20 ms·
Chinese Tokamak reaches over 100M degrees
- agoldis 8y agoPlease explain what does it mean and why is it good? :) Thank you.
- saagarjha 8y agoIt’s an important milestone in the search for sustainable nuclear fusion.
- i_am_proteus 8y agoA tokamak is a kind of fusion reactor, and basically the most prevalent. "100M degrees" (Kelvin) corresponds to 10 KeV (kilo electron volts), which is an important figure to exceed for D-T fusion. D-T fusion which is the kind of fusion the ITER Tokamak (a forthcoming fusion reactor and international megaproject) intends to demonstrate. An older fusion experiment, JET (Joint European Torus) reached these levels, so this does not break new ground, but it is important if this Chinese Tokamak is going to provide data useful for ITER. I will note that it's rather unusual to refer to plasma temperature in Kelvin rather than in KeV. I edited this comment with a few more details to try to make it easier for laypeople to understand.
- daxfohl 8y agoWhat important happens at that temperature?
- NamTaf 8y agoAs I understand, this represents sufficient energy to overcome the Coulomb Barrier [1] which naturally repels atoms apart. To cause fusion, you need to push particles together either hard enough or fast enough that they push through this repulsion and fuse. The repulsion is a product of the electrostatic repulsion of the positive charges of the nuclei (pushing the positive ends of two magnets together, essentially). The temperature of a gas is essentially a measure of the constituent particles' kinetic energy. Higher kinetic energy = higher temperature. 10keV represents enough kinetic energy for the D-T atoms to collide fast enough that they overcome the Couloumb repulsion and fuse together. [1]: https://en.wikipedia.org/wiki/Coulomb_barrier https://en.wikipedia.org/wiki/Coulomb_barrier
- saagarjha 8y agoExcept Wikipedia seems to put the barrier significantly higher, at 100 keV: https://en.m.wikipedia.org/wiki/Thermonuclear_fusion#Temperature_requirements https://en.m.wikipedia.org/wiki/Thermonuclear_fusion#Tempera...
- piannucci 8y agoA system of particles in thermal equilibrium will contain a small fraction whose kinetic energy exceeds the average by a factor of 10. Also, the energy available in the center-of-mass frame of two colliding particles is higher if they happen to be moving in opposite directions. That could give you another factor of up to 2. In any event, I don't think you want your fuel fusing all at once!
- mrpdaemon 8y agoIn addition to this there is also a quantum effect called quantum tunneling [1] which allows for a very tiny probability for particles with insufficient energy to fuse upon collision anyway. [1] https://en.wikipedia.org/wiki/Quantum_tunnelling#Nuclear_fusion_in_stars https://en.wikipedia.org/wiki/Quantum_tunnelling#Nuclear_fus...
- NamTaf 8y agoExpanding on this, this 10KeV temperature is the average of all particles, and there's a distribution around this average. Some will be higher, and thus more capable of colliding with high energy. In addition to that, whether two nuclei fuse is also dependent on how squarely they collide. A glancing blow intuitively allows both nuclei to push each other away a lot easier than if they experience a head-on collision. A graph of the fusion rate such as [1] shows that even at much lower average temperatures, fusion will occasionally happen when two higher-than-average nuclei collide head-on. As the temperature gets higher, this rate increases as more particles have enough energy and less require those head-on collisions. The peak rate for D-T according to this graph is about 70kEv. I can't speak to why the grandparent's link referenced 100kEv, as it's been a decade since I last studied this and I'm very rusty. [1]: https://en.wikipedia.org/wiki/File:Fusion_rxnrate.svg https://en.wikipedia.org/wiki/File:Fusion_rxnrate.svg
- khuey 8y agoYou overcome the natural repulsion between deuterium and tritium and fuse them together.
- rococode 8y agoYou seem to know what you're talking about - do you know what the end goal of the work in this field is? Is it working towards nuclear fusion as an energy source?
