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I am going to need some help on this one as my knowledge on physics is limited: What makes scientists believe that the solution to nuclear fusion power is only

• soperj 6y ago
  This is a lab experiment, just a huge one.
• d_silin 6y ago
  Scaling factor in fusion is pretty well understood science. Last JET tokamak was the experiment that confirmed this part. Fusion science has evolved to the point where it is necessary to bring the fusion engineering on the same level.
• petschge 6y ago
  The simple answer is that the surface only goes up a factor of 4 if you increase the radius by a factor of 2, but the volume goes up by a factor of 8. So the ratio of (energy containing) volume to surface (where energy get's lost) if getting better with increasing size. There is of course much more complicated answers, all the way up to full-device simulations using gyrokinetic codes like Gene or Gkeyll that take millions of core hours and predict that ITER will work (and that predict performance of existing devices correctly).
  • ArtWomb 6y ago
    Good answer. It's referred to as the Lawson criterion for those wishing a deeper dive: https://en.wikipedia.org/wiki/Lawson_criterion https://en.wikipedia.org/wiki/Lawson_criterion Regarding simulations, plasma physics can in a very real sense be viewed as the predominant driver for supercomputing research and funding. Ratio of fusion budget allocations to total global energy demand remains woefully pitiful. On order of something like 30B / 100T or 0.03%.
  • godelski 6y ago
    This is the main issue and I don't want to make it any more complicated. But I do want to explain something because people hear arguments between fusion scientists. Within the field no one really doubts that ITER is going to work (there's a few, of course, but the majority don't doubt). The thing they are arguing over is if it is needed. The big reason for ITER is not to generate power but to demonstrate that sustainable fusion is achievable. The idea is that if there is a demonstration people will stop shying away from it and investing would skyrocket (a government would have to be dumb not to substantially invest in PROVEN fusion devices). The counter argument is that there is enough funding and that they will beat ITER to the punch with small scale reactors (much closer to the path for devices that would provide actual energy to our grid). My take is "don't put all your eggs in one basket."
    • ArtWomb 6y ago
      >>> small scale reactors I believe this is the DoE position. Leverage AI/ML to design smaller magnetic confinement. With the goal toward commercialized products and partnerships. JET was on track to breakeven. And I think most of the researchers involved believe they would have gotten there if the funding hadn't been cut. I think what they want is simply long term commitments. The sort of thing that is risky in fiscal budgets that can change year to year ;) Final Report of the Committee on a Strategic Plan for U.S.Burning Plasma Research (2018) http://brookhaventech.com/wp-content/uploads/2018/12/Burning-Plasma-Fusion-Plan.pdf http://brookhaventech.com/wp-content/uploads/2018/12/Burning...
      • 6y ago
• nharada 6y ago
  There's a good talk here about why ITER is so large: https://www.youtube.com/watch?v=L0KuAx1COEk https://www.youtube.com/watch?v=L0KuAx1COEk The idea is essentially that to get the parameters needed to make net energy with tokamaks, you need either very strong magnets or a large device. At the time of ITER's design, they used the strongest magnets they could find and then made the thing big enough to get the energy gain they wanted. The speaker of this talk argues that it's size that stalled progress in tokamaks, since they'd become so big that building them became a massive, multinational project.
  • fabian2k 6y ago
    I wonder how much the possible magnet strength affects the design of a tokamak. There are very clear limits on the field strength you can achieve with classical superconductors, and I know e.g. in Nuclear Magnetic Resonance those limits had been almost hit maybe a decade ago or so. But very recently spectrometers based on new high-temperature superconductors have been delivered, so the technology seems to be far enough for actual production use now. I'm not sure how big the possible increase in field strength will be. Right now it's 23.5 Tesla for the largest NMR spectrometer with conventional superconductors compared to 28 Tesla for the new ones with high-temperature superconductors (actually it's a hybrid with high-temperature superconductors on the inside, and conventional ones on the outside), but I suspect there is more room with the new ones for higher fields. It would be interesting whether the availability of better superconductors would change the design of a fusion reactor much, and allow significantly smaller ones.
