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Wigner energy batteries

Carbon lattice dislocations generate heat
  [vote for,

The Windscale fire was caused by a largely unknown behaviour of materials which have been exposed to radiation. The graphite channels (which had been irradiated for some time) stored energy in lattice dislocations of the carbon atoms. When they were subsequently heated to release this energy, they did so rather more vigorously than was expected, and caught fire.

The idea is to irradiate graphite (or perhaps something else) to deliberately create lattice dislocations to store energy. Then take the graphite (which in itself isn’t radioactive much), to a place where you need to use stored energy. Trigger the release by heating it up to the critical temperature, and hey presto, you get lots of lovely heat out without radiation. You can use that to heat your house, drive a steam turbine or a thermoelectric pile.

Frankx, Sep 26 2019

Wigner Energy https://en.wikipedi.../wiki/Wigner_effect
Dislocated atoms in a lattice store neutron energy [Frankx, Sep 26 2019]

Wigner energy batteries https://www.nature..../s41598-017-01434-8
Academic paper looking at the feasibility. [Frankx, Sep 28 2019]

Beautiful steel http://m.vam.ac.uk/...-scabbard-masamune/
[Frankx, Sep 30 2019]


       [link] With the added advantage of intimate Frenkel pairs!
Frankx, Sep 26 2019

       Hmm. According to Wikipedia, "Accumulation of energy in irradiated graphite has been recorded as high as 2.7 kJ/g", which is 5-10 times higher than conventional batteries. On the other hand, it's about 20x less than hydrocarbon fuels (or maybe 10x less if you have to supply the oxidiser as well).   

       Of course, if the graphite gets hot enough it will burn, but then the dislocation energy is only making a minor contribution to the total energy.
MaxwellBuchanan, Sep 26 2019

       // largely unknown behaviour //   

       Wigner energy was a well-known phenomenon; hence the need to repeatedly anneal the moderator. The McMahon Act did severely llimit the flow of information from the much more experienced US reactor engineers, and Britain's previous experience came from GLEEP and BEPO, but the crux of the problem was the use of the GMAC design for a production reactor intended to run at high power. The RBMK is only a bit better and look what happened there ...   

       The problem with the idea is energy density. The energy stored in the lattice dislocations is comparatively small. The problem is localized overheating when the release is triggered. Outside a reactor core, it's not a problem, just inefficient.   

       You'd get better transference by just burning amorphous carbon, rather than lugging lumps of very expensive low-Boron graphite (which has to be made from petroleum coke anyway) from pllace to place ...   

       Costly, woefully ineffficient, wasteful ... go for it [+]
8th of 7, Sep 26 2019

       //The problem with the idea is energy density.// I wish I'd said that.   

       //You'd get better transference by just burning amorphous carbon// and that.
MaxwellBuchanan, Sep 26 2019

       Our anno is more comprehensive than yours, though ...
8th of 7, Sep 26 2019

       As is "War and Peace".
MaxwellBuchanan, Sep 26 2019

       I’m still convinced that there’s some practical application for a lump of carbon which can heat itself to 3750C without any oxidiser - triggered by heating it to 250C.
Frankx, Sep 26 2019

       Oh, there is, there certainly is ...   

       Just not a very pleasant or peaceable one.
8th of 7, Sep 26 2019

       They seem to gradually migrate back over time, reducing the power density. I don't think breaking the graphite would affect the crystal-scale dislocations.
Frankx, Sep 27 2019

       Yes, it does; but the heating effect is so localized that it doesn't propagate.   

       Mechanical shock will only trigger a mass release if the bulk of the graphite is already at or very near the critical temperature; then the additional energy is enough to tip it over the edge into a cascade release.   

       The Wigner effect is very interesting, but it's only really a problem if you run the core too cool. In power reactors, the core's hot enough that the dislocations are continually "baked out" by virtue of the high temperature - analogous to the way that a high neutron flux when the core's diverged keeps it from falling into a Xenon pit (although it's wise to have excess reactivity in the fuel channels to allow throttling to lower powers, as was discovered in the early Oak Ridge piles).   

