why no fusion power plants?

Question

why cant we control fusion reactions? like those in a H bomb in the same manor we can control fission reactions, why is a fusion reaction totally uncontrollable?

we have made a fusion reaction, like i said in my question, the hydrogen bomb uses a fusion reaction (like the sun) rather than a conventional atomic fission reaction.. i realise they are two very different things, i just want to know why a fusion reaction in uncontrollable

Answer 1

We have not been able to create a fusion reaction at anything less than several thousand degrees. Thus, any fusion reaction created far exceeds the thermal tolerance of any material known to man. When people talk about 'cold fusion' they mean some way to control a fusion reaction at less than a thousand degrees so there might be some chance of harnessing the power from it.

Currently nuclear power is based on fission which happens at much lower temperatures, but still needs massive cooling to be safe, and also produces harmful wastes. Fusion would not generate wastes in the same manner, but the cooling issue is the stumbling block. Some suggest using a magnetic field to contain the reaction, but the energy needed to maintain such a field is likely in excess of the energy generated by said reaction. In addition, failure of the containment field would lead to an explosion comparable to an H-bomb.

Answer 2

One of the biggest drawbacks to fusion power plants is the fact that to be a realistic solution, we have to be able to contain any accidents related to such technology and we simply don't have the means to do so at this time.

Fusion reactions are not entirely uncontrollable, but at the present state of the art of technology, fusion reactions are too difficult to control as well as fission reactions. The resulting temperatures could easily exceed the temperature of the sun's surface and there are no physical materials that can withstand such extremes.

If a nuclear accident were to occur at a fusion plant, the accident could never be contained by any means known today, so the risks to the public and to the environment far outweigh the potential benefits at this time and probably will for many years to come, unless some major scientific breakthroughs in physics occur.

A fusion power plant is theoretically possible, but it's still far beyond current technology to create a stable, safe and reliable one on a large scale.

I believe there are some experiments in progress, but it will be some time before fusion replaces fission as a power source.

Perhaps one day, but not just yet.

Answer 3

The heat and pressure required to sustain a fusion reaction are very difficult to maintain. Powerful magnetic fields are used to contain the reaction, but fusion releases so much energy that the plasma always manages to break out of the containment and stop the reaction. Also, the energy required for the magnetic confinement can exceed the energy released by the fusion reaction.

Many other challenges remain before fusion power can be used as a power source. One of the big questions is how do you efficiently capture the energy from a source at a temperature of millions of degrees.

A large experimental fusion plant being built in France is expected to be operational in 2015. The goal of this plant is not to generate usable power but just to maintain a fusion reaction with a positive energy output for half an hour at a time. If that works, they will build an experimental fusion-powered electrical power plant.

Answer 4

The first atomic bomb gave the equivalent energy of 20 kilotons (i.e. 20,000 tons of TNT). The current H-bomb has (and for several decades has had) a yield of 50 Megatons (50,000,000 tons of TNT). Cross out all the noughts and see the energy difference between the two more clearly!

This doesn't even begin to tell the story, however. Work has been going on on fusion reactors for many years now. The main problem is not that the temperature reaches several thousand degrees centigrade but several MILLION.

Clearly, as stated previously, the only way to contain such a reaction is with an (electro) magnetic field, frequently referred to as a 'bottle' but more accurately described as a toroid.

Fusion reactions have actually been generated by accellerating heavy particles into a super-heated plasma contained within a toroidal magnetic field, generated by a number of powerful electro-magnets arranged around the target.

1) The first problem is that the super-heated plasma is unstable.
2) The second problem is that it is too dangerous to provide enough plasma mass to allow a self-sustaining fusion reaction because,
3) the magnetic toroid itself becomes unstable and would release its contents at millions of degrees.

Until a stable toroidal field can be generated that guarantees to contain a fusion reaction but allows the heat to be leached out by some form of heat transfer fluid, the fusion reaction will remain a pipe-dream (a phrase referring to the illusions experienced while smoking opium).

