Compact nuclear fusion reactor is 'very likely to work,' studies suggest
nytimes.com
nytimes.com
Here's a video lecture from the MIT Professor (Dennis Whyte) who was leading the research group that provided some of the key designs for the SPARC reactor. As the NYT article explains, that research has been spun out into a startup that raised $200M.
The key breakthrough is the advancement of REBCO tape superconductors which allow you to (1) generate record breaking magnetic field strengths (2) easily disassemble the super conducting loop for fast repairs / refuels / more modular design.
It's a long talk, but it's extremely fascinating. Basically everything becomes much easier once you can increase the magnetic field strength. This talk is fairly accessible to even relative laypeople who have a vague understanding of E&M physics.
https://www.youtube.com/watch?v=L0KuAx1COEk
He goes into detail about SPARC as well and why a higher magnetic field using HTS superconductors enables performance that can otherwise be obtained by greater size as ITER is trying.
00:01:00 - introducing Dennis Whyte, MIT department head for nuclear science
00:04:24 - presentation starts
00:06:00 - identifies breakthrough with REBCO magnets
00:07:25 - explains deuterium-tritium fusion
00:12:30 - basic metrics for reactor performance
00:17:15 - energy output of other previous fusion experiments
00:19:00 - examines ITER and the problems of its approach
00:22:00 - problems solved by high energy magnetic fields
00:28:15 - full scale reactor concept, teardown of REBCO magnets
00:37:00 - design limits and margins
00:39:00 - fixes plasma instabilities found in weaker magnetic chambers
00:40:00 - maintainability, lifespan, component replacement
00:45:00 - solution to neutron damage and energy capture
00:50:30 - cost and profitability
00:54:00 - full graph of field strength vs reactor scale (and thus funding requirements)
01:01:50 - Q&A
01:30:00 - question about the biggest risks
Also a more recent video, with more numbers and even more confidence than the first: https://www.youtube.com/watch?v=rY6U4wB-oYM
Looks like they 'only' need to be at 4.2Kelvin as well to operate, which is a definite improvement
Important decisions about the future development of atomic power must frequently be made by people who do not necessarily have an intimate knowledge of the technical aspects of reactors. These people are, nonetheless, interested in what a reactor plant will do, how much it will cost, how long it will take to build and how long and how well it will operate. When they attempt to learn these things, they become aware of confusion existing in the reactor business. There appears to be unresolved conflict on almost every issue that arises.
I believe that this confusion stems from a failure to distinguish between the academic and the practical. These apparent conflicts can usually be explained only when the various aspects of the issue are resolved into their academic and practical components. To aid in this resolution, it is possible to define in a general way those characteristics which distinguish the one from the other.
An academic reactor or reactor plant almost always has the following basic characteristics: (1) It is simple. (2) It is small. (3) It is cheap. (4) It is light. (5) It can be built very quickly. (6) It is very flexible in purpose ("omnibus reactor"). (7) Very little development is required. It will use mostly “off-the-shelf” components. (8) The reactor is in the study phase. It is not being built now.
On the other hand, a practical reactor plant can be distinguished by the following characteristics: (1) It is being built now. (2) It is behind schedule. (3) It is requiring an immense amount of development on apparently trivial items. Corrosion, in particular, is a problem. (4) It is very expensive. (5) It takes a long time to build because of the engineering development problems. (6) It is large. (7) It is heavy. (8) It is complicated.
The tools of the academic-reactor designer are a piece of paper and a pencil with an eraser. If a mistake is made, it can always be erased and changed. If the practical-reactor designer errs, he wears the mistake around his neck; it cannot be erased. Everyone can see it.
Anyone could have said similar things about computers in 1953, and been just as correct.
Are nuclear reactors computers? Of course not, and neither have practical reactors kept pace in development with practical computers.
But neither is it inevitable that steady progress cannot grind down the latter set of characteristics into the former. Indeed, that's what I would bet on, and I think the Admiral would be disappointed in the progress we have(n't) made.
Many people could say similar things about software in 2020 and be just as correct. :) The good Admiral may be describing some timeless aspects of engineering, possibly related to the recently discussed observation that reality has a surprising amount of detail: https://news.ycombinator.com/item?id=16184255 .
Though, as you say, over time engineering can grind out some of the practical into practice.
Vaporware is a real problem in every discipline.
For fusion, you need to achieve a high temperature. So "thermal insulation" of the centre of the plasma from the edge of the plasma is really important. The nice thing is, that since charged particles move along magnetic field lines, and magnetic field lines never cross each other, the thermal insulation of plasma made from charged particles is enormous. That would imply it is really easy to achieve really high temperatures.
However, in 1953 they overestimated the enormous "thermal insulation" at higher temperatures by 10 orders of magnitude. That is a ratio of 1e10 between the expected and the actual value. It is still enormous, mind you, but not that enormous.
If that estimation had been correct, we would have had fusion by 1973. However, in that period it gradually became clear that fusion that way was not going to happen as people found lower and lower thermal insulations in their plasmas.
The same thing might have happened with semiconductors. What if the thermal noise were off by 10 orders of magnitude at smaller scales, compared to what was expected in 1953? Computing would not be where it is today, although it would definitely still be a good possibility if we were only pushing harder in circumventing the noise.
1. It is simple: no, nobody says here that fusion is simple.
2. It is small: well, this one is small compared to ITER, but nobody's saying it's small in an absolute sense.
3. It is cheap: sure, compared to the billions and billions poured into ITER, this is dirt, dirt cheap, but still, they have secured $200MM so far, and they will need more money until they build an actual reactor.
4. It is light: really not applicable here, since nobody's thinking of putting these reactors in submarines (which is what Rickover was really talking about).
5. It can be built very quickly: sure, the time horizon is less than the perpetual 30 years of the old fusion reactor proposals, but it's not going to be "very quick",
6. It is very flexible in purpose: no, for the time being, something that just works is fine, nobody cares about flexibility,
7. Very little development is required, it will use mostly off-the-shelf components: nope, there will be plenty of very custom made components developed for just this purpose, and lots and lots of development are required.
8. The reactor is in the study phase. it is not being built now: it is both in the study phase and being built.
In the end, what was Rickover's agenda: some people were competing with him for government funding for nuclear reactor R&D in general, and for naval nuclear reactors in particular. All those people were a nuisance to him, he had to go and plead for funds again and again, so he decided to write this letter to put this thing to rest once and for all. He managed.
