[HN Gopher] DARPA wants to bypass the thermal middleman in nucle...
___________________________________________________________________
DARPA wants to bypass the thermal middleman in nuclear power
systems
Author : bilsbie
Score : 183 points
Date : 2024-08-09 21:12 UTC (1 days ago)
(HTM) web link (www.ans.org)
(TXT) w3m dump (www.ans.org)
| xhkkffbf wrote:
| If photovoltaic cells can create power from radiation in the
| visible light range, I suppose there might be radiovoltaics that
| can do something similar. But I wonder if they can capture the
| high power fluxes from a modern core.
| actionfromafar wrote:
| Mayne one could run it in the visible range, or almost there.
| Wasn't there some new kind of IR solar cells?
| ta988 wrote:
| You have to go the other way of the spectrum toward something
| that loves to avoid interacting with matter...
| exabrial wrote:
| Finally a use for dark matter
| thayne wrote:
| But dark matter is matter that doesn't react very much
| with radiation (including light), so it would react even
| less.
| baking wrote:
| I think the issue is the low absorption rate. Eli
| Yablonovitch proposed a box of PV cells facing inward
| containing a heat source where the IR light would bounce
| around until converted to electricity or absorbed as heat.
| This could be used inside a water heater so waste heat could
| be stored. Known as thermo-photovoltaics. See this talk I
| think: https://www.youtube.com/watch?v=lDxJsa8miNQ
| not2b wrote:
| Yes, I see how direct conversion could work with alpha and
| beta radiation, but it seems the gamma and the neutrons
| would just blast through everything and you'd capture only
| a tiny percent of the energy.
| baking wrote:
| Sorry, I was responding to the part about IR.
| fulafel wrote:
| We just need some blimp attached mini suns floating in the
| sky in the night and this can power all the existing solar
| panels on the ground.
| geuis wrote:
| Helion https://www.helionenergy.com/technology/ is a commercial
| fusion company working on a design that theoretically would use
| direct energy capture from the magnetic fields generated during
| the fusion event. They made some headlines last year. Not clear
| if their approach will be successful but it certainly is an
| interesting approach.
| TheRealPomax wrote:
| Commercial _energy_ company. Not fusion company. There are no
| fusion companies on this planet yet.
| ChrisClark wrote:
| What do they plan on using to generate energy then, oil,
| coal, solar, wind? Something else?
| TheRealPomax wrote:
| So far: looks like hope and promises rather than any of
| those.
| Intralexical wrote:
| They claim to have performed fusion, but not yet produced net
| energy. So they're very much a fusion company, but not an
| energy company:
|
| > In 2023, we will end operations on Trenta, our 6th fusion
| prototype... Our results suggest that Trenta is currently the
| best performing privately-funded fusion machine in the world.
| After these last weeks of plasma operations under vacuum, we
| will retire Trenta and move all focus to Polaris, our 7th
| fusion prototype, expected to demonstrate net electricity in
| 2024.
|
| So, they have 143 days left to make good on their current
| timeline, I guess.
| TheRealPomax wrote:
| They're an energy company that has failed to produce any
| yet because of how they chose to generate that energy.
| Unfortunately, like everyone else who tried this so far,
| they can make tiny bang go flash, and that's unfortunately
| _still_ just about it.
|
| So, indeed, so far they failed at energy, and they've only
| succeeded at fusion in the same way and at the same scale
| that university labs have.
|
| So I guess you're right: they're not even _any_ kind of
| company at the moment. They don 't sell anything. They're
| an R&D lab.
| sigmoid10 wrote:
| Fusion is infinitely harder for this than fission. No company
| has demonstrated stable fusion with a positive net energy gain.
| Most of these startups are borderline scams for milking
| gullible VCs. Helion in particular has been around for more
| than a decade and was supposed to reach break even in 2023.
| They haven't even achieved a fully stable D-D reaction so far.
| The biggest thing it has achieved is siphoning tons of money
| from OpenAI's investors because of some questionable actions by
| Sam Altman.
| Intralexical wrote:
| Fusion overall is harder than fission.
|
| Is the direct energy capture part also harder for glowy
| fusion gas than scary fission rocks?
| selectodude wrote:
| I think the concepts are the same but the execution (heat
| up water with plasma) is still a work in progress.
| Intralexical wrote:
| That's the "thermal middleman" part they're trying to cut
| out.
|
| By analogy, compare Concentrated Solar Power versus
| Photovoltaics.
| thayne wrote:
| I think in a Deutritium-Tritium fusion reaction a lot the
| energy is in the neutron. And since neutrons are neutral
| you can't really directly convert that into electrical
| energy.
| DennisP wrote:
| Yep, for D-T 80% of the energy is in neutrons. Helion is
| using D-D/D-He3, and for that it's about 5% in neutrons,
| and most of the rest in fast-moving charged particles.
|
| So they have a simple way to extract electricity
| directly. They squeeze the plasma with a magnetic field
| from a copper coil, then there's an explosion of charged
| particles, which pushes back against the magnetic field
| and causes electricity to flow in the coil.
| fallingknife wrote:
| What do you know that all those investors don't that lets you
| so confidently call this a borderline scam?
| DennisP wrote:
| It's a pulsed reactor by design, it's not supposed to create
| a "fully stable" reaction.
|
| They're actually pretty much on schedule, once you account
| for the several years it took them to get the necessary
| funding.
| exabrial wrote:
| There definitely trendy since some high profile YouTubers were
| invited to tour! I sincerely hope they can succeed. I believe a
| limiting factor is going to be fuel unfortunately, as well as
| I'm not entirely sure it'll be radiation free.
| DennisP wrote:
| The original fuel is deuterium, which is absurdly abundant on
| Earth. Pure deuterium fusion results in half helium-3, and
| half tritium which decays to helium-3 with a 12 year half-
| life. Then their main reaction is D-He3.
|
| The D-D reaction is less energetic and produces a neutron,
| and the D-He3 reaction doesn't produce a neutron. The
| combined reaction would release about five percent of its
| total energy as neutron radiation. The neutrons from D-D are
| about as energetic as fission neutrons, rather than the
| extremely high energy of D-T fusion neutrons.
