after the thing has started operation, due to induced radioactivity. This includes design or manufacturing flaws that cause mere operations problems, like leaks in cooling channels, not just flaws that might present public safety risks (if any could exist.) The operator will view a smaller problem that renders their plant unusable nearly as bad as a larger problem that also threatens the public.

I was struck by a recent analysis of deterioration of the tritium breeding blanket that just went ahead and assumed there were no initial cracks in the welded structure more than a certain very small size. Guaranteeing quality of all the welds in a very large complex fusion reactor, an order of magnitude or more larger than a fission reactor of the same power output, sounds like a recipe for extreme cost.

[cyberax]

Regulation is not a problem, and even the construction costs are not terrible. We can take the Rooppur NPP as a base, it produces reliable energy at 6-7 cents per kWh. The reason for cost overruns is simply because NPPs are one-off products, the Western countries don't have a pipeline for NPP production.

For comparison, utility-scale solar with 16 hours of storage is 21 cents: https://www.utilitydive.com/news/higher-renewable-energy-cos...

Just raw solar without storage can be as low as 2-3 cents per kWh.

[pfdietz]

If I understand correctly, the cost/year of an engineer in India is maybe 1/3rd that in the US, and for general labor the disparity is even larger. So it shouldn't be too surprising NPP construction in India is cheaper than in the US. India doesn't have a large NPP pipeline, they just have cheaper labor.

[apendleton]

> The reason for cost overruns is simply because NPPs are one-off products

But there's no fundamental reason they _have_ to be one-off products. They just historically have been for at least partly regulatorily motivated reasons: because each reactor's approval process starts afresh (or rather, did until quite-recent NRC reforms), there's little advantage in reuse, and because many compliance costs are both high and fixed, there's an incentive to build fewer huge reactors rather than more small ones, which makes factory construction difficult to achieve and economies of scale hard to realize.

[epistasis]

Regulatory costs and waste disposal are not significance cost centers for nuclear, at least as far as I can tell from any cost breakdowns.

One doesn't need super high quality welding and concrete pours becuase of regulations as much as the basic desire to have a properly engineered solution that lasts long enough to avoid costly repairs.

Take for example this recent analysis on how to make the AP1000 competitive:

https://gain.inl.gov/content/uploads/4/2024/11/DOE-Advanced-...

There are no regulatory changes proposed because nobody has thought of a way that regulations are the cost drivers. Yet there's still a path to competitive energy costs by focusing hard on construction costs.

Similarly, reactors under completely different regimes such as the EPR are still facing exactly the same construction cost overruns as in the rest of the developed world.

If regulations are a cost driver, let's hear how to change them in a way that drives down build cost, and by how much. Let's say we get rid of ALARA and jack up acceptable radiation levels to the earliest ones established. What would that do the cost? I have a feeling not much at all, but would like to see a serious proposal.

[pfdietz]

> let's hear how to change

One approach would be to reduce the size of the containment building by greatly reducing the volume of steam it must hold. This would be done by attaching Filtered Containment Venting Systems (FCVS) that strip most of the radioactive elements from the vented steam in case of a large accident.

The containment building is a significant cost driver, costing about as much as the nuclear island inside of it.

If such a system had been attached to the reactors that melted down at Fukushima exposure could have been reduced by maybe two orders of magnitude. And if the worst case exposure is that low, perhaps much more frequent meltdowns could be tolerated, allowing relaxation of paperwork requirements elsewhere.

[epistasis]

Interesting! Would that require any regulation change?

[apendleton]

Oh for sure, I'm not claiming that CFS (or Tokamak Energy or Type One or whoever else) will for sure succeed, or if they do, that they've already solved all the problems that will need solving to do so. My only assertion/prediction is that I think if they end up succeeding, when future historians look back and write the history of this energy revolution or whatnot, HTSC magnets will turn out to have been the key breakthrough that made it possible.

[nandomrumber]

Fusion reactors are self destroying, just ask any star.

More seriously: what to do about the neutron flux destroying the first wall inside the reactor vessel?

[pfdietz]

> needed thickness of the first wall

I meant, needed thickness of the tritium breeding blanket.

[cesarb]

> If the plan is to use solar and storage for _all generation_, though, that's the number that matters.

And that's the problem with these Internet discussions: that's almost never the plan, but commenters trying to make solar look bad assume it is (to your credit, you made it explicit; many commenters treat it as an unspoken assumption).

In real life, solar and batteries is almost always combined with other forms of generation (and other forms of storage like pumped hydro), in large part due to being added to an already existing large-scale grid. The numbers that matter are for a combination of existing generation (thermal power plants, large-scale hydro, etc) with solar plus storage. Adding batteries for just a few hours of solar power is enough to mitigate the most negative consequences of adding solar to the mix (non-peaking thermal power plants do not like being cycled too fast, but solar has a fast reduction of generation when the sun goes down; batteries can smooth that curve by releasing power they stored during the mid-day peak).

[adrianN]

In the end we're still making steam and running a turbine. Just the steam turbine part of the power plant has a hard time competing with solar in sunny locations.