Like most other technical problems, however, it's only a matter of time, probably shorter than even most scientists would give credit for. Scientists always under-estimate the difficulties to begin with but, paradoxically tend to over-estimate the time required once they realise that THEY do not have the answer personally.

Answer 5

Unlike fission, for which there something like a critical mass (basically, any properly shaped and sized chunk of uranium or plutonium will blow up by itself), fusion reaction does not depend on the abundance and proper mapping of a neutronic flux. To achieve fusion requires a proper density -- enough nucleus so that there is a good chance two will bump into one another and fuse -- confinement time -- so that there is enough time that nucleus will eventually bump into one another -- and temperature (and we are talking about millions of degree here) -- so that nucleus will bump into one another with enough velocity so that the normal electrical repulsion of nucleus will be overcome (as the nucleus are all positively charged, like charges repel). To achieve ignition requires all those factors to be present, although it is the product that really matters (H bomb have great temperature and density, that is why they can get by with very little confinement time).

A workable fusion nuclear reactor cannot really achieve the density of an exploding H bomb, so the temperature and/or the confinement time have to be proportionally higher to compensate.
And that is mindbogglingly hard to do. The hydrogen you want to fuse (a very small quantity, actually, anyone who thinks that an eventual commercial thermofusion reactor could fail by blowing up like an H bomb is definitely talking through his hat) needs to be kept away from the walls of the confinement chamber (assuming a Tokamak type machine, inertial confinement is another way) or else it would cool immediately, and the hydrogen needs to be extremely pure (you do not want to needlessly heat atoms that will not react and that will take most of the energy away). How do you keep hydrogen plasma from touching the side of the chamber? Tokamak are using huge magnets; which ironically have to be cooled with liquid nitrogen to work. And then you have to tackle the issue of removing plasma instability (recently it has been suggested that a little turbulence could help; who woudl have guessed?), of scrubbing the resulting fused nucleii (helium) from the working machine while adding replacement hydrogen
deterium and/or trituim, as the DT reaction is the easiest to do; the proton-proton reaction will be quite another challenge)

As some are building larger and more powerful test fusion reactor, there are some who claim it is a complete waste of money, and that commercial fusion reactor will never be possible. The result is that financing is not always what to could be to really help research in that area.

So, to summarize: fusion reactors are presently not available because the design and the problems have not all been worked out yet. But there are great minds working on it, so stay tuned, and hope that financing will be steadily available. Fusion power will open up space exploration like no other technology can.

Answer 6

We can control nuclear fusion reactions with extremely large magnetic fields. These are used to control plasma materials which fuse to form larger atoms. The waste products are safe and the fuel can be taken form sea water. The problem is that the energy required to control and produce the reaction is greater than the amount of usable energy obtained. In just the past few years this has been accomplished on a small scale but not commercially applicable.

Answer 7

Actually, I'll beg to differ, on all the responses so far (at least, the ones that I saw before beginning this post). There's a possibility that's gaining steam in the physics community.

Have you ever heard of cold fusion? It's the idea that you can carry out successful fusion reactions... at room temperatures. One form, in fact, is looking promising for future employment.

It's called sonofusion, or bubble fusion. It only needs a vat of heavy water, a neutron gun, and some ultrasound equipment, and it works like this:

When you start out with your vat of heavy water, you "seed" (called nucleation) the water with neutrons. Very, very small bubbles form around the neutrons. At this point, the ultrasound is induced, and the vibrations cause the bubbles to expand to almost a millimeter in diameter. Once the ultrasound is removed, the bubbles implode. When they do, however, they produce temperatures in upwards of ten MEGAKELVINS - that is, about as hot as the center of the sun. Furthermore, the pressure becomes phenomenal - a few hundred million times that of the pressures found in our atmosphere, and it's all within these tiny bubbles.

Nowhere on Earth have these temperatures or pressures been seen before.

When these conditions are met, the deuterium atoms in the heavy water undergo fusion, releasing energy. The energy released takes the form of light, called sonoluminescence. In effect, you can produce a star within a jar.

