21 ms·

Fusion reactors: Not what they’re cracked up to be

219 points by waynenilsen 9y ago

shaqbert 9y ago
Mmmh, some of the claims in that article are debunked in this neat video from MIT (though over 1h long): https://www.youtube.com/watch?v=L0KuAx1COEk https://www.youtube.com/watch?v=L0KuAx1COEk
- Xorlev 9y ago
  Which claims does it refute? I'm not able to watch the video, but I'm interested.
  - shaqbert 9y ago
    E.g. the nuclear waste problem: With the right shielding you'll get to radioactive waste that is much easier to handle and usually decaying enough in a 60 year time span. As opposed to the millennia from fission products. So yeah it is a problem, but manageable. Or the parasitic power consumption problem. Yes, fusion reactors require a lot of energy to power that magnetic field, the cooling for the magnets, but the whole point of fusion research is to get an order of magnitude out of the energy put in, i.e. a G-factor which is > 1. Right now we don't have a fusion reactor that manages G >1, but Iter has the potential to operate around G = 5, and before long some smart kid will figure out a design that gives you G > 10. The tritium breeding problem. There are indeed some smart solutions like a FLiBe salt blanket fill. Which also is great at absorbing the neutron "waste". The nuclear proliferation problem. This is more of a theoretical problem, as there are way easier pathways to a bomb. E.g. the thorium fuel cycle to breed a U-233 based bomb is doable even with tech from the 1960'ies.
- leephillips 9y ago
  All his major claims seem correct to me, but my experience in fusion-related research was on the theoretical side. Is there a written summary of what is supposed to be incorrect?
- mrfusion 9y ago
  I think someone needs to let bill gates know about this video. It's very promising and well planned and it really just needs a minimal investment. Also someone needs to write this stuff up into an engaging article. It's hard to spread the word with an hour long video.
- politicalthrow 9y ago
  That video gives a terrific overview of the landscape of the fusion field as it exists pretty much right now. It's an extremely coherent talk. It's long but worth the watch.
  - senectus1 9y ago
    it was mesmerising.. this video needs to spread more.
madaxe_again 9y ago
"In experiments to date the energy input required to produce the temperatures and pressures that enable significant fusion reactions in hydrogen isotopes has far exceeded the fusion energy generated." Wrong. NIF and others have achieved Q>1, albeit in single events. http://www.bbc.co.uk/news/science-environment-24429621 http://www.bbc.co.uk/news/science-environment-24429621
- ohitsdom 9y ago
  I think "sustainably" is implied, and the author's next sentence makes that a bit clearer. > But through the use of promising fusion technologies such as magnetic confinement and laser-based inertial confinement, humanity is moving much closer to getting around that problem and achieving that breakthrough moment when the amount of energy coming out of a fusion reactor will sustainably exceed the amount going in, producing net energy.
- leephillips 9y ago
  No, they haven't, not even in single events, although their press releases claim that they have. Their actual papers make it clear that the claim of >1 energy gain is a result of somewhat arbitrary definitions. There has not been a single shot on the NIF where more energy was supplied by the fusion reaction than was used to fire the lasers - it's not even close.
  - SomeStupidPoint 9y ago
    Are you guys talking about different things? One seems to be talking about energy released by while the other is talking about energy captured from. I think GP was criticizing the news for making it sound like the first hasn't happened when only the second hasn't happened. (At least, in my understanding.)
    - leephillips 9y ago
      Neither one has happened.
    - 9y ago
rplst8 9y ago
What a Negative Nancy.
mrfusion 9y ago
It's weird to consider "parasitic" loss a problem. You just factor that into the total output. If it's high enough you're good.
- user5994461 9y ago
  The article says that you still need that power when the reactor is shutdown or in maintenance. You'd need to consider gain, loss and on/off cycle.
- nkoren 9y ago
  Absolutely. Net output per $ of opex (+ amortization of capex, decommission costs, etc.) is the only relevant metric. Parasitic power loss is categorically not an issue. This is a mistake that engineers frequently make when they are too narrowly focused. You see it all the time in rocket engineering. The rocket equation dictates that performance drops off rapidly as the mass of the vehicle becomes heavier, or the efficiency of the engines worsens. So rocket engineers are obsessed with saving weight and increasing engine performance. However: performance, in absolute terms, doesn't actually matter. What matters is that you get your stuff in orbit, whether that's done efficiently or not. Up to a point, you of course do need to worry about vehicle weight and engine performance -- with too much of the former or too little of the latter, you won't be able to launch any payload. This is analogous to the "break-even point" for fusion power. Beyond that point, however, there's a tradeoff to make: if you need to launch a larger payload, you can either improve the weight or the engines -- or you can just throw more propellant at the problem. Many engineers scoff at the latter approach, because it is utterly inelegant (and doesn't require as many engineers to accomplish). But rocket propellant is cheap. Really cheap. A cost-driven analysis that compares improving efficiency vs. throwing more propellant at the problem will often favour the latter. The reason SpaceX succeeded in reducing launch costs -- where NASA's engineers failed to do so for 50 years -- is because they were willing to do this analysis and go to market with a lower-performance rocket. They preferred to spend an extra $100k on kerosene than an extra $10M milling engine parts out of unobtainium. Having done so, they then iteratively figured out how to make a cheap rocket high-performance -- their rockets are now very high-performance -- which turns out to be much easier than figuring out how to make a high-performance rocket cheap. Anyhow, this article gives me a strong whiff of that kind of engineer's bias, where the good is the enemy of the perfect. [Edit: typos.]
throwanem 9y ago
Dog bites man, film at eleven.
Recurecur 9y ago
I'm interested in the approach being investigated at LPPFusion, on a shoestring budget no less. http://lppfusion.com/ http://lppfusion.com/ LPPFusion is attempting to harness hydrogen-boron fusion, which doesn't produce neutrons, only gamma radiation and helium nuclei (alpha particles). Both the gamma radiation and the alpha particles can be directly converted into electricity. There are many potential benefits of this approach, but a primary one is that with no neutrons, there is no nuclear waste (or potentially plutonium) produced. I hope LPPFusion can secure substantially more funding, it's doing more worthwhile research than the majority currently being done.
- _rpd 9y ago
  There are a whole bunch of options for aneutronic fusion ... https://en.wikipedia.org/wiki/Aneutronic_fusion https://en.wikipedia.org/wiki/Aneutronic_fusion
