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This is a bit off-topic, but can anyone here explain the expected economic advantages of fusion power over fission? My understanding is that fusion plants woul
by duvenaud 5y ago
This is a bit off-topic, but can anyone here explain the expected economic advantages of fusion power over fission? My understanding is that fusion plants would also use heat-driven turbines, and be pretty capital intensive. Would they fill a different niche, or are they expected to be fundamentally more cost-effective?
- vermilingua 5y agoOpEx > CapEx Yes, fusion is considerably more capital intensive than fission power, but the fuel is just water. You don’t need to worry about digging the fuel out of the earth, maintaining a costly disposal scheme for hazardous waste, etc.
- TheSpiceIsLife 5y agoWhere does tritium come from?
- willis936 5y agoLi6 fission in between the first wall and confinement coils. If you want some details: check out section 3.2 of the ITER research plan. https://www.iter.org/doc/www/content/com/Lists/ITER%20Technical%20Reports/Attachments/9/ITER_Research_Plan_within_the_Staged_Approach_levIII_provversion.pdf https://www.iter.org/doc/www/content/com/Lists/ITER%20Techni...
- sanxiyn 5y agoITER plans to test breeding tritium from lithium. It should work in theory, but there is no practical experience yet. Current tritium used in fusion research is entirely produced from fission reactor moderated by heavy water, and there is only one production facility in the world at Canada.
- duvenaud 5y agoThanks, but is the fuel cost a significant factor in fission plants? And the waste disposal? There's already lots of radioactive material in the ground, after all, for example in uranium mines.
- colinmhayes 5y agoBuilding one power plant is incredibly expensive. Building it again costs less. Building it 1000 times costs much less per plant. We're not building thousands of fission plants because of politics. Fusion might be an easier sell.
- sanxiyn 5y agoThis isn't really true. Yes first of a kind is expensive and there is learning curve, but learning is serial and iteration cycle is long. You can't build 1000 plants in parallel and learn 1000x. Solar power cost is falling fast because iteration cycle is short. South Korea built 28 reactors over 36 years and cost fell 1.5% per year, totalling 40% reduction. Even with this South Korean nuclear power is only about as half cheap as solar power locally (as of 2020), and South Korea is a very poor country for solar power considering its latitude and weather.
- sanxiyn 5y agoFuel cost is not significant, waste disposal even less so. (In fact, usual accounting of nuclear fuel cost includes waste disposal cost. People argue cost is not accounted in full, but as accounted, waste disposal typically costs 1/6 of fuel cost.) In terms of cost, 80% of nuclear power is CAPEX. Among OPEX, about 1/3 is fuel, rest is operation and maintenance. So from total cost, about 6% is fuel, and about 1% is waste disposal.
- ncmncm 5y agoStill, fission operational expense is very, very large when compared to solar and wind, which also have radically lower capital cost. Operational expense of neutron-emission fusion would be radically more than for fission: not for the fuel, but for everything else.
- The_rationalist 5y agoNuclear byproducts storage (let's not call it waste since MOX fuel is the future for humanity) do not cost much, it's not a point that is salient enough to male fusion relevant in any way.
- torginus 5y agoNot an expert, but off the top of my head: - The end product of Deuterium + Tritium is regular, stable Helium, making waste disposal both safe, and cheap - The input of the process, heavy water, while not safe, is way less dangerous than thorium or uranium - The whole process is no way involved with nuclear weapons, making security concerns much less relevant - Since the process produces magnetically charged plasma, steam turbines are not necessary, a solution of directly harvesting energy with electromagnets was proposed.
- systemvoltage 5y agoMissing, arguably the most important factor: It is not a runaway reaction. You don't need a giant pool of water with functioning pumps to mitigate a disaster. There are some newer designs that are self-regulating but surprised to see this is not at the top of the list.
- u320 5y agoIt's not possible to have a runaway reaction in a light water reactor either. The major incidents (TMI and Fukushima) happened as the reactor cooled down. It's just that the power output of the decay heat is enough to cause problems.
- epgui 5y ago(Note that you can drink a lot of pure heavy water without worrying about any health impact. I still wouldn't recommend it, but bad things would be unlikely to happen by accident.)
- retrac 5y agoThere are no proliferation concerns with fusion. You can't make a nuclear bomb with a fusion reactor. They'll be largely free of the nuclear materials and technologies handling and export regulations. Quite a few international deals for fission plants over the years have been scuttled over concerns about misapplication of the reactors or fuel.
- melony 5y agoThere actually is proliferation concerns, maybe even worse.
- remarkEon 5y agoIn what way? Are you implying e.g. materials science advances will lead to non-nuclear weapons proliferation?
- KiwiJohnno 5y agoCan you elaborate? Fusion reactors don't produce any fissionable material.
- ncmncm 5y agoOne is not obliged to turn ordinary, mined uranium into weapons-grade stuff, in a neutron-emitting fusion system, but you could if you cared to. I.e., a nation that had control of such a fusion plant would have little difficulty attaching an enrichment process without interfering with power output. Fortunately, no economically practical power generation system can be built using hot-neutron fusion, so it is an idle concern, but almost all the money being spent on fusion pursues that impractical goal.