- NamTaf 8y agoSustainable high-temperature plasma is what we need to create fusion as an energy source. Current fusion processes rely on pulsing a very short instant of high temperature. This creates a brief instance of fusion, but takes heaps more energy than that quick moment of fusion releases. Thus, it's a net negative of energy. One way to do this that the US uses for nuclear weapons research is to zap a small bit of gas with a tonne of high energy lasers all at the same instant. A high temperature plasma represents a continuous supply of fusing atoms. The current research at ITER, this place, etc. are attempts to create a persistent environment for fusion. If they can do that, then it creates an environment where research can focus on 1) reduce the energy required to hold it at that temperature (which includes limiting how much plasma leaks out, since leaking plasma drops the temperature), and 2) work out ways to extract the energy created by fusion. As I understand (and I could be wrong, it's been years since I last read about it), ITER plans to generate a net-negative energy situation (i.e. it'll never produce energy, just consume it) but hopes to create a sustainable plasma field at temperatures that cause fusion.
- zaarn 8y agoITER will never produce electric energy but they plan to achieve Q=5, ie, output 5 times more energy than put in. The more important work on ITER is work around enabling actual power stations using Q=5 and developing the tech to maintain operating fusion reactors (remote robots, etc.)
- therein 8y agoAt that point can't you just store the output current in supercapacitors for later use anyway? You can even feed it into the machine itself. Supercapacitors easily have better than 20% efficiency for each cycle.
- maaaats 8y ago> "100M degrees" (Kelvin) Off topic, but this distinction made me laugh. Like the difference between Kelvin and Celsius would throw everything off.
- marcosdumay 8y agoWell, there is almost certainly somebody that read the number and thought about Fahrenheit.
- jdironman 8y agoI'm that somebody.
- hkt 8y agoDo scientists use farenheit? Genuine question
- muhbags 8y agoNever. It's either no units (theoretical physics), eV (particle physics) or Kelvin/Celsius for experimental physics.
- ravar 8y agoTechnically there is Rankine if you want to do thermo in imperial units.
- EForEndeavour 8y agoTechnically, Rankine and Fahrenheit are not imperial units.
- godelski 8y agoI've only known engineers to use Rankine and they hate it. I've never known a scientist to use it.
- deleted 8y ago
- phkahler 8y agoDidn't old-school CRT televisions "heat" electrons to more than 10KeV?
- randlet 8y agoI don't know about CRT's but 10KeV is not particularly energetic. A CT unit may operate in the ~100-200kV range (so max energy of 200keV) while radiation therapy units operate in 6MV-18MV range (so electron accelerated up to 18x10^6 eV). I don't know much about fusion, but my guess is the 10keV is impressive because it is a self-sustaining fusion reaction rather than being impressive because of the absolute energy of the reaction? edit: someone down the page mentioned that containment is the issue. In a CRT you are just accelerating an electron across a few thousand volt potential and slamming it into the screen.
- phkahler 8y ago>> edit: someone down the page mentioned that containment is the issue. Right, and that was my understanding. It's easy to accelerate a particle or a stream of them to high energy. It's another thing entirely to contain a gas/plasma at those energies. The distinction becomes more obvious when they flip back and forth between impressive sounding temperatures and simple KeV measures.
- jsjohnst 8y agoConsidering that multiple particle colliders can accelerate particles over 1 TeV (LHC topping 13 TeV), yes, 10KeV isn’t a very high number taken out of context.
- sfjlksjfdldas 8y agoSure, but it costs too much energy to break even (although there are some cute devices that are being researched)
- DennisP 8y agoFusion is easily achievable in your garage. The hard part is getting out more power than you put into it. https://en.wikipedia.org/wiki/Fusor https://en.wikipedia.org/wiki/Fusor
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- agoldis 8y agoOkay, did some search: - When two hydrogen nuclei combine, they produce an enormous amount of energy. That process is known as nuclear fusion. - Light nuclei have to be heated to extremely high temperature, it is challenging to create a controlled, safe fusion reactor that offers more energy than it consumes. Once we have such we’d have a near-limitless source of clean energy. - Nuclear fusion does produce radioactive waste. However, in contrast to fission produced wastes, they are short lived and decay to background levels in a very short time. - Tokamaks try to do just that.