|
| They'll never run out of fuel; there's enough deuterium in
| your morning shower to provide all your energy needs for a
| year. But the need to breed He3 will put a limit on how fast
| they can possibly scale up. It could be that manufacturing
| will be slower than that anyway though.
| exabrial wrote:
| Thanks for the insight. I remember it being like the raw
| ingredients were plentiful, but the main reaction
| ingredients were not.
| waryFormerNuke wrote:
| I don't remember the details, but the last time I looked into
| Helion I came away with the belief that their technology flat
| out doesn't make sense and will likely never be anywhere near
| net-positive. Like, the numbers literally don't add up and
| their design could never be anywhere near net-positive.
| foobarian wrote:
| I had the impression that the energy flux required to break
| even is higher than any known materials can support, at any
| geometry. I really hope that's wrong :-)
| dclowd9901 wrote:
| Can someone who has a firm grasp on this stuff explain to me
| how nuclear reactions don't create massive amounts of
| electromagnetism that we can just capture directly? Is it
| really just heat that it produces?
| db48x wrote:
| They kinda do. When a fissile atomic nucleus splits, the
| daughter nuclei repel each other; they are both positively
| charged and the strong force is no longer holding them
| together. So they fly off in opposite directions at a
| measurable fraction of the speed of light. But they don't
| generally get very far, because they are embedded in a solid
| fuel pellet. They can push their way through a few um of
| uranium before they are stopped, bumping into thousands of
| atoms along the way. That's really where the heat comes from;
| all that electrostatic force accelerates them to high
| velocity, but they dump it all very quickly into the material
| around them as heat.
| Muromec wrote:
| > Is it really just heat that it produces?
|
| Yep, it's a big nuclear powered boiler. Boil water, get the
| steam, spin the turbin, cool the water, repeat.
| lazide wrote:
| It's amazing how many generators basically boil down to the
| same 'boring' process of 'boil water. spin turbine.
| repeat.'
| Iulioh wrote:
| I mean, that's just because water is a simple medium we
| can just literally trow out in the environment after use,
| using basically anything else to spin said turbines would
| require a closed system and cooling.
|
| Gravity batteries could be a thing but pumped water is
| the best version of that system, in this case we don't
| boil the water tho
| lazide wrote:
| Water has really awesome phase change properties and is
| nearly ideal for this kind of situation too. Only thing
| better is potentially super critical co2.
| Filligree wrote:
| It generates high-speed neutrons, helium cores, photons,
| fissile fragments, and in rare circumstances free protons.
|
| Of those, only the protons have an electric charge you could
| use in any form of generator... but I'm not aware of any form
| of reaction that predominantly creates protium. The fragments
| are also charged, but the implication that you're using
| fission means they're in the middle of a block of uranium and
| won't keep their speed for long.
|
| The others ignore electromagnetic fields for the most part,
| and will fly around until they smash into something and go
| _goooong_ like the world's smallest bell. Or smash through
| something, perhaps; it's a chain reaction after all.
|
| This mostly just makes other stuff move about. Repeat a few
| dozen times, and you've got heat.
| adrian_b wrote:
| The helium nuclei a.k.a. alpha particles are also charged,
| like the free protons.
|
| However, the alpha decay of some product of the fission
| reactions does not change the total charge of the fissile
| material, because the emission of a helium nucleus with a
| double positive elementary charge leaves a heavy nucleus
| with a diminished nuclear charge, by those two elementary
| charges.
|
| Only when the alpha decay happens to occur close to the
| surface of the material, the positive helium nuclei may
| escape from it and they could land on a collecting
| electrode, making that electrode positively charged and
| leaving the fissile core negatively charged. However such a
| process would extract only a negligible part of the energy
| produced by fission. Even if the alpha extraction could be
| enhanced somehow, the decay energy of the fission products
| is small in comparison with the energy produced by the
| initial fission of the uranium nuclei. Extracting directly
| from the fissile material the nuclei generated by fission
| would be much more difficult than extracting the helium
| nuclei.
|
| The Darpa project may succeed to stimulate the creation of
| some electric generators that could deliver additional
| energy from a fission reactor, by direct electric charge
| separation, but that would remain a small part of the total
| fission energy, most of which will still have to be
| extracted through thermal methods, like today.
| oneshtein wrote:
| 2D + 3He - 4He + 1p + 18.3 MeV 3He + 3He - 4He + 2
| 1p + 12.86 MeV
| Animats wrote:
| Nuclear batteries with beta emitters driving some kind of
| semiconductor have been around for a while, but they're very low
| power.[1]
|
| "... Betavolt's team of scientists developed a unique single-
| crystal diamond semiconductor that is only 10 microns thick,
| placing a 2-micron-thick nickel-63 sheet between two diamond
| semiconductor converters to convert the decay energy of the
| radioactive source into electric current to form an independent
| unit."
|
| "... 100 microwatts, a voltage of 3V, and a volume of 15 X 15 X 5
| cubic millimeters ..."
|
| 3-4 orders below the power requirements for a phone. An AirTag-
| type intermittent device, though...
|
| So, can those be scaled up? Are all those little beta-emitters in
| coin cell form factor going to be a problem? Nickel-63 has a half
| life of 100 years, so they'll be active for a while. Not
| dangerous unless broken up and ingested, but need to be kept out
| of the food chain.
|
| [1] https://www-betavolt-
| tech.translate.goog/359485-359485_64506...
| saulrh wrote:
| Not dangerous unless broken up and ingested, but need
| to be kept out of the food chain.
|
| No worse than a NiCad in that respect. Probably better, if
| anything, since it's so much easier to detect and track.
| giantg2 wrote:
| And set off all the NBC detectors on the highways near major
| cities.
| arcticbull wrote:
| Well yes but only if destroyed. Then wouldn't you call that
| a feature? When in their enclosures there should be no
| radiation.
| giantg2 wrote:
| No way could all the alerts be tracked.