- willis936 5y agoIt's an idle concern because fast neutron sources are cheaply available without fusion reactors.
- 317070 5y agoAll of these points are up for debate of course, but: * compared to fission, the nuclear waste management for fusion looks to be done within a human generation, rather than outlast human civilisation. So how you discount the future has a large impact on the trade-off between fusion and fission. * the fuel for fission is uranium, a hard to get and limited resource. The fuel for fusion is hydrogen. Initially only the rarer hydrogen isotopes, but we might eventually get fusion to work for the more common isotopes as well.
- duvenaud 5y agoOkay, but is the fuel a major cost for fission plants? And it's not clear to me how nuclear waste can both be extremely long-lived and also very dangerous that entire time.
- 317070 5y agoFuel is not a major cost right now, but it inevitably will be at some point. Current estimates are that we have 80-250 years of uranium left [0], so we could use a different energy source for the long run. The difference in radioactive danger, is because not all nuclear reactions are treated equally. Tritium decays once, emitting a 0.019MeV beta particle [1]. Uranium creates an avalanche of particles [2] for a total of 51.7 MeV. So it has the leeway to be both more radioactive and to be it for longer. But both the type and energy of the radiation have intricate effects on how they interact with biology and so how dangerous they really are. That said, exactly how radioactive fusion waste will be is a bit a philosophical problem, as nobody knows what the minimal requirements are for a functional plant. [0] https://bettermeetsreality.com/how-much-uranium-is-left-in-the-world-on-land-in-oceans-when-will-we-run-out/ https://bettermeetsreality.com/how-much-uranium-is-left-in-t... [1] en.m.wikipedia.org/wiki/Tritium [2] https://en.m.wikipedia.org/wiki/Decay_chain https://en.m.wikipedia.org/wiki/Decay_chain
- flaviut 5y agoFYI the bettermeetsreality site you link to is SEO spam. But anyway, those numbers sound about right, here's what wikipedia (and their source, https://doi.org/10.1787/uranium-2018-en https://doi.org/10.1787/uranium-2018-en) says: > As of 2017, identified uranium reserves recoverable at US$130/kg were 6.14 million tons (compared to 5.72 million tons in 2015). At the rate of consumption in 2017, these reserves are sufficient for slightly over 130 years of supply. The identified reserves as of 2017 recoverable at US$260/kg are 7.99 million tons (compared to 7.64 million tons in 2015). I wouldn't be too worried right now though, because Table 1.1 in uranium-2018 shows that the known recoverable uranium sources @ $40/kgU grew 50% between 2015 and 2017, and known recoverable uranium sources @ $80/kgU grew 4.6% over the same time period. No one's going to go around prospecting unless they think they can make a profit doing it.
- axg11 5y agoAs the other commenter mentioned, fuel is limitless and the waste product doesn’t need special disposal. This isn’t just a technical advantage over fission, but also a political one. In its current form though, the CapEx for fusion projects is huge. Fusion won’t play a big part as an energy source if reactors take 10+ years to come online and cost tens of billions of dollars. Fusion proponents will argue that costs will come down, but if the political and entrepreneurial pressure to reduce cost isn’t there, fusion will end up the same as fission.
- willis936 5y agoTo tack on to the last sentence: "as long as there is fossil fuel to burn".
- duvenaud 5y agoThanks. So it sounds like you're saying that, unless there is some radically different plant design in the future, that there won't be an economic advantage to fusion over fission, at least in the near term.
- colinmhayes 5y agoWell fission energy would be much cheaper if most of our energy was produced that way. Economies of scale provide huge opportunities that are currently limited by political will. I don't see a reason fusion can't quickly become a large scale source of power, because unlike fission, there would be much less political backlash.
- sanxiyn 5y agoI am sad to report that in South Korea, which produces fission power very well and does excellent fusion research, the leading anti-nuclear activist (also a member of congress) is vocally against fusion and already proposed to cut 100% of fusion research budget in 2018. (People thought that's too extreme so she haven't repeated it so far, but I don't think her position changed in any way.)
- conradev 5y agoHelion is trying to capture the energy directly using the magnetic confinement field instead of a heat-driven turbine I am not sure if any of the other designs avoid the turbine
- KiwiJohnno 5y agoA completely different approach to fusion that may or may not work but can do direct generation of electricity without a turbine is pollywell fusion
- ncmncm 5y agoBut, even less is being spent on that than on other aneutronic designs, which themselves are on shoestring budgets. Theoretical reasons make it seem like an unpromising avenue.
- willis936 5y agoConfinement approaches aren't inherently neutronic or aneutronic. What matters is the temperature, desnity, and confinement time (lawson criterion). Get it sufficiently high then DT becomes a breeze. Get it a factor of 500 higher and pB11 is on the table. No one serious talks about aneutronic fusion because we need to walk 1 mph before we sprint at 500 mph. We'll seriously discuss aneutronic fusion in 200 years when it's relevant.
- willis936 5y agoWhich will never work because of conduction losses in the coils. You can't just put solid materials inside your confinement volume and expect to make power.
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- anonymousDan 5y agoI think the main advantage of fusion is they are not susceptible to Chernobyl style meltdowns line fission reactors.