  - Recurecur 9y ago
    True, but there are many engineering tradeoffs. Any of the listed reactions involving deuterium produce some neutrons, so those aren't desirable (plus deuterium and tritium are rare). Of the other reactions, neither Li-6 or N-15 are readily available, plus lithium is highly chemically reactive. The proton-boron reaction requires the lowest input energy (temperature) of the desirable aneutronic reactions, so it's the hot ticket...so to speak.
    - _rpd 9y ago
      I agree about focusing on the proton-boron reaction. I meant to refer to other fusion technologies that can sustain the reaction. As well as dense plasma focus (the Lawrenceville group that you linked), there is Polywell, Tri Alpha, the Z-machine, and some interesting laser-accelerated proton beam experiments.
    - DennisP 9y ago
      Tritium is rare, and has to be bred from lithium, but deuterium isn't the least bit rare. There's enough deuterium in your morning shower to provide all your energy needs for a year, and enough in the oceans to last until the sun goes out. (Plenty of boron too, though it's not so absurdly abundant as deuterium.)
dsr_ 9y ago
When a reporter calls their credibility into question in the second sentence, there's a problem. "they would produce vast amounts of energy with little radioactive waste, forming little or no plutonium byproducts that could be used for nuclear weapons." Fusion products are helium, neutrons, and neutrinos. Stars eventually fuse products up to iron. To generate plutonium requires a supernova...
- deleted 9y ago
  [deleted]
- throwaway55523 9y ago
  He describes plutonium production as achievable by placing uranium into the reactor.
- hencq 9y ago
  The 'reporter' "was a principal research physicist at the Princeton Plasma Physics Lab until 1999. For 25 years he worked in areas of plasma physics and neutron production related to fusion energy research and development. He holds a PhD in astrophysical sciences from Princeton University." Do you think it's perhaps possible that the author knows what he's talking about? If you'd continued reading after that second sentence you might have come across: > In fact, these neutron streams lead directly to four regrettable problems with nuclear energy: radiation damage to structures; radioactive waste; the need for biological shielding; and the potential for the production of weapons-grade plutonium 239—thus adding to the threat of nuclear weapons proliferation, not lessening it, as fusion proponents would have it.
  - c517402 9y ago
    I don't understand why the OP considers sneaky Pu239 production a proliferation problem, but doesn't consider unaccounted for tritium in the fuel cycle and the general availability of Li6 to bread more tritium a proliferation problem. Anyone?
    - philipkglass 9y ago
adrianN 9y ago
Releasing Tritium is no problem, even if it's in kilogram amounts, because, as the author himself notes, the half life is less than two weeks. Edit: My reading comprehension is clearly lacking...
- leephillips 9y ago
  Where does the author note that? "Tritium has a half life of 12.3 years which means it will be dangerous for at least 120 years, since the hazardous life for a radionuclide is ten to twenty times longer than its half-life"¹ If you come in contact with it during that time you will get cancer. [1]https://www.nirs.org/wp-content/uploads/factsheets/tritiumbasicinfo.pdf https://www.nirs.org/wp-content/uploads/factsheets/tritiumba...
  - justinpombrio 9y ago
    Can confirm: I have a keychain thing that glows from Tritium, and has for years.
    - Synaesthesia 9y ago
      It's a very small amount. Don't eat it! Then it would be highly toxic.
  - jerf 9y ago
    If tritium is released in its atomic form, it is only a hyper-local threat, both geographically and temporally. I wasn't able to confirm this with a quick Google, but I imagine tritium will just want to go up, up, up as fast as it can, where it will never bother anybody again. (It's heavier than hydrogen but still lighter per-atom than helium, which has the same behavior). It doesn't have the problem fission fuels have where they like to seep into ground water, and be both heavy metals and radioactive. Plus, there won't necessarily be a lot of it in a plant. Even if you're accustomed to the surprisingly large energy density of fission fuels, you're still not used to the even larger power density of fusion fuels. We're not talking moving tritium around by the tons... we're talking by the kilogram, or tens of kilograms. Compared to the difficulty of building the fusion plant in the first place, handling a few pounds of tritium safely isn't challenging at all.
erikgrinaker 9y ago
Much of the (valid) criticism in this article relates to the deuterium-tritium fuel cycle. This is the easiest reaction to accomplish on Earth, so most experimental reactors are designed with this fuel in mind, and we're certainly having a hard enough time making even this work. However, I've always considered D-T fusion an intermediate step on the path to aneutronic fusion, such as Helium-3 or proton-Boron reactions. These avoid most of the radiation issues, as well as the tritium-breeding problem (although Helium-3 sourcing presents its own challenge). Since the fusion products are electrically charged the reactor could possibly also generate electricity directly, without a steam turbine and the associated energy loss. Unfortunately, it requires temperatures that are an order of magnitude higher than D-T (well beyond a billion degrees Kelvin), so we'll need to learn to walk before we can run.
- VLM 9y ago
  The nice thing about fusion neutrons is you get to control the isotopes, you have no control over fission waste isotopes. Some fission isotopes are really icky to deal with, as everyone has heard... On the other hand if you don't like dealing with cobalt-60 waste at your fusion plant, simply stop using cobalt alloys in your reactor vessel. It turns out to be "not that big of a deal" to design a fusion plant where neutron activation isn't important. The quotes are because nothing is easy in fusion but as a problem its pretty low on the list.
  - FiatLuxDave 9y ago
    This is true. Back at Fiat Lux when we designed our D-D reactor, we intended it to sit inside a pool of water and borax. Since we didn't need to regenerate tritium, just absorbing the neutrons with boron was the cheapest solution. As far as I know, Borax is the cheapest effective neutron shielding known. We would have liked to have built our vacuum chamber out of purely Al (since Al-28 has a two-minute half-life), but we went with steel for cost reasons. Unfortunately, we never made enough neutrons to activate anything worthwhile. Nevertheless, it is certainly possible to work around neutrons through design decisions.
  - erikgrinaker 9y ago
VikingCoder 9y ago
So who's going to figure out if this was sponsored by West Virginia Coal Miners Union, Exxon, and Dr. Evil?
Robotbeat 9y ago
