[HN Gopher] Will better superconductors transform the world?
___________________________________________________________________
Will better superconductors transform the world?
Author : debadipb
Score : 94 points
Date : 2024-05-19 05:35 UTC (1 days ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| punnerud wrote:
| What if we could make really light and strong superconductors
| that could transfer energy in the stratosphere where the average
| temperature is -60degF (-51degC), between large balloons or
| gliding planes.
|
| Then we could have really thin wires transferring huge amounts of
| power?
| frodo8sam wrote:
| Running cables over a long distance in the sky between balloons
| and planes sounds a lot more challenging than cooling cables on
| earth. Also High voltage DC is already quite good.
| deepsun wrote:
| Superconductors all have limits on current and voltage. So
| really thin wires cannot transmit huge amounts of power.
| barfbagginus wrote:
| Unless you're Larry Niven, in which case you can hang huge
| portions of your plot from superconducting piano wire which
| can transmit unlimited amounts of heat and current
| ben_w wrote:
| It might not work as well as you expect: the air temperate may
| be low, but because the pressure is close to a vacuum the air
| is also a great insulator, and your material is in stronger
| direct sunlight.
|
| Also politically speaking this may just be a non-starter: on
| paper, we can already build a conventional low-resistance[0]
| ground-level planetary power grid for very reasonable prices
| and material requirements, but much smaller projects connecting
| Europe to the Sahara have stalled.
|
| [0] 1 O at 40,000 km
|
| [1] material costs of a few hundred billion USD, a little over
| a year of current global aluminium production, more to actually
| install it
| huppeldepup wrote:
| What's always missing around this subject is the use of
| superconductors as energy storage devices:
|
| https://en.m.wikipedia.org/wiki/Superconducting_magnetic_ene...
|
| Tangential, high density energy storage also means things that go
| kaboom by intent.
| px43 wrote:
| Better superconductors means better magnets, which means cheaper
| fusion.
|
| Some modest improvements in high temperature superconductors from
| MIT is allowing Commonwealth Fusion Systems to scale down ITER
| from being a 65 billion dollar five story behemoth, to something
| slightly taller than the average human.
|
| With a few more iterations, it becomes very feasible to imagine
| fusion reactors the size of a rice maker to power homes and
| vehicles, or even smaller to just have personal, wearable fusion
| reactors that can provide near infinite power to any gadgets we
| want to carry with us.
|
| Also I really enjoy the idea of reducing giant MRI machines down
| to the form factor of a hula hoop. If anyone could get highly
| detailed MRI scans whenever they wanted, a huge amount of disease
| could be prevented.
| moffkalast wrote:
| What amazes me about MRI machines is that the magnetic field is
| "free" in terms of energy cost. It takes some power to start up
| but then the current just runs in a circle without losses, so
| you only have to maintain the cooling so the coils remain
| superconductive.
|
| Room temperature superconductors that wouldn't require any
| cooling would also make lots of use cases for strong magnets
| obsolete, increasing power and lowering mass for e.g. EV
| motors, generators, etc.
| credit_guy wrote:
| > which means cheaper fusion.
|
| It does not mean cheaper fusion. Fusion via magnets is a lie.
| For 70 years the fusion scientists have been telling us the
| same story: we are nearly there. We did the math, and if we can
| just increase the power of the
| tokamak/stellerator/z-pinch/whatever by a factor of 10, we'll
| get ignition.
|
| The problem is that plasma shows all sorts of instabilities.
| All these projections need to come with an asterisk: "we did
| the math, and assuming there's no new instability that will
| show up this time, then ...". But each time there is a new
| instability.
|
| ITER will get built one day (maybe) and they'll figure out that
| there's yet another issue that requires a few more tens of
| billions (or maybe hundreds).
|
| They will not get the money this time. ITER did not start as a
| genuine quest for getting fusion. It was a political project
| designed to make the US and the USSR cooperate on something
| that both could perceive as helping humanity in general. Once
| the USSR disappeared, the impetus was gone, and a third of a
| century later it remains something that will be finished in the
| distant future.
| Retric wrote:
| At the end of the day Fusion has been treated as a very
| expensive science project not some critical technology we
| really need to get working. Thus delays which have nothing to
| do with feasibility or even cost just politics.
|
| Joint European Torus (JET) built in 1983! eventually hit a
| plasma heating Q of 0.67. Scaling that up isn't some big leap
| of faith. ITER was started as an agreement between Regan in
| Gorbachev in 1985, but didn't begin construction until 2013!