But here it's fusion. Commonwealth Fusion is privately funded, they are not looking for government funding, and they are not making inflated representations to the public. They are actually keeping a low profile in general. The message of this article is simply "this time there is a glint of hope", nothing more.
https://en.wikipedia.org/wiki/Hyman_G._Rickover#Safety_recor...
First, the context. Rickover needed to get a reactor designed, series built, and operated right away. In that context, he was absolutely right.
Second, the PWR design works and it works very well for submarines. I don't know that there has been a better design concept for submarines (the USSR built a few liquid metal cooled reactors which caused them lots of problems). When you have a basic design that does work, then going ahead and building it is the right thing to do.
We can see the consequences of what that approach does to earlier stage research programmes as well because some of Rickover's people were put in charge of Argonne's reactor research programme which they did not understand and where they caused an immense amount of trouble by trying to duplicate this approach in a context where the basic approach had not been definitively decided. This lead, for instance, to spending an enormous amount of money and time pursuing an oxide fuel fast reactor concept despite being warned that there were fundamental problems with that design and that spending more time up front on metal fuel design work would be a better idea. They didn't want to hear it - oxide fuel works (which it does - in thermal PWR and BWR reactors) - so go with that and just build it.
Rickover was right of course about the principle of understanding technological predictions in the context of what we would now call Technological Readiness Levels and optimism bias but in understanding this we also have to keep in mind the other side of the coin which is not to entirely commit to premature optimisation.
> (3) It is requiring an immense amount of development on apparently trivial items. Corrosion, in particular, is a problem.
The design has molten fluoride salt circulating in a strong magnetic field. Molten salts, unlike molten metals, have low (but not zero) conductivity.
But the motion will still induce a voltage drop across the salt. If the walls are metal, there is the possibility of galvanic corrosion due to this potential. And there's the possibility that radiation could enhance this corrosion.
"Although many significant challenges remain, the company said construction would be followed by testing and, if successful, building of a power plant that could use fusion energy to generate electricity, beginning in the next decade."
In other words, "very likely" in this case means "if several roadblocks are overcome, it might be a net-positive power generator in a decade". Even so, this is still exciting given how anemic advancement in the fusion space has been for 50+ years.
At the top of my list for when I'll be king for a day is - massive, national-scale investments (think: reaching towards one percent of GDP) in fusion research.
This is a major roadblock, but things look awesome on the other side. We just need to get our stuff together to hop over this fence somehow.
You then burn it, returning it to the atmosphere.
Net CO2 impact = zero.
We could extract carbondioxide from air, turn it into hydrocarbons and burn that all day/year/century long but producing it from fossil sources is what makes it so bad.
[0] https://en.wikipedia.org/wiki/Greenhouse_effect#/media/File:...
Fusion just replaces the radioactive bit, you still need steam/electricity conversion/transmission/cooling... it's not like a suitcase you can plug wires into, you still need a massive 'factory' to make electricity, just the one bit is a safer.
Also, nuclear fusion is possibly the cleanest energy source we could get. If we touch this, we might have a real path forward.
Furthermore, not only was solar power borderline non existent when those reactors were built, it is also still intermittent. You are just glossing over the biggest challenge of energy - balancing the powe grid. No-one needs energy if it's only avaliable at the wrong time. Energy storage multiplies cost of renewable electriciry several times over, and no country-scale grid has ever operated on wind and solar.
Lastly, energy is actually cheap - you can see that because we can afford transporting a pair of jeans 4 times across the world in the process of manufacture. We could have had zero-carbon grid since the 70s with nuclear - and France did. Even though France has cheapest energy in EU, suppose energy would be 30% more expensive. So what? We would be so much better off in terms of climate change.
24/7 365 grid scale battery backed and thus load following solar runs about 8c/kWh* which is cheaper than nuclear at high utilization. Sure, France’s model of importing and exporting significant chunks of electricity allowed them to ramp up nuclear, but they where exporting power at a loss and utilization still fell into the 80% range.
*Excluding the most northern and southern areas.
We are really talking about a handful of countries. The Nordic countries have cheap alternatives in hydroelectric, wind and geothermal energy. Nuclear may have a few niche applications for northern islands etc, but that’s not really significant globally.
PS: 4% of the UK’s electricity comes from solar and their southern tip is a actually quite decent for solar.
well, that's silly: sunlight is cheaper than uranium.
If just 10% of the resources poured into nuclear development, which is a cost no one that is pro nuclear wants to tally into the bill, were instead invested into solar energy, nuclear power would not have been able to compete with solar power by 1980.
Nuclear power isn't cheap, unless you ignore the insane R&D that was paid for by tax payers by government mandate and never paid back, unless you ignore the massive cost of construction long before one watt of power is produced, and unless you ignore the massive cost of decommissioning, and unless you ignore the never ending cost of spent fuel storage. It is entirely absurd that you believe once a spent fuel storage facility is built, the costs just disappear. The costs never go away. Maintenance. Security. Testing. It isn't free and it isn't cheap.
You keep repeating this idea thay uranium is expensive, by what metric? Where do you get the idea that its expensive?
If nuclear is so expencive, why does France have cheapest elecrticity in EU? And Denmark /Germany have invested in renewables have expensive electricity.
But you raise a decent point about what metric we should choose... I meant the cost of the stuff, but there are other metrics, such as clean up costs, because mining uranium is not clean. There is also a human health cost to populations within the proximity of the uranium mine.
French electricity is likely cheap because the French tax payers already picked up the cost of constructing spent fuel storage facilities and power plant construction, and they will ultimately shoulder the burden of the cost of decommissioning. This is just an educated guess, because that is usually how nuclear economics work. Otherwise, the investors that run the plants and sell the electricity would not be interested.
One failure of Banqiao Dam killed an estimated 240,000 people. That's more than all people who have ever died from anything to do with nuclear, reactors and bombs combined.
Air pollution kills about 2,000 people every single day.
Reactor incidents are like plane crashes - they get attention. Fissil fuels are like car crashes - they kill more people every day and noone gives a shit.
Pripyat is an animal and vegetation haven. Really shows how dangerous our species is to the planet.