- i_am_proteus 8y agoI will add: - While the products of the fusion reaction are short-lived, operating a fusion reactor will active materials in the reactor and create some longer-lived radioisotopes. - Unlike a fission reactor, which is loaded with months to years worth of fuel, a fusion reactor would have fuel constantly injected. So operator action to stop injecting fuel would stop the nuclear reaction.
- afraca 8y agoCan either you or your parent poster say what "short lived" and "longer-lived" would be roughly?
- perlgeek 8y agohttps://www.quora.com/Does-nuclear-fusion-produce-waste https://www.quora.com/Does-nuclear-fusion-produce-waste says "typically less than 30 years for neutron activated fusion chamber materials"
- Nimelrian 8y agoLonger-lived would be thousands of years for the steel structure until it is manually handable. 50-100 years for remote handling. > It was shown that wait times are required in the order 50–100 years for the remote handling recycling option and hundreds (Li4SiO4) to thousands (Eurofer) years for hands-on handling. Source: https://doi.org/10.1016/S0022-3115(02)01273-4 https://doi.org/10.1016/S0022-3115(02)01273-4
- mrpdaemon 8y agoThe main challenge in working with these high temperature plasmas is confinement. In order to achieve nuclear fusion matter needs to be heated to immense temperature, so that the kinetic energy of nuclei colliding can overcome the electrostatic force of the protons pushing each other away and "fuse" into larger nuclei (held together by the "strong force"), converting a fraction of the reaction mass into a relatively large amount of energy in the process. In order to keep the plasma at the temperatures where fusion can occur, rather extreme measures have to be taken. In the Tokamak approach, the plasma is placed in a toroidal vacuum chamber, and "suspended" in the center of the torus by using electromagnets that line the Tokamak chamber's walls. At such high temperatures the plasma is so energetic that it is very hard to contain such fast moving particles. If the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly cools down to temperatures below where fusion can happen. The immense engineering challenge here is to heat plasma to ridiculous temperatures, and keep it confined in a very small volume at great temperature and pressure to mimic conditions that give rise to nuclear fusion in the center of stars.
- shusson 8y agothis is what Doctor Octavius was trying to do in Spiderman 2.
- b_tterc_p 8y agoThis is helpful. Thank you.
- qwerty456127 8y ago> If the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly cools down to temperatures below where fusion can happen. Sounds relieving. I used to think that «if the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly…» disintegrates everything around or, when the power is huge enough, causes an apocalypse…
- sergiosgc 8y ago
- docker_up 8y agoStories like this scare me. With all of the precautions, even things like Fukushima failed and will poison our ocean for millennia. What happens if we have a runaway fusion process through some pathway that was unexpected? With all the talk about the LHC possibly producing mini blackholes or magnetic monopoles that could potentially cause protons to decay spontaneously, I don't have enough nuclear physics background to know whether we are inherently safe, or if there is a real risk here.
- saagarjha 8y agoSustaining fusion is very difficult (we really haven’t solved it yet!). Runaway fusion is only really possible if you can simulate stellar conditions, which requires extreme amounts of energy that must be fed in continiously to maintain temperature and confinement. Plus, the radioactive byproducts are much shorter-lived, and so pose much less of a risk of causing lasting ecological damage. Also, just as a FYI, the LHC has not produced any mini black holes or magnetic monopoles. Anything of the sort would be a major accomplishment, far surpassing the discovery of the Higgs Boson.
