Comparing the economics of fission and fusion is quite a stretch. Even with the massive number of unknowns they've literally nothing in common.

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cornholio 4 days ago | parent [-]

Well, a dolar is still a dollar and they need to sell on the same energy market. It's well understood that fission projects have become economically infeasible because they are dominated by capital costs, and the risks these projects come with are not compatible with the decades required for economic breakeven.

Everything we know about current approaches to fusion seem to indicate they will have the same economic problems. The scaling factors of confinement, power and reaction rates push towards immense reactors with vacuum chambers the size of apartment buildings, massive superconducting magnets etc. hence the ITER project spiraling out of control trying to build one just big enough that at least have a fair chance of achieving engineering breakeven. The basic plasma physics works the same for Helion, and the best triple product they achieved places them two orders of magnitude behind tokamaks, albeit with much less capital.

So when and if the best approaches to fusion succeed, it looks like they will yield these massive plants that share the costs problems of fission. While they won't be able to meltdown, the regulatory constraints will be very similar, the intense neutron flux will activate the structure of the reactor and poses similar proliferation and decommissioning concerns, there is radiological risk to the civil population in the form of Tritium leaks etc.

And unlike fission, which is very well understood and mature, fusion plants will be much riskier economically, on par with the attempt to introduce fast fission breeders into commercial service, which notoriously failed.

So while the physics is indeed very different, we know enough to compare fusion and fission economically, and the outlook is very bleak.

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idiotsecant 4 days ago | parent [-]

Why do you think fission plants are expensive? Do you think it's the pumps and turbines and concrete?

Pro tip: it's not. It's because there is millions of man-hours of regulatory burden attached to every decision, to every bolt, to every instrument or valve installed.

There is a reason for all that regulatory burden, of course. It's the release of long lived and deadly radiation from a meltdown. If it wasn't for that regulation building a nuke plant would actually be quite inexpensive, relative to current costs- On the scale of a hydro dam.

Fusion has none of those costs because it has none of the same dangers. It's a wildly different problem with wildly different cost basis. The expensive part is research. Once that's done that cost is gone.

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pfdietz 4 days ago | parent [-]

Fission plants are expensive because malfunctions cannot be tolerated. Malfunctions cannot be tolerated because the government would not give them a liability cap if there was a significant chance of serious accident.

Guess what? Fusion reactors also can't tolerate malfunctions. Not because of public safety, but because large (DT reactors being 40x the size of a fission reactor for a given power output) complex devices that are too radioactive for hands on maintenance are unrepairable.

Helion is claiming they can go with materials with very low beyond short term activation, and that the cylindrical geometry would make swapping out hot components easier. Whether that is enough remains to be seen, but IMO DT approaches are complete dead ends.

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cornholio 4 days ago | parent [-]

Solar energy has achieved such a cost reduction that nuclear can't compete even if the actual nuclear reactor part is free. Just the classical, steam turbine parts are becoming more expensive than solar, and this is evident for new natural gas plants, who don't even have any radiation concerns. Sure, fusion energy would be dispatchable, unlike solar, but momentum is building towards large scale interconnections, perhaps even at intercontinental levels, spanning many time-zones and climates and achieving highly reliable solar.

While it's unclear when all this will be achieved, nobody is ready to bet 10 billions that it won't happen in the next two decades they need to recover costs.

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pfdietz 4 days ago | parent [-]

I agree solar is very tough to beat, and even more so as storage improves. As I've said before, I consider Helion is the least dubious fusion approach, but that doesn't imply I think their absolute chance of commercial success is high.

One very significant issue with Helion's scheme is the enormous quantity of tritium produced. To put this in context: to power the world with such reactors might require ~10 TW. If using 2DD + D3He, this would produce 12 grams of tritium per second. If this stream were all released into the environment (which it would not be, but this is for purposes of illustration) it would lift all the water in the entire biosphere close to the US legal limit for tritium in drinking water, including all 1.3 billion cubic kilometers in the oceans. Tritium capture and containment will have to be extremely good for this technology to be globally acceptable.

	▲	cornholio 3 days ago \| parent [-]
		Thank you for your very well informed perspective. Fusion proponents seem to be either industry insiders with vested interests, or less informed fanboys who are simply unaware of the technical and economic realities. This issue of safety is particularly prone to handwaving; in reality, the combined effects of activation and proliferation risks and the substantial radionuclide release potential will make the operational realities, regulations, environmental litigation and associated costs very similar to fission. That's not too say fusion is inherently dangerous, rather that modern fission projects are already very safe and fusion won't improve on that. Yet fision still failed. So if fusion can't improve on the economics - and they quite clearly can't for the foreseeable future - then they bring nothing to the table.