    • petschge 6y ago
      Yes that has a big impact. The quality of a tokamak (as meassured by the triple product density, temperature, and confinement time) goes up like B^3 (IF I remember correctly, I do plasma physics but not fusion stuff) and the fussion power goes up like B^4 or something like that. So larger magnetic fields help a lot. But back when ITER was designed we did not have such strong superconductors yet. PS: Google found DOI 10.1088/0029-5515/56/6/066003 but I didn't read it carefully.
• toohotatopic 6y ago
  >looming energy crisis Where do you see the crisis? Unless you want to provide everybody with an abundance of energy, people need food and shelter, some electricity for electronics and some transportation once in a while. Of course, any amount of energy can be burned for simulations and bitcoins but that's simply limited by supply. There will be a crisis when bitcoins and simulations are more valuable than human lives, but that's not changed by offering more energy.
  • ovi256 6y ago
    >people need food and shelter, some electricity for electronics and some transportation Modern shelter, food and transportation means a lot of energy. Modern shelter means operating energy for heating or air conditioning, plus embedded energy used to create its components. If the shelter is green, or "energy efficient", it means it is operating energy efficient, but it contains a huge amount of embedded energy in the insulation and heat exchange components. Air conditioning doesn't necessarily have a worse bottom line, energy wise, than just heating. It's all about the time * temperature difference envelope. Air conditioning usually has a much lower temperature difference between the outside and the inside. If it's 40 C (as hot as it gets in places where masses of people live) outside, air conditioning has to drop by 15 C to get the inside to 25. If it's freezing (0 C) outside, heating has to heat by 25 C. Double that for a modern workplace - office, warehouse or manufacturing, they all consume a lot of energy to keep the workers comfortable. Modern high-speed transportation means a lot of energy too. We move crash-resistant 1500 kg structures at highway speeds around daily.
    • epistasis 6y ago
      However, we need less energy by the year to maintain an identical standard of living, because we are making everything far more efficient. Our energy use has been extremely inefficient up until now. Modern heat pumps alone will revolutionize heating, requiring 2-3x less energy for heating. Moving around massive cars by burning gasoline is a perfect example of a hugely inefficient and primitive system. Mere electrification requires many times less energy. The US depends on massive amounts of energy because we outlaw city construction that enables car free living, but that will begin to change too if younger generations can ever wrest control away from the boomers.
• vosper 6y ago
  > nuclear power is the only realistic way to solve the looming energy crisis of the 21st century while still maintaining the same standard of living for everyone I assume by "energy crisis" you mean "how do we continue to generate energy while drastically decreasing climate effects"? Because if we're not worried about climate there's no looming energy crisis. There's plenty of oil, gas, and coal out there still. And so if we're talking about climate stuff... is nuclear really the only way? Renewables continue to get cheaper and scale up; grid storage with batteries and pumped hydro is already a thing, and plenty of other storage methods are in development, it seems unlikely not a single one of them will turn out to be useful? Plus, carbon capture for fossil fuel electrical generation is possible, just expensive, and not all fossil fuels are equally bad for the climate, so possibly carbon capture + cleaner fossils could be part of the future, too? I think people have been saying "it has to be nuclear, so it has to be fusion" since way before we had the alternative sources (and storage) we now have, and are continuing to develop. Is it just a trope now, that maybe should be revisited? (I find the possibility of fusion power really exciting and interesting. I'm just not sure it's necessary)
  • bawolff 6y ago
    > There's plenty of oil, gas, and coal out there still. I was under the impression we only had ~100 years worth of oil left, just that its not talked about because climate is more pressing and normal ecconomic pressures will fix the problem if we run out of supply. Is that wrong?
    • entropicdrifter 6y ago
      It's likely that we have more than that now thanks to newer methods of oil extraction like fracking. That said, hopefully within my lifetime the primary use of oil will be for plastics rather than power.