Point is, nuclear power plants, even the old ones, are nowhere near as dangerous as the media portrays them.
It is true that today's reactor designs are much safer than RBMK, but I will prefer the reactor can can't go supercritical to one that can any day, especially if it's nearby.
Newer design's can't go supercritical.
Quote: Radioactive fallout from nuclear weapons tests probably caused 17,000 cancer deaths in the United States in the latter half of the 20th century
And if anything, that shows how bad nuclear weapons are, not the power plants.
McBride and his co-authors estimated that individuals living near coal-fired installations are exposed to a maximum of 1.9 millirems of fly ash radiation yearly. To put these numbers in perspective, the average person encounters 360 millirems of annual "background radiation" from natural and man-made sources, including substances in Earth's crust, cosmic rays, residue from nuclear tests and smoke detectors.
https://www.scientificamerican.com/article/coal-ash-is-more-...
Sorry, this is just misinformation. Residual radiation worldwide from nuclear testing or Chernobyl is minuscule. We wouldn't even be able to detect anything if we didn't have incredibly sensitive instruments.
The sun is a much larger daily source of radiation. Or a banana.
That’s a significant percentage of total reactors ever built including what was considered a safe design. We could go 1000 years without another incident, but from an insurance standpoint what would you charge a new power plant next to NYC? That means you need them in an a less expensive area, but everyone feels their area is valuable. That causes vast NIMBY issues and heavy regulation.
In theory modern Nuclear should cost less and be both clean and safe, but people gonna people both inside and outside the industry.
Have you ever been near a coal ash pond? You probably haven't because it is an extreme health hazard to get anywhere near it, as it is full of mercury, arsenic, heavy metals and occasionally radioactive slurry.
There about a thousand of these ponds in the US alone totaling maybe 100,000 acres. Meanwhile all the nuclear power plant waste ever produced could fit into a single large hangar...
The Chernobyl exclusion zone is 1,000 square miles. Fukushima had a much smaller exclusion zone but Estimates of radioactivity released ranged from 10–40%[163][164][165][166] of that of Chernobyl. The significantly contaminated area was 10[163]-12%[164] of that of Chernobyl.[163][167][168]
On 12 October 2012, TEPCO admitted for the first time that it had failed to take necessary measures for fear of inviting lawsuits or protests against its nuclear plants. That’s the core issue not physics.* ... A 2008 in-house study identified an immediate need to better protect the facility from flooding by seawater. This study mentioned the possibility of tsunami-waves up to 10.2 meters (33 ft). Headquarters officials insisted that such a risk was unrealistic and did not take the prediction seriously. The U.S. Nuclear Regulatory Commission warned of a risk of losing emergency power in 1991 (NUREG-1150) and NISA referred to that report in 2004, but took no action to mitigate the risk.[149] https://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disa...
France and the US have a solid nuclear track record, but so did Japan.
Fission’s primary form of shielding is generally large pools of water or other coolant which don’t directly become radioactive. Fusion on the other hand needs to maintain a near vacuum so your pressure vessel is under heavy neutron bombardment. However, small amounts of radioactive materials get dissolved in the fission’s water which the goes on to contaminate the primary coolant loop which increased decommissioning costs. Fusion reactors primarily containment vessels becomes extremely radioactive and all the remote handling equipment also needs decontamination, but it’s unclear if the primary coolant loop will need similar types of decontamination.
And by small amounts, divers occasionally go in the same pools storing years of spent fuel rods. https://en.wikipedia.org/wiki/Spent_fuel_pool
Running the numbers the real difference is fission reactors need more protection from the outside world and containment for a potential meltdown. Thus thick though still fairly cheap walls, which generally don’t become radioactive. They last for 50 years and don’t actually cost that much to construct. Fusion however is a vastly more complex device which will also increase construction and decommissioning costs.
It would help to actually watch the presentations. They’ve solved a lot engineering problems from Routine maintenance to blanket Renewal.
But.
The fusion produces neutrons.[1] That means that at least some parts of the infrastructure can't avoid becoming radioactive. Decommissioning -- at the very least -- is still a problem.
Any actual nuclear physicists want to chime in here?
[1]Yes, the concept of "Aneutronic fusion" exists: <https://en.wikipedia.org/wiki/Aneutronic_fusion>. But read the parts about the required conditions being much more extreme than D-T fusion.
There is significant effort put into using lithium blankets to create tritium at which point arguably the fuels are lithium and deuterium. But that’s also going to require irradiate the relevant equipment.
At scale it’s significantly cheaper to produce.
https://www.fastmarkets.com/commodities/industrial-minerals/...
A 1 GW(e) reactor would burn enough tritium in a year that, if that quantity were to be released into the environment, it could contaminate 2 months worth of the flow of the Mississippi River above the legal limit for drinking water.
Tritium containment at a fusion reactor will have to be damned near perfect. This will be a major problem, as tritium permeates through all sorts of things (for example, plastic seals on containment penetrations cannot be used).
Unlike fission power plants there isn’t going to be years worth of the stuff on site. For one thing 5% of the stuff decays sitting around so you want a tight loop of production to consumption. Further, the reactor is holding low density plasma so there is very little inside at any one time.
That's not how it works. A low molecular weight gas anywhere below the homopause remains well-mixed, and does not separate by molecular weight. On Earth, that's anywhere below 100 km altitude.
As a beta emitter it’s blocked by just a few feet of atmosphere thus rendering the bulk of it harmless. Eventually, some will combine with oxygen and end up as water, but again most of that just ends up in the ocean.
Once in the troposphere, hydrogen of any kind will be oxidized to water within a couple of years, and then rain out. Of more concern would be accident processes that would cause it to be oxidized immediately. For example, any fire or exposure of hot materials to air would cause associated tritium to react.
This is all unrealistic anyway, since the plant will not have 100 kg of tritium on hand at any time. That's about the amount consumed in a year, but the reactor could not afford to have any substantial amount sitting around, decaying, or else the breeding ratio will be too low.
Anyway, for a more detailed description of what I was expecting. A least initially it’s going to act just like hot air. Hydrogen’s is 7% the density of air so Tritium is presumably 21% the density of air. Which is similar to air at 2000f without the particulate matter of smoke.