- frob 8y agoThere's most likely not even a risk to the experiment itself from runaway plasma. Experiments like these use very low-density plasma (mBar) so despite being extremely hot, it's a fairly low mass overall of heated plasma. These experiments regularly lose deconfinement of the plasma within the magnetic fields and it collides into the inner walls of the tokamak and cools back down. This is the main thing these experiments are designed to study: how to keep the plasma stable for longer. Even if there were a larger and hotter mass, we don't have the pressure from gravity here that makes fusion work in the center of stars, so it will just kinda melt things and then cool off, if that.
- Quenty 8y agoFusion is not a chain reaction. The energy maintained for this is incredible and it can’t run away. Fusion has no toxic or radioactive bioproducts. As a power source fusion is pretty good, which is why it’s such a target for research. See: http://www.fusenet.eu/node/38 http://www.fusenet.eu/node/38
- argc 8y ago100M seems insanely high, beyond what anything man made would be able to contain. Is it extremely short lived? Or over a very small area? Very interesting.
- saagarjha 8y agoBoth, really. The goal is figure out how to sustain this for an extended period of time.
- NamTaf 8y agoIt is incredibly high. We hold it in not by any material, but by magnetic fields. Plasma has the handy feature of being magnetic. The Tokamak[1] design used in ITER and this example uses a whole heap of magnets to hold this plasma in a doughnut-shaped area. [1]: https://en.wikipedia.org/wiki/Tokamak https://en.wikipedia.org/wiki/Tokamak
- arez 8y agoDoesn't it take a lot of energy to have such a big magnetic field?
- saagarjha 8y agoIt does, which is why most fusion reactions currently produce a net negative amount of energy.
- whatshisface 8y agoFundamentally it doesn't have to, because like a weight resting on the top of a ladder magnetic fields store energy and do not dissipate it. In practice it does because our ways of producing and maintaining strong magnetic fields require a lot of upkeep. This, like most things in fusion, is an example of where the realities of present day engineering are far cruler than the laws of physics.
- philwelch 8y ago> The Tokamak[1] design used in ITER and this example uses a whole heap of magnets to hold this plasma in a doughnut-shaped area. The technical term for a "doughnut-shaped area" is "torus"; "tokamak" is an abbreviation for the Russian for, "toroidal chamber with magnetic coils".
- adtac 8y agoOnce we achieve sustainable fusion, will it be possible to "share" the energy with everyone else to create more independent fusions? Kinda like keeping the candle burning so as to light more candles because matches are too costly. Now, I don't expect politics to allow sharing of fusion energy to help other countries.
- hoffs 8y agoIsn't fusion reactor basically infinite energy, I mean sure it makes total sense to no share it with other because you can sell your free energy for cash, but considering that a lot of global scientists work on it and most of the findings are published, don't think that such strategy would last long.
- Cthulhu_ 8y ago> Isn't fusion reactor basically infinite energy It's probably not that easy; the reactors are extremely complicated and expensive to build, and I'm sure operating them isn't cheap either. And the one thing I haven't heard much about yet is the yield - how much energy can it generate vs how much will it cost to run. I don't think it'll be economically viable. I'll be happy to be proven wrong though.
- SmellyGeekBoy 8y ago> I don't think it'll be economically viable. I'll be happy to be proven wrong though. I don't think current designs like the one discussed here will be. But I'm hoping it will lay the groundwork for much more useful reactors in the future.
- mirekrusin 8y agoNot really, it will wear out due to radiation so you need to change the body periodically, unless you use other fuel like helium-3, but it's got it's own problems - much higher fusion temperature and very rare on our planet (a lot of it on the surface of the moon though, it would be worth mining if we had working reactors).
- 8y ago
- jabl 8y agoAs there seems to be quite a lot of confusion in this thread about what this is, here's an excellent video giving an overview of the state of the art in fusion energy research that is understandable by a lay audience: https://www.youtube.com/watch?v=L0KuAx1COEk https://www.youtube.com/watch?v=L0KuAx1COEk (somebody posted that video on another recent HN fusion thread)
- joosters 8y agoThank you for (re)posting that video, it's an excellent introduction/overview.
