[HN Gopher] Revamped German stellarator should run longer, hotte...
___________________________________________________________________
Revamped German stellarator should run longer, hotter and compete
with tokamaks
Author : nabla9
Score : 194 points
Date : 2022-09-11 12:35 UTC (10 hours ago)
(HTM) web link (www.science.org)
(TXT) w3m dump (www.science.org)
| TaylorAlexander wrote:
| Has anyone published research on concepts for a stellarator that
| uses high field magnets like the SPARC/ARC systems? Obviously the
| idea is that it would be smaller, but I am curious if there are
| any interesting specifics for such a machine. You could imagine
| that if W7-X and SPARC show good results in the next 5 years then
| a high field stellarator design would start to look pretty
| interesting.
| willis936 wrote:
| Both Type One and Renaissance (mentioned in the article) are
| HTS stellarator startups. I'm not sure if they've published
| power plant studies, but they've certainly pitched them.
| jobstijl wrote:
| In france they are building a next privately founded stellerator
| which seems intresting. https://stellarator.energy/
| NKosmatos wrote:
| Just like COVID helped the mRNA/CRISPR technology evolve and come
| faster and closer to us, with the potential for many more usages
| in various diseases, I hope that the ongoing/coming energy crisis
| will help all nuclear fusion technologies tokamak/stellarator
| become real. We're still a few years away from having them in
| actual power plants and a few decades away from solving our
| energy problems for every, but I hope we get there sooner than
| later.
| moogly wrote:
| > We're still a few years away from having them in actual power
| plants
|
| I admire your optimism. I'd say half a century, if things go
| well, but I'm not convinced fusion will ever be economically
| feasible.
| marcosdumay wrote:
| > but I'm not convinced fusion will ever be economically
| feasible
|
| Not on Earth. But put a good enough fusion reactor on a
| rocket, and you can reach neighboring stars in 3 or 4 decades
| instead of the 15 one would expect for fission. (Of course,
| nobody is even sure reactors can get that good, but it does
| look possible.)
| mjhay wrote:
| Fission fragment rockets could actually compete with fusion
| here. The reaction mass is the fission fragments
| themselves, which could get a specific impulse of around
| 10^6 s. The technology to do this is within relatively easy
| reach, at least by interstellar rocket standards.
|
| https://en.wikipedia.org/wiki/Fission-fragment_rocket
| Retric wrote:
| Designs like that quickly start using a significant
| fraction of available fuel on earth if you want to do
| more than send a single tiny probe on a flyby.
|
| The proposed fuel is even worse as AM242 has a half life
| of 141 years making it hard to collect in bulk.
| ethbr0 wrote:
| Neat links!
|
| I think nuclear propulsion is going to be the biggest
| beneficiary of higher mass-to-orbit-for-a-reasonable-
| price advances.
|
| There are a huge number of propulsion technologies that
| are physically possible but too heavy and/or dangerous
| for near-Earth use.
|
| Cheaper lift (to bootstrap) + more ongoing destinations
| and transit work (to drive) + outside of Earth orbit (to
| alleviate safety concerns) = rapid progress
| zasdffaa wrote:
| That is highly tangential to the issue of economic
| viability, and the energy crisis.
| marcosdumay wrote:
| Economic viability only exists relative to an
| application.
|
| And there is absolutely zero chance of fusion solving our
| current energy crisis, the odds for fission are already
| low enough. There is no point on speculating on that.
| Maken wrote:
| It feels like fusion energy is perpetually 50 years away.
| Retric wrote:
| Minimal investment means minimal progress. ITER was
| basically a Regan/Gorbachev project from 1985 that's still
| not built yet. It's JET's the current largest device was
| completed in 1983. Real progress has been made, but the
| major projects have been extremely conservative by
| necessity.
|
| Early designs for ITER where for a larger device that would
| have actually produced electricity though not cheaply
| enough to be economically viable, but it got scaled way
| down.
| mjhay wrote:
| And ITER's design is already wildly outmoded now that
| high-temp superconductors exist (which they have for
| quite some time). Just a multinational pork project.
| XorNot wrote:
| ITER exists to prove that fusion plasma stability can be
| sustained to extract useful energy. _How_ it does it is
| irrelevant since the big news is having a sufficiently
| large tokamak vaccum vessel with instrumentation to
| study.