About 100kg should be roughly 500 cubic meters depending on temperature, but a more reasonable limit of ~10kg is still close to 50 cubic meters of gas. If we are talking a sudden release from say a pressurized tank rupturing outside that’s going to from an invisible but mushroom shaped blob and rise. Where a detonations mushroom cloud stops rising as the temperature cools, this thing only slows as it mixes with air which isn’t that fast. The troposphere is only ~8miles up so it’s likely to reach the stratosphere mostly intact.
If we’re talking a venting pipe or something that releases gas more slowly then you get much faster mixing. However, baring the slowest of leaks we are still likely talking going up hundreds of feet at a minimum and more likely miles before it dispersed enough to act like the rest of the atmosphere.
In the absolute worst case, you still get a lot of vertical mixing of the atmosphere from thermals and rapid dispersion from the wind which doesn’t slow down. Within days you’re talking thousands of cubic miles of atmosphere. So, a short term evacuation of those down wind might happen, but they should be able to return in days.
Nuclear fusion in the existing designs absolutely needs Tritium as one component of fuel, and Tritium can so far only be produced in Uranium reactors, in very small quantities and at an extremely high price.
This surprises me, for a number of reasons.
A fission reactor can be operated safely by a bunch of people with baccalaureates, whereas a fusion reactor will need PhDs, as I understand things. Also, its capacity factor will not be as good as that of fission reactors.
The waste from fission reactors can be made pretty small by reprocessing and in-reactor transformations. The radioactive waste from fusion is whole reactor vessels, which are large and difficult to handle (=expensive).
At commercial scale fusion reactors need ancillary fission reactors to manufacture the tritium they require. So you have two reactors instead of one.
Other factors look similar, except that fusion will carry an investment risk premium because of its novelty and complexity.
So under equivalent regulatory regimes it seems to me that fusion would cost as much or more than fission.
Can you explain why it might eventually cost less?
D is already cheap and even used by fission reactors. Extracting T from the blanket is presumably inexpensive, and one of the things ITER will test, but that’s an unknown. https://en.wikipedia.org/wiki/Breeding_blanket The real question is how expensive the physical reactor is going to be to build and maintain and does that offset the other savings. It’s expected for that cost to drop over time which is why it’s possible to eventually be cheaper than fission.
Finally, DT is easiest to achieve at a 50/50 ratio but DD fusion still takes place. So a lower mix of T is viable once very high Q values are possible, thus eventually zero T designs should be viable.
If you need a bunch of people with PhDs to operate a reactor, then you won't have a reactor. Not only does it mean that staffing is expensive and difficult, but also that it won't be reliable or predictable. If it is predictable, then steady state operation should be offloaded to computers.
A reminder of what could have been:
https://upload.wikimedia.org/wikipedia/commons/a/ab/U.S._his...
Let’s suppose this proposal works out, ITER will become a very expensive boondoggle. A technological dead end. But if you’d taken the ‘Manhattan Project’ approach and thrown 10x as much money at fusion research 20 years ago we’d most likely have spent most of it on a super-ITER. It might be operational by now and might even have reached break-even on power generation, but in the longer term would now be just as redundant and superseded by this new approach.
The GDP of the EU is apparently $18 trillion, so $20 billion is about .1% of the GDP in a single year, and of course that $20 billion is spread over 1-2 decades. If anything, it seems like as a species, we should have more of these bets going. What if we spent 1% of our GDP on 10 long-shot, high-impact projects? Or hell, half a percent on 5 long-shot projects, and half a percent on solving the dozens of problems that we could solve simply by funding them.
Er, don't you mean the early 20th century?
Rutherford's exegesis of the nuclear model of the atom was published in 1911.[1]
The problem is (1) the earlier you spend big the greater the chance you’ll pick wrong because you have less information to base a decision on and (2) Spending big doesn’t actually improve the odds that the approach you pick will end up being the right one. It just means you find out sooner.
Or maybe someone would have had enough sense to think "you know, what we really need is better superconducting magnets. Let's throw 1% of the budget at that problem."
Eventually there is a break even point (for the closest solar systems, last I checked, it's around 400 years), but in order to know what it is you need to know the amount of time to reach the goal and your rate of increase. I don't know if there's a way to estimate that with fusion research.
Obviously people are free to choose differently and there are exceptions, unique circumstances etc.
And this approach will be superceded by something else. And that will be superceded in turn. Should we wait forever? We'd still live in caves.
These new approaches don't just show up, they come from the knowledge and scientists trained in whatever the previous approaches were.
Lastly, if this approach results in having cheaper fusion power, but needs extra 20 years of R&D, thats time we don't have.
And in fact, it looks like Sparc is more of an exercise in making fusion reactors cheaper, most notably by using different magnets. ITER is more about validating the concepts, with no regard for the price. Besides the fusion itself, ITER will study how to inject fuel and evacuate the waste products as it is running. They will also tackle the problem of producing the large quantities of tritium a fusion plant requires.
So, my understanding is that Sparc is not intended to make ITER obsolete, but instead tackle a different problem. If commercial fusion reactors happen one day, I expect they will have a bit of both.
The 2020s start 2020-01-01 (just as the century called "the 1900s" started 1900-01-01).
The 21st century started 2001-01-01.
The 203rd decade starts 2021-01-01 -- but nobody talks about the "203rd decade". That's the difference in terminology between decades and centuries; we don't refer to decades by their ordinal numbers.
Yes, it's confusing and inconsistent. If only Dionysius Exiguus had known about zero.
However if you are not fussed about pope Greg and then and go with ISO 8601 or common usage it started 2000-01-01.
In the same spirit of pedantry:
Well, no, Gregory is beside the point; if you are referring to Anno Domini dates, the 21st Century (and Second Millennium) began on the first day of the year A.D. 2001, whether or not you prefer the Gregorian Calendar.
Preference for the Gregorian Calendar or not will affect when you believe A.D. 2001 started, though.
I don't believe anything in ISO 8601 refers to the century starting 2000-01-01 as "the 21st century" (though apparently it does, in some contexts, allow "20" to refer to the century that started on that date).
The century called "the 1900s" overlaps with the 20th century for 99 of 100 years.
It is not issue of Julian vs Gregorian date, but the issue that ISO 8601 uses different conventions. Traditionally, there were two disjoint timelines (AD/CE and BC/BCE), both starting at year 1. Within these conventions, it make sense that first century is 1-100 CE, second century 101-200 CE and so on.
