Controlling the nuclear fusion plasma in a tokamak with reinforcement learning
deepmind.com
deepmind.com
The best part was the name of our collaborator- "General Atomics" https://en.wikipedia.org/wiki/General_Atomics
Here's a writeup, https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.58...
> determining static settings for a subsequent run.
AFAICT, your software didn't do that. Rather it provided infrastructure for the researchers to do that themselves more efficiently.
From your paper:
> The ultimate goal of FusionGrid is to allow scientists at geographically distributed sites to participate fully in experimental and computational activities...
Exactly what are you saying has been done before?
Profound.
He was merely giving a shameless plug of whatever infra project he was involved in.
Congrats - it involves computers and fusion.
> a previous project that was sort of an ancestor to this
> it's all been done before
implying that the current work build on his work in some way, which I don't see.
I have always wondered if there is a way to detect this particular trait either using MRI or possibly smell. Once you are in a space you can usually identify them because everyone seems to slightly avoid their workspace out of fear of being infected.
Old relays (especially when switching large DC currents) are fantastic for this purpose. The arc will essentially give off a mini EMP across the whole spectrum and woe to you if your gear isn't shielded and grounded properly.
And I say that as somebody who likes dressing up for work.
Making a little effort to blend in is a question about showing respect for your co-workers. But on the other hand, how you dress is self-expression.
If you meet clients have a shirt. For daily coding, dress in what you like.
Several people confirmed that they would probably be biased against applicants for dev positions coming in for an interview in a full on business suit with tie and slicked back hair (think "slick salesman" look). Perhaps not justified or fair, but interesting as a data point nonetheless. N=4 though, so don't take it too seriously.
It was at a time I applied for jobs after university and so I thought, I might wear a collars shirt to the meeting, to get in the mood.
All of my fellow CS students (aged 25-50) were wearing tshirts and generally more casual attire.
The first thing I was asked: Oh, do you study management?
A company I worked for (that I did generally like working for) implemented a suit and tie policy for management and above. It didn't affect me but I started looking for the door immediately and left a few months after.
Don't want to be in a company that is still clinging to 19th century values.
Hygiene is pretty important in the business I work since some of our devices come in contact with drinking water. But I can assure you that hygiene often does not correlate with outside appearances.
Still, we have rules for people that have customer contact because people are still judgemental, even if they are often demonstrably wrong.
Downside for management is that we are only allowed to drink water in our offices and are not allowed to eat outside the cafeteria. With time I have grown to like it that way, even if I am a coffee junkie. But it never smells bad in the office in exchange.
There is still some strange association with cleanliness and neat shirts.
One must not support such a ridiculous look based culture by heart, its instead more a - "I want to reap the benefits & rewards from idiots in awed reference to work uniforms"
Ironically the same happened to the hoodie, after various hackermovies. Wear a hoodie and sit with a laptop, obviously improves your coding ability.
Nice clothes have a reason to exist, determining where that fits in your life or your teams’s life may be worth thinking about:)
That's very specifically about looks.
Yes, there is a distinction, no it is not relevant. Just like to a blind person it would not matter what you wore so therefore 'looks' and 'what you are wearing' are closely related, related enough to both be used in this context.
That's quite the impressive opinion. Do you eat soup with a fork?
How to simulate human connection, attraction and arousal responses? Then we could have bots that are smoother talking and far more preferable to human lovers.
How to simulate human responses to nutrition? Then we could have individualized recommendations for diets, achieving goals like holistic health or muscle definition and addressing issues like diabetes.
The exact precision doesn't seem to be the underlying problem being solve, what matters is being able to craft a stronger understanding of relationships of underlying phenomena that can then be leveraged to product new control theories.
If someone draws a map and it has some streets with the wrong names, you say, "This map is not accurate." It doesn't mean you are talking about something numerical.
In this case accuracy is appropriate :)
Accuracy is about how close to the underlying behavior that is being modeled is. In this case, the goal is modeling the controllers they are using.
Precision is about how stable I can make my controller parameters and how stable they can make the behavior or the underlying fusion.
