12 ms·
Can someone explain to a lay person what they accomplished and what it means for nuclear fusion as an energy source?
by tarr11 4y ago
Can someone explain to a lay person what they accomplished and what it means for nuclear fusion as an energy source?
- Tuna-Fish 4y agoIt's easy to trigger some fusion in a D-T mix. As in, an enterprising high school student can do it on his tabletop with parts mostly scavenged from tube televisions. The problem is that the fuel mass that undergoes fusion has a lot of mechanisms for energy loss, which mean that you need to continously apply a lot of energy into the system to keep it going. "Ignition" refers to achieving conditions where the energy output of fusion matches the energy loss from the hot spot. In this situation, it is no longer necessary to feed in energy to keep the reaction going, so long as there is sufficient fuel.
- acidburnNSA 4y agoNuclear engineer here, I can try. Before you get cosmic energy out of nuclear fusion fuel (usually isotopes of hydrogen), you have to put a bunch of energy into the fuel to get it into fusion conditions. Namely, you have to heat it up and compress it so the nuclei get close enough to fuse (after which they'll release energy). There are a few milestones along the way to commercial fusion energy: * Get more energy out of a fusion fuel than you put into it * Get more energy out of fusion fuel that it took you to make the energy you put into it * Build a way to capture the net gain energy and convert it into electricity * Demonstrate the integrated power plant as a prototype system * Build and operate the first commercial power plant * Assuming good economic and technical performance, start building a fleet * Deal with fleet scaling issues * Profit! This is a celebration of the first bullet.
- zikero 4y ago> * Get more energy out of fusion fuel that it took you to make the energy you put into it What does that mean if the cost of energy is 0 ? (e.g renewables)
- aaronblohowiak 4y agoThen why build a fusion reactor?
- giantrobot 4y agoThere's a few reasons as I understand it, the power output can be on the same order as a nuclear fission plant. So a single plant taking relatively little real estate can output gigawatts of power to the grid. The fuel is abundant to the point of being practically unlimited. The fuel also needs little in the way of refinement and is not hazardous. A fusion core is naturally fail safe since energy and fuel need to be constantly applied, an accident might destroy a core or plant but not irradiate the surrounding countryside.
- prox 4y agoIt could quite literally save the world in terms of clean energy. I can understand why one would at least try.
- ncmncm 4y ago100% false. As with fission, most of the operating costs would have nothing to do with buying fuel. Solar and wind power suffer none of these costs, so fusion, like fission, would be wholly unable to produce power at a price anyone would pay without being forced to. The fission plants still operating will find themselves increasingly unable to produce power at a price anyone will pay, so will be mothballed long short of their design life.
- ehvatum 4y agoGenerating electricity from sunlight and wind is anything but free. I prefer to pay $0.12/kWh for nuclear energy, as compared to $1.75/kWh for wind or solar, in fact.
- 4y ago
- UIUC_06 4y agoVery well said, thanks. After you do 90% of the work, you have to do the other 90%.
- ncmncm 4y agoOr, in this case, the other 90000%. This result does not bring us any nearer to civil energy production via fusion.
- quickthrower2 4y agoGood old fusion! Under such pressure. Does JWST have to result in a commercial application?
- UIUC_06 4y agoI think the general hostility is a reaction to the hype that "this breakthrough means we're closer to an infinite source of cheap, clean energy." It clearly does not. I can understand the researchers feeling unable to tell the press, "Look, this is just basic research. Like the JWST." It might lead to a massive reaction that "well, then you have to just get in line for those basic research dollars, instead of being a top-priority thing we throw money at." All those research dollars they'd be giving up!
- jjk166 4y agoThe JWST cost about 3 times as much as the NIF. The annual budget for the NIF is about the cost of 6 F-35s, which the US is acquiring 152 of in FY2022. It's not getting top-priority money.
- UIUC_06 4y agoOK, I don't think comparing research to the defense budget is at all useful, but comparing JWST research to fusion research IS. So I'll stand corrected on US money. However, ITER is a global effort, so it isn't just the US budgets we have to consider, right?
- ganzolo 4y agoExcellent explanation. Thank you!
- prox 4y agoMaybe seen to many sci-fi, but can a fusion reactor go out of control and fuse any atom it comes in contact with? I mean with more energy going out than in. Sounds a bit like a nuclear reactor.
- pfdietz 4y agoThe main way they seem to go out of control is in the schedule and budget.