ISO 8601 instead uses astronomical year numbering ( https://en.wikipedia.org/wiki/Astronomical_year_numbering ), which has signed integer year numbers including year 0. Therefore, there is no beginning of timeline and most natural way how to define centuries by div 100, e.g. years 0-99 is century 0, and so on.
I quote ISO/WD 8601-2:
Representation of a decade must be exactly three digits, leading zeros, if any, must be included. Thus the time interval 200 through 209 is represented as ‘020’ and NOT ‘20’; the latter would represent the time interval 2000 through 2099.
Here you can clearly see that the ISO definition of a decade is in keeping with the common understanding, not whatever oddball misunderstanding you've chosen to promulgate.
"Nuclear fusion. 30 years away since 1950"
Joking aside. I too am glad to see some progress of any kind, and new (seemingly credible) initiatives being funded and pursued
I feel like there should be bonus points for getting this quote to the top of every fusion article posted until there's an existing fusion reactor.
Those projections usually include the caveat "if properly funded" - https://i.imgur.com/3vYLQmm.png
Switching ITER to an updated design might be an idea.
It did not generate electricity, and given the discrete/pulsed nature of the mecanism, I have a hard time seeing how you would "even out" the output, should you decide (somehow) to attach it to a generator. Let alone imagining how you would transport said electricity back to earth.
Because, don't forget, it was possible to have an external combusion engine because it was in space. Even by 50's standards, the project was judged a non-starter for atmospheric flight, from environmental standards point-of-view.
The project itself was in theory viable for it's original objective (space travel), but highly impractical. It requires massive, robust structures (read 'heavy') that can resist very high impacts. Not a problem once you're into space, but you have to get it into space first. And no-one will let you blow up a couple of scores of nukes in the atmosphere, on a recurring basis. The thought of launching hundreds of nukes into space to a ship built in orbit is not exactly an easy proposition either.
Still, should an extinction-level meteor ever show it's face, it would be useful.
For fun : some original footage of the prototypes in flight (using high explosives) https://www.youtube.com/watch?v=Q8Sv5y6iHUM
Am I missing something? How do the lower parallel sides help capture the energy of an explosion below the shield?
A bit like this:
https://www.centauri-dreams.org/2016/09/16/project-orion-a-nuclear-bomb-and-rocket-all-in-one/He says progress stalled in 1995 and is not projected to continue until ITER is built, 10 years from now. Then the rest of the talk is actually about an alternative to ITER.
https://physicsworld.com/wp-content/uploads/2004/01/pwhoa4_0...
From the article at :
https://physicsworld.com/a/controlled-fusion-the-next-step/
more information about the triple product and the Lawson Criterion.
Given the amount of energy that comes from fusion fuel, even extracting lithium from seawater would probably be economical.
Beryllium is much less common so that could be an issue. But maybe we can find more beryllium if we look harder; right now we barely use it. If we can't find enough, we could probably design a reactor to use lead instead. Either one acts as a neutron multiplier, and General Fusion's design uses lead instead of beryllium, for the same purpose.
Tritium, however, does NOT exist in nature, and can only be conceivably produced in three ways:
1. Inside thermonuclear bombs
2. In heavy-water reactors, e.g. CANDU design, which requires Uranium, so it is not fuel-independent and totally dependent on nuclear fission technology. Getting Tritium that way is also extremely, extremely expensive.
3. possibly, in a breeding blanket of a fusion reactor. This makes fusion technology reliant on breeding reactors which is much more complicated and has many completely unsolved questions in the materials part. Also, existing fission-breeding reactors are also less safe, for example, like the Japanese Monju plant, which was cooled with liquid sodium, a highly reactive metal, which got incensed in a fire. Fusion breeder reactors will probably also require something like sodium cooling because of the high energy densities required.
And the existing research projects like ITER have not even started to address these issues - they are purely plasma physics experiments.
Section 3.2 Test Blanket Module (TBM) Testing Program in ITER
https://www.iter.org/doc/www/content/com/Lists/ITER%20Techni...
Look even closer at the fusion energy research community and you will find a lot of work has already gone into this problem. Assuming physicists sit on their thumbs is a bad bet.
Maybe I don't understand properly, but I'm watching the video linked in a previous comment (1) and around the minute 9:30 professor White says that "what comes into the plant is actually deuterium and lithium".
It seems he is saying that you need only an initial quantity of Tritium and then Helium and Lithium is used to created Tritium again. I suppose that it's what you refer as "breeding". He explain it as it's not a big deal.
Not fissionable, but many are unacceptable due to formation of long lived activtion products.
One additional problem with the alloys used is the degradation of their mechanical properties under radiation exposure. They tend to become brittle.
Testing any of these materials will require something close to a working fusion reactor (nothing else duplicates the neutron environment), but that will require the materials. Working around this loop of circular development dependency will be time consuming.
Seems like they're meeting all their planned milestones and it's going well!
Excited for their next updates...
More from their project page: https://www.ipp.mpg.de/w7x
"Wendelstein 7-X is the world’s largest fusion device of the stellarator type."
It reminds me of the principle that one shouldn't start a space travel project that is estimated to take more than x years to complete, because by that time, technological progress will have surpassed its speed and capabilities, and would physically overtake it (the 'wait calculation').
They're all extremely complicated, and while this one is harder to fabricate than a tokamak, fabricating arbitrary geometries is also something we've gotten a lot better at. If this is as complicated as it has to be in order to work as required... well, that's just physics right?
The problem is unnecessary complexity, but whether that's the case here or not is still unclear.
Episode 22 is an intro to fusion power research and tokamaks.
Episode 157 is an interview of a director at ITER.
Episode 304 interviews the author of the book you’re reading.
Episode 312 is a set of interviews with experimentalists and computational theorists at W7-X.
It's great there are seven-peer reviewed articles about SPARC, but plasma was not my specialty in physics -- would any specialists care to comment on whether there is anything particularly exciting here?
This is talked about in terms of the ‘phase diagram for superconductors’
http://www.supraconductivite.fr/en/index.php?p=supra-levitat...
As you put more current in the supercondutor, eventually you break it and it leaves the mode, as it gets hotter, likewise, as the magnetic field gets stronger, likewise.
