8 ms·

I still don't understand why people want fusion. Like fisson already does basically what you need and is easier in every way. Yes, the energy density of fusio

• AnimalMuppet 6y ago
  Fusion is much less likely to have accidents that poison the local landscape for the next 10,000 years.
  • epistasis 6y ago
    As odd as this may sound, this is not an impediment to current nuclear fission deployment. The risks are small, and many populations are very willing to accept them. See France, as well as most places in the US that already have nuclear reactors nearby. Or for that matter, many many sites in the UK.
    • Judgmentality 6y ago
      I am skeptical of this, assuming you need some sort of public support in order to build a nuclear power plant (I'm guessing voters are involved somewhere, even if it's electing their state governor). Most people are scared of nuclear power, so it seems politically problematic (at least in the United States). I went to school in Pittsburgh where there are nuclear power plants nearby and people still felt more comfortable with coal being shipped over from Virginia.
      • epistasis 6y ago
        Current sites that would welcome new nuclear, as evidenced by enthusiastic local support matched by a new construction project: * Vogtle, Georgia * VC Summer, South Carolina * a cluster of small towns in the west that are the first customers for small modular reactors * Wylfa, UK * Hinkley, UK The greater challenge with nuclear is getting the funding to construct, followed by actual engineering, procurement, and construction.
        • reissbaker 6y ago
          The funding problem is because of the safety problem. There are high regulatory costs associated with building new (fission) nuclear power plants, because: * If you don't regulate the materials and fuels used for fission nuclear power plants, most countries could easily build nuclear weapons, and * If you build fission power plants badly, or maintain them poorly, everyone and everything around them dies in a large radius, and in an even larger radius gets severely sickened. And this radius is poisoned effectively forever. If there weren't safety problems inherent to fission nuclear reactors, they would be much cheaper to build as well as being much cheaper to operate — and thus easier to fund. That's part of why fusion reactors are interesting: theoretically they should work just as well if not better than fission reactors at converting fuels to energy; the fuel is more prevalent and cheaper; and there should be lower costs associated with building and operating them since the risks are lower. We just don't know how to build them yet, and figuring that out is expensive.
          • deleted 6y ago
            [deleted]
          • pfdietz 6y ago
            > The funding problem is because of the safety problem. I have yet to see convincing evidence of this. It seems like an excuse. Perhaps it's code for "the regulators won't let us get away with screw ups", which is what happened at Flamanville.
  • nickik 6y ago
    The chance of that happening with the fission reactors currently being built is almost vanishingly small. And even the largest nuclear accidents ever did not lead to anything close to that. This is just fear mongering nonsense. And btw, even with Fusion you still produce huge amounts of high energy particles that can be just as dangerous and can be used to do bad stuff as well. Fusion is not magic.
  • pfdietz 6y ago
    On the other hand, they will almost certainly have tritium leaks far larger than from fission plants. A single 1 GW(e) DT fusion reactor would burn enough tritium each year to contaminate 2 months of flow of the entire Mississippi River above the legal limit for drinking water. Leaking even a small fraction of that could have serious consequences.
• phreeza 6y ago
  The question is why wouldn't you want fusion. More options are always better I think.
  • nickik 6y ago
    I'm not saying I don't want it. It just seems as humanity we totally fucked up. We found a revolutionary new energy source and we totally fucked up the deployment of it. We should live in a nuclear age already, fission powered space craft, trains, ships, power stations, remote electricity. There is no fundamental reason why fission should not be used an all of those. Yet we almost don't use it at all, and phasing it out at the same time as we face climate change. At the same time huge money is spent on Fusion that is much less likely to actually help. With the money spent on ITER you could literally run a matcher competitive competition to build 3-4 new fission reactors and likely multible new powerful turbines. A molten salt reactor with a brayton turbine would likely be far more revolutionary then whatever ITER can ever be. In general I just feel like fission is disliked and future has this 'wow the future could be magical', and I'm saying, the present could be magical, we don't need to wait for some magical technology. All that is required is some engineering and a general acceptance that fission is good among politicians, regulators and people. If some start ups want to work on it, I'm not against it. The point is more that even if this magical technology break-threw happens, deploying it in the real world will run against many of the same problems as fission does.
    • orthecreedence 6y ago
      The problem, in my view, is mostly regulatory capture and this incessant drive to let markets do their thing. As it stands, fossil fuels should be taxed so high that building, maintaining, and running nuclear power plants is cheap in comparison. Yet we have continued investment into fossil fuels even though we're now fully aware of the damage they're doing. And people say "oh, well we don't have nuclear, because it's so expensive." You know what else is expensive? Entire cities being under 6ft of ocean and having to relocate hundreds of millions of people. In other words, the known externalities are not imbued in the price, because yay capitalism. I think a little market tampering is warranted when planetary survival is at stake. And obviously, the ramp-up should be gradual, ie, we should have been starting this 20 years ago, when it was also painfully obvious that digging up huge amounts of carbon and burning it is a bad idea. Oops.