|
| HTSCs weren't usable when it was designed, and have only
| _just_ become usable in the last 5 years or so but they
| are a fundamentally different material. You don 't just
| drop them into a large, incredibly complex machine that
| depends on it's integrated magnetic containment system:
| you are functionally building a new device.
|
| If you can ITER, then you don't get a refund on spent
| dollars. You get a loss. And then you get to start
| another 30 year project to maybe build a new vacuum
| vessel, which you have to do because you still haven't
| actually tested plasma stability.
|
| "But but MIT skunkworks!"...yeah. It's still going along,
| and they haven't suddenly churned out a functioning
| reactor based on HTSCs because oh look, whatever the
| advantages they're a new material with different
| properties, manufacturing and handling behaviors all of
| which need to be developed, measured and inspected before
| you can use them effectively in a fusion device. If they
| look good then _great_ : they can be used to make DEMO,
| the ITER-successor commercial powerplant prototype,
| cheaper and more powerful.
| mrexroad wrote:
| 50 is the new 20!
| stormbrew wrote:
| As was predicted in the paper that spawned this joke which
| presented timelines based on funding and then we funded
| research into fusion even less than their most pessimistic
| model.
| simonebrunozzi wrote:
| I think that 50 years is a reasonable timeframe to give
| fusion the possibility of delivering results. But I agree
| with you, it's pretty much impossible that anything will come
| out of fusion in the coming 10-15 years, despite the
| publicity we keep hearing lately.
| pfdietz wrote:
| We've already given it more than 50 years.
| ForHackernews wrote:
| Solving hard engineering problems is expensive. You have
| to put lots of money into it. Say, 30% of the funds
| invested by VCs in jitney cabs and collectable JPEGs.
| 7thaccount wrote:
| It is so sad how much money and talent goes into getting
| people to click on more ads.
| Gud wrote:
| It took humans hundreds(thousands?) of years to learn how
| to fly. 50 years is not really that long.
| wongarsu wrote:
| But apart from the part that's useful for nuclear weapons
| research, we've barely given it any funding. The idea of
| "we could have useful fusion reactors in 30 years" always
| came with the sentence "if we get the funding to do it".
|
| There's this [1] famous graph comparing US research
| spending into Fusion, compared to 1976 predictions how
| long it would take with different budgets. According to
| that, the US funded fusion below the "not enough to ever
| get it done" budget. With that in mind, we have come
| remarkably far.
|
| 1: https://upload.wikimedia.org/wikipedia/commons/a/ab/U.
| S._his...
| kingkawn wrote:
| Yes, but making long predictions allows them to pretend
| they are in pursuit of something
| scythe wrote:
| But we didn't have high-temperature superconductors that
| could be made into useful ribbons for most of that time.
|
| (I know I still owe you a detailed response on the thermo
| thing.)
| FBISurveillance wrote:
| Still sooner than Linux on Desktop if you'd ask me!
| okasaki wrote:
| The UK government plans to have a fusion power plant on the
| grid by 2040
|
| https://assets.publishing.service.gov.uk/government/uploads/.
| ..
| tsimionescu wrote:
| They can also plan to bring world peace and end world
| hunger by this winter. Doesn't mean it will happen.
| okasaki wrote:
| Well, they definitely aren't planning _that_.
| lettergram wrote:
| > Just like COVID helped the mRNA/CRISPR technology evolve and
| come faster and closer to us, with the potential for many more
| usages in various diseases, ...
|
| I don't think it's actually evolved all that much. They just
| deployed something that wasn't really tested. I recall learning
| about theoretical mRNA vaccines back in 2014-2019 (granted they
| were killing the hosts and stuff). As someone who's studied
| bioengineering (university, reading papers and some projects)
| I'd really like to see 10-15 years of usage before we consider
| anything with the tech.
|
| I for one home we don't do the same thing with fusion. There is
| an amazing amount of risk as technology has expanded, we have
| to be far more cautious.
| est31 wrote:
| > Just like COVID helped the mRNA/CRISPR technology evolve
|
| About mRNA vaccines I agree with you, because they indeed have
| been a niche thing before covid, but then they were the first
| available vaccines while the alternatives were still being
| researched when the first mRNA vaccines got their emergency
| approval. But how has CRISPR benefitted from covid? It doesn't
| seem to be used anywhere in therapeutics, no?
