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Yet Another Method Of Achieving Nuclear Fusion
deglr6328 writes "Recent research has seen the use of the pyroelectric effect, the compression of bubbles using ultrasound and gas jet irradiation for producing nuclear fusion on small tabletop-scales. Yet another method can now be added to the list which uses ultraintense laser irradiation striking a borated plastic target to heat a plasma to billion kelvin temperatures and achieves aneutronic (clean) proton-boron fusion. (The PRL paper can be read online.) Though, like the other recently discovered exotic methods of attaining fusion, it does not look like a method which can be scaled up to ignition or even anywhere near break even, it still may have important use in the laboratory for the examination of such incredibly high temperature plasmas."
My question was, where does that "little bit left over" come from? You still have all the original particles in the system. The energy that was used to "squeeze" the particles together is then imparted on the remaining atoms/free particles.
So I went to look it up on Wikipedia, and it gave me an answer that was basically the same as I suggested:
Javascript + Nintendo DSi = DSiCade
You also assume that hydrogen is already available and its potential is 0 then you bring in the gravity and eventually the energy from the gravity gets emmited during fusion.
Some energy should have already been spent combining and 'creating' the hydrogen from the Big Bang soup of protons, neutrons and electrons. Of course the energy for the Big Bang should have come from some place, but that is another question [God anoyone? - *warning* lame flamebait attempt]
To release that energy you would need to break the nuclear bonds of hydrogen and then it will become helium. Think of it as wanting to get over a very tall mountain and on the other side there is a much deeper valey than the one you are on. But to get to the longer downward slope, on the other side, you need to overcome the upward slope in front of you.
In case of H and He transition, as someone already pointed out, the difference in the energy is just a little (the valey on the other side is just a little deeper than the one are on now). But when you have billions and billions of small differences -- they add up and you get the Sun (or an H bomb).
Then you need to kick-start the reaction and keep it going until it becomes self-sustainable.
Yeah. You should have been tought that in high school physics. The Strong Nuclear Force (the one which holds nuclei together) is the strongest force available to us, by a wide margin (followed by electro-magnetism, then weak nuclear followed by gravity. Someone recently figured out that the weak nuclear force can be tied into electromagnetism, and I think they actually call it "electroweak" or something like that.. I can't quite recall at this moment.. all that Grand Unifying Theory stuff's still a little vague to me).
Basically, if you can overcome the electromagnetic repulsion forces that force the protons apart due to their like charges, the strong nuclear takes over and the two protons come colliding together at emense forces. If you're looking for an answer to what actually drives the Strong Nuclear Force, well, take a ticket and get in line. Once they figure that one out, we'll have figured out what make the "fundamental forces" fundamental, and know a hell of a lot more about how our universe is put together.
It's possible that Desktop Nuclear Fusion that yields positive energy to us is just around the corner. And with all of the discoveries recently on how the internals of the "subatomic" particles work, I'd say we're closer to it than we have ever been. But these are the kinds of things that simply can't happen overnight, and I guarentee that if anyone did come up with the solution, it'd take us 60 years just to get it into service. So many industries out there who rely on this kind of technology not existing. Imagine what all of the coal refineries, natural gas refineries, solar power farms, nuclear power plants.. they'd all instantly be out of business if this thing could even pull of a 1% positive yield. But of course, this is all speculation. My guess is that we're still a good twenty years off at least, and that the positive solution will have something to do with how neutrinos work/are produced.
"Victory means exit strategy, and it's important for the President to explain to us what the exit strategy is." G.W.Bush
Why does a Hydrogen Bomb produce far more energy in the fusion phase than is put in during the fission phase? My only guess is that the extra energy is coming from the energy released by the nuclear bonds during the forceful disintegration of the atom. Any physics majors care to chime in?
Ever wonder why all those protons like to sit happily in the nucleus together even though they're all positively charged? Well it turns out that at REALLY small scales there is a force called (aptly) "the strong nuclear force" which is about a million times as strong as electromagnetism.
The amount of energy it takes to liberate a single nucleon from a nucleus is called the "binding energy per nucleon". . For different elements this value is different. The reason fusion and fission can both release energy is due to change in this binding energy per nucleon from the start of the reaction to the end of the reaction.
If you look at this graph you will see that at the begining of the graph it rises very steeply. The change from Hydrogen to Helium looks about 10MEV. This energy has to go somewhere and it's released as heat and light.
At around Iron the graph flattens out and then slowly starts to decend. Uranium sits right down at the bottom tail of the graph. Energy is released in fission because the end products sit further up the curve than Uranium.
Per reaction, Uranium fission produces a lot more energy than Hydrogen. Fission release around 250MeV and fusion releases around 17.6MeV. So why do we get so much additional power from a Hygrogen bomb? Well one mole of Uranium weighs 238 grams. In contrast, one mole of hydrogen weighs only 1 gram. The conclusion? We have a lot more hydrogen atoms per unit mass than we do Uranium. This means that we get 17 times more energy per unit kilogram than we do from Uranium . This is the reason the primary power source for the Hydrogen bomb is the Hydrogen and not the Uranium starter charge.
