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I know that tritium isn't entirely stable (half-life of about 12.3 years) and might require a lot of energy to create large amounts (and transport/handle safely), but wouldn't that still be easier (and more sustainable) than searching for and mining He-3?

EDIT: I wasn't clear.... Sorry...., Can we use ONLY tritium (and other easy-to-obtain - and cheap) materials in fusion reactors? Leaving out helium-3 entirely?

I guess I'm having a hard time understanding why some (maybe only a few, but still) fusion researchers are so eager to pursue helium-3 option(s) when fusion is going to be expensive enough as it is, without mining the moon, or whatever....

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    $\begingroup$ Not sure I understand your question, we do use deuterium and tritium as fusion reactor fuel. $\endgroup$
    – Triatticus
    Apr 19, 2021 at 12:45
  • $\begingroup$ If you have Tritium, you will have Helium-3. All you need to do is wait; it's the decay product, and the main way Helium-3 is produced industrially today. $\endgroup$
    – notovny
    Apr 19, 2021 at 14:13
  • $\begingroup$ Also, it appears that Tritium (at \$30 000/g) is more than 20 times the cost per unit mass of $^3\mathrm{He}$ at ($1 400/g) currently. $\endgroup$
    – notovny
    May 4, 2021 at 14:14

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This is a "pick your poison" situation.

The problem with helium-3 is that naturally-occurring helium is a non-renewable resource, and helium-3 is a tiny fraction of it.

The problem with tritium is that it basically doesn't occur in nature at all. With a lifetime of only twelve years, any process that consumes tritium needs a continuous source of neutrons that you can put onto (heavy) hydrogen. I guess this happens in nature, rarely, when neutrons produced from cosmic-ray spallation find deuterium. But most deuterium in nature is a trace contaminant in hydrogen chemistry. One confirmation:

Before [the era of] nuclear tests, there were only about 3 to 4 kilograms of tritium on the Earth's surface; but these amounts rose by 2 or 3 orders of magnitude during the post-test period.

Wikipedia, citing Jenkins and Smethie.

It's probably possible to engineer a helium-3-free fusion cycle. However, helium-3 has useful neutron interaction properties, and it'll be produced spontaneously in any unspent tritium fuel by beta decay, so there's probably no reason to ignore it completely.

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As already pointed out, helium 3 is just aged tritium. Tritium is most economically made by replacing some control rods in ordinary fission reactors with lithium-6 or boron rods. This was done for years to make tritium for nuclear weapons. There is no need for anything as exotic as fusion to make all the tritium anyone can want, half of which turns to helium 3 in just 12 yeqrs.

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