| marcosdumay wrote:
| > But how has CRISPR benefitted from covid?
|
| I imagine it's on the comment because it was used to create
| many of the non mRNA vaccines.
|
| But I don't think it got popularized. It was already widely
| popular.
| PicassoCTs wrote:
| ajross wrote:
| > ongoing/coming energy crisis
|
| This has been IMHO inappropriately hyped. We have an expected
| gas shortfall in Europe due to the mess made by one rogue actor
| (though Putin hasn't shut the pipes off yet, The existing price
| shocks are all speculative!). Petroleum production is fine. Gas
| production outside of Europe is fine. Existing interests in
| those industries have been exploiting the resulting price
| shocks (which are not the same thing as a crisis) to try to
| drive public policy decisions in their direction.
|
| We've been here before in the 1970's when rogue actors tried to
| exploit their production capacity for political gain. It
| sucked, but we didn't get fusion out of it then either.
|
| Frankly it's not even the first time we've had a supply
| shortfall. People tend to forget this, but we ran out of oil in
| the late 90's too! Turns out, there was lots more oil available
| at higher price points.
| actionfromafar wrote:
| Nordstream 1 is off.
| xg15 wrote:
| The Turkish and Ukrainian pipelines aren't (yet) though:
| https://berthub.eu/gazmon/
| dabber21 wrote:
| In an interview about this project with the recent changes,
| they said its investment in future energy production in 2050
| cl0ckt0wer wrote:
| "our need will be the real creator" - Plato
| SapporoChris wrote:
| "Necessity is the mother of invention" Proverb of unknown
| origins. Earliest reference Aesop's fable.
|
| I've been quoting the proverb for a long time. Thank you for
| the quote, I feel it says basically the same thing but I
| appreciate the different wording and that it is attributed to
| Plato.
| ChrisMarshallNY wrote:
| "Laziness is the mother of invention."
|
| - Forgot where I heard that. It may have been a comedian.
| hammock wrote:
| What are all the valves and ports and things in the metal outside
| of the stellarator in the lead illustration?
| willis936 wrote:
| Heating and diagnostics.
|
| https://www.researchgate.net/figure/Port-allocation-of-the-W...
|
| There's a chapter on W7-X diagnostics in this DOI (check sci-
| hub). It doesn't include a comprehensive list of diagnostics or
| their port assignments, but it was the best I found at a
| glance.
|
| 10.1007/978-1-4613-0369-5_76
| hammock wrote:
| At first I thought they lacked symmetry. Now I see they
| don't, it's just pretty convoluted
| willis936 wrote:
| W7-X has 5 periods and each period is a mirrored half
| period, so really it's one segment repeated 10 times. This
| pattern is common to symmetric stellarators.
| wincy wrote:
| This has to be the most opaque title I've ever seen on Hacker
| News. For anyone wondering, this is about a potential development
| in cold fusion reactors.
| irjustin wrote:
| How did you get cold anything from this?!
| wincy wrote:
| I dunno I thought hot fusion was a waste of time unless
| you're doing it inside of a star. So I just assumed it was
| about cold fusion.
| stormbrew wrote:
| The plasma in a fusion reactor is actually hotter than even
| the core of the sun, afaik.
| borissk wrote:
| You have no idea what you're talking about, but felt you
| need to leave a comment , waste everyone's time and
| potentially mislead someone.
| detritus wrote:
| More opaque than every nth HN title referring to some cutely-
| monikered code framework that presses all the wrong mental
| buttons in those oblivious to its nature? Surely not.
| EamonnMR wrote:
| Splark: a new phlinto framework built in blenk.
|
| And the thread is just Blenk fans arguing with Fobl fans.
| phist_mcgee wrote:
| As a fan of Fobl and their work on Spoogum, i'm not sure
| you would call it 'arguing' more sharing the obvious
| downsides of the dinglepop pipeline when combined with the
| grumpkin anti-pattern.
| amacbride wrote:
| Meh. This was all solved decades ago with the turbo
| encabulator.