Simon.
I think the yield from the original Mike shot was mostly from the huge uranium tamper. In the case of the Soviet "Tsar Bomb" the yield was mostly from fusion but that is because they (fortunately) left out the uranium tamper to reduce the yield from the planned 100Mt to about 50Mt or so.
True, most hydrogen weapons use a 3 stage approach, because like the thread starter said hydrogen lacks a lot of punch alone.
By igniting a fusion reaction the resulting neutrons can rapidly burn the uranium tamper (called "fast fission") and increase yield significantly. This is also a very unclean burn and results in high amounts of radiation.
Ivy Mike, and later Castle Bravo and Castle Romeo produced much of their yield from fast fission and NOT fusion. Fast fission in its early stages (and even now) is unpredictable as seen in Castle Bravo and Romeo, with yields almost two and half times predicted.
Tsar Bomba on the other hand was fairly unique in that it was only two stages, with like the above said, having its uranium tamper removed and replaced with a lead one. This resulted in a high majority of its yield (97%) coming from fusion.
I don't know much about fusion besides its uses in weapons, but I do know that it requires vast amounts of energy to achieve it.
Either through gravity, the intense heat of a fission explosion, or self sustaining reactions like that of our sun and the billions of stars in the universe, its all very "large".
I don't think we are close to getting a reliable fusion power plant or even fusion that breaks even (with out killing everyone for miles and miles) very soon.
The strong nuclear force holding the atom together is then converted to kinetic energy as the atom disintegrates.
NO IT DOESN'T!
The strong nuclear force holds the nucleus together and is opposed by the electrical force. It is the electrical force that causes the atom to fly apart and some of this force is converted into free energy.
As for the fusion bomb - the high pressure causes a number of the hydrogen - deturium pairs to fuse. This releases neutrons which transmute lithium into deturium. Some of these neutrons run into the uranium tampers around the compressed cores causing further fission to take place. This releases more neutrons. A chain reaction builds up until the materials are thrown far enough apart that the density drops below that which can sustain the chain reaction. Then it dies out.
As power production goes, they simply don't have enough power generation area to produce an output similar to that of existing plants.
That's untrue. It's just that nobody has bothered to scale the designs up before now. The highest capacity solar plants on the drawing board are in the 200 to 850 megawatt range - this is comparable to 1200MW nuclear and 700MW coal plants.
My local (tiny, probably 200MW) coal-fired power plant uses an area of roughly 2km by 2km (not counting space for railroad tracks) - because they require a private lake to provide cool water to the generation process.
The major solar projects that I'm aware of:
(1) Sterling Energy's 500MW facility is going to be built, with the option to increase capacity to 850MW: http://www.stirlingenergy.com/
Their development will use 4000 acres, but that's only a patch of land 4km by 4km (my local international airport uses 10 times the space). It will also work on cloudy days.
(1) EnviroMission's 200MW, 1km tall solar tower. The first full-scale tower is about to be built in Australia and they're scouting for locations to build the first one in the US: http://www.enviromission.com.au/
It's slightly less space efficient than the Stirling design, but it also works at night - the design uses the temperature differential of air between ground level and 1km up. During the day, this is boosted by the sun heating air at ground level.
So, factor in the overhead of otherwise mining and transporting coal and any lakes / cooling reserves that are needed for those systems to work - and these designs are looking very, very competetive.
Seriously, the problem here is that you're required to input a tremendous amount of force to overcome the nuclear bonds that hold the atoms together. As long as you have to put that force into the system, you're not going to get surplus energy out of the system. Simple physics. You can't get more energy out of a reaction than it takes to reverse it. The same reason why hydrogen cars that run on electrolyzed water don't work.
Nice idea, but, I'm afraid it's not like that. There are basically two forces involved here: electomagentic forces and the strong nuclear force. The EM force tends to keep atomic nuclei apart, since they are all positively charged. In "normal" matter they stay far enough apart to allow a bunch of electrons (negatively charged) to get in between and "screen" the charges. Meanwhile the strong nuclear force wants to pull nucleons together to make bigger nuclei. It's really powerful, as its name suggests, but also really short range.
The net effect of the interplay between these two forces (and some other considerations which I will overlook for now) is that the most stable (equivalently lowest energy) state for matter in quantities of less than a few solar masses (beyond which gravity starts to play a role) is as iron-56 nuclei. This is basically as many protons and neutrons as you can squash together and stillhave them all be in range of each others strong nuclear forces. Put in more and the electrostatic repulsion starts to dominate, put in fewer and the strong nuclear force would still pull in more if it could.
So, you can, in principle, get energy from any nuclear reaction that moves things towards iron -- fusion of light elements, or fission of heavy ones.