       GMACs are fine as academic tools; in fact, CP1 and its successors actually had no cooling system whatsoever, because they ran at such low powers (a few watts) that the bulk of the pile didn't get warm, and didn't even need shielding (as long as you didn't stand too close for too long while it was critcal).   

       The killer with WP 1 & 2 is that they were production piles; what was wanted was the neutron flux to cook NUM into plut, and the heat was a waste product. So they tried to run them cool because of the low specific heat of air, hence the Wigner energy buildup (and other, much worse, problems; we could tell you more, but then we'd have to kill you. Just let's say that graphite isn't the only crystalline material that can store Wigner energy ... ) and the requirement for annealing.   

       In the end it made more sense to build power piles that ran hot (like Calder Hall, MAGNOX, the WAGGER, and the subsequent AGR derivatives), sell the "cheap" power, and get the plut for free out the back end when you strip the fuel pins.   

       The Dounreay FBR would have been even better, but outside military applications LM (NAK) cooling hasn't found favour with civilian operators. BiPb is a bit better from a safety point of view, but the need for frequent regeneration is a pain. And the other thing with FBRs is that you're trying to get half a Gigawatt out of a thing the size of a dustbin ... good game, good game.   

       The point is that the UK civil nuclear power programme, up to the 1990's, was never anything more than a puppet operated by the shadowy hand of the MoD. Then they lost interest, and are now staring ruefully at their collection of Nissen huts (we kid you not, actual Nissen huts) stacked end to end with little yellow flasks of plut, all polished up and nowhere to go.   

       But that's another, darker story.
8th of 7, Sep 27 2019

       True, Dounreay PFR closing was a great shame. Lots of great research wasted.
Frankx, Sep 27 2019

       The really, really frightening thing is that the whole wind turbine program has absolutely no hidden military agenda and no useful byproducts except bisected birds. The only point of all those huge fans is to make electricity.
MaxwellBuchanan, Sep 27 2019

       [MB] - //huge fans// I agree, I’m very enthusiastic about wind power. But I think nuclear power also has an important part to play.   

       [8th] //not the only crystalline material//   

       Intriguing- can you tell us more?
Frankx, Sep 28 2019

8th of 7, Sep 28 2019


       There’s been some research into applications of Wigner energy as a power source [link] including some “feasible” implementations. As [MB] says, energy densities of up to 2.7MJ/kg, better than many batteries and/or supercapacitors, but not close to fuels. So an application where rapid discharge of heat energy with no oxidiser... submarines, torpedos, space applications... perhaps an alternative to RTGs...   

       Also noted that other covalently bonded crystal structures show the same property... Silicon, Boron perhaps? Carbides, nitrides, transition metal oxides?
Frankx, Sep 28 2019

       "As is "War and Peace", Would have spit coffee if I was drinking any. Funny to start the day. +
blissmiss, Sep 28 2019

       // other covalently bonded crystal structures show the same property //   

       They certainly do, and the consequences are extremely interesting.   

       By the way, when we said "No" we were not attempting to be offensive (for once). It is simply that the information is highly restricted and cannot be publicly disclosed.
8th of 7, Sep 28 2019

       Ok, appreciated! Thanks [8th]
Frankx, Sep 28 2019

       //Would have spit coffee// If I can cause just one person to soil themselves in any way, my day has not been wasted.
MaxwellBuchanan, Sep 28 2019

       Actually, hang on a moment.   

       Wigner energy comes from atoms being dislocated from a crystalline matrix. Neutrons are an inconvenient way of doing this. There should be a way to achieve the same result chemically. Maybe some sort of crystal which intercalates a solvent, followed by removal of the solvent to leave the crystal matrix in an uncomfortable state.
MaxwellBuchanan, Sep 28 2019

       What about mechanically? If the lattice dislocations could be designed and constructed artificially, a piston could be used to load energy. A heat spring.
wjt, Sep 28 2019

       You're going to be busy with your piston (if you'll pardon the expression). On the order of 10^20 atoms to dislocate.
MaxwellBuchanan, Sep 28 2019

