4 ms·

> This is more than double [the energy] what was achieved in similar tests back in 1997. I was excited for a little bit there.

q1w2 5y ago
Yep - we're still nowhere near break-even.
- DennisP 5y ago
  We're not that far off. JET previously achieved Q=0.67, ie. two-thirds as much energy output as input. (The new result has higher output but lower Q.) For a practical reactor we need Q around 30, which might seem far away but tokamak output scales with the square of reactor volume and the fourth power of magnetic field strength. Double the field, 16X the output, and we can generate much more powerful magnetic fields with modern superconductors than we can with JET's copper coils.
  - faeyanpiraat 5y ago
    So they just need to build the same thing, but make it gigantic in size? Why is it not yet done?
    - deleted 5y ago
      [deleted]
    - willis936 5y ago
      It is very expensive to do. HTS was known but not practical when ITER was planned, but it's almost done. ITER is almost large enough to be an LTS-based power plant. ITER will still produce a lot of useful science, but there is a now a potential class of mid-scale HTS machines that would help develop plasma models. These iterations seem frustrating and time consuming, but their results are lowering the cost of a hypothetical power plant until one day maybe society will decide they're worth making for power generation.
  - andruby 5y ago
    Any source on that Q=30 requirement for practical reactors? I’d assume that anything >1 is theoretically “profitable” and something like 2~5 might already be economically viable.
    - skykooler 5y ago
      Q=1 just means that the plasma is putting out more energy then is put in. However, that doesn't mean you can recover all of that energy; you can't run a heat engine at millions of degrees, so energy generation has to be fairly indirect, which means you need about Q=30 to handle all the various conversion inefficiencies and still come out net positive enough to be practical.
  - Aperocky 5y ago
    > For a practical reactor we need Q around 30 Did we figure out how we could harness the energy released? It appears to me that all current research are about maximizing Q without really looking at how the energy will be converted into usable form.
    - DennisP 5y ago
      For D-T fusion, the output is 80% neutrons, so the only option is to let them heat something to run a turbine. You also need the neutrons for breeding the tritium, so you let your breeding blanket heat up and run coolant pipes through that. Commonwealth plans to use molten FLiBe salt as the breeding blanket and first loop of coolant. Aneutronic fusion produces fast-moving charged particles instead of neutrons, so if anyone gets that working, we could extract electricity without a thermal cycle.
deleted 5y ago
[deleted]
yholio 5y ago
Yup, a major breakthrough in this glacial field is doubling the energy output in 25 yeas. So by the time captain Picard is born, we might have a very expensive and massive fusion reactor that will generate the same kind of energy we can generate today with very expensive and massive fission reactors. Really now, this is pure garbage and does not solve the major problems in the field nor do most of the myriad startups trying to cash in on speculative seed funds.
- JohnJamesRambo 5y ago
  Sometimes I wonder what would happen if we put the massive amounts of money we have put into nuclear fusion and fission into bone simple solar panel purchases. I wonder if anyone has done the math. There’s a fully functioning fusion reactor 91 million miles from us that sends a lot of energy our way.
  - jiggawatts 5y ago
    The levelized cost of large scale solar power is about 7 cents per kilowatt-hour. ITER alone will cost $21B minimum and won’t make power. DEMO will conservatively cost about the same, but let’s be generous and round up the total “fusion research cost” to just $30B. That would buy about 1.5e18 joules, or around the same amount of energy as the electrical generation of the United States… for a month. So, a drop in the bucket compared to what we use globally… Even if you use much bigger numbers for fusion research and assume further solar power cost improvements, fusion might still be worth it. However, it’ll only be worthwhile if the total cost the production fusion plants is not too high. If they end up costing $10B each then the whole thing will be a dead end economically.
    - JohnJamesRambo 5y ago
      Thank you!
    - yholio 5y ago
      Nothing about the current tokamak based designs suggests they will be any cheaper to build for a given power rating than existing fission designs: - They need large, highly advanced cryocooled superconducting magnets in very close proximity to a hundred million degree plasma. This only makes economic sense in massive, and expensive plants. - They are a very strong source of fast neutrons useful to transmute cheap depleted uranium into plutonium, so carry massive proliferation risks, need close regulatory scrutiny and will require mounts of paperwork to operate, thus exceptionally inflexible to improvements and rapid iteration. Just like the current fission crop. - Aneutronic fusion is a currently a purely theoretical concept, in the last 70 years nobody has been able to contain even the much cooler D-T plasma for economically viable durations and temperatures. - The structure of the reactor becomes radiologically active and cleanup operations must be considered. Highly penetrating neutron radiation means some radiation will escape regardless of containment, requiring a radiological exclusion zone. No Mr. Fusion in your car, sorry. - They operate and must breed sensitive nuclear materials - Tritium, a well known component of boosted thermonuclear weapons. The limited efficiency of tritium production from lithium-6 might require obtaining some from fission reactors to top up the fuel cycle and keep fusion reactors operating. So when you draw the line, a life time of magnetic containment research has produced a speculative design that even if it were to work, which it doesn't, would be, in the best case scenario, comparable to existing fission designs that are being phased out for cost and risk issues. A PhD money pit with zero chance of ever building anything useful.
tomxor 5y ago
I wonder, in the future when everyone's attention has been burned by turning up the volume on all headings to 11... will everyone ignore and miss a truly "major" breakthrough.
willis936 5y ago
Using the same machine. That's a pretty impressive jump.

q1w2 5y ago

Yep - we're still nowhere near break-even.

