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Comment by u320 | Hacker News Reader

> "Overnight, it basically changed the cost per watt of a fusion reactor by a factor of almost 40 in one day,"

So there is this myth that fusion enables unlimited cheap energy. This is 100% false. It's not unlimited at all. Most concepts relies on using lithium-6. That's not a super common element.

But more importantly, it's not cheap. That should be obvious, if you could reduce the cost per watt 40x and still not be competitive.

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Lithium is a super common element. They are mining tens of thousands of tons per year increasing rapidly as make electric car batteries. Lithium-6 is 5% of lithium. Fusion reactors only need tons for breeding blanket.

The original ARC design had 950 tonnes of FLiBe, which contains 115 tonnes of Li-6. This is a substantial fraction of the Li-6 produced for the entire US hydrogen bomb program, all for a single 190 MW(e) (net) reactor.

115 tonnes of Li-6 is what you get by sifting through the lithium required for ~200k electric cars.

Tesla alone could provide material for nine such reactors annually.

Sure, the input feed is not the problem. The problem is actually separating it. The technology used for the H-bombs is no longer acceptable due to mercury pollution. World Li isotope separation capacity currently is in kilograms per year (to produce pure Li-7 for pH control in fission reactors.)

And then there's the beryllium. A single one of those ARC reactors would use something like 40% of the current world annual beryllium production.

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