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Author Topic: How does nuclear fusion work?  (Read 8345 times)

Offline kiefer

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How does nuclear fusion work?
« on: 10/10/2006 18:42:58 »
can u plz tell me about nuclear fusion, what it is what happens in it and more

kiefer
« Last Edit: 24/12/2006 09:19:55 by chris »


 

another_someone

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Re: How does nuclear fusion work?
« Reply #1 on: 10/10/2006 21:32:51 »
I will give you a simple explanation, as I am not myself a nuclear physicist.

In the wider sense, to fuse something is generally to join together, and fusion is the process of joining, and so the fusion of atoms is the joining together of atoms.

The opposite of fusion is fission, fission being the splitting apart of things, and the uranium/plutonium bombs are fission bombs, while the hydrogen bomb is a fusion bomb,

In nature, one has elements from hydrogen to uranium (and in some cases, transuranic elements like  plutonium).  Hydrogen is the very smallest and lightest of atoms, with only 1 proton.  Uranium is a massively large atom, with 92 protons and upto around 146 neutrons (the common form of urnaium used for fusion bombs has 143 neutrons, but the more commonly found type of uranium atom has 146 neutrons).

In nature, the most stable atom one can have is iron, with 26 protons.  As this is the most stable atom, any atom heavier than this will give off energy as is splits apart so it can get closer to being an iron atom, and any atom lighter than this will give off energy as it joins up to try and make itself heavier and more like iron.  It is not as simple as that because it is not at all easy to get atoms to split or to join (to fission or to fuse), but when it can be done, then they will only give off energy as they get closer to becoming like iron, but when the do give off this energy, it is a vast amount of energy they give off.

Uranium, being very much heavier than iron, will give up its energy as it breaks apart (fissions).  
http://en.wikipedia.org/wiki/Nuclear_fission
quote:

[img=left]http://upload.wikimedia.org/wikipedia/commons/thumb/1/15/Nuclear_fission.svg/250px-Nuclear_fission.svg.png[/img=left]
An induced nuclear fission event. A thermal (slow-moving) neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons. The particular elements and number of neutrons produced by each single fission event are random.

















 


At the other end of the spectrum, hydrogen, being the lightest possible element, will give up energy when two hydrogen atoms fuse to make a helium atom.  This is what is used to drive the hydrogen bomb as well as powering the stars, including our own Sun.
http://en.wikipedia.org/wiki/Nuclear_fusion
quote:

[img=left]http://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/D-t-fusion.png/250px-D-t-fusion.png[/img=left]
The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power.


















George
« Last Edit: 10/10/2006 23:03:54 by another_someone »
 

Offline lightarrow

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Re: How does nuclear fusion work?
« Reply #2 on: 11/10/2006 11:55:04 »
Just to add something to what George said.
To make two nuclei fuse together it's extremely difficult because they are positively charged, so they repel each-other, and the electric repulsion at distances comparable with their dimensions is huge;

so, they (in a conventional fusion reactor) must have a huge kinetic energy (= huge temperature) to approach enough; furthermore, they have to stay close for enough time to let the strong force bind together, this means very high density of the particles.

The combination of huge temperatures (tens of millions of C) and very high densities, is extremely difficult to obtain.
 

Offline Soul Surfer

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Re: How does nuclear fusion work?
« Reply #3 on: 12/10/2006 09:02:27 »
Just to add a little to the story.  There is a balance between the temperature and pressure in an apparatus to perform nuclear fusion.  The most common ones, stars, use high pressure caused by gravity and the outer envelope of the star and temperatures of tens millions of degres K.  Man made continuous fusion devices like JET at Culham cannot get such high pressures in their discharges and so they use much higher temperatures, around a hundred million degrees, to bash the nucleii together harder.  Man made pulsed fusion devices  (hydrogen bombs)  use a precision mix of conventional and nuclear explosives to get the high pressures and temperatures more like stars very briefly.

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« Last Edit: 12/10/2006 09:08:55 by Soul Surfer »
 

Offline kiefer

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Re: How does nuclear fusion work?
« Reply #4 on: 12/10/2006 20:38:59 »
thnx evryone:D

kiefer
 

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Re: How does nuclear fusion work?
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