3 ms·

Where do they plan on getting the He3 fuel?

• tedd4u 5y ago
  “The helium-3 is produced by D-D side reactions and is captured and reused, eliminating supply concerns. Helion has a patent on this process.” —Wikipedia
  • bbojan 5y ago
    But the D-D -> He3 reaction produces a neutron. So the whole approach could hardly be called aneutronic?
    • ncmncm 5y ago
      "Not very neutronic".
• ncmncm 5y ago
  There is actually He3 in natural helium. They can buy helium, separate out the bit they need, and sell the rest on to people who have no use for the He3. The relative abundance of He3 is, numerically, really quite small (WP says 0.000137%, or 1 He3 per 730k He4 atoms), but that doesn't matter as much as you might think: they don't need much. Process a ton of helium, get 1.03g of He3. But it also says it is 70 to 242 parts per billion, which is a lot smaller than the other, 1370 ppb figure. It may be cheaper to get it from used-up tritium, from people who are finished with it because it has decayed too much. In fact the US DOE does sell He3 they have extracted from tired-out stocks held ready to inject into bombs before they are sent out to use. The DOE makes its (fresh) tritium by irradiating lithium, but it starts decaying immediately, with a half-life of ~12 years, and the bombs want it fairly fresh. These FRC reactors generate their own tritium, which is a problem, because when those fuse you get hot neutrons you don't want, and gamma rays. When you use FRC for propulsion, you can expel the tritium as reaction mass, but that doesn't work so well on the ground. On the other hand, lots of shielding is cheap on (under) the ground. But they don't make enough of it to use, and anyway who wants to bank it for years while it decays?