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I have not seen this idea anywhere, and I was wondering what everyone thought of it.
Given that free neutrons decay into protons and electrons (and an antineutrino, but we can ignore it for now) could a beam of neutrons be directed into the middle of an electric or magnetic field, and the protons
and electrons of the eventual decay event be harvested directly for electrical power?
I am thinking specifically of storing Ultra Cold Neutrons in a powerful magnetic field (causing them to circle due to their dipole moment) and when they decay, the protons and electrons would hit strategically placed collection grids.
Neutrons are mostly (always?) lefthanded, so the electrons and protons would tend to be ejected in the same direction each time - right?
Could this be a way to harness more energy from a fusion reaction?
Fudge the facts day
Fudge_20the_20Facts_20Day
[quantum_flux, May 12 2007]
neutron handedness
http://discovermaga...ig591/article_print
In 1957 researchers studying the beta decay of cobalt nuclei found that electrons tended to fly off the spinning nuclei in the left- handed direction more often than in the right-handed direction. [Khous, May 13 2007]
ORNL review vol 37, no. 1, 2004
http://www.ornl.gov...04/article_17.shtml
"It is an astonishing fact that the universe seems to make a big distinction between right and left," Greene adds. "We don't really know why radioactivity is left-handed, meaning that when a radioactive nucleus decays, it emits more electrons in one direction than another. Nuclear radioactivity is really the decay of a neutron within the nucleus. The study of the decay of the free neutron may help us better understand the origin of parity violation." And it will help Greene and his colleagues better understand the universe. [Khous, May 14 2007]
hydrogen formation
http://www.newton.d.../phy00/phy00843.htm
[jhomrighaus, May 15 2007]
Pion, not neutron, decay
https://www.nytimes...semimetals-ibm.html
Looks quite different, but the math - and the result - is very similar [lurch, Jul 20 2017]
[link]
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No, as it is already part of the process. |
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//Neutrons are mostly (always?) lefthanded, so the electrons and protons would tend to be ejected in the same direction each time - right?// |
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Considering that the power output will be something like one trillionth the input, this is truly a bakery idea! |
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Save it for fudge the facts day! |
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Actually, I think he's got that (mostly) right, due to the non-conservation of parity in weak nuclear interactions. (T. D. Lee, C. N. Yang, et al, q.G.) |
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that was what I said lurch, it is already part of the process, The left handed stuff is totaly bunko though. |
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jhomrighaus - I am serious - left handed chirality of neutrons is not bunko as lurch points out. |
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I will post links, but you can google - "neutron handedness" to see for yourself. I did the google search (on this and many other related topics) myself prior to posting here. |
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Please explain how capturing the energy of the electron/proton recombination is already part of the process? I am not trying to be confrontational, nor am I trying to hoodwink anyone, or be "outrageous" for comedic intent. I am trying to understand. please be patient. |
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My understanding is that neutrons generated in fission (and one would assume fusion) reactors are quenched in some working fluid (water, lithium, sodium, etc) to harvest the heat and then allowed to decay. I am sugesting that after all the thermal energy has been extracted, there may be additional electrical energy to extract. Heat engines are not that efficient. |
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Lt_Frank, you are correct, and I did not forget about that part. But of course that could be a powerful *permanent* magnetic field, so it would not neccessarily be a power consumer. Google "neutron turbine" to see how the neutrons are made *ultra cold* it yields energy too, but I didn't want to complicate the issue any more than it has to be. |
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ldischler - I am not suggesting that a beam of neutrons be generated solely to harvest the 1 EV/neutron from the recombination of the decay products, but rather to collect and utilize what is currently considered a hazardous waste. |
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I'm not commenting on the left handedness, I know that they are. |
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I am commenting on the fact that that in some way relates to the direction in which they will discharge they're decay particles in a nuclear cascade reaction(millions on millions of decay particles being generated). It makes a measurable difference in normal Radioactive decay, but that is quite a different animal than a fission reaction. |
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Also The energy released from the decay of the neutrons IS part of the energy that is released in a fission reaction(a small part). |
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A neutron initially breaks up into a proton and a negative pi-meson. That negative pi-meson then proceeds to break up into an electron and an electron anti-neutrino. |
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....hmmm, when you think about it, a neutron is basically an unstable hydrogen atom (lasting about 900 seconds in a moderator) where the electron is held on top of the nucleus by an electron anti-neutrino. Although there is a high concentration of these slow moving neutrons in the heavy water, but neutrons in there don't quite prefer left handed over right handed up-spin, or vice versa, because nature makes no such distinction in these regaurds. Also, to say that parity is not conserved in the decay process is something entirely different than to say that neutrons are mostly left handed or right handed. Finally, protons and electrons in a moderator are going to be less susceptible to a magnetic field than to the thermal vibrations of the molecules around it, and would be more likely to recombine into a hydrogen atom than to seperate and diverge in opposite directions unless there were a strong electric field. |