| based on a significantly scaled down and very conservative
| design from 2001, with an expected completion date of
| 2025-2030. It's terrible, but under funded multinational
| projects don't move quickly.
|
| That's why nothing got done with fusion, you need experiments
| to make progress running computer simulator and toy machines
| isn't enough. Further, you can start site prep and building
| the facilities well before a design is finished. So much of
| these delays were completely political in nature not
| technical, we could start site prep for DEMO today but expect
| site selection and prep to add a few years of completely
| avoidable delay to that project as well.
|
| Of course being able to build a working device is only part
| of the story, it also needs to make economic sense. But
| that's a different matter from why things have taken so long.
| pfdietz wrote:
| I agree that fusion has been treated as a science project,
| but I take a different implication from that. The
| importance of the science has been overstated, when more
| mundane engineering considerations are likely more
| important. There's this pervasive idea that once the
| science is done, that once the plasma is contained well,
| we're golden and fusion will be a sure thing. This is very
| far from the truth.
|
| Lawrence Lidsky pointed out back in the 1980s that there
| are serious arguments against DT fusion, even if you assume
| the physics isn't a problem at all. Just assuming you have
| a magic black box that can make DT go and you still need to
| capture the neutrons, and this simple sounding engineering
| problem makes DT fusion unattractive compared to
| alternatives, with volumetric power density at least an
| order of magnitude worse than fission reactors.
|
| Subsequent experience bears this out. Even supposedly
| compact designs like ARC will still be a factor of 40 worse
| than PWRs by this metric. Note that better superconductors
| than the HTSs in ARC would not help, since the mass of ARC
| is dominated by the structural material needed to keep the
| magnets from flying apart. Any stronger magnetic field is
| ruled out by practical considerations of strength of this
| structure.
|
| _Maybe_ the limits can be relaxed somewhat if the reactor
| has thick liquid lithium as the first wall, so power /area
| can be increased (the liquid would be exposed directly to
| vacuum; at sufficiently modest temperature the vapor
| pressure of liquid lithium can be very low). Zap uses that
| approach, but notably Zap doesn't use external magnets
| (superconducting or otherwise); the magnetic field is
| generated by current flowing in the plasma. Zap doesn't
| cover all 4 pi steradians around the plasma with flowing
| metal though, so neutron load on exposed components may
| still limit their power density.
| Retric wrote:
| Volumetric energy density is largely meaningless when the
| inside is a low density plasma. It's not like you need to
| pay for that volume of steel or something it's basically
| free.
|
| What matters is the cost of the walls which mostly scales
| with surface area not internal volume.
| pfdietz wrote:
| > It's not like you need to pay for that volume of steel
| or something it's basically free.
|
| I'm talking about the volume of the reactor, not the
| plasma, and no, it's not "basically free". Very far from
| it! The size and cost of the reactor is _the_ big issue.
| In a DT fusion reactor, you 're basically (from an
| economic point of view) burning the reactor, not burning
| the fuel. The reactor is the consumable that drives the
| cost of produced energy. The cost of the reactor is a
| function of its size and complexity. A fusion is reactor
| is both much more complex than, and much larger than, a
| fission reactor of the same thermal output. So, if you're
| using both as heat sources, the fusion reactor will not
| be able to compete with a fission reactor.
|
| Fusion reactors also have strong diseconomies of scale,
| since they are limited by power through the first wall,
| but (contrary to your assertion) cost scales more with
| volume. So, you want to make a DT fusion reactor as small
| as possible. However, size is limited from below by the
| need to absorb neutrons in the blanket, and this distance
| is set by nuclear cross sections.
|
| These considerations are what drives the desire the use
| fusion directly to produce electrical energy, not produce
| heat, so the apples-to-apples comparison with fission can
| be evaded. For this reason, I consider Helion the least
| dubious of the fusion enterprises.
| Retric wrote:
| > I'm talking about the volume of the reactor
|
| Again, the reactor's physical structure and cost doesn't
| scale 1:1 with the internal volume, so it's a meaningless
| metric.
|
| As to your assumptions, a smaller device may be cheaper
| or more expensive depending on what it takes to make it
| smaller. It's a complex machine you can't just price
| things by weight or something.
|
| Really the argument is like complaining about fission
| reactors because all that water is heavy what matters is
| cost not vague proxies for cost.
