4 ms·

A number of these steps become easier if the reactor is physically small. A plant that fits in a shipping container has a way easier path to commercial viabilit

by ccleve 7y ago

A number of these steps become easier if the reactor is physically small. A plant that fits in a shipping container has a way easier path to commercial viability. Small plants require less capital. They're easier to manufacture. They can iterate faster. They have less environmental impact, and therefore fewer regulatory hurdles. They require less labor to build and a smaller supply chain. I expect that the engineering is harder, because scale can bring efficiencies. But still, I think the winner is going to be a small device, not a behemoth, if only because a small device can come online years earlier.

throwaway894345 7y ago
I expect that you lose efficiencies with respect to security. I.e., it's not easy to secure one large nuclear reactor (fission or fusion), but it's a lot easier than securing dozens of small reactors.
- Someone 7y ago
  If that’s a problem, you can locate hundreds of small reactors together.
- kbenson 7y ago
  There might also be less security needed if you have dozens of smaller reactors. You have to secure the one because losing it affects so much. If losing a couple is not as big a problem, you an rely more on the redundancy of the system than on the redundancy of the component. This depends on the threat model to some degree, but there's security in knowing that it's vastly harder for a threat to affect multiple targets at once, no matter the threat.
  - jacobedawson 7y ago
    Isn't this just the same scenario as we currently have, just with different underlying technology? Do coal-powered plants have additional security outside of a few private guards?
  - caymanjim 7y ago
    There's not much security around existing power plants, even nuclear ones. There's vastly more security around a casino or even a large shopping mall. I don't think it's a limiting factor, especially for non-weaponizable fusion reagents.
  - numpad0 7y ago
    For fission reactors that is not the case, a fission core can be as small as few liters in volume without losing power, but are artificially kept to less dense forms, such that runaway supercritical events(intended or not) can only result in Fukushima and not a Nagasaki. That might be different for this fusion device, but for outdated looking fission reactors it’s artificial dilution for NPT purposes and by no way a technological limitation.
- goda90 7y ago
  Nuclear fission reactors need more security than other power plants because of the implications of stolen fuel/waste, or fallout from sabotage. A fusion reactor like the one this group is working on probably doesn't have as high as security concerns. In fact the only concern might be that it is critical infrastructure(like our entire power grid), and a distribution of smaller reactors would be better for reliability anyway.
  - LeifCarrotson 7y ago
    Traditional fusion reactors do produce fast neutron radiation, which, in addition to causing problems like weakening the structure (which can be mitigated with better materials, better engineering, and by replacing subcomponents over time) is able to irradiate U238 into PU239. Drop a chunk of U238 in/near the fusion reactor somewhere, let it absorb stray neutrons, and you'll soon have some plutonium. That's bad for control of nuclear weapons proliferation, which relies on high-energy neutron sources like breeder reactors being difficult to build and expensive. Not sure about the radiation profile from this system though.
    - goda90 7y ago
      I'm not very knowledgeable about fusion, but it looks like this system is aneutronic fusion, so those concerns would be lessened too. https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron
    - mrfusion 7y ago
      A simple security camera or hank the security guard could easily guard against someone setting up shop and producing plutonium.
      - earthboundkid 7y ago
        If you have the uranium, couldn’t you afford to bribe Hank?
      - philipkglass 7y ago
- lallysingh 7y ago
  If these reactors are low heat, not radioactive, and use plentiful fuel, what's the threat model? Is it just worried about availability of power?
  - jandrese 7y ago
    "Not Radioactive" is the trick. Even if the fuel isn't hazardous you have lots of radiation being kicked off by the reaction that irradiates the surrounding equipment and the waste products.
    - DennisP 7y ago
      The HB11 reaction doesn't produce neutron radiation. I've seen claims that there would be side reactions, generating neutron radiation totaling under 1% of the energy output, but the only source of that I can think of is if deuterium isn't removed from the hydrogen, and we could do that if necessary. It might not be, since neutrons from deuterium fusion are a lot less energetic than D-T neutrons. The energy output of HB11 consists of fast-moving alpha particles, which is good because that's the energy you capture, along with x-rays. None of this would activate reactor components. The waste product is non-radioactive helium.
      - Retric 7y ago
        It’s not that simple. 1% of even 1MW is a lot of radiation so it comes down to what the walls are made of more than the total neutron flux. ITER style lithium blankets would be recycled for tritium without producing much net waste. Light water nuclear reactors have several feet of water to absorb fast neutrons, which makes a huge difference. The walls of this are a more open question.
        DennisP 7y ago
        So I looked it up, and found there actually are two side reactions from the primary fuels, no deuterium required. In a thermal plasma the resulting neutrons would carry less than 0.2% of the energy output. I don't know what the percentage would be for this reactor, since the fuel isn't a thermal plasma while fusion is happening. https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron Neutron energy would be a bit under 3 MeV, comparable to fast fission neutrons but in much lower quantity for the power output. https://en.wikipedia.org/wiki/Neutron_temperature https://en.wikipedia.org/wiki/Neutron_temperature Interestingly, that page says the thermal neutrons in a conventional nuclear reactor are better at activating materials than fast neutrons. According to a presentation I saw by the leader of MIT's fusion program, the inner wall of a D-T tokamak would be activated by the neutrons, but would only need to be stored for a few decades. D-T releases 80% of its energy as 14 MeV neutrons. According to LPP, which is working on a different boron fusion design, a 20MW reactor would activate the walls with short-lived radiation, but it could be safely opened for maintenance after about twelve hours (iirc).
- mrfusion 7y ago
  Fusion shouldn’t need any more security than a coal plant.

by ccleve 7y ago

throwaway894345 7y ago

I expect that you lose efficiencies with respect to security. I.e., it's not easy to secure one large nuclear reactor (fission or fusion), but it's a lot easier than securing dozens of small reactors.