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// My understanding is that neutrons generated in fission (and one would assume fusion) reactors are quenched in some working fluid (water, lithium, sodium, etc) to harvest the heat and then allowed to decay. |
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Not really. Water is used as a medium to slow the neutrons, yes, but only to make them more potent for fission reactions. The real work is all the result of the reactions being really hot, in the thermal sense. Fission/fusion products weigh less than the ingoing reactants (about 0.4% less in the case of basic 4H to 1He fusion, I recently learned). The difference in mass is transformed directly into energy, either in the form of high-energy photons (gamma radiation) or simply (mostly) making the remaining mass really really hot. The heat is used to boil water, which makes steam, etc. |
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Hence nuclear meltdown as the failure mode of a fission power plant. If the reaction gets out of hand, or the coolant gets stopped for some reason, the atomic pile literally melts. Imagine a giant self-fueling thermite bomb that's also deathly radioactive. |
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q-flux - as I said, I was thinking about what would happen in a strong magnetic field. The idea would be to get the neutrons out of the moderator, slow them down (cool them down) even further with neutron turbines, and then dump them in a vacuum chamber under a strong mag field. |
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All the neutrons would line up with their spin vectors pointing in the same direction and slowly circle within the magnetic field. |
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Contrary to what jhomrighaus is saying, the left handed chirality of the neutrons will influence the direction the decay products wil be emitted. That is the definition of handedness (see my links above) |
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Some references I have found said their is just a little more (~60:40) in one direction than the other. Other references seem to indicate that it depends on the orientation of the neutron in the first place, which makes me think that if you can get all of the spin vectors lined up, you could have nearly 100% control on the direction of the ejected proton and electron. |
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the collections grids should be slightly charged so as to slow down the incoming particle (proton or electron) thus directly generating a little more energy. The electrons are then fed into grid, and allowed to recombine with the protons (making hydrogen gas) allowing even more energy to be generated. |
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I do not think this will be huge amounts of power, but would it be enough to tip the balance on a fusion reactor while simultaneously dealing with a big waste product. |
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Neutrons aren't a waste product in a fusion reactor: they're an essential part of the process. You want to capture as many of them as possible in the blanket where you produce the tritium, which is half the fuel for your reactor. You'll be doing extremely well if you can produce as much tritium this way as the reactor consumes. |
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Otherwise, you're dependant on fission reactors for the neutrons to produce the tritium you need. |
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What you are not addressing is what determines the direction, (ie where to place your collectors) While the spin is left handed the direction of discharge will depend on where in the "rotation" the particle degrades and what else is in the area. While you could try to vector through magnetic fields that is different than being able to predict the location where the electrons will go. Further if you siphon off all the neutrons to do this then you will no longer have a fission reaction as that is caused by the neutrons that bet knocked out by other neutrons. |
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Your links are refering to the emmision of radiation from inside an atom, not the by procucts of nuclear fission or the free decay of a neutron. A point that both make quite clearly. Did you actually read them before you posted them? They both indicate that this effect is marginal but measurable(just slightly over parity), and that it only to date applies to radiation emmited from whole atoms. |
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You have made some theoretical leaps that your references are not really supporting. |
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Further if I recall you actually need to input a certain amount of energy to get a proton and electron to merge into a Hydrogen atom, which releases a small amount of light as well. |
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Where are you getting that Neutrons are some huge volume of waste product?? They degrade into electrons protons and energy. Wheres the waste?? |
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[jhomrighaus] You need those neutrons to make your tritium anyway. You can't afford to let more than a tiny fraction of them decay without using them. |
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[Cosh i Pi]
I'm not really trying to talk about fission (I was using a fission reactor as an analogy since no one has a working [controlled] fusion reactor yet) I am trying to talk about fusion. In fusion, the neutrons are bad because they cause other materials to degrade and / or become unstable themselves. They also remove energy from the system. |
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Using aneutronic fussion is a fine solution, but it seems to be power-hungry, have a poor cross section, isn't really anuetronic due to side reactions, and for a whole host of other reasons people are talking D-T as the easiest fuel cycle, and therefore, I think the first fusion reactors (if any) will be a heavy neutron source. |
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I see where you are going with the neutrons being required to breed more tritium. Certainly I agree one should do everything possible to convert protium into deuterium, or tritium whenever possible but I think a decent fraction of the neutrons (as opposed to a tiny fraction) will not be taken up into tritium production. |