• fastball 6y ago
  - no radioactive waste - no nuclear meltdowns / runaway processes - more abundant fuel (on earth and the rest of the solar system) - less pre-processing of fuel - fuel cannot be used to easily make weapons Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion.
  • hairytrog 6y ago
    - there is waste, it's just shorter lived than fission waste and lower in quantity. The expectation is that fusion reactors will have to be regulated in almost exactly the same way as fission reactors because they are nuclear sites, with nuclear waste, and proliferation concerns. - there is lot's of pre processing of the fuel to breed the Tritium in a molten salt blanket that surrounds the reactor and separating from the salt and then feeding it into the chamber - there is plenty of fission and fusion fuel. Yes, there is more hydrogen around. - tritium is used in nuclear weapons as a booster, to dramatically lower the amount of necessary fissile material - each fusion reactor is a fast neutron source, which means it can be used to make weapons grade materials. Conveniently, it has a breeding blanket for tritium, in which other fertile fuels can be place to make weapons material: proliferation concerns are a real problem for fusion
    • willis936 6y ago
      - tritium is used in nuclear weapons as a booster It is, but tritium is not put into bombs. Lithium is. - proliferation concerns are a real problem for fusion Unless all fissile materials are banned. It is very easy to check for the existence of fissile materials. If there were no legitimate, safe reasons to have any fissile materials in use on the planet, then a global ban on fissile materials is on the table. A treaty where every nation checks on the other is reasonable. It is hard to build a secret fusion reactor, just as its hard to build a secret uranium centrifuge.
      • philipkglass 6y ago
        It is, but tritium is not put into bombs. Lithium is. Both are put into bombs. The main concern when it comes to tritium supply, regards tritium used for boosting of fission charges. Both applications are crucially important, but fusion boosting appears to require significantly larger quantities of tritium. Tritium and deuterium for boosting are supplied to the weapon from an external reservoir (gas bottle) as part of the arming process of the weapon. Since about 5.5% of existing tritium decays every year, the tritium assigned to each weapon must be regularly replenished. This is done by removing the weapon’s tritium reservoir and exchanging it with a newly refilled reservoir (5). Figure 1.3 shows what may be such a reservoir. From Norwegian Defence Research Establishment report "Tritium production": https://publications.ffi.no/nb/item/asset/dspace:6780/20-01388.pdf https://publications.ffi.no/nb/item/asset/dspace:6780/20-013... Also see this Savannah River Site page about tritium supply for weapons: https://www.srs.gov/general/programs/dp/index.htm https://www.srs.gov/general/programs/dp/index.htm And for a deeper dive, this fascinating blog post: "U.S. Tritium Production for the Nuclear Weapons Stockpile – Not Like the Old Days of the Cold War" https://lynceans.org/all-posts/u-s-tritium-production-for-the-nuclear-weapons-stockpile-not-like-the-old-days-of-the-cold-war/ https://lynceans.org/all-posts/u-s-tritium-production-for-th...
• Robotbeat 6y ago
  It is, of course, the regulatory cost they want to attack. Fusion can’t continue melting down. Unlike fission. The fact that it’s much harder to get to work at all is considered kind of an advantage here because it means the reactor can’t accidentally keep producing energy when you don’t want it to. Second, if you get really good at fusion there are some reactions that don’t produce neutrons means you don’t get all this activated material. And that lack of neutrons also makes it proliferation-resistant (and can allow more compact ways of generating electricity than a typical thermal cycle). But even with the low hanging fruit type of fusion with tritium & deuterium, you don’t get these long lived transuranic isotopes. Also, fusion has some important very long term applications in human spaceflight (& interstellar travel). And the fusion fuel infrastructure is much less susceptible to being diverted to making weapons. But overall I agree with you. Fusion makes fission look really easy, and there are advanced fission designs and processes which address most of the above issues.
  • pfdietz 6y ago
    If we built a fission reactor with the low power density of a fusion reactor it would be so big it couldn't melt down, just from its own thermal inertia.
