Hot answers tagged fusion
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To answer the question simply, $E=mc^2$.
Energy is a manifestation of mass, and mass is a manifestation of energy. In a fusion or fission process, the total "energy" of the system remains constant, it just changes shape.
By "energy" I mean the totality of the already present energy, and the bound energy of the mass that takes part in the reaction.
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There are quite a few novel energy technologies coming through. I guess that without quantification, "breakthrough" is a subjective term. Below, I've tried to list all the energy technologies that I know of, that are not yet at commercialisation, but could be within 50 years, and that could offer at least tens of gigawatts of power. They are, in descending ...
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The analogy is facile. Helium fuses at a temperature ($10^8\ \text{K}$) roughly ten times higher than hydrogen ($10^7\ \text{K}$), so a better analogy would be alcohol and thermite. That higher temperature is achieved only by massive gravitational contraction after hydrogen fusion [EDIT: in the core] is exhausted.
EDIT:
To expand, different mass stars ...
9
The reaction rate doesn't increase that quickly with temperature, but pressure does. If you perturb a solar model, making a zone near the core marginally hotter, the increased pressure will rapidly (at roughly the soundspeed divided by a characteristic length) cause it to expand. That lowers the pressure and temperature enough to substantially quench the ...
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As far as a catastrophic plasma disruption is concerned, it might be a problem for the first wall, and hence the ability to use the reactor. But despite the high energy per nucleon, the desity of the plasma is extremely low, the total energy is dominated by the energy in the magnetic fields, and thats not tremendous.
Of course you do have the radioactivity ...
8
The next serious advance that is not an speculative/fringe idea is most likely to be fusion power. Harnessing the power of nuclear fusion has long been a goal for energy production since the first hydrogen bomb was created in the 1950s. Creating controlled fusion, rather than the chaotic variety has proven a rather challenging task here on Earth however. ...
7
Elements heavier than iron are only produced during supernovae; in these extreme energetic conditions atoms are bombarded by a very large number of neutrons. Rapid successive neutron capture, followed by beta decay, produces the heavier atoms. See http://en.wikipedia.org/wiki/Supernova_nucleosynthesis.
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These are valid questions. I am a graduate student in the program so it won't surprise you that I will advocate for it, nonetheless, if you'd like to double check my claims, you're welcome to.
Let's go in order:
We are hoping that the next major breakthrough does come from ITER: the first burning plasma. But it is BECAUSE of the fact that a machine like ...
7
You actually make reference to something which is of crucial importance to the answer to this question:
"With a tokamak, I imagine that if you double the linear dimensions, the plasma volume (and hence the power production) will increase eightfold, whereas area that you have to protect against fast neutrons will only quadruple. So once you master the ...
7
The binding energy curve for nucleons in nuclei shows which atoms can take part in fusion, releasing energy in the process.
Fusion happens as one goes from left to right, until reaching Fe, iron. From there to the right it is fission that will release extra energy
This is an example of a fusion reaction, the one that is actually being materialized in ...
7
This is a very difficult question to answer. There are (at least) two reasons. First, we have detailed, numerically exact wave functions for stable, light nuclei only up to, just recently, $A=12$ (like $^{12}C$). The Argonne-Los Alamos-Urbana collaboration uses quantum Monte Carlo (QMC) techniques to evaluate the ground and excited states of bound nucleons ...
6
This question is a near duplicate of Does the "Energy Catalyzer" generate energy by converting Nickel to Copper? , but perhaps it is ok, because some time has passed, and there is more confidence in the assessment.
It is not reasonable to reject Rossi out of hand, because there are observed unexplained nuclear reactions in Palladium/Deuterium ...
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This'll be a very rough order of magnitude estimate, but as you'll see it's good enough.
Suppose that two hydrogen atoms bump into each other. In order to fuse, the nuclei have to tunnel to within about a nuclear distance of $10^{-15}$ m of each other. The tunneling probability is something like $e^{-(2mE)^{1/2}L/\hbar}$, where $E$ is the energy gap, $m$ ...
6
There will be no attempt to utilize the energy released from fusion reactions at NIF. NIF's goal is to demonstrate that a sustained fusion reaction is possible. Such a demonstration is termed "ignition" and there is a good chance it will be achieved within the next three years.
The next step is a project called LIFE which involves a prototype power plant ...
6
Fission doesn't happen in the sun.
Elements are neatly divided at Iron, atoms smaller than this are energetically capable of fusion - they give off energy when fused. Atoms heavier than this can in theory be fissile, energy would be needed to fuse them but they give off energy when they split. These heavy atoms are only formed in a supernova where there is ...
