4 ms·

>You might argue that it's "safe", but the bureaucrats won't care about your opinion. They'll be worried about perception in an era where people set communicati

>You might argue that it's "safe", but the bureaucrats won't care about your opinion. They'll be worried about perception in an era where people set communication towers on fire because they want to stop 5G "radiation". I agree with all the other stuff you said, and I would accept this as a fair characterization of what is in store for nuclear plants historically. I wonder though how much of that experience would transfer in the event that we have real fusion reactions, given climate considerations and a novel technology that won't necessarily become entangled in the same narratives, and (maybe?) comes with a different set of environmental implications than traditional nuclear power plants.

jiggawatts 5y ago
All practical (but not yet viable!) forms of fusion are moderately "dirty" in that they produce sufficient neutron radiation to make the reactor itself dangerously radioactive. Compared to fission, it's much better overall, but you're still talking about remote manipulation, robots, lead shielding, etc... There is just no way that a shipping container-sized fusion reactor will be allowed to be "plopped down" anywhere without a metric ton of paperwork and justification. It wouldn't be safe to go anywhere near it while it is operating! It couldn't possibly have sufficient shielding in that form factor. Even if it had solid lead walls it would still be dangerous. Fusion would be perfectly fine as base load in dedicated power plants similar to nuclear power plants. There would be thick concrete shielding, containment buildings, etc... Less than you'd need for fission, and also less waste, but there's still nuclear waste that needs to be handled in much the same way.
- labawi 5y ago
  Doesn't Helion design require using D-He-3 fuel, which should be largely aneutronic, hence doesn't require (much) shielding? It's not like you could plop a neutronic fuel as a substitute in a design that expects aneutronic fuel.
  - bbojan 5y ago
    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?

jiggawatts 5y ago

All practical (but not yet viable!) forms of fusion are moderately "dirty" in that they produce sufficient neutron radiation to make the reactor itself dangerously radioactive. Compared to fission, it's much better overall, but you're still talking about remote manipulation, robots, lead shielding, etc... There is just no way that a shipping container-sized fusion reactor will be allowed to be "plopped down" anywhere without a metric ton of paperwork and justification. It wouldn't be safe to go anywhere near it while it is operating! It couldn't possibly have sufficient shielding in that form factor. Even if it had solid lead walls it would still be dangerous. Fusion would be perfectly fine as base load in dedicated power plants similar to nuclear power plants. There would be thick concrete shielding, containment buildings, etc... Less than you'd need for fission, and also less waste, but there's still nuclear waste that needs to be handled in much the same way.

labawi 5y ago
Doesn't Helion design require using D-He-3 fuel, which should be largely aneutronic, hence doesn't require (much) shielding? It's not like you could plop a neutronic fuel as a substitute in a design that expects aneutronic fuel.
- bbojan 5y ago
  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?