A half baked article I wrote about Nuclear Fusion a while ago. Some aspects of it are vague for the simple reason that I am not a Nuclear physicist. Please feel free to jump in and point out any errors you spot or indeed to expand on anything I have glossed over.
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I’ll start with a quote by renowned rocket scientist and bongo player Dick Feynman:
“If, in some cataclysm, all scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or atomic fact, or whatever you wish to call it) that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence you will see an enormous amount of information about the world, if just a little imagination and thinking are applied.”
Feynman here is recounting the basic physical laws that govern matter on the atomic scale (ie very, very small). We can exploit these laws to create a large amount of energy in Nuclear Fission (aka splitting the atom) whereby uranium is arranged into a critical mass that starts a chain reaction whereby huge amounts of energy are released (governed by Einsteins famous formula E=MC2). In this case the part of the statement above that refers to “attracting each other when they are a little distance apart” is the source of the energy.
This is quite common today with many countries supplying large amounts of their energy needs by the process. The problem, of course, is that this creates large amounts of highly radioactive nuclear waste that will be deadly for thousands of years. One of these waste products is also Plutonium which can be used in Nuclear bombs. So all in all its a pretty nasty technology but we keep using it because we get such phenomenal amount of energy from it for not very much work and it does not emit Carbon Dioxide (though the mining and refining processes release large amounts).
But the last part of the above statement that says it is in the nature of atoms to be “repelling upon being squeezed into one another” underpins the premise of Fusion. Fusion works by superheating a gas (typically Hydrogen) so hot that it is basically a miniture Sun inside a special chamber. The gas gets so hot that it enters a 4th state of matter known as plasma (the other 3 being solid, liquid and gaseous). The temperature required to cause the reaction is in the order of a hundred millions degrees. At such a temperature the Hydrogen completely dissociates into a cloud of nuclei and electrons called a plasma. The plasma is far too hot to confine with material (ie solid) walls but because the electrons and nuclei are charged and moving they can be deflected by magnetic forces and with a suitably shaped magnetic field, confined and directed. Somehow at this point the process becomes self sustaining and no more energy input is needed but the plasma continues reacting and now you basically have a small Sun under your control. The plentiful and non-polluting element hydrogen acts as a fuel (in which the hydrogen is in the form of deuterium, which is a hydrogen atom that contains a neutron) which then reacts with Tritium in the walls of the reactor chamber to sustain the reaction. The end-product is helium so no radioactive waste is created.
the whole reaction is so finely balanced that if there were to be the slightest loss of equilibrium it would die immediately. So no chance of meltdown. it is basically the ideal renewable energy source.
Research on Fusion has been going on for about 50 years but commercially it probably won’t be ready for another 100 or so. A big problem is creating a chamber that will withstand the intense forces of the plasma and sustain the reaction. It needs to be lined with a special blanket made of a material called Tritium. There is less than 100kg of Tritium on planet Earth (most of it owned by the USAF) and it is estimated more than double this amount will be needed to get the first functioning reactor.