There's nothing quite like trying to get fusion to work for a while to make you appreciate how awesome fission technology is. If we applied even half the cleverness needed for fusion to making better fission technology, we'd probably be way better off. ...and then there's solar. Why even bother with producing the energy, just capture it with a very thin solid state device! Just need to automate the planting of solar panels in the desert, and we could produce all of our electricity from the Sun. Using just a fifth to a tenth of the land (and much crappier land that nothing much can grow on) that we use for /ethanol/ production alone. (Yes, storage is tough, but is getting cheaper, and we can just plant more solar panels so there's enough power even during cloudy days... Although this is mostly a thought exercise. The best plan for deep decarbonization by far is to operate with a mix of clean power sources optimized for high capacity factor, including at least our current nuclear fleet... They help provide a reliable baseline which drastically reduces the amount of storage and over-installation required. That last 20% of power produced by nuclear is worth its weight in gold and should be protected at least until all fossil power production is ended.)
- sjcsjc 9y ago
  Re solar: not just deserts (there aren't many in the UK) - https://www.fastcompany.com/3053998/these-sky-high-balloons-could-generate-more-power-than-solar-panels https://www.fastcompany.com/3053998/these-sky-high-balloons-...
  - Robotbeat 9y ago
    Yes, I was being US-centric. I know most about the energy situation in the US, and I happen to live here. :) Thinking deeper into the future, floating solar farms could also be a thing. The oceans are huge, and most nations are not land-locked. They'd have their own engineering challenges, for sure, but those challenges look like patty-cake compared to fusion power.
- mrfusion 9y ago
  Not just deserts. You could also float them in the ocean, no? We have 70% of our planet we're not using. Spread them far enough apart and add some movement and shadows wouldn't hurt wildlife much.
Robotbeat 9y ago
(Thinking about the far future, here.) Inertial fusion using Deuterum and Helium 3 would solve a lot of these problems. Of course, He3 is rare here on Earth. I don't think mining the Moon for He3 makes much sense. It's just too rare in the lunar soil. Instead, my favorite concept is mining it from Uranus (whose gravity at Earth-like pressures is actually slightly less than 1g...). There's vast amounts available at useful concentrations (in addition to deuterium). You'd need a reusable two-stage nuclear thermal rocket to get it back to orbit, but luckily there's lots of hydrogen for propellant in the atmosphere (unlike Earth where that hydrogen must be chemically split from water or methane) and we've built and tested nuclear thermal rockets before (with more recent NTR designs achieving sufficient performance for such a vehicle to close). I'm not a fan of NTR for Earth launch (a lot of cost, plus it actually requires a lot more energy since all the propellant is hydrogen, instead of a mix of methane and mostly oxygen), but it would be enabling for Uranus launch. Here's a concept for mining Helium 3 in Uranus using floating hot-air balloon mining facilities: https://solarsystem.nasa.gov/docs/5.6_Reinert.pdf https://solarsystem.nasa.gov/docs/5.6_Reinert.pdf
- DennisP 9y ago
  Another option is to simply breed He3 with pure deuterium fusion; the output of the D-D reaction is He3 half the time, and otherwise tritium, which decays into He3 with a 12-year half-life. D-D produces neutrons but at normal fission energies, not the really high energy of D-T neutrons. Fusion startup Helion, which is funded by YCombinator, is attempting a hybrid D-D/D-He3 reactor, saying the combined reaction would produce only 6% of its energy in the form of neutron radiation.
  - dkirtley 9y ago
    6% is about the best we can do with a closed cycle. Extra-terrestrial sources could push those numbers even lower by running up to a pure D-He3 reaction.
    - DennisP 9y ago
      Yep. I think 6% is pretty good...it's enough so you don't need a heat cycle to extract electricity, and dealing with the neutron damage is easier than going to Uranus. But working fusion reactors probably also means working fusion rockets, and if we find ourselves going to Uranus anyway, all the better. If we get really good at fusion we could also use boron fusion. It uses the most common isotope of boron, which is plentiful on Earth, plus regular hydrogen, and the main reaction is aneutronic. There'd be some minor side reactions but it'd be under 1% of energy as neutron radiation, probably better than you'd get with deuterium in the mix.
cfv 9y ago
This is one article that can be greatly improved by adding "fucking" before every instance of "sun". I would also appreciate a number of citations, since it's hard for me to take things at face value after this modern fake news panic thing
- Nadya 9y ago
  >since it's hard for me to take things at face value after this modern fake news panic thing A part of me is glad to see more people becoming increasingly skeptical. A part of me is sad to see that people think that the problem is only a modern one.
cletus 9y ago
I've been hearing about and hoping for fusion power since probably the 1980s. The more I think about it the more I think it's probably a pipe dream. The idea appears so simple an elusive: combine Hydrogen into Helium (and there are variations that use Helium, particularly He-3 as a fuel), which releases energy. Hydrogen is essentially limitless (He, particularly He-3, less so). Stars do it all the time. The two big problems are of course: 1. Containment. How do you contain something that's heated up to millions of degrees? Magnetic containment has been the obvious candidate since hydrogen heated sufficiently loses it's electrons and becomes a H+ ion but this so far seems far easier said than done; and 2. Neutrons. Fusion using deuterium, tritium, He-4 and He-3 releases varying amounts of neutrons. These can't be magnetically contained (obviously) and they're destructive. We can achieve fusion but neutrons end up pretty quickly destroying the containment vessel. Stars solve the first problem quite easily: with gravity. This isn't something that's useful to us. A star exists in a state of a balance of two opposing forces: gravity from the sheer their sheer mass trying to crush them vs the outward pressure of the fusion processes they're undergoing. The differences in potential size are massive. A star like our own sun will eventually become a red giant extending about to the orbit of the earth. That's 150 _million_ km. Likewise a star larger than ours can end up compressed to something 10 miles or less across. This just illustrates the differentials in forces involved. At this point I'm honestly not convinced that this is an economically solvable problem. It's not sufficient to output more energy than you input either. Let's say a fusion reactor costs $1B to produce, has maintenance costs of $20m/year and has a life of 50 years. That's (at least) $2B you need to recover in capital costs from your "free" energy. I honestly think burning a fuel of some sort will be here for a long, long time. I don't want to discount the rising importance of wind and solar. I do believe that with the ever decreasing costs these will become even more important, even critical, in the future. They simply won't completely replace some kind of combusted fuel. Now what that fuel economy looks like is an unknown. There is a course a limit in