- ncmncm 4y agoThe thousands of tons of molten lithium needed for useful operation would, if ever exposed to air, prove extremely difficult to put out. That would be what they might call an "expensive setback".
- prox 4y agoWhat happens if its exposed to air?
- ncmncm 4y agoThere are some great videos on YouTube about how alkali metals behave in contact with air or, for extra amusement, water. Those don't generally present superheated, molten alkali metals.
- Ekaros 4y agoIt burns very hot. Also water won't help you. On other hand amounts used are relatively minor so it isn't massively bad issue.
- pfdietz 4y agoMolten lithium (or Pb-Li) probably won't be used in magnetic fusion reactors, because the magnetic forces from induced currents in the flowing metal would cause unacceptable pressures to develop. There was hope that insulating coatings for metal structures could be developed to deal with this, but apparently even small cracks are too much.
- the8472 4y agoIs commercial ICF realistic though? Each shot needs a carefully prepared fuel pellet. To get commercial power they'd have to fire a shot per second or so. That seems like a really expensive manufacturing operation to keep it going.
- acidburnNSA 4y agoThere is an incredible dichotomy that I learned about from David Deustch, which is that things are either: a) ruled out by the laws of physics, or b) possible. Commercial ICF is in the latter category as far as I can tell. In other words, maybe?
- magila 4y agoWhile obviously true, I think it's also useful to distinguish where items in category b fall on the spectrum from "this will be commercially viable with minor refinement" to "this is three orders of magnitude away from commercial viability and we don't even have a theoretical path to get there". AFAIK energy generation with ICF is much closer to the latter than the former.
- panick21_ 4y agoNot sure I agree. Fusion solves non of the problem of fission actually has. - Will Capx be lower compared to a advanced fission plant. Almost certainty not. - Will Fusion plan be significantly cheaper to fuel. Almost certainty not, uranium and thorium are available in waste quantities. - Will it solve proliferation concerns? No, if you have a control of a fission reactors you have the potential to do all sorts of things. - Will it solve the nuclear waste issue. Maybe slightly but advanced fission can produce waste that need to be stored for around 300 years and that is not actually that difficult. And that is of course if you assume that the 100s of billions in investment required will not have be be paid back in any way. That is partly fair because fission didn't have to do that either, but there the investment is shared with nuclear weapons (for better or worse). So I would say its closer to the second suggestion. I don't see a theoretical path of how a fusion reactor can be built cheaper then a comparable fission reactor. But I'm not a expert on fission, I have heard of some fission that could be built very small but all actual real designs for suggestion of commercial fission I have seen do not fall into that category.
- tomp 4y agoHas the first bullet (“ignition”) been achieved before, or is this the first time?
- oofbey 4y agoThis is not the first time. But it’s the biggest net gain so far by a good wide margin. Still a very long way to go before becoming similar to a fossil burning power plant. They got equivalent of 1 megawatt for a single second. A typical coal plant is hundreds of megawatts continuously.
- _ph_ 4y agoYes it has. For example JET achived 16 MW of fusion power output in 1997. (https://en.wikipedia.org/wiki/Joint_European_Torus https://en.wikipedia.org/wiki/Joint_European_Torus) Its successor, ITER is supposed to produce more energy than used in creating the fusion process. It is still under construction in France.
- alok-g 4y agoThanks a lot! I vaguely recall reading a long time back that managing the emanating free neutrons was also a challenge. Has that been solved?
- ncmncm 4y agoVery far from: no one is working on it. They know it would be a waste of time.
- ivoras 4y agoThanks for the great explanation! Would you mind answering a layman's question on where the energy comes from in fusion: my understanding is that the problem here is that energy has to be put in to overcome electromagnetic repulsion between atom nuclei so that the strong force can take over and combine them into a new nuclei, releasing energy at that time. Is this interpretation correct-ish?
- einpoklum 4y agoSomewhere between the second and fourth bullet you need to significantly limit the process' energy overhead (almost certainly, heat) to something manageable at scale. If you can't do that, then a net gain is not good enough: If you can power a town but boil a lake's worth of water with the excess heat, that's not much of a viable process.
- danans 4y agoHere is a video by Sabine Hossenfelder explaining exactly that: https://www.youtube.com/watch?v=LJ4W1g-6JiY https://www.youtube.com/watch?v=LJ4W1g-6JiY