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What to do with them? If the neutrons can be slowed down and stored, without simply being slammed into something else, until they expire (half-life 15 minutes) then there will essentially be no harmful radiation from a D-T fusion reactor. The biggest NIMBY argument goes away. |
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Then it comes down to the question of how much energy is used to collect and store the neutrons that escape vs how much energy we can generate from them while they are here or their decay products once they aren't. Is it net loss, or net gain? |
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[jhomrighaus]
// They both indicate that this effect is marginal but measurable(just slightly over parity), and that it only to date applies to radiation emmited from whole atoms. // |
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Those reports are also both somewhat out of date, and I was wondering if the recent work with Ultra Cold Neutrons (UCN) would be, in effect, like an artificial atom, in that it would provide an external forcing of the neutron spin vector that would otherwise be lacking in a typical free-flying neutron. (link to follow) |
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So if the direction of decay for these magnetically constrained neutrons can not be predicted, (not yet sure I agree with that, but just for completeness' sake) can the products be directed nonetheless? This decay event would happen inside a powerful magnetic field, where the source particles will be orbiting and rotating around magnetic lines of force. I admit I am not familiar enough with the EMF rules to know how the proton and negative pi-meson -> electron/antineutrino would behave if they were to come into being under these conditions. I have looked for, but cannot find, any treatments of the particle paths, energies, lifetimes, or percentage likelihood of various sidereactions. |
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Certainly one could force them with an electric field, but it seems counter productive to maintain a potential difference to do work when we are trying to get the system to do work for us (as much as possible anyhow). |
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Some (very small) additional deuterium and (more rarely than that) tritium would be created, probably not even worth the separation costs. If there would be some way to arrange things so that the majority of collected neutrons became tritium or even deuterium, I would agree that would be a much better use for them. I don't know of any way to ensure or help create the proper conditions for that outcome. |
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The end result of all of this would be pure hydrogen, ready for a regular fuel cell (not much, granted, but every little bit helps pay back the cost of the neutron collection. |
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//Further if I recall you actually need to input a certain amount of energy to get a proton and electron to merge into a Hydrogen atom, which releases a small amount of light as well.// |
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No. This I am certain of; it takes energy to separate unlike charges. They come together on their own very nicely and always yield energy when they do so. However, you are correct: in a free system, there should be a photon as well (think laser), but in this system, that energy is being supplied by the electron to some electrical load. PV is an even worse energy conversion technology than a heat engine. |
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Perhaps you are thinking of the monatomic Hydrogen to diatomic Hydrogen reaction, which does have an activation enegy requirement? |
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Collecting the electron and allowing it to come into contact with the proton under controlled conditions will yield almost 100% of the recombination energy as electricity. |
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Think of it as a topping stage for a fuel cell. Instead of Hydrogen and Oxygen forming water, this is proton and electron forming Hydrogen. Normally, it would cost energy to separate a proton and an electron, here it's going to happen for free whether we want it to or not. |
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Normally it would cost energy to place the electron and the proton in the middle of a High B mag field or an electrical potential; here, the neutron can slip in for very little energy because it is uncharged, and is only very slightly suseptible to a mag field (which is why we need a strong field in the first place.) |
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If one can also recover the recoil energy of the proton and/or electron (preferably as work _against_ an electrical potential field) then I would think there might be some small chance the energy gained would at least equal, if not slightly exceed the energy required to collect and store them. Even if it should only make back half the energy, I would think it might be worthwhile to do simply to eliminate the leftover neutrons as a radiation-inducing threat. |
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Huh, I stand corrected.... well, then, you really could orient the magnetic poles of the cooled neutron gas in the vacuum chamber, and thereby control the direction of electron/proton radiation with an emission of charges alinged along the magnetic field lines.... But, will the electrons be emitted in a favorable initial direction 40% of the time or 60% of the time? |
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i.e. Given that the electron is emitted in 1 direction 60% of the time, and in the opposite direction 40% of the time, and given that the handedness of the electron determines the direction that the electrons get accelerated by the magnetic field once they are emitted.... IS the cross product of Vl) [the velocity vector of the emitted charges projected onto the plane lateral to the magnetic field] crossed with Bz) [the magnetic field vector] in the same direction or in the opposite direction of Vz) [the velocity vector of the emitted charges projected into the direction of the magnetic field] on average? |