    • RandallBrown 6y ago
      I think typically those predictions mean there's ~100 years of oil that's extractable with current prices and technologies, not that there won't be any oil left at all in 100 years.
• Certhas 6y ago
  It's simply not true that nuclear is the only way. Renewables plus methanization can definitely do it at a price not much above what we currently pay. It's not clear at all that nuclear is cheaper, though it would require less restructuring of infrastructure.
  • Avicebron 6y ago
    I'm not familiar with how you are using methanization in this context. Are you referring to deliberately pumping methane into the atmosphere?
    • Certhas 6y ago
      You generate hydrogen using excess renewables, then turn that into methane and store it to burn in conventional gas power plants. Look up various versions of Power2Gas. It's not economical right now because we have few times when renewable production exceeds demand but is a natural component of a fully renewable power grid.
      • pfdietz 6y ago
        Or, just store the hydrogen.
        • lorenzhs 6y ago
          Hydrogen is really hard to store, though. EDIT: should have qualified my statement with "in man-made objects"
          • pfdietz 6y ago
            No, actually it's pretty easy, in underground caverns (cheapest is solution mined cavities in salt; cost per kWh of capacity about 1/200th the per-energy cost of batteries.)
            • 6y ago
• andrepd 6y ago
  I'm also a fusion power fanboy but >nuclear power is the only realistic way to solve the looming energy crisis of the 21st century while still maintaining the same standard of living for everyone This is just not true, there's no way you can say this. Solar costs are going down massively. Hydro is dirt cheap already. So renewables can absolutely be part of an energetic transition in the near future, while fusion is at best many decades away. So while I think fusion energy has the potential to transform energy generation, and by extent everything about our life, it's wrong to assume renewables aren't probably our safest bet in the near future. Also there's something amusing about "Here's my sure assessment. Anyway I checked the wiki page on fusion power and".
  • scythe 6y ago
    >This is just not true, there's no way you can say this. Solar costs are going down massively. Hydro is dirt cheap already. So renewables can absolutely be part of an energetic transition in the near future, while fusion is at best many decades away. So while I think fusion energy has the potential to transform energy generation, and by extent everything about our life, it's wrong to assume renewables aren't probably our safest bet in the near future. We need nuclear to meet baseload because the storage requirements (for PV particularly, by far the largest renewable) would be absurd without it. But since peak load can be several times average and nuclear plants can't be spun up in a day, we also need storage, and with storage around renewables can be cheaper than nuclear. It's not an either-or question; both should be used. Climate agreements have largely avoided the thorny question of providing nuclear power to the developing world, but if they're to achieve a prosperous standard of living in a sustainable future based on foreseeable technology, this has to be addressed.
    • kbenson 6y ago
      > We need nuclear to meet baseload because the storage requirements (for PV particularly, by far the largest renewable) would be absurd without it. The problem with statements like this is that when they're proven wrong (they aren't always, but when they are), it's often because of some massive underlying shift that makes a bunch of assumptions wrong, leading to a wrong prediction. If we envision a system where not only delivery, but storage is centrally managed, then yes, there's a massive amount of energy storage required, and that's hard to justify and invest in for large companies. If instead you assume that maybe electric cars will act like large battery reservoirs, and stuff like the powerwall will also be used to supplement it, then we end up with a massive amount of battery storage already distributed to different endpoints, an d paid for by individuals instead of a few massive companies. Whether that's all that likely, or even possible at a huge scale because of required rare materials is a question, but that's an entirely different type of scenario than "energy companies invest in massive batteries to leverage solar/wind for efficiently", and the type of thing that's hard to predict and because of that often overlooked. That doesn't mean stuff like that doesn't happen all the time. In fact, I would say there's a major shift like that every decade or so, we just don't necessarily notice them unless we look at them. The internet itself was a major thing. Just relating to the internet, there have been major advanced every few years. The rollout of new major advancements is unevenly distributed and often over the span of a decade, leading to it being hard to notice them. Just this last year, the massive increase in remote work will likely cause a major shift in the economics of many markets, and change how many predictions would play out. Bringing this back to energy, consider that it seems like every year California is having massive fires, and is bankrupting its public utility provider to the point that the state is prepared to take it over if it gets much worse. At that point, if the state decides it needs to actually replace a lot of infrastructure that PG&E needs to maintain, maybe pushing for some partially distributed model starts to make sense. These are all things that go into making predictions about energy really hard, since we're at an inflection point where a lot of stuff that used to work is not working very well, and new technologies are just at the cusp of being useful.