| jacobgkau wrote:
| Yeah, you bring up another angle to look at it from: even
| if the alerts didn't go off when the batteries are being
| used/stored properly, it would make it easy to create a
| lot of noise/false positives as part of an actual attack
| (were those batteries to be readily available).
| arcticbull wrote:
| They were for a long time, betavoltaics were used in
| pacemakers. They started using more conventional
| batteries because the betavoltaics far outlasted the
| actual pacemakers.
| thadt wrote:
| Not Nickel-63 - Beta particles don't go very far in air,
| and are shielded by almost anything. You'll be unlikely to
| be alarming on beta emitters anywhere, unless they're right
| up against your specialized Beta detector.
| KiwiJohnno wrote:
| My understanding is, the danger with Beta emitters is if
| they are broken up into dust, and you breathe the dust in
| (or eat/drink it) then you are toast, as your lungs and
| internal organs get a small, but continuous bombardment
| of Beta particles which will eventually give you cancer.
|
| If you are contaminated internally, with radioactive dust
| then there is no way to fix that.
| lazide wrote:
| Also nearly impossible to detect. No roadside detector
| will, anyway.
| hilbert42 wrote:
| Without going into too many specifics, for a period during my
| career I was involved with an organization whose
| responsibility it is to track nuclear materials and keep them
| under safe surveillance--in fact my job had the words _'
| surveillance engineer'_ in its title.
|
| I say that only bring to your attention how difficult this
| would be in practice. Putting safety aside for a moment, in
| most countries the regulatory restrictions are enormous
| because they are signatories to the NPT--Treaty on the Non-
| Proliferation of Nuclear Weapons which tightly bind them to
| how they use and handle nuclear materials. This involves,
| use, tracking, short and long-term disposal thereof not to
| mention how to keep radioactive materials away from bad
| actors/those who've ill intent.
|
| With safety, there are so many issues involved that I can
| hardly even mention them here. Just as an illustration, the
| once lack of regulations covering the manufacture and use of
| luminous radium paint turned out to be a disaster.
|
| I've thought about this a great deal, whenever the batteries
| in my flashlight die I wish I had some nuclear powered ones
| and evey time I'm brought back to reality when I think how
| difficult it would be to implement in practice.
| saulrh wrote:
| I meant precisely what I said. Tracking NiCads to the
| standards of the NPT would presumably be impossible. If
| your standard is "keep it out of the food supply", though,
| I guarantee that there's a little bit of NiCad in that hot
| dog in your fridge, and there'd be much less NiCad in your
| hot dog if they tripped a radiation detector before they
| hit the incinerator or the landfill.
| XorNot wrote:
| I've always said that I'm more afraid of heavy metal
| contamination then nuclear material contamination.
|
| There are no hand held devices which will tell you if the
| soil you're vaguely near has heavy metals in it, nor how
| much.
| CamperBob2 wrote:
| _There are no hand held devices which will tell you if
| the soil you 're vaguely near has heavy metals in it, nor
| how much._
|
| Well, technically, there are, but now you're back in the
| ionizing-radiation business:
| https://www.youtube.com/watch?v=KdfHVcU8U7U
| im3w1l wrote:
| I've been thinking for a while that there are so many
| possible sources of poisons it's very hard to monitor
| them all. But there is only one of me. So logically I
| should check if I have elevated levels of poisons. Then,
| and only then does it make sense to start monitoring my
| surroundings to trace where it came from.
| hilbert42 wrote:
| Whether it's warranted or not is immaterial given the
| current situation with regulations and there seems little
| chance of that changing.
|
| Personally, I've a healthy respect for radiation/nuclear
| materials but I'm not afraid to work with them so long as
| I know what I'm dealing with--and that's the key point.
| It'd be a bit pretentious to describe situations where
| I've been exposed to radiation levels above background
| except to say they were deemed occupationally safe. That
| said, I've always avoided such situations when and
| wherever possible.
|
| Let's put my view into perspective: here's NileRed (a
| YouTube channel I like and watch often) making uranium
| glass in his home lab:
| https://m.youtube.com/watch?v=RGw6fXprV9U.
|
| Note: I'd _never_ do this despite the low level radiation
| because of the potential for breathing in uranium dust,
| albeit a small risk. That said, I nevertheless own
| several old wine glasses made from uranium glass which I
| keep not to use for drinking but as a demonstration of
| how uranium glass fluoresces under UV light.
|
| It's very difficult to put information about radiation
| into proper perspective or in ways that the lay public
| can properly understand and appreciate, thus the need for
| tight regulations. Then, as I mentioned, there are the
| bad actors and of course a small collection of damn fools
| who are a danger not only to themselves but also to
| others.
|
| No doubt, you're right about cadmium and traces of it in
| food. That comparison isn't lost on me either. It just so
| happens at another time I ran a business maintaining
| handheld portable cassette recorders of the type used in
| exhibitions, etc. and they used rechargeable NiCd
| batteries that needed replacement. It was not unusual for
| me to have to dispose of upwards of 500 old, often
| leaking batteries. Being concerned about Cd contamination
| and disposing of it in an environmentally-friendly manner
| was just part of the job.
|
| Contamination from heavy metals is a very real problem
| and it's not only Cd but also Pb, Tl, Hg, As and orhers.
| Moreover, assessing the actual risk can be very difficult
| and depends very much on circumstances.
|
| Like its more notorious mate mercury, cadmium is a
| poisonous heavy metal, nevertheless that hasn't stopped
| it from being used in industry for plating etc.
| (passivated cadmium plating makes a very nice surface).
| Thus, in the recent past cadmium has been deemed safe
| enough for these purposes in the same way mercury was
| considered safe enough for tooth amalgam/fillings. That
| said, just add a couple of CH3 methyl groups to Cd and we
| get one of the most diabolical poisons available--
| dimethylcadmium (same goes for Hg--dimethylmercury).
| Fortunately, these diabolical compounds aren't that
| common so we must take that into account when assessing
| the dangers of these heavy metals.
|
| Heavy metals are everywhere in the environment both from
| natural sources and from pollution, so when assessing the
| risks several factors predominate, concentration and
| their potential for forming compounds that are far more
| toxic than are the base metals. Also, these compounds are
| often soluble which adds to their danger.