You want the largest ‘area under the curve(s)’ to handle more and more ‘superconductivity’
New materials are enabling this which has the cubic effect mentioned for reducing confinement volume and making things more affordable and increasing energy densities that can be contained, etc.
ITER (and the LHC) used NbSn magnets, since it was designed in the 90s. Newer designs will use newer superconductors.
Superconductors are like magic, but they aren't actually magic. They have limits.
Why can't natural laws be more simple and linear? (joking, sure, but it does feel that way sometimes)
1 - https://www.fusionenergybase.com/concept/rebco-high-temperat...
2 - really great talk from a few years ago about this from MIT's Plasma Science Fusion Centre: https://www.youtube.com/watch?v=L0KuAx1COEk (really, if you like this stuff, give the talk a watch. It's great.)
The problem is that all known superconducting materials known will lose their ability to superconduct when exposed to a sufficiently strong magnetic field. The large field strengths induce eddy currents in the material which disrupt the propagation of the cooper pairs in its superconducting mode. The current sufficient to self-induce this field is called the critical current.
Layered rebco tape appears to shield against this effect or otherwise trap the eddy currents in a way that superconductivity is preserved even in the presence of extremely strong fields. The critical current in REBCO tape is enormously higher than in previously known materials or winding configurations.
Obviously the bigger the reactor volume is, the smaller the magnetic field needed to steer and confine the plasma within it can be. So back when they were designing ITER, engineers figured out the strongest magnet they could make, then they designed the reactor to be small enough (lol) that said magnet could still sustain confinement.
However now that we have stronger magnets we can make reactors smaller. This is even something of an gross understatement as the relationship is cubic. For a doubling in field strength, the reactor can be 8 times smaller. That effect is very meaningful when considering that you are essentially talking about shrinking something the size of ITER's 28m main reaction vessel to something that might fit into a garage.
I'm not really any kind of expert on this, so please treat this explanation as very simplistic.
I have not yet personally seen anything about this new lattice confinement modality that seems to give me anywhere near the same level of confidence that they will see viable applications compared to the magnetic confinement approach. (NIF already stood down their tries at laser inertial confinement) Maybe someone has some good insight on whether or not this is all still speculative fanfare or if researchers are finding real meat.
Good job recording MIT.
They were specifically looking at the tapes ability to function in high magnetic environments such as a tokamak type reactor.
In the sun, isn't energy production occurring at something like 100-1000 W/m3? So, if you want to build a multiple MW fusion plant, shouldn't these plants be ridiculously huge compared to, say, a wind turbine rated at a couple of MW?
Is the density of the plasma so much higher in a fusion reactor?
Also, something else I never grokked, how do you get the power out? The plasma heats up, but how do you turn that into useful electrical energy?
Nevertheless of course I hope it does work as advertised... someday.
Edit: thanks everyone for the thoughtful, insightful replies!
The trick is in higher temperature plasma. The sun fuses protium (lone protons). We don’t have the confinement necessary on Earth to do this, so we fuse deuterium (1p+1n) and tritium (1p+2n). This reaction is more energetically favorable and is achievable on Earth. Coupled with giant microwave ovens and clever geometry and electromagnetic tricks, we can make plasmas much hotter (faster moving particles) than the sun can.
Once a plasma is fusing, it emits a lot of heat (alpha heating and fast neutrons). A plasma that requires no external heating (no microwave ovens) is said to be “ignited”. We don’t necessarily need or want ignition to have a successful reactor, but it’s a cool thought.
The major trouble with fusion reactors is keeping particles in the bottle long enough to fuse. Since they’re leaving anyway they have to go somewhere. You can tune vessel geometry and magnetic fields to have designated strike points where most of the plasma will exit confinement. These are called divertors. Run some coolant through your divertors and you have a heat source that can boil water and spin a turbine.
Here my knowledge gets shaky because I know that the fastest particles coming out of a D+T reaction are neutrons (they weigh much less than an alpha particle). Since neutrons are electrically neutral I think they are much less likely to become thermalized (they are not likely to bump into another particle on their way out). I’m not sure how neutron thermalization happens in reactor simulations, but I’m under the impression that it does.
We would have never entered the industrial era without boilers.
In theory, one could have "generate heat, and have the apparatus surrounded by a vacuum, surrounded by infrared photovoltaics" be the new universal backend for power generation. I have no idea about the associated efficiencies, of course.
To collect energy, heat would be transferred to a working fluid (e.g., molten salt) by exposing that fluid to the hot plasma. Then the working fluid would be used to boil water and spin a turbine.
Inducing a current by moving something in a magnetic field, or vice versa, may seem like simple designs, but perhaps that's why we haven't replaced them yet. Rotational motion seems easy to service and efficient.
Same with water being particularly easy to turn into a gas using heat, as well as being super plentiful on Earth. There are just a lot of things going for a steam turbine
We haven't found a better way to convert heat to electrical energy. We've done great things with solar, kinetic, gravity, etc.
I think the better analysis is to chart the efficiency of the conversion over time. I couldn't easily find a chart showing this, but I assume gigawatt scale turbines operating at 50%+ efficiency are modern engineering marvels compared to the earliest 7kW prototype made by Charles Parsons in 1884.
[0]: https://en.wikipedia.org/wiki/Thermoelectric_generator#Effic...
[1]: https://en.wikipedia.org/wiki/Steam-electric_power_station#E...
> Also, something else I never grokked, how do you get the power out? The plasma heats up, but how do you turn that into useful electrical energy?
Steam turbines; same as fission or coal. Or gas turbines, if you want to get fancy.
- fusion is developed
- b/c of fusion, the cheapest "rocket fuel" is basically water heated into steam by the fusion reactor
- people on Earth get upset about the "spacers" taking all of the "earthers" water
- the spacers then have to go to other sources of water in the solar system (I think it was either rings of Saturn or the asteroid belt)
The thing that struck me at the time was the "water as propellant" without the extra step of breaking H2O into hydrogen and oxygen.
Heat it sufficiently and it will be broken down.
It's just an average. Fusion occurs only in the core, which is pretty tiny, relatively speaking.
> The plasma heats up, but how do you turn that into useful electrical energy?
The same way you can turn any kind of heat into useful energy.
Terrestrial reactors try for much higher reaction rates. But most designs still have power density issues that would make them uneconomical even if they could make net power. Net power is actually a very low bar, corresponding to an EROI of 1.
