2 ms·

FRCs have been around a long time but Helion isn't just making an FRC, they're making two, slamming them into each other, and then compressing with a magnetic f

FRCs have been around a long time but Helion isn't just making an FRC, they're making two, slamming them into each other, and then compressing with a magnetic field. The neutrons from D-D fusion are much lower energy than D-T fusion, and don't cause the same damage to materials. They're similar to fission neutrons, and modern fission reactors last sixty years without refurbishment. According to Helion and other sources I've seen, their hybrid reaction would only release 6% of its energy as neutron radiation, compared to 80% from D-T. They could also build reactors dedicated to D-D and hence He3 production, designing their power plants to mostly burn D-He3. That would reduce power plant neutrons to less than 1% of power output. Regarding net power and scaling, I'm not competent to talk about it but here's the CEO of Helion going into some detail on their view: https://www.youtube.com/watch?v=G1vyMcqiVtA https://www.youtube.com/watch?v=G1vyMcqiVtA

_0w8t 4y ago
With Helion pulse design peak neuron flux luminosity will still be much higher than that was observed in nuclear reactors. Compared with tokamaks their magnets will be directly exposed to it. Plus their idea to convert fusion energy directly into electricity depends on many unknowns to assert that it will work with reasonable efficiency. So even if their approach may work to produce positive energy output in few years, a practical device will still be far away. Edit: Helion itself admits that net positive in electricity with D-3He is tricky even with their design at that presentation. So most likely their first prototype will be D+D with all the problems associated with high-energy neutrons.
- DennisP 4y ago
  Bear in mind that Helion's magnets will not be superconductors. Last I saw, they were looking at an aluminum alloy. Exposure to D-D neutrons isn't likely to be a structural problem at least, since you don't get the helium buildup in materials that you get with D-T. The presentation says they think they can get a 5X gain with D-3He, and they think that's sufficient given the efficiencies of their heating and extraction.
  - _0w8t 4y ago
    The new video by the same guy https://youtube.com/live/wK5v1Nw98xs https://youtube.com/live/wK5v1Nw98xs from 32 min describes how Helion will get a lot of D+T neutrons from the secondary reactions despite all their efforts. Even without that the neutron flux from D+D reaction by Helion own admission will be enough to do a lot of damage within days of operation based on experience with slower fission neutrons.
- smaddox 4y ago
  Helion as already demonstrated recovering 95% of the energy from non-fusable plasmas and Q << 1 plasmas. Thousands of times. It's perhaps worth noting that the high speed, high power electronics required to implement their approach are fairly new. I don't know how old the concept of FRC merging is, but if it existed in the 70's they wouldn't have had the technology to build it. Edit: and to be clear, I'm talking about the dynamic control circuits, not the capacitors. That's old technology.
  - _0w8t 4y ago
    The new video by the same guy who created the original criticism https://youtube.com/live/wK5v1Nw98xs https://youtube.com/live/wK5v1Nw98xs starting from 2:03:00 explains that 95% recovery efficiency is not the whole story.
    - deleted 4y ago
      [deleted]
    - smaddox 4y ago
      Ion escape might be a significant consideration, but given the plasma density and magnetic field strength, I'm guessing it wouldn't degrade the efficiency too much. Presumably they've done the calculations. I have not. As for the input heating loss, presumably that's included in the 95% recovery figure. If it's not, then it would definitely be good to know what the actual figure is including input heating losses.
      - DennisP 4y ago
        The nice thing about colliding two FRCs is that they form a new FRC with all their kinetic energy converted to heat, and it's very efficient to accelerate an FRC.
cpleppert 4y ago
The theoretical problem with fusion energy isn't neutron activation; if you could generate electricity you could easily amortize the cost of disposal of any induced radioactivity over the lifetime of the plan. But no known projected fusion reactor is anywhere close to even being financial viable with todays technology. Iter won't demonstrate actual D-T fusion until 2035 and it is too small to project what the economics of a takomak power plant would look like. To make fusion viable you have to generate a substantial surplus of power that can be converted into usable energy. Nothing in that video touches on that subject at all. The most he can say is that it is possible D-He3 can reach scientific breakeven, which of course, is no where close to net power generation. It is strange to see claims about Q > 10 using D-T fusion being possible and then immediately pivot to talking about being excited about Q > 1 using D-He3. If you can build a fusion reactor that could produce Q > 10 why would you bother pursuing Q > 1? The 'benefits' of direct electrical generation from D-He3 are not relevant if you can't even produce net positive energy in the first place. Electrical generation is a solved problem; if you can produce net energy you can produce heat that can power a turbine. If the most you can do is talk about how Q > 1 is possible it seems unlikely you are going to start producing electricity any time soon.
- _0w8t 4y ago
  Heat to electricity conversion ratio with a realistic Tokamak design will have 30% efficiency at best, accounting for other losses will require Q at least 5. But even that may be too low so to play safe the latest Tokamaks target at least 10 or more. But Helion hopes that with their design where the theoretical efficiency of electricity generation is 100%, they do not need such high Q allowing one to be excited about Q > 1. Their models predicts Q around 5. The problem is the model uncertainty. If the real Q will be just 2, I very much doubt that they can limit the total losses below 50%. But even if they can get net gain in power per pulse, they are too optimistic about neutron flux and its consequences. Again, model uncertainty is big. So overall there is very little room for unexpected in their design so I am very skeptical based just on that alone.