| pfdietz wrote:
| It seems like you are engaging in magical thinking. A
| larger, more complex object will be more expensive than a
| smaller, simpler object. We can quibble on the exact
| ratio, but making your heat source 40x larger has to have
| an effect.
|
| One consideration that implies accelerating cost
| increases is reliability. A fusion reactor will have many
| Criticality 1 features (like welds that, if they fail,
| leak coolant into the vacuum vessel). The larger the
| reactor, the more reliable each such component must be.
| Reliability is expensive.
| Retric wrote:
| > A larger, more complex object will be more expensive
| than a smaller, simpler object.
|
| That assumes the larger device will be more complex when
| it's often simpler to make something larger than it is to
| scale it down. At the extreme end the sun is vastly
| simpler than any reactor design we are considering, those
| are complex _because_ we need to operate on a smaller
| scale.
|
| Hell we could have built a combined fusion/fission
| reactor in the 1960's using Hydrogen bombs and a large
| enough underground body of water to absorb the energy.
| Would need to be huge, but not that complicated.
| pfdietz wrote:
| I'm comparing fusion reactors to fission reactors there.
| The complexity of a fusion reactor is _obviously_ much
| higher than that of a fission reactor. So is the size,
| for a given power output.
| Retric wrote:
| You mentioned "Fusion reactors also have strong
| diseconomies of scale" so that's what I am referring to.
| A fusion reactor 2x larger with the same energy flow per
| m2 of wall could be cheaper per kWh than a more compact
| reactor. The exact details matter a great deal and not
| every design works at every scale.
|
| Anyway, a fission reactor's complexity is mostly outside
| the device. Things like multiply redundant cooling
| systems, backups for your backup generators, fuel
| processing, etc that are completely unnecessary or
| simpler on a fusion reactor. So overall a large fusion
| power plant could easily be a simpler overall system.
| pfdietz wrote:
| The diseconomy of scale follows thus:
|
| The magnetic pressure (and hence density, at given beta
| and temperature) scales as B^2. The fusion power density
| scales as density squared, or as B^4. Now, the mass of
| the support structure scales as volume x B^2. So, power
| per support structure mass (and hence, per cost of that
| structure) scales as B^2.
|
| However, fusion power density is limited by what the
| first wall can withstand. Therefore, a large reactor must
| reduce B (or, reduce beta) to stay within this limit.
| Reducing B reduces the power/support mass, and hence
| power/$ of support structure cost.
|
| Fusion reactors require equipment outside the reactor as
| well, probably much more complex than in a fission
| reactor. Online tritium recovery, robotics equipment for
| internal maintenance, and space for first wall
| replacement (since known materials do not survive the
| life of the reactor, unlike structures in a fission
| reactor core.) If you look at ITER, there's a large
| volume around the core where robotic maintenance devices
| can slide on a track. The ARC concept required volume and
| machinery for lifting the entire top of the reactor and
| replacing the vacuum vessel (then disassembling the old,
| activated vessel.)
| Retric wrote:
| > Now, the mass of the support structure scales as volume
| X B ^2
|
| No it does not, just as an example the fusion blanket is
| a constant thickness for a given level of neutron flux
| per m2 and sub linear scaling as flux increases. Same
| deal with your cooling loop etc.
|
| You're making several other mistakes, but because at a
| fundamental level the costs relationships are more
| complex than what you're modeling.
|
| Consider despite being a novel experimental design and
| having a huge research staff etc, Vogtle Electric
| Generating Plant still cost more than ITER to build. Sure
| the scale is an order of magnitude smaller, but fission
| has been around for a half century at this point is
| seemingly much simpler and you'd assume there was a great
| number of efficiency gains to be had. https://en.wikipedi
| a.org/wiki/Vogtle_Electric_Generating_Pla...
| pfdietz wrote:
| Yes, it does. This follows from the fact that structural
| mass is proportional to stored magnetic energy, just as
| the mass of a pressure vessel is proportional to volume x
| pressure (for materials of a given strength).
|
| Viewed another way: if we double B, we quadruple the
| forces on each segment of conductor, and therefore must
| quadruple the strength of the supports.
|
| I explicitly said "support structure", the structure that
| is resisting the force of the magnets. There are other
| parts that scale more slowly, but I don't need to show
| that all components scale poorly to show that overall
| there are diseconomies of scale.
