[moloch-hai]

Seems like you would want to run the power reactor especially 3He-rich, so the 2H can mostly find a 3He. Presumably 3He is hard to make fuse with itself or with waste He4 or tritium. But 2H is much more eager to fuse with 3H than anything else, so it would be important to get the 3H product out quickly. Separating waste 3H and H from the 2H/3He mix cannot be easy.

I have encountered an assertion that 3He eagerly turns into tritium, I guess when struck by a stray hot electron, which will certainly be milling about. Wondering how much of the 3He they breed will be lost to this.

[joak]

You are right, it's a pulsed system. The operation goes like this:

1. Fill the chamber with D and He3

2. Ionize the fuel and compress the plasma

3. The fusion starts and pushes back the magnetic field producing electricity

4. Stop everything

5. Vacuum and start again

So before the plasma is polluted with p, T and He4, the pulse has ended. The side reaction D+T does not get the time to happen much.

I'm using a different notation than yours: 3He, 3H, 2H, H are He3, T, D, p

T is tritium, D is deuterium, and p is protium (a proton)

[moloch-hai]

Thank you.

Terminology is a nuisance here mainly because we don't have a nice name and one- or two-letter abbreviation for ³He. Somebody suggested "hellion", "Eh". Whoever is first to make it work might deserve naming rights.

[joak]

I'm not aware of He3 easily becoming T. I know T spontaneously becomes He3 (emitting a positron and a neutrino) with some probability, a very low one, not relevant at the scale of a pulse

[moloch-hai]

I am wrong. To absorb an electron would need a coincident neutrino.

Instead, a neutron strikes ³He producing T, H and a photon.

[pfdietz]

Yes, and that's not a problem either here, because the neutrons don't stick around. If you had a lithium blanket making T you'd want to clear out any 3He as it was produced from T decay so they don't hoover up too many thermalized neutrons, though.

I don't think that (n,p) reaction on 3He normally produces a photon, btw.

[moloch-hai]

I suppose the 764 keV could be kinetic:

  n + 3He → 3H + 1H + 0.764 MeV

I expect the concentration of ³He in your blanket would be extremely low, relative to the Li, so an unlikely target.

Really, if it takes neutrons, it is not a problem.

[pfdietz]

> I have encountered an assertion that 3He eagerly turns into tritium,

That assertion is nonsense. That would be a weak nuclear interaction, very low cross section.