- Santosh83 8y agoLet me ask a different question to the knowledgeable folk here. It has been noted that producing the temperature is not the hardest part but confining the plasma for long periods of time is. On this note, do we have any reason to be particularly confident that magnetic confinement will ever break even and produce surplus energy? In nature fusion seems to occur through gravitational compression, so what makes us sure that we can simulate this by other means that will ever amount to more than just demonstrations?
- DrNuke 8y agoBasically we have good enough materials to bear ignition, we need better materials to keep it running long enough for demonstration, we need even better materials to make it approved and viable.
- thinkcontext 8y agoITER is designed to address exactly what you have asked. "The ITER thermonuclear fusion reactor has been designed to produce a fusion plasma equivalent to 500 megawatts (MW) of thermal output power for around twenty minutes while 50 megawatts of thermal power are injected into the tokamak, resulting in a ten-fold gain of plasma heating power." https://en.wikipedia.org/wiki/ITER https://en.wikipedia.org/wiki/ITER
- nickdothutton 8y agoIs it just me, or have we converged on 1 reactor design (the tokamak) relatively early on in the process? I appreciate that funds need to be concentrated in order to have an impact, but we have built dozens of this design since the 1950s, yet here we are.
- majewsky 8y agoWendelstein 7-X in Germany is a stellarator-type reactor: https://en.wikipedia.org/wiki/Wendelstein_7-X https://en.wikipedia.org/wiki/Wendelstein_7-X
- tim333 8y agoAnd YC is invested in Helion Energy using pulsed inertial fusion. Though the tokamak seems closest to being functional. The MIT ARC design is theoretically supposed to be able to work, at least on paper: >The ARC design aims to achieve an engineering gain of three (to produce three times the electricity required to operate the machine) while being about half the diameter of the ITER reactor and cheaper to construct. (Wikipedia) It's not been built because of the $5bn or so cost, though given global warming / saving the planet type issues I'd be happy enough as a tax payer to have governments fund one and maybe knock 1% off the defence budget to counter that. It'd probably do more for world peace than churning out some more f35s.
- DennisP 8y agoARC has some funding now. They spun off a startup called Commonwealth Fusion Systems, which has $50M so far, from an Italian oil/gas company. https://en.wikipedia.org/wiki/Commonwealth_Fusion_Systems https://en.wikipedia.org/wiki/Commonwealth_Fusion_Systems
- pfdietz 8y agoThe ARC reactor would have a net power output of something like 190 MW(e). At $5B, that's $26/W(e), which is an order of magnitude too high, especially given how high the operating costs are likely to be.
- dmos62 8y agoCan someone comment on what kind of economic effect that working fusion reactor technology would have? I hear sometimes contradictory hear-say on the lines of "unlimited energy", "reactor would have to be fed constantly".
- yreg 8y agoOne liter of ordinary seawater would still produce as much energy in a fusion reaction as 500 liters of fossil fuels in a chemical reaction. — random guy on Quora https://www.quora.com/Is-there-a-limited-amount-of-fuel-for-nuclear-fusion https://www.quora.com/Is-there-a-limited-amount-of-fuel-for-...
- Dylan16807 8y agoOh, that sentence is a bit misleading, that's talking about using purely the 0.015% of deuterium in the water.
- aiCeivi9 8y agoEven with free & unlimited source of heat there will be always a cost for generating each MWh.
- quotemstr 8y agoI'm not sure that it would have a profound effect at all. Fission is very power dense as well and fission fuel cost is not the primary driver of overall costs in existing nuclear designs. Fusion might end up looking a lot like fission, but hopefully with a lower perceived safety risk and thus more public acceptance. Granted, modern fission designs aren't actually unsafe, but that doesn't matter for PR purposes.