| hotpotamus wrote:
| Others are pointing out that this is (very) hot fusion. But I'd
| just say that if you know the first thing about fusion, the
| title is actually very simple, ie, stellarators and tokamaks
| are competing designs for magnetic confinement fusion. Of
| course, no one is born knowing anything about nuclear physics,
| and it's not really a casual subject of conversation, so there
| might be a lesson here that people could take about writing in
| domain specific jargon and how inaccessible it is for
| outsiders.
| kQq9oHeAz6wLLS wrote:
| And if you know nothing about fusion, the title seems to be
| crafted of made up words.
|
| But if you take one glance at the comments, it becomes clear.
| So I guess the title was sufficient to pique my interest,
| which, after all, is the purpose of a title.
| Jabbles wrote:
| > cold fusion
|
| This isn't "cold".
| trebligdivad wrote:
| There's nothing cold about this.
| throwawayben wrote:
| Standard (hot) fusion, not cold fusion.
|
| Having read a few articles previous on fusion, I'm familiar
| with the words tokamak and stellarator, so it was obvious to me
| that it was about fusion from the title.
|
| I wonder how many other titles you would consider opaque if you
| didn't happen to know the terms?
| DennisP wrote:
| Hot fusion, not cold fusion. It runs at a hundred million
| degrees C.
|
| Hot fusion is a well-known process that powers the sun. Cold
| fusion is a supposed low-temperature process that most
| scientists doubt is real, and if it is real we don't understand
| the physics of it.
| ben_w wrote:
| Sometimes I like to say that the 15 million kelvin core of
| the sun is actually a cold fusion reactor, on the grounds
| that fusion within it is dominated by quantum tunnelling,
| rather than classical kinematics, overcoming the Columb
| barrier.
|
| Also like to surprise people with a fusion process that works
| at temperatures in the single-digit kelvin range:
| https://en.wikipedia.org/wiki/Muon-catalyzed_fusion
|
| But yes, the linked reactor isn't that, and the thing
| commonly referred to as "cold fusion" probably isn't real.
| [deleted]
| dleslie wrote:
| Forgive my ignorance; what with all the effort made to isolate
| the exceedingly hot plasma from connecting with any surface, what
| are the plans to extract the heat in order to generate power?
| mpweiher wrote:
| From the fine article: "Over the past 3 years, W7-X's creators
| stripped it down and replaced all the interior walls and
| fittings with water-cooled versions, ..."
|
| I am guessing that the water used to cool the interior walls
| will get hot in the process...
| Someone wrote:
| https://www.iter.org/sci/MakingitWork:
|
| _"The helium nucleus carries an electric charge which will be
| subject to the magnetic fields of the tokamak and remain
| confined within the plasma, contributing to its continued
| heating. However, approximately 80 percent of the energy
| produced is carried away from the plasma by the neutron which
| has no electrical charge and is therefore unaffected by
| magnetic fields. The neutrons will be absorbed by the
| surrounding walls of the tokamak, where their kinetic energy
| will be transferred to the walls as heat.
|
| In ITER, this heat will be captured by cooling water
| circulating in the vessel walls and eventually dispersed
| through cooling towers. In the type of fusion power plant
| envisaged for the second half of this century, the heat will be
| used to produce steam and--by way of turbines and alternators--
| electricity."_
|
| That's about ITER, but the two devices do not differ in this.
| dathinab wrote:
| Makes me wonder if given the increasing value of water this
| has to change a bit (for reactors not close to shore).
|
| I.e. instead of letting the steam escape into the air after
| going through a turbine using some mechanism to passively
| cool/condense it "somehow", reusing _all_ coolant water, only
| having closed loop(s) (the "inner" cooling loop is often
| closed anyway for various reasons transferring the heat to an
| outer loop before its used for anything).
| baking wrote:
| For Deuterium-Tritium reactions, the easiest to achieve, 80% of
| the energy is contained in neutrons which pass through the
| first wall and must be captured in a blanket. The rest of the
| energy could be carried to the first wall by photons, called
| radiative cooling, but you can also use divertors that allow
| the fusion products to escape the plasma carrying away some of
| the heat.
|
| I think in a stellarator you will need divertors to remove the
| fusion products because of the continuous operation.
| ak217 wrote:
| By capturing neutrons (which, not being charged, escape the
| magnetic confinement continuously as the reaction goes on) with
| a moderator blanket which is then cooled with water/steam.