what we can dig up out of the ground and to continue using it or something akin to it we need to solve the carbon problem. So what we really need is: 1. Some method of sequestering atmospheric carbon at scale; and 2. Some method of storing excess renewable energy. There are multiple solutions to (2), the most common of which today seems to be using batteries. Current battery technology has come a long way but it has a lot of disadvantages, not the least of which is its current reliance on something that itself is limited (lithium). Plus obtaining all the materials for batteries seems to be highly environmentally destructive. It's unclear to me that without some major innovation batteries will only ever be a niche technology for the likes of a few Teslas and airplanes. Now I'm not saying that innovation won't happen. I'm simply saying current battery tech isn't there yet. Another potential solution for (2) is to use energy to construct a fuel that can be transported and combusted eg [1]. Synthetic hydrocarbons have a lot of advantages. Convenience, relatively simple tech and high energy density (important for weight). Large scale carbon sequestration remains a huge sticking point however. Plus actual fossil fuels remain cheaper than synthetics but this will eventually change either because fossil fuels become much rarer or renewable energy costs get sufficiently low. [1]: https://www.quora.com/How-do-I-get-gasoline-from-wind-power https://www.quora.com/How-do-I-get-gasoline-from-wind-power
theptip 9y ago
I think the four objections here can really be summarized as two: 1) there are energy/fuel losses involved in operating a fusion reactor which aren't present in other types of power source. This doesn't seem fatal to me; either we get the losses down low enough that this system is cost-competitive, or we don't. There's no way to know in advance where this tech will end up, and it doesn't seem like a reason to stop investing in R&D now. 2) Fusion as currently designed produces lots of neutrons, so there is the same sort of waste and proliferation concern as a normal (or fast breeder) fission reactor. I think this is actually the interesting one; the international community will not permit this tech to spread beyond the current nuclear powers if there's a strong proliferation risk. I hadn't realized that the current design of fusion plants were basically breeder reactors, and that's very significant; look at how the theoretically-appealing fast breeder fission reactors have been hamstrung for a prequel to this fight. Of course, if fusion gets to an integer factor cheaper than the next-best source, then it will be hard to keep a lid on this tech, but development is currently relying on many billions of dollars of research funding from the very countries that could be turning away from it out of political/security concerns.
ChuckMcM 9y ago
This is an interesting article from Dr. Jassby who has both patents and papers on Fusion going back to 1977 at least. And there are at least two things that stand out for me, the first is that he goes out of his way to craft a narrative that is negative, and the second he doesn't mention the half dozen or so fusion efforts that are on going beside the NIF and ITER projects. The interesting thing about the narrative is that it takes 'positive' things and puts them in a negative context. For example it takes power to run a fusion reactor, and while the reactor can generate that power it lowers the net output. At the same time, if there is a problem and the reactor turns off, and there is no 'cool down' problem like there is in a fission reactor. No steaming pile of intermediate fission products decaying to generate way too much heat long after you turned the off switch to off. You can portray that as "gee it has to waste a huge chunk of energy just keeping itself running." but that seems trivial given that things like cars have the same issue. Part of the engine power goes into run the fuel pump, or the alternator. This sort of thing recurs in the article and is perhaps most egregious in characterizing the neutron flux as a proliferation hazard. While it is absolutely true you could design a fusion reactor whose purpose was to create fissile material for bombs, that design would look nothing like a power reactor, nor could you easily (maybe even possibly), actually 'convert' a design that had been built and deployed to generate power into one that could create fissile material. So what is the goal of combining the 'facts' that high neutron fluxes of low energy neutrons can weaponize U238, and that fusion power generation can generate high neutron fluxes, without also explaining that a fusion reactor designed to make power couldn't possibly be co-opted to make bombs? Why leave the inconvenient fact off unless you're attempting to mislead the reader? And what is the point of misleading them? And that really makes me wonder, what exactly is Dr. Jassby trying to say here? I could completely understand an article that says "Hey, while fusion has some desirable properties, it is going to be expensive, and from where I sit it is going to be more expensive than the power it generates is worth." That is a perfectly reasonable discussion to have and one that should be had with people looking at building fusion devices. It also makes me wonder why he doesn't mention some of the other groups who are designing and building much simpler and perhaps more efficient systems (in terms of net energy production). Does he not keep up with the field or does he omit them because they don't add to the generally negative tone? All in all this article left me with more questions than insights.
SubiculumCode 9y ago
I predict that SpaceX and SolarCity will eventually roll out vast solar cell arrays in space, because the sun puts out an unthinkable amount of energy that misses earth entirely. ie The sun is already a spectacular fusion reactor. Use it.
MR4D 9y ago
There are many good points here, but I'm dismayed at the complete lack of discussion (heck, no mention even!) of stellarators. It seems to me that computing power has made them quite viable (as shown by the German Wendelstein Stellarator), while the Tokamak design is basically an extremely old Russian design that has never performed to expectations. So if I were stuck with his assumption that fusion = tokamak, then yes, he'd be completely right. But if stellarators achieve their promises, then he's missing the answer completely (and given the Germans success with the Wendelstein, I have a strong confidence that tokamaks will be shuttered within a decade; abandoned to the better technology of the stellarator).
sundvor 9y ago
I thought I'd link in DotNetRock's recent geek out session on fusion power - others might like it, very much on topic: https://player.fm/series/dot-net-rocks/fusion-power-update-geek-out https://player.fm/series/dot-net-rocks/fusion-power-update-g...
cowardlydragon 9y ago
High energy neutrons makes LFTR's issues with volatile chemicals degrading its pipes a child's task ... At least LFTR can be scaled down to "cell" sizes (the Oak Ridge reactor was slated as an perpetually flying aircraft powerplant) that can be regularly replaced/recycled. Fusion reactor designs of any practicality are HUGE and can't be rebuilt on a regular basis...