|
| Note that this is NOT like in a fission reactor. In a
| fission reactor, everything scales just about linearly
| with power.
| Retric wrote:
| > I don't need to show that all components scale poorly
| to show that overall there are diseconomies of scale.
|
| Yes you do. If A represents 0.001% of the cost then
| increasing it by 20x doesn't matter and the support
| structure is cheap.
|
| Same deal with a fission reactor there's several
| diseconomies of scale for example around the length of
| control rods passive cooling after an accident etc, most
| of them just don't matter much.
| pfdietz wrote:
| Very well. I will simply note that 2/3rds of the mass of
| ARC is the support structure for the magnets. And the
| rest of the mass includes the blanket.
| Retric wrote:
| Now just look up how expensive steel is per kg vs
| superconductors or lithium and ... ahh yea weight is a
| poor predictor of cost.
| pfdietz wrote:
| You do realize that almost all the mass of a PWR reactor
| is steel, right? The steel pressure vessel, steel
| supports for the fuel bundles. So the argument you are
| making there is that the mass discrepancy between fusion
| reactors and PWRs grossly understates the difference in
| cost.
| Retric wrote:
| Your point? The cost of the reactor is just a fraction of
| the total cost of a fission power plant.
| reaperman wrote:
| In a separate line of inquiry, this is what I've been
| thinking about wrt fusion lately. Even if the "fusion"
| part were free, how much would the electricity cost just
| based on the steam generator turbine part? (More
| generally, the sum of all the non-fusion parts of a
| fusion power plant)
|
| Further, if electricity from a fusion plant were
| effectively free (like it didnt need turbines or
| something) what would large-scale desalination cost even
| if it did use truly free energy? This is what I'd be
| excited for from fusion power, because potable water
| scarcity is a huge upcoming/ongoing problem in some
| developing nations with very large populations.
| Retric wrote:
| Nuclear fission and fusion power plants can use sea water
| for most of their needs no need for desalination when you
| just want thermal mass. Remember nuclear subs operate
| under the ocean.
|
| Deuterium requires processing a great deal of water, but
| can be moved around the world cheaply at the levels
| needed for fuel.
|
| As to the costs of fusion or fission power if the nuclear
| bits were free, it's roughly half the cost of coal.
| reaperman wrote:
| I meant the economic effects of using fusion as a cheap
| energy source to provide drinking water to ~1 billion
| people or so (some part of the population who live in
| places which currently cannot afford to provide their
| citizens with proper potable water). Desalination uses a
| ton of electricity. It's a very significant portion of
| the cost (~50%). But even if the energy from fusion was
| magically absolutely free, it would "only" reduce the
| cost of desalination by about 50%. This might not be
| enough for those who need it.
|
| It's a parallel to how with a fusion power plant, even if
| the reactor only cost $50,000 (some comically small
| amount near zero), the electricity from the overall power
| plant connected to the reactor might still be fairly
| expensive. Like - if you have access to free steam, is
| turbine generation actually cheaper than solar? Even
| assuming absolute best-case, fusion's place might not be
| "lowest cost source of energy" but rather "a notably
| cleaner and lower-cost base load" which can provide
| electricity when weather causes the solar and wind farms
| to underproduce. In 30 years in developed nations, its
| competition will be batteries, pumped hydro, and other
| energy storage farms.
| Retric wrote:
| Ops accidentally removed: Compared to PV free energy
| might reduce the cost of desalination by 1/3, but fusion
| isn't going to be free.
|
| The core issues is drinking water is isn't generally a
| lack of water. People in rainforests still have issues
| getting clean water because maintaining a distribution
| system requires a functioning society/government which
| simply isn't available in extremely poor countries.
|
| Similarly keeping water supplies drinkable requires
| pollution controls which is basically non existent in
| such countries.
| reaperman wrote:
| Yep - so it's kind of a check for "Am I overexcited about
| fusion energy?". Seems like it would be nice to have the
| fusion option if it works out but we can maybe get the
| same benefits promised by fusion from wind + solar + a
| few days of energy storage. Either way it doesn't _seem_
| like it will be truly revolutionary at this point - as
| you showed, our problems are bigger than just cheap
| /clean energy, and we do have seemingly viable options
| for that on the near horizon anyways without fusion.
|
| I'm pro-fusion, I'd like to see more resources allocated
| towards its development, but my outlook on its potential
| impact is very tempered.