|
| How to keep the blanket from quickly degrading and becoming
| nuclear waste seems to be an open problem (not too different
| from what goes on in fission reactors though)
|
| https://en.wikipedia.org/wiki/Fusion_power#Energy_capture
| Tuna-Fish wrote:
| > How to keep the blanket from quickly degrading and becoming
| nuclear waste seems to be an open problem
|
| Not really. Most reactors plan to also use the neutrons to
| breed the tritium fuel for the reactor, so the blanket would
| consist of liquid metallic lithium. The only products from
| neutrons reacting with lithium nucleii (either 6 or 7) are
| He-4 and tritium.
|
| The open problem is how to safely maintain the reactor-facing
| wall of the lithium blanket. It gets bombarded by a _lot_ of
| neutrons, yet needs to contain the hot lithium. It helps that
| the lithium can be unpressurized, but it 's still a problem,
| because molten metallic lithium is not fun to have leak into
| anywhere.
|
| The plan of the ARC guys appears to be to design the reactor
| so that the lithium vessel is easy to remove and swap for a
| new one, and just use steel for the vessel. The downside of
| this is that it's going to result in a lot of low-activity
| waste -- actually probably quite a bit more than what fission
| plants produce. There are other approaches, including using a
| material that doesn't really get activated by neutrons, and
| which is maintained above it's annealing temperature so
| embrittlement caused by dislocations is repaired as it
| happens. The downside of this is that materials above their
| annealing temperatures can be kind of soft.
| imglorp wrote:
| It looks like all the isotopes of LI are very short lived.
| Is the problem some of the daughters, or perhaps the Fe and
| C in the steel that are the problem?
|
| https://www.thoughtco.com/lithium-isotopes-radioactive-
| decay...
| Tuna-Fish wrote:
| Yes, the problem is the steel.
| ak217 wrote:
| Would zircaloy work better?
| marcosdumay wrote:
| I imagine low-activity steel should be easy enough to
| purify and recover some 99% of it... But wouldn't an
| aluminum wall fare better?
| warinukraine wrote:
| amelius wrote:
| Since the plasma runs hotter than the Sun, and the magnetic
| field cannot confine photons, my guess is that the hull will
| become insanely hot, and you could use it to drive a steam
| engine.
| dleslie wrote:
| Ah interesting, so then the coolant for the shielding is also
| the means to power a generator.
| pfdietz wrote:
| This would be for DT fusion, so most of the energy would come
| out as neutrons.
|
| And it would face the same showstoppingly bad volumetric power
| density as tokamaks, because of limits on that energy flow
| through the surface of the reactor.
| sidkshatriya wrote:
| > And it would face the same showstoppingly bad volumetric
| power density as tokamaks, because of limits on that energy
| flow through the surface of the reactor.
|
| I do think it is worth persevering though. The future of
| energy is Solar/Wind but Fusion should not be ignored. It is
| one of Nature's fundamental processes. Mastering fusion could
| turn out to be useful in ways we cannot possibly fathom at
| the moment right now.
| GordonS wrote:
| I agree. If we were able to eventually miniaturise fusion
| reactors, they would be incredible for space flight. Back
| on Earth, if they could be made safe enough, maybe we could
| even use them to run container ships?
| sidkshatriya wrote:
| With all the fast neutrons emanating from a fusion
| reactor (and the heavy confinement that it requires) I
| don't think a container ship would be a safe enough
| environment (threat of disaster at sea, constantly
| jostling which might affect plasma stability etc.).
|
| But yes, there is a potential for a lot of space
| applications and other things we haven't thought of yet.
| ClumsyPilot wrote:
| what kindof disaster could be relevant in this context?
| If the ship sinks, the minor radioctivity of a shutdown
| reactor will not be relevany
|
| Technically, container ships are enormous and can use
| ballast water for shielding. I can't judge the ecobomics
| ofcourse
| sidkshatriya wrote:
| Well fusion reactors are likely to cost a huge amount of
| money when they do become operational. No point having
| them sinking in a storm. Probably just safer to charge a
| huge battery and put it on a ship (if you don't want to
| use fossil fuels). Avoids a lot of unfoseen commercial
| risk. Even though you could use water for shielding, the
| metal container and other things that hold the reactor
| would be highly radioactive and brittle due to continuous
| neutron bombardment. You wouldn't want that to be lost at
| sea spewing radiation (even though the reactor itself
| would shutdown automatically).