219 points by waynenilsen 9y ago

Mmmh, some of the claims in that article are debunked in this neat video from MIT (though over 1h long): https://www.youtube.com/watch?v=L0KuAx1COEk https://www.youtube.com/watch?v=L0KuAx1COEk

Xorlev 9y ago
Which claims does it refute? I'm not able to watch the video, but I'm interested.
- shaqbert 9y ago
  E.g. the nuclear waste problem: With the right shielding you'll get to radioactive waste that is much easier to handle and usually decaying enough in a 60 year time span. As opposed to the millennia from fission products. So yeah it is a problem, but manageable. Or the parasitic power consumption problem. Yes, fusion reactors require a lot of energy to power that magnetic field, the cooling for the magnets, but the whole point of fusion research is to get an order of magnitude out of the energy put in, i.e. a G-factor which is > 1. Right now we don't have a fusion reactor that manages G >1, but Iter has the potential to operate around G = 5, and before long some smart kid will figure out a design that gives you G > 10. The tritium breeding problem. There are indeed some smart solutions like a FLiBe salt blanket fill. Which also is great at absorbing the neutron "waste". The nuclear proliferation problem. This is more of a theoretical problem, as there are way easier pathways to a bomb. E.g. the thorium fuel cycle to breed a U-233 based bomb is doable even with tech from the 1960'ies.
leephillips 9y ago
All his major claims seem correct to me, but my experience in fusion-related research was on the theoretical side. Is there a written summary of what is supposed to be incorrect?
mrfusion 9y ago
I think someone needs to let bill gates know about this video. It's very promising and well planned and it really just needs a minimal investment. Also someone needs to write this stuff up into an engaging article. It's hard to spread the word with an hour long video.
politicalthrow 9y ago
That video gives a terrific overview of the landscape of the fusion field as it exists pretty much right now. It's an extremely coherent talk. It's long but worth the watch.
- senectus1 9y ago
  it was mesmerising.. this video needs to spread more.

madaxe_again 9y ago

"In experiments to date the energy input required to produce the temperatures and pressures that enable significant fusion reactions in hydrogen isotopes has far exceeded the fusion energy generated." Wrong. NIF and others have achieved Q>1, albeit in single events. http://www.bbc.co.uk/news/science-environment-24429621 http://www.bbc.co.uk/news/science-environment-24429621

ohitsdom 9y ago
I think "sustainably" is implied, and the author's next sentence makes that a bit clearer. > But through the use of promising fusion technologies such as magnetic confinement and laser-based inertial confinement, humanity is moving much closer to getting around that problem and achieving that breakthrough moment when the amount of energy coming out of a fusion reactor will sustainably exceed the amount going in, producing net energy.
leephillips 9y ago
No, they haven't, not even in single events, although their press releases claim that they have. Their actual papers make it clear that the claim of >1 energy gain is a result of somewhat arbitrary definitions. There has not been a single shot on the NIF where more energy was supplied by the fusion reaction than was used to fire the lasers - it's not even close.
- SomeStupidPoint 9y ago
  Are you guys talking about different things? One seems to be talking about energy released by while the other is talking about energy captured from. I think GP was criticizing the news for making it sound like the first hasn't happened when only the second hasn't happened. (At least, in my understanding.)
  - leephillips 9y ago
    Neither one has happened.
  - 9y ago

rplst8 9y ago

What a Negative Nancy.

mrfusion 9y ago

It's weird to consider "parasitic" loss a problem. You just factor that into the total output. If it's high enough you're good.

user5994461 9y ago
The article says that you still need that power when the reactor is shutdown or in maintenance. You'd need to consider gain, loss and on/off cycle.
nkoren 9y ago
Absolutely. Net output per $ of opex (+ amortization of capex, decommission costs, etc.) is the only relevant metric. Parasitic power loss is categorically not an issue. This is a mistake that engineers frequently make when they are too narrowly focused. You see it all the time in rocket engineering. The rocket equation dictates that performance drops off rapidly as the mass of the vehicle becomes heavier, or the efficiency of the engines worsens. So rocket engineers are obsessed with saving weight and increasing engine performance. However: performance, in absolute terms, doesn't actually matter. What matters is that you get your stuff in orbit, whether that's done efficiently or not. Up to a point, you of course do need to worry about vehicle weight and engine performance -- with too much of the former or too little of the latter, you won't be able to launch any payload. This is analogous to the "break-even point" for fusion power. Beyond that point, however, there's a tradeoff to make: if you need to launch a larger payload, you can either improve the weight or the engines -- or you can just throw more propellant at the problem. Many engineers scoff at the latter approach, because it is utterly inelegant (and doesn't require as many engineers to accomplish). But rocket propellant is cheap. Really cheap. A cost-driven analysis that compares improving efficiency vs. throwing more propellant at the problem will often favour the latter. The reason SpaceX succeeded in reducing launch costs -- where NASA's engineers failed to do so for 50 years -- is because they were willing to do this analysis and go to market with a lower-performance rocket. They preferred to spend an extra $100k on kerosene than an extra $10M milling engine parts out of unobtainium. Having done so, they then iteratively figured out how to make a cheap rocket high-performance -- their rockets are now very high-performance -- which turns out to be much easier than figuring out how to make a high-performance rocket cheap. Anyhow, this article gives me a strong whiff of that kind of engineer's bias, where the good is the enemy of the perfect. [Edit: typos.]

throwanem 9y ago

Dog bites man, film at eleven.

Recurecur 9y ago

I'm interested in the approach being investigated at LPPFusion, on a shoestring budget no less. http://lppfusion.com/ http://lppfusion.com/ LPPFusion is attempting to harness hydrogen-boron fusion, which doesn't produce neutrons, only gamma radiation and helium nuclei (alpha particles). Both the gamma radiation and the alpha particles can be directly converted into electricity. There are many potential benefits of this approach, but a primary one is that with no neutrons, there is no nuclear waste (or potentially plutonium) produced. I hope LPPFusion can secure substantially more funding, it's doing more worthwhile research than the majority currently being done.

