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Comment by pfdietz | Hacker News Reader

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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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.

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.

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.

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