- conjectures 8y agoAnyone know what the 'standard' and state of the art approaches to inference are for fusion? I.e. going from sensor readings to inference of the plasma state.
- nscalf 8y agoSince I don't see any comments mentioning this, I've heard a lot of talk about skepticism on other forums regarded Chinese scientific breakthroughs. I know on the state level, their numbers are not considered reliable (economic data for instance). Does anyone have thoughts on the reliability of this?
- throwaway857384 8y agoWhat if the discrediting of Chinese data was a type of state propaganda on America's side?
- _Microft 8y agoAs far as I know temperature is one of the important but not the only important parameter. Density and confinement time can be taken into account as well to get a number that better characterizes the performance of a reactor, iirc. Edit: I think this is what I meant: https://en.wikipedia.org/wiki/Lawson_criterion https://en.wikipedia.org/wiki/Lawson_criterion
- stevespang 8y agogravitational compression on the level of what occurs in the stars cannot be achieved on earth - - therefore, net positive fusion will never occur. Why not invest all that money in solar, wind and wave energy instead ? Anything radioactive at large scale seems to always be aligned with government / military industrial complexes.
- rio517 8y agoIf you added one gram of 100M degree material in a 5 sq meter room at 15 degrees C, how hot would the room get?
- emeijer 8y agoWell.. assuming the room is about 3 meters high, that's a room volume of 15 cubic meters. Assuming it's filled with air, and air weighs about 1,29 kg per cubic meter, that's 19,35 kg or 19350 grams of air. 15 degrees C is 288 Kelvin, so that's 19350*288 = 5.572.800 gram-kelvins of energy in the room initially. Now we add 100.000.000 gram-kelvins (the one gram of hot stuff) to it, and assuming this energy distributes over the air contents, our air now has a heat energy of 105.572.800 gram-kelvins. Dividing it back the same way (over the 19350 grams of air) gives us 105572800/19350 = 5456 gram-kelvins per gram of air, so a temperature of 5456 kelvins or 5183 degrees C. Still pretty hot.
- dwaltrip 8y agoI think a gram is significantly more material than fusion reactors need to use.
- creeble 8y agoHow are these results more (or less) significant than the stellerator (Germany) achieved earlier this year? I thought the stellerator had already achieved 100M Kelvin?
- gwbas1c 8y agoI know very little about fusion. Did the reactor produce more energy then was put into it? I just don't understand enough about the field to figure that out by reading the article.
- DennisP 8y agoNo, they've just reached fusion temperatures. It's a step along the way but we're not at net power yet.
- w323898 8y agoFusion was, and for the foreseeable future will be, a boondoggle. In the US it was a cold-war-era arms race program intended to scare the USSR and have them overextend, and now the Chinese are using it for propaganda and scientific Keyensianism. The fact is, fusion generates neutron radiation that destroys the reaction vessel, making it an unviable technology. Nobody takes it seriously as a source of energy, aside from uninformed people. As cool as the idea of controlled fusion is, it is and will remain science fiction.
- voxl 8y agoOh sorry, we didn't realize that you completely understand all of physics and can qualify, without any possibility of error, that any configuration, period, that utilizes fusion will necessarily be impossible because of this physical restriction.
- pfdietz 8y agoFor DT fusion, that's been known for 35 years. It's not just materials, it's power density. http://www.askmar.com/Robert%20Bussard/The%20Trouble%20With%20Fusion.pdf http://www.askmar.com/Robert%20Bussard/The%20Trouble%20With%...
- dbingham 8y agoI dunno, my buddy who just got a degree in high energy plasma physics working on fusion reactors might disagree with you. And really, you just sound like every crank ever who thought X technology was totally unfeasible and always would be -- until it wasn't. So currently attempts haven't found a solution to the reaction vessel destruction problem. That does not mean someone in the future couldn't figure that one out.
- jeffreyrogers 8y agoOP at least gave a reason: neutron radiation destroys the reaction vessel. No one who's responded has given any evidence for why this is false.