| pfdietz wrote:
| And it wouldn't be a (small) fraction of the cost of a DT
| fusion power plant.
|
| The NSS, nuclear steam supply system, is estimated by the
| following link to be 12% of the cost of a NPP.
|
| https://world-nuclear.org/information-library/economic-
| aspec...
|
| So, a fusion reactor an order of magnitude more expensive
| would double the cost of the entire power plant.
| Retric wrote:
| Again that would be more relevant if that was the only
| fission specific cost. That giant concrete building
| designed to survive an aircraft strike etc isn't cheap.
| The equipment for handling spent fuel including the
| cooling pond and safety systems is more expensive than
| the reactor.
|
| Fuel rods end up 0.6c/kWh and on top of that requires
| weeks of downtime for refueling etc. People hear nuclear
| reactor and think that's the most expensive bit, but it's
| really not.
|
| I personally doubt fusion will be cost effective vs
| renewables + storage, but there's reasons to suspect it
| could beat fission at scale.
| snarfy wrote:
| I think a bigger issue that is not discussed much is
| synchrotron radiation. If you try to control a charged
| particle's trajectory with a magnet, it releases radiation.
| The more you try to heat a plasma up and control with
| magnets, the more it releases light and cools down. A tokamak
| design needs to be large to limit this effect, and is why if
| we ever have a Mr Fusion it won't be a tokamak design.
| pfdietz wrote:
| I think the common idea is that the inner surface of the
| reactor's first wall will be conductive, reflecting the
| synchrotron radiation back into the plasma, where it will
| be reabsorbed. Bremsstrahlung, on the other hand, can't be
| handled this way.
|
| Keeping electrons cold helps limit both effects, which is
| one reason why Helion's approach is interesting: the ions
| there are much hotter than the electrons.
| rowanG077 wrote:
| I have never heard anyone claim "we are nearly there" on
| fusion. It's always "it's decades away if we get good
| funding" and then there is not good funding.
| tambourine_man wrote:
| > fusion reactors the size of a rice maker
|
| Mr Fusion is almost 10 years late, according to Back to the
| Future. I'm still waiting for my hoverboard.
| 1992spacemovie wrote:
| Ah that movie brings back good childhood memories for me.
| According to my mom I was addicted to watching Back to The
| Future when I was like 4-5.
| tambourine_man wrote:
| I believe in your mom
| ithkuil wrote:
| Well, perhaps somebody fiddled with the timeline and
| destroyed the future we deserved and stranded us in this
| shit. They probably made a lot of money in the process. A new
| reason to hate the billionaires
| jl6 wrote:
| Lockheed Martin's Compact Fusion Reactor was announced in 2013.
| It's still up on their website[0] but the project seems to have
| been cancelled a few years ago, without any concluding remarks.
|
| [0]https://www.lockheedmartin.com/en-us/products/compact-
| fusion...
| sushibowl wrote:
| > Better superconductors means better magnets, which means
| cheaper fusion.
|
| Notably, what is required for this is superconductors with a
| higher critical field strength. A higher critical temperature
| eases cooling requirements somewhat but does not in itself make
| fusion easier.
|
| Also, quite a few other advances are required before home
| appliance-sized fusion reactors become feasible. After all, the
| largest part of most fission plants has to do with generating
| power from steam, not so much the nuclear reaction itself.
|
| > If anyone could get highly detailed MRI scans whenever they
| wanted, a huge amount of disease could be prevented.
|
| I think this is oversold. Regular MRI screening without any
| indication is generally regarded as unproductive not because of
| the cost of the scan, but because of the high number of false
| positives. Any normal human body is bound to contain some
| number of benign growths.
| rowanG077 wrote:
| Isn't the high number of false positives not just a symptom
| of us using it almost always on sick people? I would imagine
| if everyone got their monthly MRI we would learn far more
| about healthy bodies and the false positive rate would drop.
| drowsspa wrote:
| If you scan everyone, the prior probability is the rate of
| occurrence within your population. So the test has to be
| more sensitive than that. For things that have an
| occurrence of less than 1%...
| ijustlovemath wrote:
| Not to mention that MRIs represent a significant portion of a
| person's yearly allowable radiation dose. Not worth it to
| irradiate people without having a reason.
|
| There's also a recent trend in some medical diagnostics of
| having a lighter touch, instead of running all the tests and
| potentially drawing the wrong conclusion from heaps of data.