_0w8t 4y ago

With Helion pulse design peak neuron flux luminosity will still be much higher than that was observed in nuclear reactors. Compared with tokamaks their magnets will be directly exposed to it. Plus their idea to convert fusion energy directly into electricity depends on many unknowns to assert that it will work with reasonable efficiency. So even if their approach may work to produce positive energy output in few years, a practical device will still be far away. Edit: Helion itself admits that net positive in electricity with D-3He is tricky even with their design at that presentation. So most likely their first prototype will be D+D with all the problems associated with high-energy neutrons.

DennisP 4y ago
Bear in mind that Helion's magnets will not be superconductors. Last I saw, they were looking at an aluminum alloy. Exposure to D-D neutrons isn't likely to be a structural problem at least, since you don't get the helium buildup in materials that you get with D-T. The presentation says they think they can get a 5X gain with D-3He, and they think that's sufficient given the efficiencies of their heating and extraction.
- _0w8t 4y ago
  The new video by the same guy https://youtube.com/live/wK5v1Nw98xs https://youtube.com/live/wK5v1Nw98xs from 32 min describes how Helion will get a lot of D+T neutrons from the secondary reactions despite all their efforts. Even without that the neutron flux from D+D reaction by Helion own admission will be enough to do a lot of damage within days of operation based on experience with slower fission neutrons.
smaddox 4y ago
Helion as already demonstrated recovering 95% of the energy from non-fusable plasmas and Q << 1 plasmas. Thousands of times. It's perhaps worth noting that the high speed, high power electronics required to implement their approach are fairly new. I don't know how old the concept of FRC merging is, but if it existed in the 70's they wouldn't have had the technology to build it. Edit: and to be clear, I'm talking about the dynamic control circuits, not the capacitors. That's old technology.
- _0w8t 4y ago
  The new video by the same guy who created the original criticism https://youtube.com/live/wK5v1Nw98xs https://youtube.com/live/wK5v1Nw98xs starting from 2:03:00 explains that 95% recovery efficiency is not the whole story.
  - deleted 4y ago
    [deleted]
  - smaddox 4y ago
    Ion escape might be a significant consideration, but given the plasma density and magnetic field strength, I'm guessing it wouldn't degrade the efficiency too much. Presumably they've done the calculations. I have not. As for the input heating loss, presumably that's included in the 95% recovery figure. If it's not, then it would definitely be good to know what the actual figure is including input heating losses.
    - DennisP 4y ago
      The nice thing about colliding two FRCs is that they form a new FRC with all their kinetic energy converted to heat, and it's very efficient to accelerate an FRC.

cpleppert 4y ago

The theoretical problem with fusion energy isn't neutron activation; if you could generate electricity you could easily amortize the cost of disposal of any induced radioactivity over the lifetime of the plan. But no known projected fusion reactor is anywhere close to even being financial viable with todays technology. Iter won't demonstrate actual D-T fusion until 2035 and it is too small to project what the economics of a takomak power plant would look like. To make fusion viable you have to generate a substantial surplus of power that can be converted into usable energy. Nothing in that video touches on that subject at all. The most he can say is that it is possible D-He3 can reach scientific breakeven, which of course, is no where close to net power generation. It is strange to see claims about Q > 10 using D-T fusion being possible and then immediately pivot to talking about being excited about Q > 1 using D-He3. If you can build a fusion reactor that could produce Q > 10 why would you bother pursuing Q > 1? The 'benefits' of direct electrical generation from D-He3 are not relevant if you can't even produce net positive energy in the first place. Electrical generation is a solved problem; if you can produce net energy you can produce heat that can power a turbine. If the most you can do is talk about how Q > 1 is possible it seems unlikely you are going to start producing electricity any time soon.

_0w8t 4y ago
Heat to electricity conversion ratio with a realistic Tokamak design will have 30% efficiency at best, accounting for other losses will require Q at least 5. But even that may be too low so to play safe the latest Tokamaks target at least 10 or more. But Helion hopes that with their design where the theoretical efficiency of electricity generation is 100%, they do not need such high Q allowing one to be excited about Q > 1. Their models predicts Q around 5. The problem is the model uncertainty. If the real Q will be just 2, I very much doubt that they can limit the total losses below 50%. But even if they can get net gain in power per pulse, they are too optimistic about neutron flux and its consequences. Again, model uncertainty is big. So overall there is very little room for unexpected in their design so I am very skeptical based just on that alone.