• mjfl 6y ago
  With tokamaks, there is a concept of confinement time. It turns out that plasma is not stable in a standard donut configuration and it likes to twist and break the continuous column, sending all the plasma shooting at the walls. The confinement time is how long it takes for this to happen. After the many plasma experiments over the decades, scientists have a really good idea of how the confinement time scales with magnetic field strength and volume of the plasma. It turns out that you want a big machine. With the JET tokamak they were really close. Iter is designed to have the confinement time well within the requirements for net positive energy, with like a 10-fold margin of safety. IMO it should work, but it is taking an unacceptably long time to construct.
  • Xixi 6y ago
    If I recall correctly, the ITER project was very badly managed until 2015, resulting in the project being about 6 years late. A new management took over then, and the project is now moving on pretty swiftly. But indeed it's taking way too long...
• ummonk 6y ago
  Containment energy is proportional to surface area, while power produced is proportional to volume. Thus, scaling up should make it easier to generate energy.
• abraae 6y ago
  If as you say... "nuclear power is the only realistic way to solve the looming energy crisis of the 21st century" because... "most people around the world think that nuclear fission is scary" then we are fucked as a species. Science does not respect people's feelings. If people have scary feelings about energy/climate change/wearing masks to prevent a disease that travels in the air, then those feelings need to be changed, or those people need to be sidelined. What we must not do - what we cannot afford to do - its to derail the science to assuage the deniers.
  • devonkim 6y ago
    Given the opposition from our left to nuclear and painting any nuclear proponent as a right-wing science denier trying to defund renewable energy I’m not sure what we can do. Michael Schellenberger has been pilloried by our left despite the decades he put into different approaches before arriving at his nuclear advocacy (and perhaps also deeming for a lot of the climate change doom and gloom as alarmists for the 12 year cliff being cited). But in my view climate change is already here and even if we cut all emissions to zero worldwide we’d be kind of screwed, just not as badly screwed. Holistic yet science-driven conversation on climate change doesn’t seem possible anymore in public discourse and everyone is angry, which doesn’t make them sound exactly objective either.
    • epistasis 6y ago
      Viewing this in terms of left-right politics rather than in terms of hard data is one of the primary reasons that nuclear fails again and again as it is tried in the West. The problem isn't politics, the problem is construction logistics. Nobody knows how to build large projects effectively anymore, whether it's the Big Dig or something super complicated like miles of piping with precision welds and specialized concrete pours. If you want to find out why nuclear hasn't worked, look into all the individual cases of construction from Vogtle to VC Summer to Hinkley to the UK's Sizewell C, to all of France's EPR efforts. What you will find is that political fear and regulations are not the problem. It's just management. And when you go back to the US's failures in the late 70s and 80s, you see a similar story of management failure causing construction financial disasters. Even South Korea's apparent successes in construction have been rocked by revelations that inspections were skipped and completed through corruption, nor competence. The primary reason nuclear survives in discussion, IMHO, is as a political wedge issue. Actual political discussion has no connection to reality of the subject matter (as is the case with too much of politics). Shelleneberger is a prime example of the afactual debate when it comes to nuclear. He's looking for ways to convince people, and attract followers, not in rational and informed discussion, and a few minutes of fact checking typically makes short work of his screeds. The anti-nuclear political argumentation is just as bad, and as easily destroyed. The solution is to elevate the debate, and look for actual ways to build nuclear if one thinks it will be a useful tool. That means abandoning the large reactor model and trying SMRs; however I have little hope of those being economical, unless the waste heat or primary has some specialized industrial uses that are uneconomical from electrically driven processes. But at least the will likely be constructable.