What they did was changed the fidelity of the model. Rather than parameterizing it using a known controller model (e.g., a PID controller) they used the neural network to fundamentally discover the important parameters that they can understand and how they interact.
The simulation can be accurate or not accurate entirely independently of how much fidelity of the actual phenomenon you model. You need to have a high fidelity model, and that model needs to be accurate, and they behavior needs to be precise and stable.
An example would be how wing profiles in aircraft are simulated/modeled. I can do it in 2D with high accuracy and high precision - it's a GOOD 2D simulation. But its low fidelity. I might be better off with a lower accuracy model of a high fidelity model, like a 3D model that lets me look at how the ends of the wingtip perform as well. Increasing the accuracy of that model might make the results less stable (because numerical techniques...great). A lot of improvements in computing power and simulation techniques have resulted in the ability to simulate systems more completely and learn about the interactions - not just making the simulation more accurate to what it contains.
So this is a good tool for the computationalists but we still need the experimentalists. This is science.
> So this is a good tool for the computationalists but we still need the experimentalists. This is science.
I would say that this is a good example of collaboration between the groups.
Not far off and you want perfect results? Go with actual data. Very far off where it's not even usable? You'd need to go back to the training environment and redo the reward function.
Generally speaking (and I'm not sure if this is the case from reading the link but I may have missed it) reinforcement learning for optimal control is done to fine tune while traditional control methods are used for coarse adjustments. Since this is deepmind they probably want to use RL for everything
There is a video of one of these experiments in the linked blogpost (figure 2), where we show imagery taken from a camera looking into the vessel. Next to it is a reconstruction of the shot, visualised on a cross-section of the torus.
The simulation not perfectly matching reality is indeed a major challenge, and the nature paper is mainly about showing how you can overcome that challenge. As others have said, plasma is a pain to model, and you cannot collect a ton of data on these machines. But it seems technology is coming at a point where we know how to work within these limits and still get it to work.
Do you think this line of research will eventually feed back into improved designs of electromagnets, chambers and so on? My limited understanding of the field is that the optimal reactor design is a moving target that's changed a lot over the years due to engineering improvements in manufacturing, material sciences and so on.
I'm imagining optimizing the plasma configuration, reactor shape, coil/sensor placement and controller all in one giant computational optimization. All the algorithmic components and models humanity needs to attempt this seem to be there.
Stellarators are particularly fun. First you optimize a last closed magnetic flux surface (a 3D sheet) with relatively simple plasma models, then you optimize coils (you need to weight things like magnetic field error, gaps big enough for heating and diagnostics, and coil complexity a la minimum radius), then you perform more accurate simulations to start the overall optimization loop again.
Episode 22 is an intro to fusion power research and tokamaks, but could be skipped if you are aware of the big concepts. Episode 157 is an interview of a director at ITER: the largest fusion power project in terms of scale, ambition, and funding. ITER is expected to demonstrate net energy gain fusion within the next ten years. Episode 157 gives a good sense of where the cutting edge of fusion power research exists currently and its potential place in society. Episode 304 interviews the authors of a recent popular science book on tokamaks. This episode covers the history of fusion power research, and the economics involved in future power plants. Episode 312 is a set of interviews at W7-X: the current largest stellarator. This episode take a deeper dive into what fusion research is like and how threads are being tugged on.
This same podcast also has interesting episodes on plasma physics and superconductors. The superconductor episode is especially worth listening to more than once.
Do you think this approach of controlling plasmas also translates to these types of reactors?
Reading your article I didn't understand a lot of things and wondered if there was some kind of fusion-reactor-physics word-list where the most important keywords are explained a little. (without reading a whole book on plasma physics :-))
Also the timescales are fascinating. How long is 200ms in a tokamak? How long does this reactor need to ignite or shut down the plasma?
- They need large, highly advanced cryocooled superconducting magnets in very close proximity to a hundred million degree plasma. This only makes economic sense in massive, and expensive plants.