DennisP 5y ago
We're not that far off. JET previously achieved Q=0.67, ie. two-thirds as much energy output as input. (The new result has higher output but lower Q.) For a practical reactor we need Q around 30, which might seem far away but tokamak output scales with the square of reactor volume and the fourth power of magnetic field strength. Double the field, 16X the output, and we can generate much more powerful magnetic fields with modern superconductors than we can with JET's copper coils.
- faeyanpiraat 5y ago
  So they just need to build the same thing, but make it gigantic in size? Why is it not yet done?
  - deleted 5y ago
    [deleted]
  - willis936 5y ago
    It is very expensive to do. HTS was known but not practical when ITER was planned, but it's almost done. ITER is almost large enough to be an LTS-based power plant. ITER will still produce a lot of useful science, but there is a now a potential class of mid-scale HTS machines that would help develop plasma models. These iterations seem frustrating and time consuming, but their results are lowering the cost of a hypothetical power plant until one day maybe society will decide they're worth making for power generation.
- andruby 5y ago
  Any source on that Q=30 requirement for practical reactors? I’d assume that anything >1 is theoretically “profitable” and something like 2~5 might already be economically viable.
  - skykooler 5y ago
    Q=1 just means that the plasma is putting out more energy then is put in. However, that doesn't mean you can recover all of that energy; you can't run a heat engine at millions of degrees, so energy generation has to be fairly indirect, which means you need about Q=30 to handle all the various conversion inefficiencies and still come out net positive enough to be practical.
- Aperocky 5y ago
  > For a practical reactor we need Q around 30 Did we figure out how we could harness the energy released? It appears to me that all current research are about maximizing Q without really looking at how the energy will be converted into usable form.
  - DennisP 5y ago
    For D-T fusion, the output is 80% neutrons, so the only option is to let them heat something to run a turbine. You also need the neutrons for breeding the tritium, so you let your breeding blanket heat up and run coolant pipes through that. Commonwealth plans to use molten FLiBe salt as the breeding blanket and first loop of coolant. Aneutronic fusion produces fast-moving charged particles instead of neutrons, so if anyone gets that working, we could extract electricity without a thermal cycle.

deleted 5y ago

[deleted]

yholio 5y ago

Yup, a major breakthrough in this glacial field is doubling the energy output in 25 yeas. So by the time captain Picard is born, we might have a very expensive and massive fusion reactor that will generate the same kind of energy we can generate today with very expensive and massive fission reactors. Really now, this is pure garbage and does not solve the major problems in the field nor do most of the myriad startups trying to cash in on speculative seed funds.

JohnJamesRambo 5y ago
Sometimes I wonder what would happen if we put the massive amounts of money we have put into nuclear fusion and fission into bone simple solar panel purchases. I wonder if anyone has done the math. There’s a fully functioning fusion reactor 91 million miles from us that sends a lot of energy our way.
- jiggawatts 5y ago
  The levelized cost of large scale solar power is about 7 cents per kilowatt-hour. ITER alone will cost $21B minimum and won’t make power. DEMO will conservatively cost about the same, but let’s be generous and round up the total “fusion research cost” to just $30B. That would buy about 1.5e18 joules, or around the same amount of energy as the electrical generation of the United States… for a month. So, a drop in the bucket compared to what we use globally… Even if you use much bigger numbers for fusion research and assume further solar power cost improvements, fusion might still be worth it. However, it’ll only be worthwhile if the total cost the production fusion plants is not too high. If they end up costing $10B each then the whole thing will be a dead end economically.
  - JohnJamesRambo 5y ago
    Thank you!
  - yholio 5y ago
    Nothing about the current tokamak based designs suggests they will be any cheaper to build for a given power rating than existing fission designs: - They need large, highly advanced cryocooled superconducting magnets in very close proximity to a hundred million degree plasma. This only makes economic sense in massive, and expensive plants. - They are a very strong source of fast neutrons useful to transmute cheap depleted uranium into plutonium, so carry massive proliferation risks, need close regulatory scrutiny and will require mounts of paperwork to operate, thus exceptionally inflexible to improvements and rapid iteration. Just like the current fission crop. - Aneutronic fusion is a currently a purely theoretical concept, in the last 70 years nobody has been able to contain even the much cooler D-T plasma for economically viable durations and temperatures. - The structure of the reactor becomes radiologically active and cleanup operations must be considered. Highly penetrating neutron radiation means some radiation will escape regardless of containment, requiring a radiological exclusion zone. No Mr. Fusion in your car, sorry. - They operate and must breed sensitive nuclear materials - Tritium, a well known component of boosted thermonuclear weapons. The limited efficiency of tritium production from lithium-6 might require obtaining some from fission reactors to top up the fuel cycle and keep fusion reactors operating. So when you draw the line, a life time of magnetic containment research has produced a speculative design that even if it were to work, which it doesn't, would be, in the best case scenario, comparable to existing fission designs that are being phased out for cost and risk issues. A PhD money pit with zero chance of ever building anything useful.

tomxor 5y ago

I wonder, in the future when everyone's attention has been burned by turning up the volume on all headings to 11... will everyone ignore and miss a truly "major" breakthrough.

willis936 5y ago

Using the same machine. That's a pretty impressive jump.