6
The Sun's energy, of course, comes from fusion.
I think there's a small and totally insignificant amount of fission going on as well.
The majority of the Sun's mass is hydrogen, and the vast majority of what isn't hydrogen is helium (with the ratio changing over billions of years as hydrogen is fused into helium). But since the Sun formed from the same ...
5
Hydrogen-1 (i.e. hydrogen with no neutrons) has a mass of 1.007825 AMU. To get energy from fusing it you have to preserve baryon number. So you look for the atom that has the lowest mass per nucleon (i.e. lowest mass average over the protons and neutrons that make it up).
This lowest (most stable) atom turns out to be iron-56, which has a mass of ...
5
I find the idea of a breakthrough technology presented by the other answers to be extremely modest. I'm almost positive that I'll get downvoted and flamed for my answer, but I have a strong desire to impress the potential for, and the implications of, a truly breakthrough energy technology.
I want to begin calling attention to Jevons Paradox, as well as ...
5
A heck of a lot of energy in one place always represents a local danger.
The question of a more wide spread danger depends on a lot of details. Does the core reaction produce neutrons? How bad is the activation rate in the plant? Would a disaster event spread activated material over a wide area?
In the absence of data I would guess "less dangerous than ...
5
Can it sustain a reaction for more than a few seconds?
Yes, at JET.
Lifetime of the plasma: 20–60 s
At ITER:
It will operate over a wide range of ITER plasma scenarios, from short plasma pulses (a few hundred seconds) with enlarged fusion power (700 MW) to long plasma pulses of 3,000 s
Are these devices still huge or have they been made on a ...
5
I will give you an analogy.
Molotov bombs are made by filling a plastic bottle with gasoline, attaching a wick ingeniously, lighting it and throwing it on a target, usually a car or a policeman controlling a demonstration.
Now there are a number of BTUs of energy in this bottle of gasoline. I can ask paraphrasing you
Could we put these Molotov s to ...
5
The big problem with controlled fusion is that the equations governing the plasma are highly non-linear. So each time the physicist increase the size of the Tokamak, new effects are discovered. So I guess that the answer is no-one really knows the correct scaling laws !
This contrasts a lot with fission reactors, where the relevant equations are ...
5
To understand binding energy and mass defects in nuclei, it helps to understand where the mass of the proton comes from. The news about the recent Higgs discovery emphasizes that the Higgs mechanism gives mass to elementary particles. This is true for electrons and for quarks which are elementary particles (as far as we now know), but it is not true for ...
5
For some recent information on the running battle between cold fusion researchers and myself over my proposed conventional (non-nuclear) explanation of the Fleishmann-Pons(-Hawkins) effect, you might want to look here:
https://docs.google.com/open?id=0B3d7yWtb1doPc3otVGFUNDZKUDQ
(referenced in this:
...
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A subtle problem you seem to overlook is that the proton-proton cross section is very small, about 0.07 barns (a barn is $10^{-28}$ square meters) at the LHC energies and not dramatically different at your lower "fusion energies". It means that at the LHC, much like at your dream machine, most of the protons simply don't hit their partners. It is not really ...
5
There are other interactions to consider besides the Coulomb interaction. A very nice model of the nucleus is the liquid drop model, in which one models it as a constant-density liquid with various interparticle interactions. The result is known as the semi-empirical mass formula, which I summarize here.
Let $Z$ be the number of protons, $N$ the number of ...
4
I was going to comment, but am making it into an answer.
The experimental proof that fusion works with small amounts of matter ( no need of gravity to work) is the H-bomb.
The engineering problem is large and people are working on it with various designs. The world community has put its money on ITER which is currently being built in France. The design ...
4
While the figure seems relatively low (and it may be a mistake by an order of magnitude), it is still way above $O(1\,eV)$ which are the chemical energies of electrons in atoms, so can't occur as a thermal fluctuation. It's almost excluded that any single atom at reasonable temperatures would collect enough energy to get through the barrier (although ...
4
During the 1970s, the Los Alamos National Laboratory carried out the PACER project, to explore the use of thermonuclear explosions as a way of generating electrical power and breeding nuclear materials. The general layout of the initially proposed fusion power plant can be seen in the following illustration:
The system parameters were under exploration, ...
4
ITER is aiming for 150.000.000K. Please note that this temperature of the plasma, i.e. average kinetic energy of the ions is in electron volts
For example, a typical magnetic confinement fusion plasma is 15 keV, or 170 megakelvins .
15 KeV is enough to assure that the plasma does not neutralize itself and the bare nuclei have a high enough statistical ...
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