• spaetzleesser 6y ago
  "is if a laboratory experiment cannot even produce desired outcomes, " the lab experiments delivered the desired results. The data made it possible to project how a fusion reactor can work. The same happened with nuclear bombs. They did a lot of small scale experiments until they knew what was needed to produce a function nuclear fission and later fusion bomb.
• Xixi 6y ago
  I don't know about the details of why size matters, but in terms of producing energy: "When supplied with 300 MW of electrical power, ITER is expected to produce the equivalent of 500 MW of thermal power sustained for up to 1,000 seconds" [1] That's thermal power, not electricity, so that's not enough yet to break even as a power plant, but it's a big step in the right direction. [1] https://en.wikipedia.org/wiki/Fusion_energy_gain_factor https://en.wikipedia.org/wiki/Fusion_energy_gain_factor
• jagiammona 6y ago
  An excellent quantity that indicates progress on fusion and how far designs are from breakeven is the triple product. Here is an EXCELLENT review of fusion progress so far. (https://www.fusionenergybase.com/article/measuring-progress-in-fusion-energy-the-triple-product/ https://www.fusionenergybase.com/article/measuring-progress-...)
• lopmotr 6y ago
  Is it really clear the fusion power, even if it's achieved, will actually be cheap enough to use? Sure, the fuel is almost free, but the fuel for solar, wind, and hydroelectric power is also free and that doesn't make them cheap. If we're not worried about cost, we could build enormous batteries using existing technology and use solar and wind to power everything. Fusion has to be cheaper than that, and judging by the cost of ITER, it doesn't seem obvious that it can achieve that. Remember how nuclear fission was going to be "too cheap to meter"? Turned out it's expensive to build and operate the plants, regardless of how cheap the fuel is.
  • willis936 6y ago
    Well, fusion has the benefit of having much lower operating costs. Violent terminations, quench events, and tritium containment breaches are serious concerns, but a risk assessment of a fusion power plant would give a much cozier feeling than a risk assessment of a fission power plant. The neutron activated materials are safe after a century and there is not much of it. All of the cost in a fusion plant sits on manufacturing and maintenance. If you can build a GWe plant for $30Bn or less, then it’s a no brainer. The five trillion dollar question is how much investment fusion power research needs before we get to that point.
    • pfdietz 6y ago
      Fusion will likely have much MUCH higher operating cost. Fusion reactors are fearsomely complex things that will be too radioactive for hands on maintenance. They will be operating at much higher levels of radiation damage and thermal stress than fission reactors. That all adds up to a reliability and maintainability nightmare. The fuel being cheap doesn't mitigate this. Also, the need to replace major reactor components many times over the life of the reactor, due to cumulative neutron damage, will itself cause very large operating costs.
• bouncycastle 6y ago
  > What makes scientists believe that the solution to nuclear fusion power is only a matter of scale? The sun is nuclear fusion, so it is proven to work if your scale is big enough ;-)
• imtringued 6y ago
  >I desperately want nuclear fusion to work because nuclear power is the only realistic way to solve the looming energy crisis of the 21st century while still maintaining the same standard of living for everyone. If that's all you care about we can do without nuclear fusion. We have a sun in our neighborhood so we can just harness its energy in various forms such as wind, fossil fuels, biomass or via PV. The real reason we need nuclear fusion is because it is necessary for interstellar travel. There's no sun in deep space. You'll have to bring your own fusion reactor with you.
• blazekp 6y ago
  > What makes scientists believe that the solution to nuclear fusion power is only a matter of scale? I guess there are too many physicists who can lobby well and their income depends on it. I don't expect any results after the many attempts (as opposed to fission, which had almost immediate results).
  • willis936 6y ago
    In case anyone read this comment and wanted the real answer: empirically derived scaling laws from a series of machines increasing in size. The last/largest is JET. http://fusionwiki.ciemat.es/wiki/Scaling_law http://fusionwiki.ciemat.es/wiki/Scaling_law