| krastanov wrote:
| There is no ionizing radiation in MRI. Only strong low-
| frequency magnetic fields.
| fragmede wrote:
| You're thinking of CT scans. MRIs use Magnets and Radios to
| make Images, not radiation. you're thinking of CT scans,
| which use X-rays. we can't get random MRI scans done
| because they're very expensive.
| krastanov wrote:
| The R stands for Resonance, not for Radio.
| perihelions wrote:
| Since it's a resonance of radio-frequency waves, the
| parent's not really in error.
| assmanreturns wrote:
| And why is that? How does resonance alter the fact that
| the radiation is non ionizing and therefore not cancer
| causing.
| KingMob wrote:
| The comment you're replying to isn't debating that point,
| I think. They're saying "you got the precise acronym
| wrong, but what you did write is still technically
| correct".
| demosito666 wrote:
| > we can't get random MRI scans done because they're very
| expensive.
|
| How come then that outside of Western Europe and US it
| costs $100-200? Or is it because the MRI machines were
| amortized in EU/US first?
| fnord77 wrote:
| > Also, quite a few other advances are required before home
| appliance-sized fusion reactors become feasible. After all,
| the largest part of most fission plants has to do with
| generating power from steam, not so much the nuclear reaction
| itself.
|
| RTGs are not very large, so the technology already exists.
| BobaFloutist wrote:
| More financially available MRIs _would_ be pretty nice for
| sports /exercise injuries.
|
| Find out cheaply and quickly if something's a break, a
| sprain, a connective tissue injury, or something else.
| bananapub wrote:
| > Better superconductors means better magnets, which means
| cheaper fusion.
|
| obviously that's untrue, since fusion for power use at the
| moment isn't "too expensive", it's "too hard". literally
| hundreds of billions of dollars have been spent and we're still
| not close.
|
| I can't tell why there are so many uninformed posters on this
| topic on HN. is astroturfing by the nuclear/fossil fuel
| industry to delay doing the hard work to eliminate fossil fuel
| use? is it just that people read too much scifi as a kid and
| then didn't read any real science on the topic for thirty
| years?
| barfbagginus wrote:
| ITER will have 10x more volume and 6.6x greater thermal
| efficiency (Q factor) than any previous reactor. It fires in
| 2025.
|
| The reactor will use around 600mw of electricity to generated
| 500mw of heat, in 10 minute runs. Not break even by any
| means, but getting much closer than ever before.
|
| ITER uses - I'm estimating - about 5 billion dollars of
| cryogenic superconductors - 10,000 tons of superconducting
| tape. These require let's guess an extra 3 billion dollars in
| cooling capacity and cryonics. Cooling these magnets costs
| around 150mw of energy, reducing reactor efficiency
| significantly.
|
| We also use much bigger magnets than theoretically necessary,
| because cryogenic superconductors quench - instantly lose
| superconductivity - if they take too much power.
|
| Now imagine we have some 10x cheaper room temp superconductor
| that is 10x to 100x harder to quench:
|
| + Magnet mass drops 10-100x (to 1000 tons or 100 tons)
|
| + Magnet cost drops 100x-1000x (to 50 million or 5 million)
|
| + Cryonics system is 1.5 billion cheaper
|
| + We cut the reactor's electricity budget by 150mw, to 450mw
|
| Overall we saved over 6 billion dollars, thanks to a non-
| fusion innovation.
|
| Keep in mind these numbers are guesses and wishful thinking.
| But it suggests that a miracle superconductor could push ITER
| like devices closer to break even, perhaps even achieving it.
| tsimionescu wrote:
| > With a few more iterations, it becomes very feasible to
| imagine fusion reactors the size of a rice maker to power homes
| and vehicles, or even smaller to just have personal, wearable
| fusion reactors that can provide near infinite power to any
| gadgets we want to carry with us.
|
| No, because fusion reactors (of any currently realistic design)
| produce extremely harmful radiation in the form of neutrons.
| Since neutrons are neutral, they can only be stopped by a large
| shielding mass when they directly collide with atoms in that
| mass. The mass itself then turns highly radioactive (with a
| half-life of a hundred years or so, so much more radioactive
| than spent fission fuel).
|
| Plus, if the magnets fail while the fusion reaction is
| happening, then the superheated plasma will violently explode
| in all directions, killing anyone nearby, and spreading the
| radioactive remnants of the vessel all around.