_rpd 9y ago
There are a whole bunch of options for aneutronic fusion ... https://en.wikipedia.org/wiki/Aneutronic_fusion https://en.wikipedia.org/wiki/Aneutronic_fusion
- Recurecur 9y ago
  True, but there are many engineering tradeoffs. Any of the listed reactions involving deuterium produce some neutrons, so those aren't desirable (plus deuterium and tritium are rare). Of the other reactions, neither Li-6 or N-15 are readily available, plus lithium is highly chemically reactive. The proton-boron reaction requires the lowest input energy (temperature) of the desirable aneutronic reactions, so it's the hot ticket...so to speak.
  - _rpd 9y ago
    I agree about focusing on the proton-boron reaction. I meant to refer to other fusion technologies that can sustain the reaction. As well as dense plasma focus (the Lawrenceville group that you linked), there is Polywell, Tri Alpha, the Z-machine, and some interesting laser-accelerated proton beam experiments.
  - DennisP 9y ago
    Tritium is rare, and has to be bred from lithium, but deuterium isn't the least bit rare. There's enough deuterium in your morning shower to provide all your energy needs for a year, and enough in the oceans to last until the sun goes out. (Plenty of boron too, though it's not so absurdly abundant as deuterium.)

dsr_ 9y ago

When a reporter calls their credibility into question in the second sentence, there's a problem. "they would produce vast amounts of energy with little radioactive waste, forming little or no plutonium byproducts that could be used for nuclear weapons." Fusion products are helium, neutrons, and neutrinos. Stars eventually fuse products up to iron. To generate plutonium requires a supernova...

deleted 9y ago
[deleted]
throwaway55523 9y ago
He describes plutonium production as achievable by placing uranium into the reactor.
hencq 9y ago
The 'reporter' "was a principal research physicist at the Princeton Plasma Physics Lab until 1999. For 25 years he worked in areas of plasma physics and neutron production related to fusion energy research and development. He holds a PhD in astrophysical sciences from Princeton University." Do you think it's perhaps possible that the author knows what he's talking about? If you'd continued reading after that second sentence you might have come across: > In fact, these neutron streams lead directly to four regrettable problems with nuclear energy: radiation damage to structures; radioactive waste; the need for biological shielding; and the potential for the production of weapons-grade plutonium 239—thus adding to the threat of nuclear weapons proliferation, not lessening it, as fusion proponents would have it.
- c517402 9y ago
  I don't understand why the OP considers sneaky Pu239 production a proliferation problem, but doesn't consider unaccounted for tritium in the fuel cycle and the general availability of Li6 to bread more tritium a proliferation problem. Anyone?
  - philipkglass 9y ago

adrianN 9y ago

Releasing Tritium is no problem, even if it's in kilogram amounts, because, as the author himself notes, the half life is less than two weeks. Edit: My reading comprehension is clearly lacking...

leephillips 9y ago
Where does the author note that? "Tritium has a half life of 12.3 years which means it will be dangerous for at least 120 years, since the hazardous life for a radionuclide is ten to twenty times longer than its half-life"¹ If you come in contact with it during that time you will get cancer. [1]https://www.nirs.org/wp-content/uploads/factsheets/tritiumbasicinfo.pdf https://www.nirs.org/wp-content/uploads/factsheets/tritiumba...
- justinpombrio 9y ago
  Can confirm: I have a keychain thing that glows from Tritium, and has for years.
  - Synaesthesia 9y ago
    It's a very small amount. Don't eat it! Then it would be highly toxic.
- jerf 9y ago
  If tritium is released in its atomic form, it is only a hyper-local threat, both geographically and temporally. I wasn't able to confirm this with a quick Google, but I imagine tritium will just want to go up, up, up as fast as it can, where it will never bother anybody again. (It's heavier than hydrogen but still lighter per-atom than helium, which has the same behavior). It doesn't have the problem fission fuels have where they like to seep into ground water, and be both heavy metals and radioactive. Plus, there won't necessarily be a lot of it in a plant. Even if you're accustomed to the surprisingly large energy density of fission fuels, you're still not used to the even larger power density of fusion fuels. We're not talking moving tritium around by the tons... we're talking by the kilogram, or tens of kilograms. Compared to the difficulty of building the fusion plant in the first place, handling a few pounds of tritium safely isn't challenging at all.

erikgrinaker 9y ago

Much of the (valid) criticism in this article relates to the deuterium-tritium fuel cycle. This is the easiest reaction to accomplish on Earth, so most experimental reactors are designed with this fuel in mind, and we're certainly having a hard enough time making even this work. However, I've always considered D-T fusion an intermediate step on the path to aneutronic fusion, such as Helium-3 or proton-Boron reactions. These avoid most of the radiation issues, as well as the tritium-breeding problem (although Helium-3 sourcing presents its own challenge). Since the fusion products are electrically charged the reactor could possibly also generate electricity directly, without a steam turbine and the associated energy loss. Unfortunately, it requires temperatures that are an order of magnitude higher than D-T (well beyond a billion degrees Kelvin), so we'll need to learn to walk before we can run.

VLM 9y ago
The nice thing about fusion neutrons is you get to control the isotopes, you have no control over fission waste isotopes. Some fission isotopes are really icky to deal with, as everyone has heard... On the other hand if you don't like dealing with cobalt-60 waste at your fusion plant, simply stop using cobalt alloys in your reactor vessel. It turns out to be "not that big of a deal" to design a fusion plant where neutron activation isn't important. The quotes are because nothing is easy in fusion but as a problem its pretty low on the list.
- FiatLuxDave 9y ago
  This is true. Back at Fiat Lux when we designed our D-D reactor, we intended it to sit inside a pool of water and borax. Since we didn't need to regenerate tritium, just absorbing the neutrons with boron was the cheapest solution. As far as I know, Borax is the cheapest effective neutron shielding known. We would have liked to have built our vacuum chamber out of purely Al (since Al-28 has a two-minute half-life), but we went with steel for cost reasons. Unfortunately, we never made enough neutrons to activate anything worthwhile. Nevertheless, it is certainly possible to work around neutrons through design decisions.
- erikgrinaker 9y ago

VikingCoder 9y ago

So who's going to figure out if this was sponsored by West Virginia Coal Miners Union, Exxon, and Dr. Evil?