- They are a very strong source of fast neutrons useful to transmute cheap depleted uranium into plutonium, so carry massive proliferation risks, need close regulatory scrutiny and will require mounts of paperwork to operate, thus exceptionally inflexible to improvements and rapid iteration. Just like the current fission crop.
- Aneutronic fusion is a currently a purely theoretical concept, in the last 70 years nobody has been able to contain even the much cooler D-T plasma for economically viable durations and temperatures.
- The structure of the reactor becomes radiologically active and cleanup operations must be considered. Highly penetrating neutron radiation means some radiation will escape regardless of containment, requiring a radiological exclusion zone. No Mr. Fusion in your car, sorry.
- They operate and must breed sensitive nuclear materials - Tritium, a well known component of boosted thermonuclear weapons. The limited efficiency of tritium production from lithium-6 might require obtaining some from fission reactors to top up the fuel cycle and keep fusion reactors operating.
So when you draw the line, a life time of magnetic containment research has produced a speculative design that even if it were to work, which it doesn't, would be, in the best case scenario, comparable to existing fission designs that are being phased out for cost and risk issues.
A PhD money pit with zero chance of ever building anything useful. I know it, you know it, I'm ready for the proverbial downvote protecting one's paycheck from their own knowledge.
Citation needed.
There exist purely theoretical models where neutron multiplication is used so that the single fast neutron generated in a D+T reaction can breed more than a single tritium atom when it hits li-6 (which would be clearly insufficient to have a self fueling rector).
It's all a complex mess of absorption cross sections and neutron spectra, dependent on lithium blanket geometries, coolant and structural material parasitic interactions. The tritium breeding efficiency today sits at exactly 0% and until that changes, concerns that it may never reach the required 110% are at least somewhat warranted.
ITER's TBM will be doing important work to test theory.
It isn't clear to me that external sources of tritium will be necessary. Between Li-6 fission and Be neutron multiplication there is theoretically plenty of neutrons to go around even though they aren't easy to capture.
Viability of blanket breeding hasn't been demonstrated to work yet, but my original point is that it hasn't been demonstrated to not work. I see now the "might" in your statement.
My point was that fueling is in itself a very difficult and complex problem that has yet to be solved, far from the "it runs on seawater" popular tropes.
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.
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%20Techni...
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.
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.
- 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.
People, especially mothers were somewhat worried about magic heavy chemical water with different nuclear properties...
That seems a bit dismissive. I would naively assume that there have been exactly zero studies to see if there are any problems with babies drinking heavy water, beyond some LD50 extrapolation.
But there’s tons of inert things that we don’t need to study because it makes no sense.
https://en.wikipedia.org/wiki/Heavy_water#Effect_on_biologic...
From reading that, it seems the mechanisms aren't really understood.
But wouldn't that require aneutronic fusion to be viable? I had thought that the prevalence of neutron radiation otherwise would have made directly tapping the plasma for electricity impractical.
"Side reactions" produce neutrons and gamma rays, and fusion products can get involved in side reactions too, also producing neutrons and gamma rays. If you can keep recirculating the desired reactants, filtering out the products and side products, those reactions can be kept to a low level.
Even better. Helium is a relatively scarce resource, there would be no shortage of people to take it off of your hands.
> If one ton of deuterium were to be consumed through the fusion reaction with tritium, the energy released would be 8.4 × 10^20 joules[1]
That's 0.84 exajoule(233 TWh) per kilo of deuterium or 0.42 exajoule(117 TWh) per kg of helium produced. World energy consumption is 1.6 exajoule per day[2] so less than 4 kg helium will be removed per day if energy extraction is perfect or few 10s of kg assuming imperfection
[1]: https://www.britannica.com/science/nuclear-fusion/Energy-rel... [2]: https://www.statista.com/statistics/265598/consumption-of-pr...
New level of appreciation. Thank you.
