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What is Nuclear Fusion?

By: Maggie Wakefield - Updated: 24 Aug 2012 | comments*Discuss
 
What Is Nuclear Fusion?

Nuclear fusion is the most powerful source of energy known to man. It is the process that creates the heat of the sun and the stars.

Unlike nuclear fission, nuclear fusion does not involve high levels of radioactivity. We believe that if we could control the process of nuclear fusion, we would have a clean, safe and virtually unlimited energy source.

Releasing Energy from Fusion

If two hydrogen isotopes – deuterium and tritium – are fused together, the act of fusion releases helium, which is a harmless gas; a neutron; and, crucially, a lot of energy. This is what happens in the hydrogen bomb, but here it is an uncontrolled reaction that results in explosion.

Various ways of initiating a process of controlled fusion have been investigated; however, one recurring problem is the huge amount of power necessary to trigger fusion. The reason so much power is needed is that every hydrogen atom naturally repels every other hydrogen atom. Their nuclei all contain protons with a positive charge, so trying to squeeze two of them together is like trying to force two magnets into contact. The forces involved are tremendous. Naturally-occurring nuclear fusion at the core of the sun is possible because of the massive pressure exerted by the sun’s forces of gravity.

Producing Electricity from Nuclear Fusion

Various approaches can be taken to creating the extreme heat and pressure needed for fusion to occur. But in order to use nuclear fusion as a commercially-viable method of generating electricity, the amount of energy used in achieving fusion must not be so great that it cancels out most of the energy that is subsequently released. The challenge is to find a method of inducing fusion that uses a minimum of energy, and alternative methods of achieving this are being explored.

An experimental reactor currently being built in France (the International Thermonuclear Experimental Reactor in Cadarache, Provence-Alpes-Cote d'Azur) uses the magnetic confinement method. This reactor will use magnetic and electrical fields to create pressure and heat. The first stage will be to turn hydrogen gas into plasma by subjecting a stream of gas to extreme heat inside the reactor. The plasma will then be squeezed by super-conducting magnets to achieve fusion. The heat released during fusion will be used to produce steam to drive turbines and power a generator.

Another reactor under construction in the USA (the National Ignition Facility at Lawrence Livermore Laboratory) is working on the inertial confinement method, using lasers to create the necessary heat and pressure. High-energy laser beams will bombard a small pellet of deuterium-tritium, sealed inside a small cylinder, to first convert the pellet into plasma, and then to compress it until fusion takes place. Again, the energy released will be converted into steam. At the time of writing, a multi-million pound project led by British scientists is being planned, based on the same laser technology but using a more advanced technique which, it is hoped, will enable the fusion reaction to take place at lower pressure.

Once controlled fusion can be achieved in laboratory conditions, this could pave the way towards the launch of a new generation of nuclear power stations.

Advantages of Using Nuclear Fusion

Scientists believe that nuclear fusion power stations have the potential to generate sufficient electricity to meet global demand, without damage to the environment. It will create no air pollution and no greenhouse gases. Very little waste will be produced, and it will not be dangerous because the level of radioactivity in the waste material will be low. Once the process of fission has started, it will be self-sustaining, and it will be safe because the amount of fuel used in the reactor will be so tiny. The fuel itself is more abundant and more easily obtained than the uranium used for nuclear fission; deuterium and tritium, the two hydrogen isotopes used as fuel for fusion, can be obtained from seawater.

If nuclear fusion power plants fulfil all our hopes, we would no longer have to worry about the possibility of an energy crisis. We would at last have found a clean, safe method of producing unlimited supplies of electricity. We can’t do it yet, but a lot of progress has been made. A hundred years ago, the notion of producing electricity from nuclear fusion would have been dismissed as science fiction. Now it seems it may only be a matter of time before commercial nuclear fusion reactors become a reality.

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