|
| Finally, these fusion reactors need some quantity of tritium,
| which is an extremely rare and extremely radioactive form of
| hydrogen (half life of only a few years) , that is never going
| to be easily available to sell on a consumer market.
| XorNot wrote:
| > Plus, if the magnets fail while the fusion reaction is
| happening, then the superheated plasma will violently explode
| in all directions, killing anyone nearby, and spreading the
| radioactive remnants of the vessel all around.
|
| No. Just...no. This is _entirely_ wrong. The density of _any_
| proposed fusion plasma is 250,000 times _less_ then the earth
| 's atmosphere[1]. Fusion plasma would be _crushed_ the
| surrounding air rushing in, not "explode".
|
| Fusion plasma's are incredibly light, and incredibly thin. In
| the event of a full magnet quench, the only significant
| damage would be from magnetic quench boil off of
| coolant...which is a designed for failure mode, and would
| vent either liquid nitrogen (in HTS designs) or liquid helium
| in LTS designs like ITER.
|
| [1] https://www.ipp.mpg.de/15144/zuendbedingungen
| sandworm101 wrote:
| People always think that the heart of a big machine will be
| some massive block of dense metal. The heart of these
| machines is, for failure mode purposes, an empty void. Be
| more afraid of the associated refrigeration plant. That is
| the bit more likely to explode.
| worik wrote:
| True, very thin but very hot
|
| Yes It would initially collapse, but still a lot of heat to
| dissipate, and I would expect an explosion
| rcxdude wrote:
| The fact that it's very hot doesn't mean an explosion,
| especially if it's also very thin. The total amount of
| heat energy actually stored in a theoretical miniature
| fusion reaction needn't be much.
| gravescale wrote:
| Not that much heat, because the heat comes from an
| ongoing process, rather then being extracted from a dense
| thermal mass of something under pressure. Intuition about
| mass, flow and inertia can be misleading. If there's even
| a tiny leak or magnetic wobble, the plasma just goes out
| instantly. The cooling blanket is at a steady state with
| the reaction so once the plasma goes out, excess heat
| from the walls is very quickly absorbed.
|
| The thermal flux in the wall is high when the reaction is
| happening (multiple megawatts per square metre), but the
| temperature where the beryllium face is bonded to the
| copper-steel backing structure is below 300 Celsis, so
| there's not a huge heat storage of immense temperature in
| the structure.
|
| The plasma itself is 1 gram of mass at 150 million
| degrees. The tokamak full of sea-level air would be 1
| million grams of air, more or less. So it won't superheat
| 800 cubic metres of air into an explosion, even if there
| was a huge leak and pressure equalised very fast.
|
| The bigger explosion hazard is the 800 cubic metre vacuum
| chamber imploding (unlikely, it's only 1 atmosphere
| difference, it's not a submersible), a magnet quench
| (which _does_ store a lot of energy that can be released
| at once, just ask CERN, though the result isn 't exactly
| catastrophic because it's part of the design, but it
| might not be good for the magnet) or some mundane but
| dramatic electrical, hydraulic, pneumatic or steam system
| failure that could happen in a coal power station. Future
| reactors may have a cooling blanket that could leak
| liquid lithium.
| newZWhoDis wrote:
| This is why you fuse He3-He3, no neutron emissions/everything
| is charged, much easier to contain.
|
| The problem is getting it hot enough.
| __MatrixMan__ wrote:
| Tritium is only necessary because the magnetic confinement is
| poor. If we assume that it gets much better then it becomes
| economical to use deuterium fuel.
|
| Also, I question the explosion claim. Without confinement,
| the energy drops below the threshold necessary for fusion and
| the reaction stops. An explosion would require a self
| sustaining reaction of some kind and I'm just not sure where
| that would come from. It's not like there's much inertia in
| it.
|
| But you're right about the neutrons. Maybe you can get away
| with a rice maker sized reaction chamber, but you're going to
| want it shielded in something the size of a couch. Probably
| best to just put it in a deep hole and pump water down there.
| Then you can provide the neighborhood with steam for heating
| and electricity for everything else.
| worik wrote:
| > Also, I question the explosion claim. Without
| confinement, the energy drops below the threshold necessary
| for fusion and the reaction stops
|
| I am not a physicist
|
| I expect the sudden failure of magnetic confinement would
| lead to a chemical explosion because of super heated plasma
| nine_k wrote:
| The amount of plasma in such a reactor would likely be
| fractions of a milligram.