The whole research program gets its funding as what amounts to a jobs program to keep high-neutron-flux physicists employed and available to draw upon for weapons work. That is one reason why any fusion process that does not emit neutrons is not given any of the research funds: weapons work doesn't need high-alpha-flux physicists. (Secondarily, they have papers that purport to show e.g. p-B fusion could never work.)
If we ever do get practical fusion, it won't be in a Tokamak, it probably won't be on the Earth's surface, and it certainly won't help resolve global climate disruption.
The money being spent on Tokamaks, on the other hand, absolutely could help a great deal with global climate disruption. But not while also maintaining the all-important high-neutron-flux population.
I appreciate that many people are commenting 'you couple the plasma to a working fluid', but I think the original comment was more along the line of how you couple a confined plasma to a working fluid. By definition the plasma is in a hard vacuum, magnetically bottled. What, then, is the coupling method? Thermal photons escaping confinement? I genuinely have no idea myself, but would really like to know.
Do you know how far along are we in understanding how to build an effective blanket that can withstand the neutron flux while maintaining its physical integrity?
So, what is that blanket made of?
It needs to be a material which:
- can withstand high temperatures and radiation
- does not becomes radioactive itself
- facilitates production of Tritium by breeding
- operates in very high magnetic fields, which means high forces
No such material is known so far.
It is a bit like some engineer from 1700 said: "Well, you could just build a more efficient and compact and light steam engine, and connect it to a machine which has flapping wings, and then you have a transport vehicle which can carry people across the Atlantic ocean at supersonic speed, and at little cost."
It would have had to have been an unusually well informed and far-sighted engineer though, as Savery's engines first worked in 1698 and the first for-sale commercial engine, Newcomen's, wouldn't happen until 1712. And they were incredibly inefficient: 0.01% to 0.1%.
I looked up the effects of neutron radiation on materials[]. Sounds like a hell of an engineering challenge to come up with a robust way of getting that energy out!
Radiation damage to materials occurs as a result of the interaction of a [neutron] with a lattice atom in the material. The collision causes a massive transfer of kinetic energy to the lattice atom, which is displaced from its lattice site, becoming what is known as the primary knock-on atom (PKA). [...] The magnitude of the damage is such that a single 1 MeV neutron creating a PKA in an iron lattice produces approximately 1,100 Frenkel pairs.
Yep. And anything touched by the neutron flux would become radioactive if it captures neutrons. For example steel, normal steel contains carbon, carbon captures neutrons, so the steel becomes radioactive, and also brittle. And then you need wiring and insulation and coolant and pumps and all that.
~250W/m3.
So, is this ‘just’ a matter of ITER being obsoleted by improvements in magnet tech before it is completed, or is there more in this design than scaling down ITER?
https://www.psfc.mit.edu/files/psfc/imce/research/topics/spa...
I'd recommend watching the whole thing, I found it quite interesting.
https://en.wikipedia.org/wiki/ITER#Criticism
"The project however was significantly delayed at the design stage as result of purposeful decision to decentralize its design and manufacturing among 35 participating states, which resulted in complexity that was unprecedented but consistent with the initial ITER goals of creating knowledge and expertise rather than merely producing energy."
IMO jobs facilitating knowledge, experience & wisdom transfer between so many countries is worthwhile on its own, nevermind that the goal is to help solve our energy problems. If we get experience developing a massive international moonshot program from a jobs program, so be it.
It also says it can be built much cheaper than the total cost for ITER.
The article doesn’t say it, but I would guess that it also can be built for less money than the money needed to complete ITER.
If so, what’s not obsolete about ITER? Are there useful experiments that can be done with it that one can’t do with a more modern design?
Making a tiny machine quickly, skimming over the hard engineering problems is more of a moonshot approach. It's halfway to a startup with actual MIT startups selling HTS coils. Be wary of anyone selling something.
https://arxiv.org/abs/1409.3540
Some additional features (besides the magnets) that jump out at me:
The reactor vessel has joints to allow it to open up for maintenance access (previous tokamak designs have a reactor vessel that cannot be opened up once constructed, so maintenance inside has to be done through small access ports using remote manipulators).
The external current drive for heating the plasma to ignition looks like it is more efficient than previous designs.
The blanket around the reactor vessel is liquid instead of solid, using a fluorine-lithium-beryllium compound.
The power density of the reactor is 0.5 MW/m^3, which is 1/40th the power density of a commercial PWR primary reactor vessel.
The reactor (a single one!) uses something like 40% of the world's current annual production of beryllium. If all the world's estimated resource of Be is used to make these reactors, it would be enough for reactors producing just 1% of world primary energy demand.
That's crazy. I guess if the design works out we can start casting about for a beryllium replacement.
The remote manipulators are an amazing piece of technology; having the movements of your arms and hands replicated exactly by a robot is mind-blowing.
here is the original presentation by Dr Whyte of MIT behind this Sparc project: https://youtu.be/KkpqA8yG9T4?t=1511
he talks about the impact of these newer magnets at around 26min mark.
It seems that if we can't make fusion work for SPARC it won't likely work in ITER either since they're both based on the same understanding of the physics. Am I wrong on that point? Is there some reason to think that ITER will succeed even if SPARC does not?
As far as "why", you can take your pick of:
- ITER's design is older, and maybe could be considered "lower risk" (that it will work at all)
- Sunk cost
- Academic jobs program
- Money has already been allocated to member states, and none are happy to give that up
- Big changes take time
I'm not optimistic on stuff like this, so IMO it's another JWST, but it's not totally crazy to keep working on a plan (for a while) when new avenues of research arise.
> Europe is responsible for the largest portion of construction costs (45.6 percent); the remainder is shared equally by China, India, Japan, Korea, Russia and the US (9.1 percent each)
See my other brief comment: https://news.ycombinator.com/item?id=24634894
https://www.cambridge.org/core/journals/journal-of-plasma-ph...
[1] https://lockheedmartin.com/en-us/products/compact-fusion.htm...
So they changed to a subsonic approach, and also moved to a spherical tokamak arrangement. This means the target now has a solid conductor running down the central axis, and this conductor would be exposed to utterly hellish levels of neutrons (orders of magnitude worse than conventional fusion reactors) as well as forces from 100T magnetic fields. I have no confidence this could be made to work, even for a single shot. Also, in subsonic implosion, there is pressure equilibrium in the pusher, so the outside of the chamber feels the same extreme pressure as the inside. 100T gives a pressure several times that of the bottom of the Marianas Trench.