Now, there are some drawbacks to this form of energy. The first and foremost is that the experiment is hard to duplicate - certain parameters, such as the frequency of the ultrasound and concentration of heavy water, make it a very finnicky reaction. Also, it's not a very efficient reaction. Currently, scientists only get about a 10% return on energy - that is, they only get back 10% of the energy we put into generating the reaction. Until it reaches the break even point - the point at which we get back 100% of the energy we put into it - sonofusion won't be a feasible source of energy. This is why fossil fuels and nuclear fission reactions are attractive - put forth a little bit of energy, get a lot of return.

If we could get this to work, however, it would solve our energy problems. Water, as you know, is rather abundant on our planet - it covers 70.1% of our surface. We could even use salt-water, and deuteriated water is found in the ocean. This reaction could be carried out at room temperature, which eliminates costly containment, cooling, and controlling systems. Also, it produces only a very, very small amount of tritium - a radioactive form of hydrogen - that decays FAR more quickly than the traditional waste from fission reactions. If we could employ it, every house, vehicle, plane, and boat could have a portable fusion reactor that is quiet, cool, won't blow up, and needs it's fuel changed about once every six months.

Like I said, our energy crisis would be solved - if only we could get it to work like we need it to.

Hope this helps!

Answer 8

The fusion reaction requires the reactants to meet at a very high relative velocity in order to overcome long range electrostatic repulsion and come close enough for strong, but short range nuclear forces to take effect. The high velocity corresponds to temperatures on the order of 10 million degrees K. Secondly, the probability of a collision scales with the density, so both high temperature and high density are required. The problem is that these are technically very difficult to achieve. It may be more freasible to detonate a bomb underground and use the heat trapped in the rock to generate stream over time.

Answer 9

1: energy/mass release.
The mass enery curve of ellements goes through the origin with a nice parabolic / logarithmic type of curve, peaks at Iron and then falls parabolically. The x axis is the atomic number and the y the energy per mol.
All the light elements on the left of Fe that can undergo fussion (joining), the energy/mass differential is huge. The most extrem hydrogen to helium (not that it happens that way as dueterium is just one of many steps)
All the heavy elements to the right of Fe undergo fission (splitting), this is were relatively smaller energies can be released.

2: reaction type:
Fission relies on heavy particle propogation, the decaying element releasing protons/neutrons (not to mention neutrinos and their counter parts to balance quantum equations), there sits happily a fuel atom until it gets hit by a bit fast sub atomic particle and then anouther atom decays. Control rods can absorb these instigators and slow the reaction rate.
Fussion relies on temperature and preassure to cause plasma (ellectrons lose their orbits) the state where fusion has a chance of occuring, since the reaction produces huge energy amounts, it creates a positive feedback loop. Hence Boom!

Answer 10

Yes, why no fusion power plants? All we can do is rip things apart. We know how to break things up to produce energy and stuff – this is no good. We need to do better. We know how to bomb nuclei of an atom with nasty gamma rays to cause serious tragic break-ups. But why can’t we learn to put things together. Why can’t we take two simple hydrogen atoms, press them together really hard until they, sort of start having sex with each other. What is wrong with that? It will be a proper marriage with stable internal relations. Our Sun does it; Alpha Centurion - our neighbouring Sun - does it. They do this all the time – putting things together to make bigger and better things. No, I do not want to know about scientific mumbo-jumbo and all that stuff about extreme temperature and pressure required, and extreme temperature and pressure that will be produced once things get heated up between atoms, and no body will be able to control the **** like we control the fission be sliding nice forward graphite bars, or something, to reduce radiation bombardment upon plutonium atom nuclei etc.

I would say where there is will there is way. I have been to a parallel universe and you would not believe what I say. The started putting things together centuries ago and now they have planet hatcheries where they put together the whole planets for their solar systems. The names of their companies sound like – Comets R Us, Intergalactic Planet Transportation Limited, and Moon Delivery Services, and the **** etc.