  • nickik 6y ago
    Arguably a fusion reactor has a much higher chance of harming the population around as a breach in containment could release highly radioactive gases. > But even with the low hanging fruit type of fusion with tritium & deuterium, you don’t get these long lived transuranic isotopes. You don't get these in a good fission cycle either. > Also, fusion has some important very long term applications in human spaceflight (& interstellar travel). Yes but and fission has a lot of applications in human spaceflight too. And not some theoretical interstellar travel, but rather in things that are actually useful and that we need now. Mars surface power most importantly. Nuclear Electric Propulsion second most importantly. Its all fine to dream of interstellar travel, but by any logical view to world, Mars is a closer term thing then interstellar space travel. Also, if we just want to send interstellar probes. Lasers driven by fission are much more likely to be a good solution in the next 100 years.
• willis936 6y ago
  Fission has a few unavoidable issues: long radioactive isotope half-life, weapons proliferation, and the runaway scenario. Fusion has none of these issues plus the fuel being abundant. It's the answer to the question "how do we meet the growing energy demands of humans over the next thousand years?". The only real danger is that of a tritium leak, but the short half-life makes the prospect of a leak less concerning.
  • hairytrog 6y ago
    Since the reactors would ostensibly be continuously operating, the danger is the same. 10+ year half life is about as dangerous as 10000 years because you are always generating the waste.
    • reissbaker 6y ago
      Er, no. If you generate the same volume of waste per year, but for a fusion reactor the waste stops being a problem within a century and for a fission reactor it takes 10,000 years, at any point in time after the first 100 years, waste from a given fusion reactor will be less prevalent than waste from a given fission reactor. It also doesn't matter that no specific nuclear reactor will have a lifetime of 10,000 years. The problem is that per megawatt of energy generated, fission theoretically creates (much) longer-lived waste than fusion. Over a longer-than-one-hundred-year timeframe, equivalent amounts of energy generation result in vastly different waste carrying costs. Fusion's waste carrying costs are much lower. And obviously that number is even more in favor of fusion if it only takes 10 years. (ITER claims 100 years though: https://www.iter.org/sci/Fusion https://www.iter.org/sci/Fusion)
    • willis936 6y ago
      The danger is not the same between fusion and fission. Firstly, 10 years worth of energy is inside a fission reactor and is capable of releasing most of that energy in an instant if not properly controlled. This cannot happen in a fusion reactor. A year's worth of fuel is in a gas tank on the wall and needs absurd conditions to ignite. It cannot happen spontaneously. Secondly, the exhaust is helium-4: a stable isotape of a valuable element. Thirdly, the neutron bombardment in a fusion reactor activate the materials they hit. If they hit lithium then they make tritium: a much needed isotape for fuel in first generation fusion reactors. The other materials they hit are chosen to have half-lives of less than 100 years. So you have a nuclear site that no one's allowed to touch for a while then you can recycle the materials. It's nothing like the transuranium nuclear waste from fission plants.
• deleted 6y ago
  [deleted]
• runarberg 6y ago
  I guess people are increasingly frustrated with the failure of the current nuclear reactors to cost scale in the modern economy, so they look forward for a fundamental shift in technology. That is, there is no hope in fission, it has not stood the test of time so far, and it there is no reason it will in the near future. If we want nuclear we can only hope for fusion. Note that this is me projecting. I don’t have a horse in this race. I’d be perfectly happy with nuclear free Earth; with renewables being our primary method of generating energy; a future which as of now looks the most likely. And if people develop fusion at some point in the future... cool.
  • pfdietz 6y ago
    Yes, it's magical thinking born of frustration, not something that one should truly expect.
• wcarss 6y ago
  I imagine that the popular view of fusion will be better, because of the impossibility of meltdown and the much easier to manage spent materials. If that translates into less NIMBYism, the regulatory costs should be much lower. If the inputs can then ever be scaled, it could present a gateway to powerplant "mass production", which would be truly revolutionary. Especially for those crazy rocket concepts!
  • pfdietz 6y ago
    If a fission reactor had a power density as low as a fusion reactor, it would also be impossible to melt down, just because the thermal inertia of the core would be so large. Of course, it would also be uneconomical, because of the cost of that larger core (just as a fusion reactor would be uneconomical.)
• krasin 6y ago
  re: regulation. This is the problem with fission. but not necessarily so with fusion. The reason is that unlike fission, where it's impossible to a small company to get a handle on fuel and build a fission plant in a less-regulated country, with fusion that becomes a lot more approachable. But I am just as skeptical as you about the future of fusion and fission in the US and Europe.
• reissbaker 6y ago
  People want fusion because fission reactors leave long-lived radioactive waste, can melt down dangerously, and use the same fissile materials as nuclear weapons, making combating nuclear proliferation difficult. That's why there are extremely high regulatory costs associated with fission reactors. (I'm not saying we should wait for fusion reactors, but there's a lot of good reasons to develop them, and once fusion reactors are available there's a lot of good reasons to stop building fission reactors at that point.)