Robotbeat 9y ago

There's nothing quite like trying to get fusion to work for a while to make you appreciate how awesome fission technology is. If we applied even half the cleverness needed for fusion to making better fission technology, we'd probably be way better off. ...and then there's solar. Why even bother with producing the energy, just capture it with a very thin solid state device! Just need to automate the planting of solar panels in the desert, and we could produce all of our electricity from the Sun. Using just a fifth to a tenth of the land (and much crappier land that nothing much can grow on) that we use for /ethanol/ production alone. (Yes, storage is tough, but is getting cheaper, and we can just plant more solar panels so there's enough power even during cloudy days... Although this is mostly a thought exercise. The best plan for deep decarbonization by far is to operate with a mix of clean power sources optimized for high capacity factor, including at least our current nuclear fleet... They help provide a reliable baseline which drastically reduces the amount of storage and over-installation required. That last 20% of power produced by nuclear is worth its weight in gold and should be protected at least until all fossil power production is ended.)

sjcsjc 9y ago
Re solar: not just deserts (there aren't many in the UK) - https://www.fastcompany.com/3053998/these-sky-high-balloons-could-generate-more-power-than-solar-panels https://www.fastcompany.com/3053998/these-sky-high-balloons-...
- Robotbeat 9y ago
  Yes, I was being US-centric. I know most about the energy situation in the US, and I happen to live here. :) Thinking deeper into the future, floating solar farms could also be a thing. The oceans are huge, and most nations are not land-locked. They'd have their own engineering challenges, for sure, but those challenges look like patty-cake compared to fusion power.
mrfusion 9y ago
Not just deserts. You could also float them in the ocean, no? We have 70% of our planet we're not using. Spread them far enough apart and add some movement and shadows wouldn't hurt wildlife much.

Robotbeat 9y ago

(Thinking about the far future, here.) Inertial fusion using Deuterum and Helium 3 would solve a lot of these problems. Of course, He3 is rare here on Earth. I don't think mining the Moon for He3 makes much sense. It's just too rare in the lunar soil. Instead, my favorite concept is mining it from Uranus (whose gravity at Earth-like pressures is actually slightly less than 1g...). There's vast amounts available at useful concentrations (in addition to deuterium). You'd need a reusable two-stage nuclear thermal rocket to get it back to orbit, but luckily there's lots of hydrogen for propellant in the atmosphere (unlike Earth where that hydrogen must be chemically split from water or methane) and we've built and tested nuclear thermal rockets before (with more recent NTR designs achieving sufficient performance for such a vehicle to close). I'm not a fan of NTR for Earth launch (a lot of cost, plus it actually requires a lot more energy since all the propellant is hydrogen, instead of a mix of methane and mostly oxygen), but it would be enabling for Uranus launch. Here's a concept for mining Helium 3 in Uranus using floating hot-air balloon mining facilities: https://solarsystem.nasa.gov/docs/5.6_Reinert.pdf https://solarsystem.nasa.gov/docs/5.6_Reinert.pdf

DennisP 9y ago
Another option is to simply breed He3 with pure deuterium fusion; the output of the D-D reaction is He3 half the time, and otherwise tritium, which decays into He3 with a 12-year half-life. D-D produces neutrons but at normal fission energies, not the really high energy of D-T neutrons. Fusion startup Helion, which is funded by YCombinator, is attempting a hybrid D-D/D-He3 reactor, saying the combined reaction would produce only 6% of its energy in the form of neutron radiation.
- dkirtley 9y ago
  6% is about the best we can do with a closed cycle. Extra-terrestrial sources could push those numbers even lower by running up to a pure D-He3 reaction.
  - DennisP 9y ago
    Yep. I think 6% is pretty good...it's enough so you don't need a heat cycle to extract electricity, and dealing with the neutron damage is easier than going to Uranus. But working fusion reactors probably also means working fusion rockets, and if we find ourselves going to Uranus anyway, all the better. If we get really good at fusion we could also use boron fusion. It uses the most common isotope of boron, which is plentiful on Earth, plus regular hydrogen, and the main reaction is aneutronic. There'd be some minor side reactions but it'd be under 1% of energy as neutron radiation, probably better than you'd get with deuterium in the mix.

cfv 9y ago

This is one article that can be greatly improved by adding "fucking" before every instance of "sun". I would also appreciate a number of citations, since it's hard for me to take things at face value after this modern fake news panic thing

Nadya 9y ago
>since it's hard for me to take things at face value after this modern fake news panic thing A part of me is glad to see more people becoming increasingly skeptical. A part of me is sad to see that people think that the problem is only a modern one.