Someone 7y ago
If that’s a problem, you can locate hundreds of small reactors together.
kbenson 7y ago
There might also be less security needed if you have dozens of smaller reactors. You have to secure the one because losing it affects so much. If losing a couple is not as big a problem, you an rely more on the redundancy of the system than on the redundancy of the component. This depends on the threat model to some degree, but there's security in knowing that it's vastly harder for a threat to affect multiple targets at once, no matter the threat.
- jacobedawson 7y ago
  Isn't this just the same scenario as we currently have, just with different underlying technology? Do coal-powered plants have additional security outside of a few private guards?
- caymanjim 7y ago
  There's not much security around existing power plants, even nuclear ones. There's vastly more security around a casino or even a large shopping mall. I don't think it's a limiting factor, especially for non-weaponizable fusion reagents.
- numpad0 7y ago
  For fission reactors that is not the case, a fission core can be as small as few liters in volume without losing power, but are artificially kept to less dense forms, such that runaway supercritical events(intended or not) can only result in Fukushima and not a Nagasaki. That might be different for this fusion device, but for outdated looking fission reactors it’s artificial dilution for NPT purposes and by no way a technological limitation.
goda90 7y ago
Nuclear fission reactors need more security than other power plants because of the implications of stolen fuel/waste, or fallout from sabotage. A fusion reactor like the one this group is working on probably doesn't have as high as security concerns. In fact the only concern might be that it is critical infrastructure(like our entire power grid), and a distribution of smaller reactors would be better for reliability anyway.
- LeifCarrotson 7y ago
  Traditional fusion reactors do produce fast neutron radiation, which, in addition to causing problems like weakening the structure (which can be mitigated with better materials, better engineering, and by replacing subcomponents over time) is able to irradiate U238 into PU239. Drop a chunk of U238 in/near the fusion reactor somewhere, let it absorb stray neutrons, and you'll soon have some plutonium. That's bad for control of nuclear weapons proliferation, which relies on high-energy neutron sources like breeder reactors being difficult to build and expensive. Not sure about the radiation profile from this system though.
  - goda90 7y ago
    I'm not very knowledgeable about fusion, but it looks like this system is aneutronic fusion, so those concerns would be lessened too. https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron
  - mrfusion 7y ago
    A simple security camera or hank the security guard could easily guard against someone setting up shop and producing plutonium.
    - earthboundkid 7y ago
      If you have the uranium, couldn’t you afford to bribe Hank?
    - philipkglass 7y ago
lallysingh 7y ago
If these reactors are low heat, not radioactive, and use plentiful fuel, what's the threat model? Is it just worried about availability of power?
- jandrese 7y ago
  "Not Radioactive" is the trick. Even if the fuel isn't hazardous you have lots of radiation being kicked off by the reaction that irradiates the surrounding equipment and the waste products.
  - DennisP 7y ago
    The HB11 reaction doesn't produce neutron radiation. I've seen claims that there would be side reactions, generating neutron radiation totaling under 1% of the energy output, but the only source of that I can think of is if deuterium isn't removed from the hydrogen, and we could do that if necessary. It might not be, since neutrons from deuterium fusion are a lot less energetic than D-T neutrons. The energy output of HB11 consists of fast-moving alpha particles, which is good because that's the energy you capture, along with x-rays. None of this would activate reactor components. The waste product is non-radioactive helium.
    - Retric 7y ago
      It’s not that simple. 1% of even 1MW is a lot of radiation so it comes down to what the walls are made of more than the total neutron flux. ITER style lithium blankets would be recycled for tritium without producing much net waste. Light water nuclear reactors have several feet of water to absorb fast neutrons, which makes a huge difference. The walls of this are a more open question.
      - DennisP 7y ago
        So I looked it up, and found there actually are two side reactions from the primary fuels, no deuterium required. In a thermal plasma the resulting neutrons would carry less than 0.2% of the energy output. I don't know what the percentage would be for this reactor, since the fuel isn't a thermal plasma while fusion is happening. https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron https://en.wikipedia.org/wiki/Aneutronic_fusion#Boron Neutron energy would be a bit under 3 MeV, comparable to fast fission neutrons but in much lower quantity for the power output. https://en.wikipedia.org/wiki/Neutron_temperature https://en.wikipedia.org/wiki/Neutron_temperature Interestingly, that page says the thermal neutrons in a conventional nuclear reactor are better at activating materials than fast neutrons. According to a presentation I saw by the leader of MIT's fusion program, the inner wall of a D-T tokamak would be activated by the neutrons, but would only need to be stored for a few decades. D-T releases 80% of its energy as 14 MeV neutrons. According to LPP, which is working on a different boron fusion design, a 20MW reactor would activate the walls with short-lived radiation, but it could be safely opened for maintenance after about twelve hours (iirc).
mrfusion 7y ago
Fusion shouldn’t need any more security than a coal plant.