| GordonS wrote:
| > Probably just safer to charge a huge battery and put it
| on a ship
|
| Large container ships burn through 16 tons of bunker oil
| per hour, and each journey can last up to 3 weeks - any
| idea what size of battery such a ship would need? I have
| no clue how to calculate that), but I'm guessing it would
| be completely impractical, even if we made huge strides
| in battery energy density.
| stormbrew wrote:
| There seem to be efforts towards battery powered
| container ships out there[1], independently of any
| speculated use of nuclear power to charge them. Most
| likely they'd be battery banks in containers that get
| swapped out and charged at port using the same equipment
| as is used to load and unload cargo I believe.
|
| I remember reading that they would have more limited
| range and lower top speeds, but that this might not be as
| much of a problem as it seems because the current routes
| are built around large container + long haul but that's
| not necessarily required (for all shipping at least).
|
| [1] eg. https://maritime-executive.com/editorials/could-
| battery-powe...
| ClumsyPilot wrote:
| here fuels like hydrogen might make sence, but why not
| 'normal' nuclear?
|
| There are hundreds of nuclear powered ships already -
| submarines, Icebreakers, carriers, etc.
| pfdietz wrote:
| DT fusion would be just ridiculous for space flight.
| Anything a DT reactor could do a fission reactor could do
| much better -- much smaller, much higher power density,
| much less complexity. And similarly for use in ships down
| here on Earth.
|
| In practice, synfuels would be better than either for
| ships on Earth.
| GordonS wrote:
| I don't understand this; if fission reactors were
| "better", we wouldn't be pouring so much into fusion?
|
| Also, if it makes a difference, I didn't mean we'd be
| bolting a first gen tokamak to a container ship; I meant,
| much later down the line, if we were able to miniaturise
| (similar to how we have nuclear powered subs and ice
| breakers).
| pfdietz wrote:
| You seem to think that government decisions are rational.
|
| Fusion is a meme technology. People just have this
| assumption that's it's valuable, without having
| rationally arrived at that conclusion (which, when you
| examine it in detail, is very difficult to justify.) I
| suspect this was because it started back in the 1950s
| when consent was easier to manufacture and nuclear was
| being pushed. Fission lost that glamour with most people,
| but fusion somehow has retained it.
| GordonS wrote:
| It's not only governments pouring cash in, but private
| equity too.
|
| With all due respect, it seems ridiculous to me that
| fusion is a "meme technology" - aside from money, are all
| those many thousands of scientists _really_ working on a
| technology they know can 't work?
| pfdietz wrote:
| Some of that private investment has been sadly lacking in
| critical due diligence.
|
| Look at Tri-Alpha. The people involved with that
| (Rostoker, Binderbauer and Monkhorst) were told 23 years
| ago that their colliding beam H-11B concept didn't work,
| for multiple reasons. Yet look at how much money they
| raised.
|
| https://www.researchgate.net/publication/235032059_Commen
| ts_...
| dmichulke wrote:
| Isn't the main reason for us not having fission rockets
| the fact that we don't want to have radioactive material
| explode a few kms above our head aka a dirty bomb?
| pfdietz wrote:
| A DT fusion reactor would have a thrust/weight ratio much
| less than 1, so it could not be used in a launch vehicle.
| It would be purely for use up in space. So, none of this
| "a few kms above our heads" nonsense.
| [deleted]
| Galaxeblaffer wrote:
| We already have the perfect way to create heat and the
| science around it has been long solved and understood.
| Solar and wind won't save us and fusion certainly won't. It
| amazes me how solar and wind dreamers all seem to like
| fusion but fission is just super evil.
| sidkshatriya wrote:
| From what I've understood from previous discussions (don't know
| much about plasma physics though): It is a multistep challenge.
| Step 1: Figure out how to get a self-sustaining fusion
| reaction. Step 2: figure out how to extract the energy in a
| useful, safe, non-destructive (to the reactor) way.
|
| Doing Step 1 alone is very difficult so the've postponed Step 2
| to the future. I may be wrong though.