Actual fuel fuel estimate: “a 1000 MW coal-fired power plant requires 2.7 million tonnes of coal per year, a fusion plant of the kind envisioned for the second half of this century will only require 250 kilos of fuel per year, half of it deuterium, half of it tritium.” https://www.iter.org/sci/FusionFuels
“Global electricity consumption in 2019 was 22,848 terawatt-hour”
22,848 * 1000 / 365 / 24 = 2608 different 1GW reactors each producing 250kg of helium per year. So 652,000 kg/year if all the worlds electricity was made from fusion or ~3,650,000 cubic meters or ~130,000,000 cubic feet of helium.
PS: Efficiency numbers could wildly change those estimates, but that’s the rough ballpark for electricity let alone stuff like transportation or home heating etc.
The ~300 cubic foot tanks are 9 inches in diameter, 55 inches tall, with about 130 pounds and contain about 1.5kg of helium.
The most important factor.
Helium-3 fusion produces charged particles, which it might be possible to directly harvest as electricity. The He3 fusion reaction has a high activation energy, which is currently unachievable, and there is no Helium-3 on Earth. We'd have to get it from space, somehow. (The movie "Moon" was set on a Helium-3 mining outpost on the Moon.)
D-D fusion does produce neutrons but they're much lower energy than D-T neutrons. Fusion startup Helion is working on a hybrid D-D/D-He3 reactor, saying the combination will produce only 6% of its energy as neutron radiation, low enough so they can do direct conversion.
They've built half a dozen reactors, and now they're working on a seventh that they'll use for a net power attempt around 2025. They recently had a fundraising round led by Sam Altman, and raised $500M with another $1.7 billion of commitments based on milestones.
Surely we are missing something in this discussions?
A couple other fusion companies think they can achieve net power at least, around the same time.
Another choice is fusion of ordinary hydrogen, usually labeled "p" for the proton, with boron, B, thus "pB". But that is even harder to achieve. Still, it is being worked on.
There is no route to commercially viable fusion extracting heat from Tokamak reactors, as any such reactor would need to be enormously bigger and much more expensive to operate than the same-rated fission reactor, which is not today competitive, and gets less so all the time.
Some people hope that something can be learned from Tokamak work that might be applicable to potentially practical designs, but the money is all going to Tokamak, while the others mostly go begging.
Depends on which company you're talking about.
Helion, for a coutner example, is directly harvesting energy out of plasma.
Not the same as "is".
Hellion hopes someday to be extracting more than they put in.
[1] https://en.wikipedia.org/wiki/Heavy_water#Effect_on_animals
(And to point out the obvious, every other liquid apart from drinking water is more toxic when you ingest literal bucketfuls, including harmless household liquids like vinegar, shampoo, ethanol, olive oil.)
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.
Maybe because it's the US cold war blueprint and doesn't require any innovation. To be clear: no public program has used magnetic mirrors for enrichment but they are so cheap/small and so hot that they really are a sure thing. Maybe MRI magnets are difficult to source. I feel like the true answer is not rooted in any technical explanation but rather some kind of political explanation.
If I was a warlord trying to make industrial quantities of weapons grade fissile material in 2022 I personally wouldn't go the centrifuge route, but everyone's a critic.
Keeping our copy of the Oak Ridge source operating, and the current world order destabilized, for those 78My seems difficult; and we anyway have made only a Kg. So, this seems like not a practical way to generate a geopolitically effective amount of Pu-239 or U-235.
So the idea is not to use magnetic mirrors for power generation, but as a DD-fusion-powered cheap fast neutron source. I have a hunch that radioisotope companies and government organizations are doing this right now.
0. https://vant.kipt.kharkov.ua/ARTICLE/VANT_2012_6/article_201...
Nuclear fusion emits neutrons.
If you can soak up surplus neutrons in uranium 238 you can breed plutonium 239.
By design intent fusion does not intend making fission happen. A side effect of the nuclear physics makes fission products, if you want to.
You can make weapons grade fission materials, with neutrons from a fusion reactor.
Regardless of this hypothetical: the fact remains that no part of a fusion reactor increases weapons proliferation risks, unlike a fission reactor. You could plop one down anywhere on the planet and locally source fuel.
If you want a neutron source then you can make one in your basement with a fusor or linear magnetic mirror.
* 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.