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[khous] I know you're not talking about fission. But neutrons are an essential part of the fuel cycle in fusion too, to make the tritium which is one of your fuels. Tritium is produced by absorbing neutrons in a lithium blanket around the fusion reactor. |
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It is in fact difficult (not in principle completely impossible) to make enough tritium this way. If you can't make enough this way, then you need fission reactors to produce the extra tritium required for your fusion reactor. |
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thanks for the link on hydrogen formation [jhomrighaus] |
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//When a neutron decays into a proton, electron, and neutrino, it also releases energy, 780,000 eV, as the sum of the kinetic energy of the 3 particles.// |
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I didn't realize the decay energy was so high. I knew it was an exothermic reaction and all that, but I didn't realize the magnitude. I wonder how much of this 780 Kev goes into the neutrino? |
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The other point of the article, that electron / proton recoupling requires precise conditions is satisfied by the design. That is, if one can get the protons to collect at one grid, and the electrons to collect at another, (a big if, I admit) then an external current pathway between the two will "transport" the electron to the proton, and recombine them forming hydrogen, and no photon (the photon's energy instead is taken up by the external circuit and can power a load) |
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The larger point however, should be the difference between the recombination energy (20 ev or so) versus the raw kinetic energy of products (780,000 ev).... Now I *really* want to turn the kinetic energy of the proton and electron into power. |
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I have no idea how to answer your questions. It is one of the reasons I posted here, I was hoping someone else might be able to explain what would happen, and what directions the proton / electron would travel. |
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I did some more reading on UCN, and I am even more confused about how the neutrons (and the mag field) are actually aligned within the trap. It seems the neutron spin vector points in the direction of increasing Mag field strength??? Which in the neutron trap I looked at seemed to in the radial direction. |
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As Vinny Barbarino would say, "I'm Soooooo confused!" |
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if anyone can shed light on this, I would be most grateful. |
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[Cosh i Pi] I know that neutrons are required to make the tritium fuel, I didn't know it was so difficult to reach break even on tritium production, but there are still a lot of "waste" neutrons. That is: neutrons which fail to create any tritium, and which would otherwise decay or implant themselves in various parts of the reactor. |
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I see now why you thought I wanted to do this in the moderator layer. That would seem to be the best place. Then each neutron would have maximum chance to transmute a lithium. |
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but I think the neutrons can be given 90% of their lifetime to transmute the lithium, without endangering the amount of tritium produced. The final 10% should be enough time to cool down the neutrons, and line them up. |
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Whoops! Hang on there; that last statement contains excess bogusity. |
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The neutron is quoted as having a "mean lifetime" (symbol tau) of 887 seconds, plus or minus. The "mean lifetime" is the arithmetic mean of the lifetime of all of the individual particles. It is related to another term that may more easily bring to mind the proper activity mode - the "half life" (symbol tau with subscript 1/2) - by the following expression: |
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half life = ln(2) * mean lifetime
half life = 0.693 * 887
half life = 614 seconds. (approximately) |
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Thus, if you wait for 90% of the mean lifetime, well over half of the neutrons will have already decayed. |
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D'oh! I should have known that. Thanks for the catch [lurch] |
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Sigh, I guess that puts me back in the soup (or at least in moderator fluid.) where thermal effects will dominate etc. etc. etc. |
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OK - I admit defeat - never mind - thanks to all for letting me get this stupid idea out of my head. |
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//Given that the electron is emitted in 1 direction 60% of the time, and in the opposite direction 40% of the time, and given that the handedness of the electron determines the direction that the electrons get accelerated by the magnetic field once they are emitted.... IS the cross product of Vl) [the velocity vector of the emitted charges projected onto the plane lateral to the magnetic field] crossed with Bz) [the magnetic field vector] in the same direction or in the opposite direction of Vz) [the velocity vector of the emitted charges projected into the direction of the magnetic field] on average?// |
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The answer to this question could be found by answering this question....is the electron that is emitted in the decay process left-handed 40% or 60% of the time? |
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Actually, the direction the electron is accelerated by the magnetic field is not related to its handedness, but to its charge. Which, of course, is always negative, so the math is moot. (You've still got the initial decay vector, so this is not a show killer; it just means you gotta make do with the separation that comes naturally.) |
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The figures we keep bouncing around here of a 60:40 ratio - has anyone a source? The original experiments with cobalt nuclei back in 1957 came up with 56:44, and I've not seen any experiments which yeilded higher ratios, though I know there are those looking for such. If anyone knows where to find said results, please drop in a link. |
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