cletus 9y ago

I've been hearing about and hoping for fusion power since probably the 1980s. The more I think about it the more I think it's probably a pipe dream. The idea appears so simple an elusive: combine Hydrogen into Helium (and there are variations that use Helium, particularly He-3 as a fuel), which releases energy. Hydrogen is essentially limitless (He, particularly He-3, less so). Stars do it all the time. The two big problems are of course: 1. Containment. How do you contain something that's heated up to millions of degrees? Magnetic containment has been the obvious candidate since hydrogen heated sufficiently loses it's electrons and becomes a H+ ion but this so far seems far easier said than done; and 2. Neutrons. Fusion using deuterium, tritium, He-4 and He-3 releases varying amounts of neutrons. These can't be magnetically contained (obviously) and they're destructive. We can achieve fusion but neutrons end up pretty quickly destroying the containment vessel. Stars solve the first problem quite easily: with gravity. This isn't something that's useful to us. A star exists in a state of a balance of two opposing forces: gravity from the sheer their sheer mass trying to crush them vs the outward pressure of the fusion processes they're undergoing. The differences in potential size are massive. A star like our own sun will eventually become a red giant extending about to the orbit of the earth. That's 150 _million_ km. Likewise a star larger than ours can end up compressed to something 10 miles or less across. This just illustrates the differentials in forces involved. At this point I'm honestly not convinced that this is an economically solvable problem. It's not sufficient to output more energy than you input either. Let's say a fusion reactor costs $1B to produce, has maintenance costs of $20m/year and has a life of 50 years. That's (at least) $2B you need to recover in capital costs from your "free" energy. I honestly think burning a fuel of some sort will be here for a long, long time. I don't want to discount the rising importance of wind and solar. I do believe that with the ever decreasing costs these will become even more important, even critical, in the future. They simply won't completely replace some kind of combusted fuel. Now what that fuel economy looks like is an unknown. There is a course a limit in what we can dig up out of the ground and to continue using it or something akin to it we need to solve the carbon problem. So what we really need is: 1. Some method of sequestering atmospheric carbon at scale; and 2. Some method of storing excess renewable energy. There are multiple solutions to (2), the most common of which today seems to be using batteries. Current battery technology has come a long way but it has a lot of disadvantages, not the least of which is its current reliance on something that itself is limited (lithium). Plus obtaining all the materials for batteries seems to be highly environmentally destructive. It's unclear to me that without some major innovation batteries will only ever be a niche technology for the likes of a few Teslas and airplanes. Now I'm not saying that innovation won't happen. I'm simply saying current battery tech isn't there yet. Another potential solution for (2) is to use energy to construct a fuel that can be transported and combusted eg [1]. Synthetic hydrocarbons have a lot of advantages. Convenience, relatively simple tech and high energy density (important for weight). Large scale carbon sequestration remains a huge sticking point however. Plus actual fossil fuels remain cheaper than synthetics but this will eventually change either because fossil fuels become much rarer or renewable energy costs get sufficiently low. [1]: https://www.quora.com/How-do-I-get-gasoline-from-wind-power https://www.quora.com/How-do-I-get-gasoline-from-wind-power

theptip 9y ago

I think the four objections here can really be summarized as two: 1) there are energy/fuel losses involved in operating a fusion reactor which aren't present in other types of power source. This doesn't seem fatal to me; either we get the losses down low enough that this system is cost-competitive, or we don't. There's no way to know in advance where this tech will end up, and it doesn't seem like a reason to stop investing in R&D now. 2) Fusion as currently designed produces lots of neutrons, so there is the same sort of waste and proliferation concern as a normal (or fast breeder) fission reactor. I think this is actually the interesting one; the international community will not permit this tech to spread beyond the current nuclear powers if there's a strong proliferation risk. I hadn't realized that the current design of fusion plants were basically breeder reactors, and that's very significant; look at how the theoretically-appealing fast breeder fission reactors have been hamstrung for a prequel to this fight. Of course, if fusion gets to an integer factor cheaper than the next-best source, then it will be hard to keep a lid on this tech, but development is currently relying on many billions of dollars of research funding from the very countries that could be turning away from it out of political/security concerns.

ChuckMcM 9y ago

This is an interesting article from Dr. Jassby who has both patents and papers on Fusion going back to 1977 at least. And there are at least two things that stand out for me, the first is that he goes out of his way to craft a narrative that is negative, and the second he doesn't mention the half dozen or so fusion efforts that are on going beside the NIF and ITER projects. The interesting thing about the narrative is that it takes 'positive' things and puts them in a negative context. For example it takes power to run a fusion reactor, and while the reactor can generate that power it lowers the net output. At the same time, if there is a problem and the reactor turns off, and there is no 'cool down' problem like there is in a fission reactor. No steaming pile of intermediate fission products decaying to generate way too much heat long after you turned the off switch to off. You can portray that as "gee it has to waste a huge chunk of energy just keeping itself running." but that seems trivial given that things like cars have the same issue. Part of the engine power goes into run the fuel pump, or the alternator. This sort of thing recurs in the article and is perhaps most egregious in characterizing the neutron flux as a proliferation hazard. While it is absolutely true you could design a fusion reactor whose purpose was to create fissile material for bombs, that design would look nothing like a power reactor, nor could you easily (maybe even possibly), actually 'convert' a design that had been built and deployed to generate power into one that could create fissile material. So what is the goal of combining the 'facts' that high neutron fluxes of low energy neutrons can weaponize U238, and that fusion power generation can generate high neutron fluxes, without also explaining that a fusion reactor designed to make power couldn't possibly be co-opted to make bombs? Why leave the inconvenient fact off unless you're attempting to mislead the reader? And what is the point of misleading them? And that really makes me wonder, what exactly is Dr. Jassby trying to say here? I could completely understand an article that says "Hey, while fusion has some desirable properties, it is going to be expensive, and from where I sit it is going to be more expensive than the power it generates is worth." That is a perfectly reasonable discussion to have and one that should be had with people looking at building fusion devices. It also makes me wonder why he doesn't mention some of the other groups who are designing and building much simpler and perhaps more efficient systems (in terms of net energy production). Does he not keep up with the field or does he omit them because they don't add to the generally negative tone? All in all this article left me with more questions than insights.

SubiculumCode 9y ago

I predict that SpaceX and SolarCity will eventually roll out vast solar cell arrays in space, because the sun puts out an unthinkable amount of energy that misses earth entirely. ie The sun is already a spectacular fusion reactor. Use it.

MR4D 9y ago

There are many good points here, but I'm dismayed at the complete lack of discussion (heck, no mention even!) of stellarators. It seems to me that computing power has made them quite viable (as shown by the German Wendelstein Stellarator), while the Tokamak design is basically an extremely old Russian design that has never performed to expectations. So if I were stuck with his assumption that fusion = tokamak, then yes, he'd be completely right. But if stellarators achieve their promises, then he's missing the answer completely (and given the Germans success with the Wendelstein, I have a strong confidence that tokamaks will be shuttered within a decade; abandoned to the better technology of the stellarator).

sundvor 9y ago

I thought I'd link in DotNetRock's recent geek out session on fusion power - others might like it, very much on topic: https://player.fm/series/dot-net-rocks/fusion-power-update-geek-out https://player.fm/series/dot-net-rocks/fusion-power-update-g...

cowardlydragon 9y ago

High energy neutrons makes LFTR's issues with volatile chemicals degrading its pipes a child's task ... At least LFTR can be scaled down to "cell" sizes (the Oak Ridge reactor was slated as an perpetually flying aircraft powerplant) that can be regularly replaced/recycled. Fusion reactor designs of any practicality are HUGE and can't be rebuilt on a regular basis...