|
| BTW, it's often been said that one cubic meter of soil
| from the average backyard has enough naturally occurring
| arsenic to kill someone--or at least sufficient to make
| them very sick. I've never seen assays to prove that one
| way or other but assuming it's true it puts the risks
| from heavy metals into perspective.
| lazide wrote:
| You can also order (natural) Uranium ore via the mail or
| on Amazon, some of which has pretty high disintegration
| rates and a decently high amount of Radium in it. 80-100k
| CPS.
|
| Or just walk to a number of known sites in Utah and pick
| up chunks of ore off the ground.
|
| A real danger IMO with Alpha and Beta emitters is that
| most Geiger counters aren't going to pick them up at all
| - most are only meaningfully sensitive to Gamma.
| hilbert42 wrote:
| _" ...(natural) Uranium ore via the mail or on Amazon,
| some of which has pretty high disintegration rates and a
| decently high amount of Radium in it."_
|
| I'm in Australia and there's no shortage+ of the stuff
| here. Moreover, mining it has always been politically
| controversial.
|
| Whilst it wouldn't happen now, when I was at school
| decades ago we had radioactive sources in the science lab
| and we did experiments showing how alpha rays could be
| stopped by paper, beta with tin foil and so on.
|
| I also recall the lab had a round section of metallic
| uranium a bit bigger than a US silver dollar and about
| twice as thick, it was handed around the class for all to
| feel how heavy the element was. It was also a source of
| radioactivity for our Geiger counter (but not the only
| one).
|
| To some degree, we have to be pragmatic about access to
| such materials but I'd be the first to agree that finding
| the right balance is difficult. Scaring everyone out of
| their wits about radioactivity is counterproductive (as
| we've seen in recent decades), similarly overfamiliarity
| is as equally dangerous.
|
| I'm glad I had that early experience at school together
| with proper instruction that put its dangers into
| perspective.
|
| The same went for mercury which we had at school in
| reasonable quantities. We were taught its dangers and to
| be very careful with it, especially so its compounds.
|
| In recent times I've met young people who've never
| actually seen mercury and who are terrified of even the
| mention of it. Clearly no one ever wants a repeat of the
| Minamata tragedy but being scared of elemental mercury to
| this extent isn't right either.
|
| I've often said our best approach is proper education,
| that is by providing factually accurate information from
| early on.
|
| Seems to me in recent years we've not done a particularly
| good job at doing that.
|
| __
|
| + https://en.m.wikipedia.org/wiki/Uranium_mining_in_Austr
| alia
|
| https://en.m.wikipedia.org/wiki/Radium_Hill
| jessriedel wrote:
| > With safety, there are so many issues involved that I can
| hardly even mention them here. Just as an illustration, the
| once lack of regulations covering the manufacture and use
| of luminous radium paint turned out to be a disaster.
|
| I think it's telling that the big health disaster everyone
| remembers happened like a hundred years ago and occurred
| not just before regulation, but before the danger was even
| understood. There are negligible annual deaths in the US
| from either acute radiation exposure or nuclear-material-
| related chronic radiation exposure.
| defrost wrote:
| Three US workers died in 1961 when the SL-1 reactor went
| prompt critical and the core explosively vaporized.
|
| All up there are at least seven or eight fatalities in US
| reactor | research facilities in that general time frame,
| Los Alamos National Laboratory, et al.
|
| The Columbus radiotherapy accident 1974-76 led to 10
| deaths and 88 "immediate severe complications"
|
| There was another in Houston in 1980 with 9 deaths and
| additional complications.
|
| https://en.wikipedia.org/wiki/SL-1
|
| https://en.wikipedia.org/wiki/Columbus_radiotherapy_accid
| ent
|
| REAC/TS Radiation Accident Registry: :
| https://www.irpa.net/irpa10/cdrom/00325.pdf
| jessriedel wrote:
| Thanks but I think this proves my point? A handful of
| deaths each decade, in an industry with hundreds of
| thousands of workers. Like, being killed by a falling I
| beam or in a car accident while commuting to work are
| vastly more likely.
| defrost wrote:
| I agree with your point; there are negligible annual
| deaths in the US from meteorite strikes.
|
| I've had a career mapping environmental radiation across
| entire countries; background uranium, potassium, and
| thorium _and_ residual traces from testing, mining and
| accidents.
|
| Deaths are rare in the US, a bit more common elsewhere,
| that's a fact.
|
| I can't say that's an argument for relaxing standards or
| being less safety conscious in reactor design, building
| codes, or medical and industrial procedures.
|
| The Union Carbide Corporation (UCC) of the United States
| demonstrated pretty well what can happen if you shirk
| safety and that was just manufacturing pesticides.
|
| There's always that one meteorite.
|
| Mind you, there's a steady supply of radioactive waste
| from rare earth processing that gets offshored and swept
| under the carpet .. it's okay to have an addiction to
| fancy electronic gadgets, less so to be ignorant of by
| products and the harm caused in _other_ peoples
| backyards.
| roenxi wrote:
| > The Union Carbide Corporation (UCC) of the United
| States demonstrated pretty well what can happen if you
| shirk safety and that was just manufacturing pesticides.
|
| > There's always that one meteorite.
|
| But we just ignore the meteorite. Nobody has made any
| attempt to stop either of us being hit by a meteorite. We
| just let it fall where it may.
|
| We've _had_ safety standards shirked, we 've had multiple
| disasters and the worst case scenario so far appears to
| be order-of-magnitude equal to a normal year of current
| practice using fossil fuels. It seems to be well within
| our tolerance for risk.
|
| The issue here is that progress on one of the most
| promising sources of energy we have has been blocked and
| it is hard to find someone who can articulate a reason
| why, let alone a good reason. Between Germany and Japan
| we've had countries that appear to be more willing to
| risk deindustrialisation than just keep on with a
| perfectly acceptable nuclear status quo. It is madness.
| It is akin to trying to move civilisation underground to
| avoid the inevitable meteor strike that is going to wipe
| out humanity - we can't afford that expensive a risk
| mitigation and it doesn't seem clear that it would even
| help.