  • dmitrygr 6y ago
    The issue is that the current fusion choices (deuterium) produce neutrons during fusion, that hit your containment vessels, and ... create long-lived radioactive isotopes while slowly embrittling the containment vessel. When you replace it, it is in fact, a long lived radioactive husk that you need to safely contain for a long time. There are other fusion options that do not, but they are MUCH harder to fuse than deuterium (what we are still trying to achieve)
    • reissbaker 6y ago
      While true, it's still better than fission in terms of waste. (And much less liable to Fukushima-style meltdowns, and less likely to lead to nuclear weapon proliferation.)
      • dmitrygr 6y ago
        Well, actually, a nice source of a large number of neutrons is a HUGE proliferation thread: weaponizable Pu-239 is produced out of easily-available U-238 by neutron capture. Only generation 2 (or 3) fusion, when we move past deuterium, will be proliferation-safe.
        • reissbaker 6y ago
          It's a threat comparable to fission reactors only if fusion reactor containment vessels are built out of uranium, which they aren't. To put it another way: operating a nuclear reactor today is expensive due to regulatory constraints meant to prevent nuclear weapon proliferation. If the fuel for your reactor can't be mistaken for nuclear bomb parts, and the components of your reactor can't be mistaken for nuclear bomb parts, it's a lot cheaper to build and operate. And it's a lot safer for someone to sign off on "Yep that's a whole bunch of lithium for a fusion reactor" than looking at a bunch of uranium and being like... Well...
• Valgrim 6y ago
  There are several advantages: A fusion reactor doesn't create create long-lived radioactive waste (or any kind of pollution). A fusion reactor cannot be used to create nuclear weapons. A fusion reactor doesn't require any form of mining for it's fuel. A fusion reactor cannot meltdown in any way. Due to these inherent safety features, the costs associated with the regulation and engineering a fusion power plant could be much lower than a fission plant.
  • gizmondo 6y ago
    It will be easy to use neutrons from DT fusion to get weapon-grade plutonium. This may be easier to police, i.e. "there should be no uranium nowhere near a fusion plant", but that's a much subtler statement. And of course mining for lithium as a fuel is still necessary, so you should perhaps say "no additional mining" or something.
    • willis936 6y ago
      The need for lithium is a valid point. The amount required for fuel is very small though. A 1 GW plant would use more on initial filling than a 30 year lifetime of refilling and even that first filling would be on the order of a metric ton (unverified ballpark, dependent on reactor size, blanket thickness, and plumbing overhead). 80,000 metric tons of lithium are mined each year. We consume about 18 TW. So I estimate that converting all electricity sources to fusion would use about 1/4 of a year’s worth of lithium, but would be enough to make 30 year plants, which would still have most of their lithium left over for recycling/reuse afterwards.
    • pfdietz 6y ago
      And enriching lithium is necessary. A single ARC reactor would use a good fraction of all the 6Li produced for the US thermonuclear weapons program. The tritium produced in a fusion reactor program would make it much easier to engineer high yield fission bombs, via boosting.
    • rnhmjoj 6y ago
      > And of course mining for lithium as a fuel is still necessary, so you should perhaps say "no additional mining" or something. True, but the quantity of lithium required to breed tritium for power generation is ridiculously low. Operating a DEMO-like reactor for 30 years would consume 2 tons of lithium, which is nothing compared to the annual consumption for battery manufacturing (around 30000 tons).
• Florin_Andrei 6y ago
  > I still don't understand why people want fusion. > That said, I want fusion for crazy rocket concepts. There you go, you answered it yourself. Fusion rockets would open up the Solar System the way the steam engine opened up the oceans. Also on Earth, fusion would be cool. It's less dirty than fission, and the fuel is FAR more plentiful.
• clarkmoody 6y ago
  Fusion could be a great equalizer in terms of global access to large amounts of energy: if you have moderately good access to the ocean, you have a nearly inexhaustible source of the hydrogen isotopes available in seawater and required as fuel for a fusion reactor. Contrast this with both fossil fuels and fission materials. Those resources are the foundation of modern geopolitics. Seawater is not, and way more people have access to it.
  • nickik 6y ago
    Literally every country in the world has enough thorium in the ground for 100s of years. Go look up how much thorium is in the earth. You can literally go in-front of your house, dig a whole and in theory you can have enough thorium for a year. Thorium is literally waste material that comes out of rare earth mining, its not a limited resource in any way.
• marcosdumay 6y ago
  From my point of view, fusion is incredibly important for long term space exploration... but I would agree, not much else. Even the "not so long" term space exploration can be done with fission.