|
| What would scare me more is an _asymmetric_ loss of the
| magnetic field, which would produce a huge and not-
| designed-for mechanical stress, potentially leading to
| pieces of the superstructure breaking off and flying at
| high speeds, pushed by the very strong magnetic field.
| __MatrixMan__ wrote:
| Also, a fraction of a milligram of plasma, suddenly free
| to roam about the entire to toroid rather than confined
| to a small part of it would lose temperature rapidly.
|
| But yeah, magnets throwing around chunks of each other,
| and chunks of radioactive shielding, would be an
| unpleasant thing.
| andrewflnr wrote:
| Not to necessarily feed into fear mongering, but: an
| explosion only needs pressure. A can of compressed air can
| explode. And residual heat from the reaction helps, too. So
| the question is whether there's enough hot gas under
| pressure to push past the volume of the reaction chamber...
| perihelions wrote:
| - _" Tritium is only necessary because the magnetic
| confinement is poor."_
|
| Startup hype notwithstanding, the other fusion reactions
| are only incremental improvements over D-T, in terms of
| emitting less neutron radiation. From the standpoint of
| _radiation protection_ it 's all utterly moot--you'll never
| have a fusion reactor in a "rice-maker" to "power homes and
| vehicles". The amounts of radiation are absurdly extreme,
| and of an exotic kind that's really, really, unshieldable.
| (Infamously, the whole point [0] of the neutron bomb was a
| Cold-War tactical antitank weapon. Something that heavy
| steel tanks, envisioned to be in a nuclear land war in the
| Fulda Gap or whereever, would have no chance of surviving--
| not even with all the efforts the superpowers threw at the
| military challenge).
|
| A sobering fact for those unfamiliar with nuclear physics.
| The point of less-neutronic nuclear fusion reactions isn't
| to render them mild enough not to disintegrate humans. It's
| to make them mild enough to not disintegrate _steel_ [1].
|
| [0] https://en.wikipedia.org/wiki/Neutron_bomb#Use
|
| [1] https://www.nature.com/articles/nphys3735
| spacephysics wrote:
| As much as a fallout nuclear energy world would be cool
| (with cars running on fusion), I think in our lifetime
| it'll make more sense to just have the power plants run off
| fusion and delivery energy via the grid
|
| We're already seeing very promising improvements in
| batteries (some without even needing lithium), so probably
| sooner we'll get wildly high battery energy densities
| __MatrixMan__ wrote:
| I agree, it's just not as practical as wind and solar and
| grid-connected energy storage for 95% of the things you'd
| want it for.
|
| But the reasons are that its complex and expensive, not
| that it's accidentally a bomb.
| tekla wrote:
| This is what you get when you learn fusion physics from sci
| fi comic books
| gcanyon wrote:
| I learned fusion from Doc Brown -- you get me some banana
| peels and stale beer and we're in business!
| wolfram74 wrote:
| Daily reminder that the sun is incredibly bad at making power
|
| core power volumentric density: 276 w/m^3
|
| core density: 150000 kg/m^3
|
| alternative units:
|
| 1.8 mw/kg .276 w/L
|
| hello practical says a typical powered push mower might have
| about 1.7 KW and might weigh ball park 30 kilos, so ~60 W/kg or
| tens of thousands more power dense than the sun's core
|
| useful fusion is hard because we're not trying to recreate our
| sun, we're trying to recreate fusion environments so intense I
| suspect they don't show up outside of supernovas or shortly
| after the big bang.
| pgtan wrote:
| Does someone have stock portfolio of superconductor manufacturer
| to share? I watch Furukawa, Sumitomo, and AMSC and they are
| performing not bad.
| freitzkriesler2 wrote:
| I really want to see super conductor high voltage transmission
| lines and power delivery.
|
| Would be the most game changing level of efficiency for our world
| we'd ever see.
|
| I still think we're pretty dang close to it actually happening.
| teleforce wrote:
| Last month there is a news of a novel discovery of one layer of
| atomic gold that can act as semiconductor ala graphene hence they
| called it goldene [1]. This can be really expensive innovation
| but given the ubiquitous nature of gold in the semiconductor wire
| bonding industry they might as well use the gold for the IC
| itself since one layer of atomic gold is puny.
|
| [1] Goldene: A single atom layer of gold:
|
| https://news.ycombinator.com/item?id=40071956
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