| defrost wrote:
| 'We' is doing a great deal of heavy lifting for you
| there.
|
| South Korea has fast build times, China has 100 reactors
| _planned_ with 10(?) (IIRC) currently under construction,
| a large MW scale pilot SMR completed and tested for a
| year, ground broken for a low GW 2nd gen salt reactor
| based on the pilot, and plans for a large high GW third
| gen version waiting on the 2nd gen being completed and
| bedded in for any modifications to plan.
|
| The economics vary by country and demand, here in
| Australia there's no economically feasible near term path
| for nuclear power gen. for a number of good reasons, not
| the least being the short term return from putting any
| available money into renewables and batteries - but this
| is a particular economic constraint setup that differs to
| other countries.
| jessriedel wrote:
| > Deaths are rare in the US, a bit more common elsewhere,
| that's a fact.
|
| > I can't say that's an argument for relaxing standards
| or being less safety conscious in reactor design,
| building codes, or medical and industrial procedures.
|
| It's prima facie evidence you're picking the wrong trade-
| off between safety and productivity. Because of the
| nature of diminishing returns, the optimal point in a
| cost-benefit trade-off usually results in both non-
| negligible cost and non-negligible benefit. When your
| safety regs are so strong as to have driven risk to
| ~zero, but where the compliance cost of the regs are
| reflected in every aspect of the industry, there ought to
| be a presumption of over regulation that would need to be
| rebutted _quantitatively_. It 's irresponsible to set
| degree of regulation without estimating the costs of
| compliance.
| kelnos wrote:
| Maybe the reason for the low number of deaths is the high
| levels of tight regulation.
| Weryj wrote:
| Yeah, I was about to say.
|
| We consider it safe because it's tightly controlled and
| very centralized, but that has no connection to how safe
| it would be as a consumer product. Just because it
| contains the same material, doesn't mean anything,
| because the methods of harm that could emerge have never
| existed.
|
| Ingestion, trash disposal, recycling contamination, the
| infinite ways you could accidentally destroy a device.
| jessriedel wrote:
| Of course. But whenever you're balancing downside X
| against upside Y, and the downsize is now essentially
| zero, this is prima facie evidence you're picking the
| wrong trade-off.
| ben_w wrote:
| > I think it's telling that
|
| That's putting the cart before the horse.
|
| Those regulations came to be _because_ of things like
| that (plus also "we don't want everyone getting nukes or
| radioisotope weapons" because this is more general than
| just industrial accidents).
|
| The only way to compare is to look at times (or places)
| without the legislation.
| FooBarWidget wrote:
| I regularly see thrown away batteries on the streets of
| Amsterdam. This worries me.
| xtiansimon wrote:
| Meanwhile and just a few days ago...
|
| "Rising rates of cancer in young people prompts hunt for
| environmental culprit (ft.com)"
|
| https://news.ycombinator.com/item?id=41178776
| db48x wrote:
| Pretty dangerous when burned though.
| swores wrote:
| > _"... 100 microwatts, a voltage of 3V, and a volume of 15 X
| 15 X 5 cubic millimeters ... "_
|
| > _3-4 orders below the power requirements for a phone. An
| AirTag-type intermittent device, though..._
|
| If my maths is right (and it's past midnight, and I'm not
| entirely sober, so might not be) and my search results are too,
| 15 x 15 x 5 cubic millimeters is approximately 9.68 times
| smaller than an iPhone battery (95 mm x 37.6 mm x 3.05 mm,
| ish), but if energy capacity scales linearly to volume then its
| ~12,500 times lower capacity per volume than an iPhone battery.
| K0balt wrote:
| That's 100 microwatts x100 years, so about 876 wh, or 292 amp
| hrs (292,000 mah)
|
| But, still, only 80mah a day . So 750mah scaled up to iPhone
| battery size. So abut 1/5 of the average daily power
| requirement for an iPhone. Even at that rate you'd need to
| use a supecapacitor to even out the load profile.
|
| OTOH, in terms overall energy, it would be about the same as
| about a 50 litre lithium ion so it is rediculously dense,
| just low output
| timschmidt wrote:
| 1/5 the daily power requirement is surprisingly decent.
| Swapping out the screen for an eink display or ultra low
| power LCD like those from PixelQi and downclocking the SoC
| might be enough to make up that gap.
| swores wrote:
| FYI, your comment made me look up PixelQi and Wikipedia
| says that conpany died almost a decade ago (although 2015
| feels to me like much, _much_ less than a decade ago):
|
| > _" By 2015, PixelQi's team and offices were
| unreachable, and the company is presumed defunct.[3] The
| intellectual property is now owned by the original
| investor of Pixel Qi, while the right to manufacture
| Pixel Qi technology contractually rests with Tripuso
| Display Solutions.[4][5]"_
|
| https://en.m.wikipedia.org/wiki/Pixel_Qi
| com2kid wrote:
| Or half the battery size that came with the iPhone 4s.
|
| It could be made to work if software wasn't so violently
| inefficient (both CPU and data usage) and screens weren't
| so large.
| refulgentis wrote:
| TFA states this and replies to this, in detail :)
| wizardforhire wrote:
| I always thought super conducting ccds with plasma scintillating
| cell intermediaries were the way to go.
|
| Capture the alpha and beta radiation with the plasma
| scintillators. Plasma being ideal because it wont degrade with
| bombardment.
|
| Capture the em radiation with ccds.
|
| We normally think of ccds as low power capture devices for
| cameras. Theres no reason they couldn't be scaled up to handle
| the power requirements. Perfect use case for super conductors.
|
| This of course for moderate to large scale fusion reactors where
| cost is a negligible object.
|
| Of course the dream is solid state Hau arrays. Which Dr Lene Hau
| postulated 15 years ago... but thats a whole other story.
| wizardforhire wrote:
| Of course plasma will degrade its just easier to separate out
| the products. You could feed the plasma back into the reactor
| and use cyclotron resonance. Alpha and Beta decay being one of
| the big problems with reactor design as the walls degrade over
| time. So designing for that with an active system seems to me
| to be a way a viable solution to minimize maintenance.