| onlyrealcuzzo wrote:
| I would imagine since, combined, we're spending tens of
| billions of dollars on Fusion research - someone must have
| some ideas for step 2, right?!
| stormbrew wrote:
| 10s of billions... Over many decades. We spend very little
| on fusion research overall.
| pfdietz wrote:
| There are currently major unsolved problems with step 2.
|
| https://cpb-
| us-w2.wpmucdn.com/research.seas.ucla.edu/dist/d/...
| kortex wrote:
| We have some ideas, of course. The rough idea is: surround
| the reactor with a lithium blanket. This gets bombarded
| with neutrons, breeding fuel and heating the lithium, which
| transfers its heat to coolant to spin turbines. The devil
| is in all the engineering details, like: how do we make
| alloys to deal with neutron bombardment/hydrogen
| embrittlement, what's the optimal geometry to capture flux
| while being serviceable, etc.
|
| Much of that work can and is researched in parallel, but
| there will be inevitable integration hell that has a
| burning fusion reactor core as a prerequisite.
| TedDoesntTalk wrote:
| What is done with the "spent" lithium blanket? Is it
| radioactive waste?
| esteth wrote:
| It depends on how it's engineered. The lithium itself
| wouldn't be "radioactive waste" but the vessel for the
| lithium would likely be.
| trebligdivad wrote:
| I'm not sure, but there's a thing called the 'Divertor' in some
| designs, it's said to be for removing inpurities, but some
| things talk about it being used for removing heat as well:
| https://www.iter.org/mach/Divertor
| trebligdivad wrote:
| oh, and the other thing is some of the walls they talk about
| having 'blankets' that absorb the neutrons and ... somehow
| get the heat out; one of them is 'flibe' which is a lithium
| salt: https://www.tandfonline.com/doi/full/10.1080/00295450.2
| 019.1...
| willis936 wrote:
| I was going to make a comment about divertors. W7-X has 10
| strike points and an island divertor. It's pretty wild
| physics.
| Maken wrote:
| Because no known material can withstand direct contact with the
| plasma. Even with the air gap the walls require a cooling
| system, and therefore a continuous hot stream of fluid will be
| generated like in any other thermal power plant.
|
| However, at the stage fusion research is, the main problem is
| figuring how to create a device to keep the plasma fluid stable
| for long periods of time. As far as I know, none of the
| existing prototypes aims to be a functional electricity
| generator.
| exitheone wrote:
| Is this not false? The plasma is so incredibly thin that it
| would cool down immediately the moment it touches the walls.
| Afaik the heat generated here is mostly due to neutron
| bombardment and not because of the plasma.
| homarp wrote:
| https://www.energy.gov/science/doe-explainsstellarators A
| stellarator is a machine that uses magnetic fields to confine
| plasma in the shape of a donut, called a torus.
|
| Over tokamaks, the other main technology that scientists are
| exploring for fusion power, stellarators require less injected
| power to sustain the plasma, have greater design flexibility, and
| allow for simplification of some aspects of plasma control.
|
| However, these benefits come at the cost of increased complexity,
| especially for the magnetic field coils.
| snovv_crash wrote:
| Stellerators aren't really in a torus, they are in a weird
| fractally twisted torus, sort of like a many-twisted Mobius
| strip. You really need to see a picture to understand.
| snarfy wrote:
| If a tokamak is a donut, then a stellerator is a French cruller.
| davesque wrote:
| What's the theoretical advantage of the German stellarator over a
| tokemak? Seems like a complex design but I assume there must be a
| reason for the complexity.
| sac_ wrote:
| The main advantage is that a Stellerator can be continuously
| operated while a Tokamak only works in pulsed operation.
|
| The complex design of a Stellerator's magnectic coils
| essentially avoid the need for a transformer as it is being
| used in a Tokamak. The transformer is the reason why a Tokamak
| can only be operated in pulsed mode. However, there is ongoing
| research to achieve continuous operations e.g. by means of
| high-frequency waves.
|
| Much better explanation here:
| https://www.ipp.mpg.de/14869/tokamak
| speeder wrote:
| I am complete layman here. Still from what I read the whole
| point of stellarator is to be same as tokamak except you use
| CAD to make it twist in the same way plasma naturally would
| twist, to make it easier to keep the plasma in the path you
| want.
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