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Comment by StanAngeloff | Hacker News Reader

Some years ago, likely around 2010, I had the priviledge to visit Culham Centre for Fusion Energy (it was called UKAEA Culham back then). During my visit, we were shown around various experiments and after a long evening, we had the opportunity to attend a Q&A with the staff. The question everyone wanted to know the answer to was When will it be ready? The scientists and everyone else involved honestly thought 10 years would be more than enough time for the technology to mature and find its way into everyday lives.

We are not quite there yet.

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I’ve heard the argument that it’s a matter of money rather than time. The physics is such that a big device is a good choice. Even the compact designs based on high field HTS coils will need to overcome their high power density in the divertor, that hasn’t come up much yet but it will. So we want a big device to figure out divertors and breeding and managing instabilities. Great. We’ll a just make the one, ITER. Well we’re still waiting. If someone with a lot of money wanted it to happen Right Now they could. You just need a 40 billion dollar c(r)ash program.

That argument simply assumes money will solve the problems with fusion. There's very good reason to think it won't.

And that reason is? I have very good reason to think it will, as do the plasma physicists who work on magnetic confinement.

The volumetric power density of fusion reactors is inherently lower than fission reactors, because of the square cube law and the need for the fusion reactor to radiate it's output through the wall of the reactor. This means th e nuclear core of the fusion reactor will be both much larger and much more complex than a fission reactor.

Certainly a fusion reactor will be a large, expensive, and complicated device. If it’s going to be directly compared to fission solely on cost to generate power then yes fission is less expensive. The allures of fusion is its lack of ability to meltdown, global abundance of fuel, and the ability to choose what elements get activated. That seems like things that add value to me, but I don’t think the conversations on funding fusion research are at that level. I’ve read the transcripts of the US House Subcommittee on Science, Space, and Technology’s discussions on fusion energy science. It’s clear that the politicians that represent fusion scientists when the budget is made don’t have a strong grasp of what the devices are, their potential impact, the realistic failure modes for these projects, etc. It’s simply a game of politics.

You are repeating the hoary old argument for fusion. That argument depended on it competing only against fission, and making grand nebulous claims that environmental and safety credits would let it pull ahead, even though it was otherwise more expendive than fission.

But fission has now lost to renewables, which are now at a levelized cost 3-4x lower than fission. Fusion's putative safety/env benefits mean nothing now.

The program now is existing on institutional inertia. I don't see this coming to anything but an inglorious end.

Wind/solar aren't that cheap if you include enough storage to get through a windless night, and enough overcapacity to get through cloudy winter weeks.

If you're backing them up with fossil, then sure, they're pretty darn cheap.

You back them up with short term storage and hydrogen. With plausible costs for 2030 a CO2-free grid optimizes to 0% nuclear.

How about today's costs? After all, presumably you're using today's cost for nuclear.

It's plausible that, for example, some molten salt reactors currently under development will be a lot cheaper than light water reactors, so it doesn't make sense to compare future renewables with nuclear today.

No molten salt reactor could be available by 2030. Simply resolving material issues would take at least that long. Proving materials will last X years takes at least X years.

More importantly, the decision whether to build such a reactor will depend on decline in costs of its competition in the future, not just now, when the business case for the reactor requires it operate for 40 years or more.

There are several ways to fix the materials issue, pursued by active projects. One is simply to replace the reactor core every few years; Terrestrial Energy and Thorcon are using that approach.

So I'll ask again: how do the numbers look if you compare today's wind/solar/storage costs without fossil backup to today's nuclear costs? We can argue until our fingers wear out about what the costs will be in eleven years, but there are hard numbers for today.

If they replace the entire core every few years the economics will suck. If they replace every, say, 7 years, then this will take long enough to demonstrate that commercial operation will be at 2030 or beyond.

Insisting on looking at today's solar and wind numbers ? Ok, then I also insist we stick with the numbers for currently available nuclear reactors. You wouldn't want to hypocritically allow only projections of future nuclear, right?

Yes, I mean today's nuclear. But for solar/wind I mean what I said above: enough storage for a windless night and enough overcapacity for cloudy winter weeks, so it's the cost to actually run a grid on wind/solar/storage alone.

Seems like there are still plenty of scenarios for power generation that aren’t easily amenable to wind and solar: mountainous, high latitude or small countries; at sea, underwater, or in space; on Mars; or in the event that storage technologies don’t pan out the way we hope.

If there is a niche somewhere like that fission would be fine. Btw in the inner solar system solar is vastly superior.

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