If?
Like, in classical terms, you can get a repulsive force to come out of Newton's law of gravitation if you plug in a negative mass. But that doesn't mean you've designed a hoverboard.
Must we spoil all my dreams?
The simple line of reasoning being that if energy becomes 100 times cheaper, humanity will fast find ways to consume 100 times the amount of energy. A high amount of that energy will end up as heat.
The second reason... and you'll find it apparent I'm not a physicist, but reading about fusion research always has me worried. We're basically talking about starting a "controlled" chain reaction at millions of degrees, "like the one on the sun". The sun isn't a nice place, and the sun's fusion happens to be controlled just because it's surrounded by lightyears of vacuum.
-Yeah but we'll have magnetic fields and super coils and stuff. It's totally safe. -Totally safe? -Yes, our calculations say its totally safe. -Your calculations based on current theory? Guess what, theory is a moving target. Just a few years ago you didn't even know if the Higgs particle exists?
Global warming isn't about heat generation. The sun (the free fusions reactor in the sky) sends more heat our way then we could ever hope to produce. It is heat dissipation that is the problem. Greenhouse gasses prevent the sun's heat from dissipating. This is the problem, we will only make it better by stopping greenhouse gas emissions.
Cities Snub Plan to Save Nuclear Power With Mini Reactors:
https://www.bloomberg.com/news/articles/2020-09-28/cities-sn...
Kaysville withdraws from nuclear power project:
Small Modular Reactor Decision Made With Inadequate Information:
https://losalamosreporter.com/2020/09/14/small-modular-react...
ITER and similar projects are abject failures from non-scientific perspectives, they fail to improve on the economic weaknesses of fusion (radiological waste, massive capital costs, scarcity of fuel, proliferation risk), and only deliver on issues that have become irelevant for modern fision, like the risk of a meltdown.
There is zero economic potential for any ITER direct descendant.
While I agree the quantity of waste is low, that doesn't really matter for the general public. We had for decades the technology to put fission waste in deep geological storage, what held it up were political concerns - the same for fast breeders that could burn the waste. So I cannot for the life of me understand how NIMBY-ism, the major cost driver of fission plants (via political challenges, court actions, schedule slips etc.), is allayed, when the plant will regularly ship out tons of hazardous materials through the communities they serve.
As for the fuel cost issue, you cannot use natural Lithium due to low cross section, but blankets made up of tons of enriched Lithium that has a large Li6 content, that are continually circulated and need to be topped off as H3 is bred. No estimate of cost for this feed-stock exists, but it is likely more expensive than natural uranium that can be burnt in a heavy water reactor, for example. (that reactor design has it's own issues with heavy water inventory costs, but this material is most probably easier to produce than enriched Li6, and is not consumed as a fuel)
When you draw the line, the best prospects of ITER derived fusion plants (not existing experiments, mind you, but the theoretical future, practical designs) is at best comparable to existing fusion plants. Why should we waste money on them, if they cannot improve on the current state of the art?
The hard part is getting the reaction to produce more energy than it requires to sustain. Given a breakthrough that solves that problem, fusion would be a really appealing energy source given the abundance of hydrogen.
The hard part is getting more energy out than you put in.
The sun does this all the time, basically by having so much mass that hydrogen gets sucked in by gravity to collide with other particles. Keeping hydrogen close enough to smash into each other is hard, the sun is just so big that it can do that.
Hydrogen bombs do this by using other explosives to push hydrogen together. This isn't a good power source.
We can't use gravity to cause hydrogen to collide here on earth (we have no artificial gravity). But we have magnets, so we try to bounce hydrogen particles around super fast in a small space with magnets instead of using gravity.
Now getting more energy out is a bit like starting a fire. You need to apply heat for a while with a lighter before the fuel ignites, then the burning fuel keeps releasing energy.
Same basic idea with fusion. You put in energy to start fusing hydrogen. Once the hydrogen is releasing power, it will cause other hydrogen particles to bounce around super fast and continue fusing, releasing more energy.
The part that hasn't really been done yet is proving that the "fire" can stay lit, and that is what people are trying to do. It's hard for a bunch of reasons, but the theme is "making a tiny sun-like place on earth is challenging". When this article mentions "q" that is what it is referring to. q=2 means for every joule of energy put in you get 2 joules out.
(disclaimer: this is a quick version that omits a lot)
I thought this was impossible due to law of conservation of energy.
Well eventually we get lucky with things like gravity, and water cycles doing the work for us by giving us rivers and we build a dam around it.
But you can never design a process where you can take more than what you put in.
Both fission and fusion are elaborate ways of converting a small fraction of the mass of the fuel to energy.
Also, "you can't get more than you put in" applies to closed systems. Reactors are open systems.
“ The activation of the reactor’s structural material by intense neutron fluxes is another issue. This strongly depends on what solution for blanket and other structures has been adopted, and its reduction is an important challenge for future fusion experiments.”
Seriously though, the article reads like "Remember SPARC? We're still trying to build it." I wish them luck, but if past experience with fusion can be extrapolated, they will run into some unexpected, crippling problems.
If we could make efficient fusion reactors the size of a truck, the solar system will become our backyard.
https://en.wikipedia.org/wiki/Electrically_powered_spacecraf...
Realistically, if we had good electric propulsion we could just slap a conventional fission reactor in there. We already launch plutonium on many deep-space missions for steady nuclear power. For now chemical propulsion is simply faster and more reliable, electric propulsion is still in the early stages, and there are many other problems to solve in human spaceflight.
Who will pay for the cost overruns?
Just one of the big problems with nuclear is that it is very centralized and takes individual control away from the consumers, who foot the bill through increased taxes and fees, and who could otherwise be using their money to finance options that give them individual control over their energy costs.
Decommissioning costs should be negligible because the reactors won't generate radioactive fission byproducts. The reactor chamber is designed for a 10 year lifespan and easy replacement. The old chamber is slightly radioactive (due to neutron bombardment) for a few decades, which is much less of a problem than the highly radioactive waste from fission plants that has to be stored for thousands of years.