Nuclear waste is not actually that dangerous that long. Everyone (including the planners) like to hype it up for their own reasons.
Fusion has many fusion pathways, some of which are pretty light on the dangerous radiation, others that are pretty heavy on it. Most advocates don’t know which one they’re advocating for.
The radiation ‘activates’ and damages the interior of the fusion reactor, making it radioactive. This is not a solved problem yet. It may never be.
Can you elaborate? E.g. Plutonium-239 has a half life of 24000 years. That hardly sounds like "not that long"? Leftover uranium-238 even stays radioactive for billions of years (half life of 4.5 billion years).
But there are other long-lived isotopes, as well. Safe disposal is not a difficult technical problem, but is a political football causing limitless distraction.
Some of these elements have pretty high overall energy levels released in their decay chains (so it’s not just one decay) some less - but sources that are more radioactive are decaying and releasing energy faster, have shorter half lives, and are very dangerous for shorter periods of time.
You can literally buy Uranium 238 ore through the mail and handle it with no more special precautions than washing your hands afterwards and not eating it. It’s seriously fine.
Except in a few spots where it was heavily concentrated, most of the legitimately dangerous stuff has decayed to ‘meh, not that bad’ levels already even at Chernobyl.
It’s still not a good idea to lick it, or spend all your time in the main reactor hall, but give it another 50 years and you’ll probably be able pet the elephants foot on a tour.
Hiroshima and Nagasaki has been fine for awhile. People do tours at ground zero of the Trinity test site.
Some of these elements are chemically active in weird ways, and even without the radioactivity, eating plutonium, cesium, or uranium will be a bad time. Same with mercury, lead, cadmium, etc. so I’m not advocating for being careless with them.
But the idea of a big chunk of radioactive waste being a glowing orb in 10k years is fantasy.
All reactors are still at best early scientific experiment level, and have been for some time.
Fission exists now, and we understand the economics. With all the political friction and the like, the west basically builds no new plants.
So we’d be comparing ‘no clue it’s even possible to build a plant’ to ‘expensive and generally not building new ones’
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-t... [1] en.m.wikipedia.org/wiki/Tritium [2] https://en.m.wikipedia.org/wiki/Decay_chain
But anyway, those numbers sound about right, here's what wikipedia (and their source, 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.
This is a really good question, and as someone who knows nothing about this, here's what I've found:
There's 4 kinds of nuclear waste:
- Very low-level waste
- Low-level waste
- Intermediate-level waste
- High-level waste
You just dump very low-level waste into a landfill[1]. This stuff is basically random concrete, etc. that comes from demolishing a nuclear power plant.
Low-level waste is still pretty boring stuff like clothing and rags that got irradiated somehow, and is 90% of the volume and 1% the radioactivity of radioactive waste[1]. The radioactivity in this mostly comes from atoms with a half-life of less than 5 years, although it seems like trace amounts of slightly long-lasting radioactive isotopes are allowed[2].
Intermediate-level waste looks like it's pretty varied things: sludges, fuel cladding, reactor parts from decomissioning. It's 7% of the volume and has 4% of the radioactivity[1]. Looks like this stuff is generally pretty long-lived: takes about 1000 years to become 10x as radioactive as low-level waste, and 100k years to become as radioactive as low-level waste.
High-level waste is basically spent fuel. It's special in that it requires some kind of cooling, at least for a few decades. It's 3% of the volume and 95% of radioactivity[1]. It can often be re-processed into more fuel. After about 200 years, it becomes about as radioactive as intermediate-level waste, and 100k years to become as radioactive as low-level waste.
[1]: https://world-nuclear.org/information-library/nuclear-fuel-c... [2]: https://en.wikipedia.org/wiki/Low-level_waste [3]: https://www.radioactivity.eu.com/site/pages/ML_LLW.htm [4]: https://www.radioactivity.eu.com/site/pages/HLW_Waste.htm
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.