| carabiner wrote:
| Could this cause a resonance cascade?
| wizardforhire wrote:
| Unlikely as resonance in this case is referring the
| minuscule difference in mass between isotopes which results
| in preferential orbits within a tokamak which can be
| exploited for separation. I guess depending on what you're
| separating and whether or not someone is paying attention I
| guess conceivably a runaway event could occur but I think
| the masses and densities involved are too small to be of
| any concern.
| epistasis wrote:
| This is pretty much the _only_ hope for nuclear power in the
| future. Current reactors are way too expensive, and they do not
| get cheaper the more we build of them.
|
| Miles upon miles of pipes with high-performance welds meant to
| last decades is no way to build a cheap and cost-effective
| electrical generation system. We need something better.
|
| Also, getting off a thermodynamic heat engine means the chance
| for far greater efficiency. Going through a heat cycle is hugely
| inefficient.
|
| For example, just extending the lifetime of the Diablo Canyon
| reactor pair in California, for five years extra life from 2025
| to 2030, is expected to cost a minimum of $8.3B. That's the
| utility's claim before the work has been done, and life all
| nuclear/construction projects, it will almost certainly balloon
| midway.
|
| TL;DR nuclear needs a tech breakthrough like direct conversion.
| cinntaile wrote:
| If they utilize the waste heat for eg. district heating, the
| equation looks a lot better. Unfortunately most cities don't
| have district heating.
| pfdietz wrote:
| There are already lots of sources of low grade waste heat.
| Since we aren't exploiting them, it must not be worth doing.
|
| So, for nuclear district heating, you'd need higher quality
| heat, probably steam.
| cinntaile wrote:
| You don't use steam for district heating. There are two
| problems here, the first one is that district heating
| doesn't exist in a lot of places so the infrastructure
| needs to be built. The second problem is that people are
| afraid of nuclear so running water through their house
| warmed almost directly with nuclear heat is a sensitive
| topic. It's not actually dangerous of course, but
| perception matters. Actually there is a third reason now
| that I think of it. Nuclear plants are usually not close to
| big enough cities to absorb that heat, but it's possible to
| transport the water over 100km while still retaining enough
| heat for district heating.
| pfdietz wrote:
| Some district heating systems do in fact use steam.
| epistasis wrote:
| Losing 50%-67% of the energy to waste heat is not the
| roadblock to new nuclear.
|
| The roadblock is the immense expense of a massive,
| complicated, intricate machine requiring massive workforces
| of highly skilled construction labor.
|
| Shifting from heat conversion to some sort of direct
| conversion, and in the process ideally eliminating a huge
| amount of the construction expense, is the way out.
|
| As our economies become ever more advanced, skilled labor
| becomes ever more expensive. Our existing fleet of nuclear
| reactors is much like the intricate cathedrals of past
| centuries. We could build in that style, but the expense is
| much higher today than it was back when the cathedrals were
| first made.
| cinntaile wrote:
| You mentioned energy efficiency, I simply provided a
| possible way to boost that efficiency up a bit.
| epistasis wrote:
| You are right! I must have been thinking of different
| types of efficiency and written very unclearly. A pet
| peeve of mine is people talking about "efficiency" in
| energy and not defining it or switching between
| definitions sloppily, and I seem to have done it there.
| In any case apologies for not being consistent.
| tiku wrote:
| But why is it so hard. A steam engine in itself is not complex,
| we had locomotives for a long time, they didn't have high
| performance welding for example. Why can't we dumb down nuclear
| reactors? While keeping it safe. Perhaps by using material that
| won't cause meltdowns or using heat from nuclear waste?
| epistasis wrote:
| If you have 20,000 welds that each need to last 30 years
| without being fixed later, that's an order of magnitude
| difference in quantity than the corresponding 2,000 for a
| coal boiler, in addition to a few orders of magnitude
| difference in the necessity of lasting a long time without
| repair.
|
| It's a hell of a lot more than a steam boiler, even if
| ultimately that's the goal. The nuclear island is a hell of a
| beast of complexity, size, and quality.
| at_a_remove wrote:
| This is one of the reasons why, as an undergrad, I switched from
| nuclear engineering to physics: at the end of the day, we're
| still using heat and turbines, just with extra, more dangerous
| steps; although the materials engineering aspect is recognizably
| challenging, I found it not particularly thrilling.
|
| At other, far end of the scale, if Hawking radiation does exist,
| black holes could be considered converters of mass to energy,
| skipping all of the conservation of baryon and lepton numbers ...
| although at very large timescales until you have a fizzy, spicy
| nano black hole on hand.
|
| Controlled capture of the various types of radiation (sometimes I
| find that word to be sloppy) to extract the kinetic energies does
| not seem to be physically impossible, but I have oft wondered
| _how_ as I think about various nuclear batteries which have
| existed. Indeed, the article doesn 't even break it down enough:
| beta ought to be split into beta-plus (positrons) and beta-minus
| (electrons), and they skipped some _2p_ emissions. My guess is
| that not only will each need its own approach, but that each of
| those would be subdivided into different energy bands, not unlike
| having different compounds for chlorophyll-A and chlorophyll-B,
| only for, say, fast neutrons versus thermal neutrons.
|
| And I think that's gonna be materials engineering again. Whoops!
| mannykannot wrote:
| In fission, it seems that most of the energy release is in the
| form of the kinetic energy of the daughter nuclei rather than
| gamma radiation or the kinetic energy of neutrons (from
| Wikipedia: _For uranium-235 (total mean fission energy 202.79
| MeV), typically ~169 MeV appears as the kinetic energy of the
| daughter nuclei, which fly apart at about 3% of the speed of
| light, due to Coulomb repulsion. Also, an average of 2.5 neutrons
| are emitted, with a mean kinetic energy per neutron of ~2 MeV
| (total of 4.8 MeV.) The fission reaction also releases ~7 MeV in
| prompt gamma ray photons._ )[1]
|
| Given this, I'm guessing that, for direct conversion to be at all
| efficient here, a significant fraction of this energy would have
| to be converted into electrical potential energy rather than be
| dissipated as heat in collisions between these nuclei and any
| part of the apparatus. Are there any nascent technologies of this
| sort?