So, why is the whole universe not made of iron already? Basically the answer is that it got stuck!. When the universe was very hot and very dense indeed, it was a see of protons and neutrons constantly smashing into one another, sticking briefly to make nuclei and then being smashed apart by the next collision. The temperature was so high that thermal motion of the particles overcame the electromagnetic repulsion. When it cooled, it did so so quickly that the protons and neutrons didn't have time to form into iron nuclei, or indeed into many nuclei at all. That's why, before stars got into the game the universe was mostly hydrogen, with a decent amount of helium and only traces of other things.
Now, at the temperatures found in most of the universse, when two light nuclei collide, the electromagnetic forces cause them to bounce before they get close enough for the strong forces to make them stick. In a star, or a hydrogen bomb, or one of the pieces of borated plastic in this laser experiment, temperatures and densities are high enough that sometimes two nuclei smash together had enough to get past the EM repulsion and feel the strong force attracting them, whereupon they "snap" together, releasing a lot of energy.
If you want a very poor analogy, consider a room with a powerully magnetic roof a vibrating floor and a lot of ball-bearing. Initially, all the bearings are on the floor. Even though it would be a lower energy state for them to be stuck to the magnets in the roof. It we turn up the vibration (temperature), initially not much happens, but eventually we reach a temperature where a few bearings get close to the ceiling and are then pulled in hard by the magnets, releasing lots of energy as they "thunk" into the ceiling. This is what we are trying to do in a fusion reaction.
If we take the same analogy and turn up the heat still hotten, we recreate conditions in the original big bang. Now the room is full of flying ball bearings moving so fast that they are as likely as not to knock free any that get stock to the ceiling.
And at least one of the devices mentioned, using sonoluminescence, has never been proven to actually produce fusion.
The work done by Taleyarkhan with deuterated acetone is highly disputed and later papers have argued that the neutron release was consistent with random coincidence.
Karma: Bad. Calmer, good.
Muon catalysed fusion.
The point of anuetronic fusion is that they are *not* planning to transfer the heat to a steam turbine (who the hell wants a steam turbine - that's why current powerstations cost so much to build and maintain - and why they're so inefficient).
In a neutronic reaction such as D + T -> He + n high energy neutrons are transfer their energy to water and a steam turbine takes a little bit of that energy back out and coverts a little bit of what it takes into electricity. This is very bad for the environment as it releases huge amounts of waste heat.
In an aneutronic reaction such as p + B11 (5+) -> 3He (2+) high energy helium ions (alpha radiation) is released. This is a large current (moving charge) which can directly induce a current in a coil.
pB11 reactions don't seem to be expected to acheive ignition (ie become self sustaining), the are expected to be pulsed reactions, where a portion of their output is immediated consumed to prepare and force another reaction. All that is needed then to be a useful power source is break even.
However, p + B11 -> 3He is not the only reaction to occur, but I don't know what consequences to expect from that.
"Some energy should have already been spent combining and 'creating' the hydrogen from the Big Bang soup of protons, neutrons and electrons."
This needs some clarification. We are talking about nuclei here, not atoms. A hydrogen nucleus is nothing but a proton (p) and thus is not 'created' from the particles listed in the quote. The fact that protons themselves are bound states of quarks is not very relevant here. The energy scale of the processes discussed here is to low.
"To release that energy you would need to break the nuclear bonds of hydrogen and then it will become helium"
Since hydrogen is just a proton there are no nuclear bonds to break up here.
Here is what happens in the sun. The first step in the suns fusion cycle is actually a weak interaction process:
p + p -> d + e+ + nu
Where d denotes deuterium (pn) and nu a neutrino.
There is more than one continuation of the cycle but the most important one is the following.
d + p -> 3He + photon
3He + 3He -> 4He + p + p
The numbers in front of the He symbol are not multipliers but indicate the isotope. 3He is (ppn) and 4He is (ppnn). This process yields about 26.7 MeV free energy.
The reaction rate of the weak interaction process in the first step is far too low to use this cycle in fusion reactors. That is why one rather tries to use d + 3H -> 4He + n which yields about 17.6 MeV. Where 3H is tritium (pnn). One could also think of d + d -> 3H + p and d + d -> 3He + n but these yield only 4 MeV and 3 MeV, respectivlely.
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Minor nitpick: as far as I know, the problem really isn't that the super hot plasma would melt the container walls, because the mass of the plasma is really really small (high pressure comes from temperature, not density). The real problem with solid container is that the plasma would rapidly cool down if it could touch container walls, and fusion temperatures could not be reached.
What part of TOTALLY CHEMICALLY INERT did you not understand?
- "Hear that?! The percolations are imminent! Cease your ingress!"
Yeah under extremely uncommon circumstances when it is reacted with fluorine. Helium is TOTALLY inert.
- "Hear that?! The percolations are imminent! Cease your ingress!"