Certainly, containing fusing plasma magnetically requires developing a much better understanding than we now have of plasma fluid dynamics under conditions of high pressure and complicated, variable magnetic field geometry, but studying plasma fluid dynamics for itself does not need multi-billion dollar equipment. Nobody wants to give plasma physicists a dime just to learn about plasma, even though it would be fantastically cheaper than what is being done instead.
The chart here shows the energy difference pretty well: https://www.nuclear-power.com/nuclear-power/fission/nuclear-...
More fuel + more energy from fuel = superior for most uses long term. If we pull it off.
Fission is already not competitive, so a technology much more expensive to build and operate is even less so. In ten years, solar and wind will be even cheaper than today, and will be supplying most of our energy needs.
(Not every place is Southern California where there are no clouds and the sun shines all year. Solar is cheap in some places, but not at high latitudes.)
Wind does not confine itself to lower latitudes.
Such reactors would also quickly destroy themselves, so would have no opportunity to pay back the investment.
The only hope for useful fusion is if work on existing designs turns out to be applicable to actually practical, aneutronic forms. Current spending on those is negligible.
Consider that the majority of startup companies with apparently good ideas never get to market. People like to think the hardest problem they know of right now is all that matters, but often it is a boring problem that sinks the company. Maybe it is technically solvable, but costs enough to destroy the value proposition.
So long as solar and wind costs are still falling fast, any prediction about the viability of competing tech is at best provisional.
Solar and wind benefit from the opposite effect: there are known problems, but they have lots of known viable solutions that are just competing for which ones (plural) will end up cheapest, or have the most side benefits, or are easiest to deploy.
It used to be that poor round-trip efficiency would sink a storage technology, but generation has become so cheap that losses matter less than other considerations. 50% loss? Build out more panels!
Hydrogen still has awful efficiency, electrolysers and fuel cells need platinum-group metals, and liquid hydrogen needs really rigorous handling, but H2 is so useful that those don't matter. Efficiency and cost will only improve. Ammonia synthesis is similar: super-useful, but maybe easier to make starting with water. (There will be a lot of waste oxygen soon.)
Iron-air batteries likewise have poor efficiency, and low discharge rate, but the material basis is very, very cheap. You can gang up thousands in parallel to get the rate you need, and stick lithium or lead cells on the front to handle load spikes. Useless for cars, fine for utilities.
Liquifying air is very mature tech, so as the basis for a storage medium it's a safe bet. Storage capacity grows with cheap tankage. And, excess LN2 is valuable, so when your tanks are full you still have revenue.
It turns out there are myriad elevated basins that would be perfect for pumped hydro storage, another very mature technology. Unlike hydro generation, you don't need a whole watershed and river valley, just hills with a dip.
Even if fusion fizzles for utilities, the mostly-aneutronic sort might be perfect for outer solar system propulsion, where a completely different set of constraints apply. And, military deployments will often not be able to lay out much solar where they land. So, even though fission is, relative to solar, super-expensive, places can be found where nothing else will do.
Fission (will?) have the advantage of being able to produce energy whenever we need it. Solar or wind need storage. And as far as I know, there are no viable storage solution as of today.
> It turns out there are myriad elevated basins that would be perfect for pumped hydro storage, another very mature technology. Unlike hydro generation, you don't need a whole watershed and river valley, just hills with a dip.
In some countries, all possible places of hydro generation have already been used. What would be the potential for new hydro solutions in Europe for example, where hydro has been exploited for decades? Again, not an expert, but I don't think that there is an obvious path in countries where population density is pretty high and without large swathe of lands, to build hydro storage to be able to produce enough energy on a sufficient long period of time. Curious to know what you think.
Using any sort of battery, based on a chemical process, will also probably have high impact on the environment. Current battery relies on rare earth material or industrial processes that are very impactful. Creating enough batteries to ensure safe power distribution for billions of people will probably be terrible for the environment.
My point is that there is no silver bullet as of now so putting all you eggs in the same basket does not seem to be a sane strategy. Investigating fusion is worth a shot I think.
And if we worry about money, there's plenty of money to go around. We are talking about the survival of civilization here. 16 billions were poured into the a company providing ways to share pictures of your baby to your high school friends ten years ago (yes Facebook). I am sure we can find the money to finance Fusion AND research on energy storage. It's a question of political will. In the end, we'll get what we deserve...