|
| [1] https://en.wikipedia.org/wiki/Nuclear_fission
| db48x wrote:
| It's been proposed as an extremely efficient spaceship drive.
| Make 1um beads of fissile fuel embedded at below critical
| density in aerogel. A thin sheet of aerogel with these fuel
| pellets in it is then inserted into the engine right inside a
| very strong magnetic field. Bombard the fuel with neutrons to
| ramp up the fission rate and those same daughter nuclei come
| streaming out of the pellets. They are still charged, so in the
| magnetic field they take a curved path. They push the magnet
| forward as the field pushes them out the back of the engine.
| With an exhaust velocity of 3% of the speed of light, they can
| get enough DV out of a few kilograms of fuel to zip out to
| Pluto and back in a few years.
| drivebyhooting wrote:
| That sounds very cool. Like a nuclear ion drive. Is there a
| technical paper about it?
| Intralexical wrote:
| Sounds like what Wikipedia calls a "Fission-fragment
| rocket", I think?
|
| So check the citations for papers:
|
| https://en.wikipedia.org/wiki/Fission-fragment_rocket
| mannykannot wrote:
| Very interesting - I had not heard of this before. I see
| that the entry on the "dusty plasma" design says that the
| exhaust flow can be decelerated for power (presumably
| that applies to other designs as well.) It does not
| mention how the deceleration is performed
| (electrostatically, a bit like a reverse Van der Graaff
| particle accelerator?) or how efficient and compact this
| could be.
| db48x wrote:
| Wikipedia has a short list:
| https://en.wikipedia.org/wiki/Direct_energy_conversion
| jpk wrote:
| Now knowing that small quantities of space dust settle on our
| roofs, I presume you'd have to reach some safe distance from
| populated planets before using such an engine?
| db48x wrote:
| Orbit is sufficiently safe. The exhaust products are
| individual atoms rather than grains of rock that can fall
| on a roof.
| jpk wrote:
| Yeah, but those atoms are fission products!
| Intralexical wrote:
| Eh, they're moving at 3-5% the speed of light. Just don't
| point it towards the planet.
| lazide wrote:
| One of my fav. points in one of the classic sci-fi books
| (a deepness in the sky maybe?) is how the main engines of
| their ships (bussard ramjet fusion drives) were also such
| incredibly powerful weapons, that merely pointing one
| (even when off) at anyone was seen as a clear declaration
| of war/hostile intent.
|
| Which, if you do the math, is definitely the case. Ain't
| nobody walking away from getting one of those to the
| face.
| db48x wrote:
| Yes, Vernor Vinge's A Deepness in the Sky had Bussard
| ramjets, and using one inside a civilized solar system
| was usually a great crime since the magnetic fields may
| be extremely large. But you can't point them; they're
| more of an area-effect weapon.
|
| Larry Niven's Known Space stories coined the phrase
| Kzinti Lesson when a peaceful Human crew turned their
| photon drive on an attacking Kzinti ship, slicing it in
| half. The Kzinti had acquired an anti-gravity drive from
| aliens (who they then enslaved and ate) so they didn't
| have a good visceral sense of the energy required to
| visit the stars the hard way. Their telepaths kept
| reporting that the Humans were peaceful and didn't have
| any weapons on their ship right up until the ship flipped
| over and sliced them in half. That kind you can point.
| db48x wrote:
| Irrelevant. They are moving fast but they are tiny
| individual atoms. There would be no harm in having them
| impact the atmosphere. They would bump into a few
| thousand or perhaps a million gas molecules on their way
| down to the surface, turning their tiny kinetic energy
| into a tiny amount of heat. And since there is only a few
| kilograms of fuel, there can only be a few kilograms of
| exhaust. With a low thrust and high specific impulse, the
| engine would burn that fuel continuously for most of the
| trip, spreading the exhaust from here to Pluto and back.
| It's not going to be sufficiently concentrated to bother
| anybody.
|
| In fact, even though the fuel pellets are only about 1um
| across, they still bump into enough atoms on their way
| out that the pellets heat up significantly. A major
| engineering consideration of the engine would be to
| absorb or deflect the heat radiated by the >1000degC fuel
| pellets without letting that heat quench your
| superconducting magnets.
| ben_w wrote:
| On the one hand, I also think it's likely safe: we've had
| a huge nuclear reactor in the sky since before life
| happened, the atmosphere and the magnetosphere are pretty
| effective barriers. (I think they're more worried about
| actinides than impactors).
|
| On the other, I'm not sure where your 15 kg came from.
|
| This matters, because fancy fuels matter a lot more for
| higher-mass or high-Dv payloads than smaller ones.
|
| A fission fragment rocket can be Isp of 1,000,000[1]
| depending on the exact details -- thrust is proportional
| to momentum (mv), not energy (0.5(mv^2)), and that means
| four million times the energy density is two thousand
| times the momentum and thrust, so that 15 kg is like 30
| tons of conventional propellant: a nice saving, but you'd
| use a lot more than that for e.g. a manned mission to
| Mars.
|
| For missions where the payload rather than the speed is
| critical, fuel is also a small fraction of total mass, so
| you also get a performance boost from being able to
| approximate the Tsiolkovsky rocket equation as linear.
|
| But that's perhaps another factor of 10, which is still
| roughly 25% of a Starship upper stage, so even then I'd
| expect at least 60 kg even if the engine itself can be
| considered negligible in both cases.
|
| And that's likely to be burned through much sooner than
| Pluto, though it depends on the details of the design.
| The ship would likely melt if you tried to thrust at 1
| gee, but I think it would still be comparable to the
| Earth-Moon distance, give or take a factor of 3.
|
| If you want something that burns from here to Pluto,
| then... huh, I was going to say you're likely back in
| Tsiolkovsky's realm, but apparently still not, and also
| still sub-relativistic (~ 1 milli-c for the specific
| values I was using).