       Isn't a dislocation then going to be stronger than the next location ready to dislocate?
wjt, Sep 29 2019

       It depends if you exceed the material's elastic limit and either induce a fracture or drive it into plastic flow.
8th of 7, Sep 29 2019

       //hence the need to repeatedly anneal the moderator//   


       Quench hardening of steel is a perhaps similar property: many atoms are dislocated from the regular crystal lattice - in steel’s case forming martensite. So tempering is analogous to Wigner annealing, and should be exothermic (if only very slightly)   

       Work-hardening is the mechanical analogue- repeated strains cause accumulation of dislocations in the crystal lattice which pin the slip planes - and again, annealing allows them to find their lowest-energy arrangement.   

       It might be worth looking at semiconductors for interesting analogies too. Dislocations in a crystal lattice are a bit like vacancies in doped silicon. Is there some electro-thermal cascade poperty?
Frankx, Sep 30 2019

       How about a Wigner motor for a torpedo/submarine? Water is ducted into a graphite core, heated to steam, and ejected as a high speed jet (or driving a turbine/propeller)
Frankx, Sep 30 2019

       // Quench hardening of steel is a perhaps similar property […] in steel’s case forming martensite //   

       So can you make martensite by irradiating steel?   

       // How about a Wigner motor for a torpedo/submarine? Water is ducted into a graphite core, heated to steam, and ejected as a high speed jet (or driving a turbine/propeller) //   

       Or for an aircraft. This could be the long-sought solution to getting airliners off of hydrocarbons. All a jet engine needs is a source of heat; the fact that all current practical ones use combustion of fuel to do that doesn't mean another heat source wouldn't work.
notexactly, Sep 30 2019

       // the long-sought solution to getting airliners off of hydrocarbons. //   

       <Points at [MB]'s anno about energy density at top of thread/>   

       <Glares at [not]/>   

       <Brings board duster to launch readiness/>
8th of 7, Sep 30 2019

       *looks at mentioned anno*   

       // 5-10 times higher than conventional batteries //   

       So 5–10 times more likely to be the solution than conventional batteries are. Right?
notexactly, Sep 30 2019

       ... but 10 - 20 times less than hydrocarbon fuels.   

       Electrochemical batteries aren't practical; a Wigner battery is better, but still nowhere near as good.   

       To be a " replacement", the solution needs to be at least as good as the existing one.
8th of 7, Sep 30 2019

       In terms of inducing defects, the linked paper has:   

       "defects [can be generated by] neutron, ion or electron bombardment, or through laser irradiation"   

       Also I'd note that 2.7MJ/kg is the extreme for graphite - a first-generation practical device would probably be far lower.   

       That said, this property was an undesired side-effect in graphite; it wouldn't be surprising to find a material with higher energy densities/more practical properties following research and development. Compare, for instance, the first electrochemical batteries with current (oops, sorry) ones.
Frankx, Sep 30 2019

       //aren’t practical//   

       ...but getting closer.   

       //as good as//   

       ...or has some other advantage that outweighs some of the downsides of the existing technology.
Frankx, Sep 30 2019

       [notexactly] //martensite by irradiating steel//   

       Lots of metals suffer embrittlement in reactors, mostly (probably) from neutrons knocking atoms out of their crystal lattice. Martensite is a specific thing with carbon steels when they’re quenched (very distorted crystal structure, and carbon-iron regions in various ratios)   

       Probably, with neutron embrittlement you get some of the properties (hardness, strength, brittleness) but I wouldn’t think you’d actually get martensite.   

       //for aircraft// Perhaps, but I would imagine that the high cost of production limits use to esoteric applications where (comparatively) high energy density and no oxidiser/oxygen are constraints
Frankx, Sep 30 2019

       // I wouldn’t think you’d actually get martensite. //   

       ... and you wold be correct not to do so; not only embrittlement, but swelling and distortion.
8th of 7, Sep 30 2019

       //swelling and distortion//   

       ...which, in the hands of Masumane, make one of the most beautiful artefacts ever created by mankind [link]
Frankx, Sep 30 2019


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