Where an elevated natural basin can be found, that can radically increase the storage capacity from hours to, potentially, weeks, and for even less expense: just the penstock needs to be built. Elevated basins are much more common than the elevated river valleys needed for pure hydro generation. A hybrid approach is to wall up one end of an elevated box canyon: a dam, technically, but inflow is pumped from below rather than drainage from above. There is some construction cost, but radically less per unit volume of storage than a complete tank. Dams with penstocks are extremely mature tech.
While fusion doesn't need containment for radioactive fuel, a reactor must be much larger than a fission plant because the volumetric energy flux density of fusing plasma is enormously lower than of uranium. And, the heat has to be collected by blasting neutrons right through the magnetic coils and into a "blanket" of thousands of tons of molten, radioactive lithium, in pipes all around, the which does need to be contained. People get testy when that much molten, radioactive lithium runs downhill.
The lithium needs to be confined in plumbing which will be weakened by the neutron blast and need to be replaced frequently, but will be deadly radioactive so need to be replaced using robots. That plumbing is really most of the reactor. Probably it should all be underground, so that when it is seen to cost more to refurbish every couple of years than it is worth, it is already buried.
Meanwhile, the lithium needs to be processed continuously to extract transmuted tritium to use for fuel. It is hard to imagine molten lithium processing being as cheap as managing the water and steam in a fission reactor.
Then, you need to move the heat from the lithium into liquid that will not pick up its radioactivity, thence to water for steam for the turbines. And, you need to maintain the steam turbines frequently, same as in a fission reactor.
Contrast this to negligible upkeep cost for solar and wind, which mostly amounts to unbolting and replacing them as they pass two decades of service. Your storage method might need some upkeep, but you chose it for its low cost.
This potentially creates room for fusion that never existed for fission:
- innovation and entrepreneurial pressure. Best case, we get SpaceX efficiency fusion innovators versus SLS pork barrel subsidy patients.
- insurability. Fusion energy production might become privately insurable.
- political support. If the political buyin required is mainly limited to capex, that's a very big advantage versus fission.
As for short to medium term political motivation, one might hope fusion energy research is to benefit from the tension between Russian and western leadership.
This sounds like a great thing for humanity, but humanity's interests are not properly represented by the existing political power structures.
I am not sure if any of the other designs avoid the turbine
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.
I'm reminded of Alastair Reynolds' sci-fi short story "Weather"
<spoilers follow>
The twist of the story is that the alien/incomprehensible starship drives are controlled by an embedded, augmented, disembodied human brain. I've long felt the gimmick was a bit silly because what system would require an actual human brain over a normal control algorithm.
Well...
"It's a monstrosity."
"Not to us," she said sharply. "We see a thing of wonder and beauty."
"No," I said firmly. "Let's be clear about this. What you're showing me here is a human brain, a living mind, turned into some kind of slave."
"No slavery is involved," Weather said. "The mind chose this vocation willingly."
"It *chose* this?"
"It's considered a great honour. Even in [our] society, even given all that we have learned about the maximization of our mental resources, on a few are ever born who have the skills necessary to tame and manage the reactions in the heart of a [star]-drive."
…
"The degree of concentration is quite intense. He can barely spare any resources for what we might call normal thought. He's in a state of permanent unconscious flow, like someone engaged in an enormously challenging game. But now the game has begun to get the better of him. It isn't fun anymore. And yet he knows the cost of failure."
…
"It'll be more like one very long dream. Someone else's dream, certainly, but I don't doubt that there'll be a certain rapturous quality to it. I remember how good it felt to find an elegant solution, when the parameters looked so unpromising. Like making the most beautiful music imaginable. I don't think anyone can really know how that feels unless they've also held some of that fire in their minds. It's ecstasy, Inigo, when it goes right."
"And when it goes wrong?"
Steve Brunton - Sparse Nonlinear Models for Fluid Dynamics with Machine Learning and Optimization