|
| Which is still _safe_ , I just don't think it's quite as
| trivial as you say.
|
| [1] https://en.wikipedia.org/wiki/Fission-fragment_rocket
| db48x wrote:
| Honestly, I might have misremembered the fuel mass. I
| tried looking for the paper I read about this design, but
| I couldn't find it. It's been a whole year since I read
| it, and I guess they don't think hosting it is useful
| anymore.
| db48x wrote:
| But they're also just individual atoms. They're not a
| chunk of radioactive material that can sit on your roof
| for years.
|
| Besides, the whole ship would have maybe 15kg of fuel.
| That means that there can only be a maximum 15kg of
| fission products. It would burn fuel that for several
| years, spreading the exhaust out over the distance from
| here to Pluto and back.
| satvikpendem wrote:
| Atoms are atoms, by definition.
| epistasis wrote:
| > which fly apart at about 3% of the speed of light, due to
| Coulomb repulsion
|
| So is that at first an electrical force that results in kinetic
| acceleration?
| tmiku wrote:
| What do you mean by "at first"? The protons are pushing each
| other away via that Coulomb repulsion while they're all in
| the pre-fission nucleus, but at that time it's not enough to
| counteract the strong force
| (https://en.wikipedia.org/wiki/Strong_interaction) holding
| the nucleus together. Once that once nucleus has been split
| into parts that can move freely, the daughter nuclei are both
| accelerated by an electromagnetic force.
| epistasis wrote:
| Well, yeah, once the distance gets out of the well of the
| strong force, the nuclei are at the top of a big electrical
| force gradient that gets converted to kinetic energy. With
| proper ionization of the daughter atoms that kinetic energy
| could potentially be converted back to electric, well,
| potential.
| analog31 wrote:
| This is just a speculation. What if we were to use the heat from
| fission to generate hydrogen instead of electricity? Would that
| help at all?
|
| For instance a high enough temperature will cause water to
| dissociate.
| geuis wrote:
| As far as I know (and its not very far to be fair), the main
| way to generate hydrogen would be via electrolysis in water,
| which requires electricity. Which means you have to turn that
| heat into electricity first anyway. This is one of the big
| critiques of using hydrogen as an everyday fuel source. Takes
| more energy to produce that you can recover. Its super hard to
| store (requires very cold temps, or high pressure), and it has
| a habit of wiggling through any other material's atomic bonds
| and overall weakening the container material.
|
| But if there is another chemical method that used thermal
| energy in the process to produce hydrogen then there might be
| some possibilities in the idea.
| rgmerk wrote:
| There's been some research into high-temperature electrolysis.
|
| The idea is that a lot of the energy to split the hydrogen and
| oxygen can be provided as heat; that means you need a lot less
| electrical energy. To a rough approximation, for every three
| units of heat energy produced by a nuclear plant, you get one
| unit of electricity, so the process could in theory
| considerably reduce the cost of zero-carbon hydrogen.
|
| In practice, it seems like it's going to be very hard for a
| nuclear plant to beat an electrolyser that runs when near-free
| solar electricity is available.
|
| As you say, if you get hot enough you can do away with
| electrolysis entirely. A little bit of casual reading suggests
| that the temperatures required by a naive approach are in
| excess of 2000 degrees Celsius, far, far beyond the point where
| any existing or near-term reactor design would turn into a
| puddle of very radioactive molten metal.
| g15jv2dp wrote:
| And then what do you do with the hydrogen? Unless you plan on
| fueling your spaceship with it, you must burn it off to harvest
| the thermal energy... I'm sure you see the issue here.
| defrost wrote:
| Ammonia, Methanol, etc - Fertilisers and fuels for marine
| shipping in addition to being transportable "energy" that's
| less slippery than hydrogen and can travle further than an
| HVDC transmission line "extension cord".
|
| Currently green hydrogen plants are expanding and ammonia |
| methanol marine fuel ships have been built and trialed -
| there are contracts signed and in the works to both build a
| 4,000 km HVDC "suncable" and to ship hydogen products longer
| distance.
| orbital-decay wrote:
| One of the previous attempts at that, with a "power density of a
| gasoline tank", according to the authors:
| https://en.wikipedia.org/wiki/Optoelectric_nuclear_battery
| elevaet wrote:
| What's the typical efficiency of a nuclear power plant? i.e. what
| fraction of the energy from the fission reaction gets converted
| into electricity?
| Muromec wrote:
| I remember something like 1/3 of thermal energy.
| worik wrote:
| Makes the use of depleted uranium look benign
|
| Imagine thousands of soldiers with battery powered tools that
| _must not_ (!!!) be dismantled
|
| So long as it happens "over there" I guess
| kccqzy wrote:
| Nuclear generation didn't always require a steam turbine.
| Radioisotope thermoelectric generator is an old tech that doesn't
| need any kind of turbines or liquids to function. It's still
| being used on the two Voyager spacecrafts. Of course it doesn't
| meet DARPA's requirement of bypassing the thermal middleman but
| it can be scaled to be reasonably small and can generate a few
| hundred watts.
| lupusreal wrote:
| The thermocouples those use are wildly inefficient and only
| make sense in cases where no moving parts that might break is
| the utmost priority (spacecraft, extremely remote lighthouses
| or radio relays, etc.)
|
| Betavoltaics are another option, which actually skip the
| thermal step, but those are only good for very small amounts of
| power.
| bitmasher9 wrote:
| The issue with RTGs is that they don't scale up, not that they
| don't scale down. I'm not sure what the biggest RTG is, but
| they are usually measured in hundreds of watts.
|
| Then there is the issue of the radioactive waste.
|
| It's useful for situations where refueling or maintenance are
| not options and access to solar light is poor. Pretty niche
| requirements, and the radiation issue limits applications to
| military levels of security.
| gweinberg wrote:
| Aug 30 seems like a ridiculously short deadline for proposals
| considering that this is as cutting edge as it gets.
| tconbeer wrote:
| It's an RFI, not an RFP. They are basically looking to build a
| list of vendors who might be interested in bidding an RFP or
| competing in a domain-relevant contest.
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