Nuclear Fusion

Saturday, January 30th, 2010

Here’s an exciting news article I found on the BBC website.  Basically, there’s been a breakthrough bringing us one step closer to Nuclear Fusion power plants… maybe.   The breakthrough involves the process of starting the Nuclear Fusion Reaction with lasers.  In the past, it was thought to be a very uneconomical process requiring almost as much energy, or more, to begin the reaction as the reaction would produce.  This breakthrough however demonstrates that this is not the case,  and puts High Power Energy Lasers in the running for the first commercial nuclear fusion power plant.

http://news.bbc.co.uk/2/hi/science/nature/8485669.stm

Some info on Nuclear Fusion

In it’s basics, nuclear fusion is a process where atoms are combined to produce new elements and hopefully energy.  The most favoured of these reactions for nuclear fusion power generation is the deuterium and tritium reaction.  Both deuterium (D) and tritium (T) are isotopes of Hydrogen, meaning that they have additional Neutrons for a total of 2 in D and 3 T.  This reaction produces Helium, one neutron and lots of energy.  I say it’s the most favoured because it produces the greatest amount of net energy of any fusion reactions.   Net energy being the difference between the energy given off by the reaction and the energy required to start the reaction.  Net energy is how much energy is available for electric power production.

D + T → He + 1n + 17.6 MeV

How do these lasers fit into the grand scheme of things?

As mentioned above, lasers are just one of the methods being investigated to start the nuclear fusion reaction.  Another popular method is to apply a current to the reactants while being held in a plasma state.  The plasma is contained by tokamak (magnetic confinement fusion).  Already, there is a demonstration plant being built to test this technology, and bring it to a level of understanding where a commercial plant can be produced.  This project called ITER is being built in France and is expected to switch on in 2018.

This laser technology does have some advantages to the magnetic confinement fusion method employed by ITER.  Namely:

• The reactor core is mostly exposed, as apposed to being wrapped in a huge magnet
  • making energy removal and maintenance easier
  • allowing the use of low-activation materials in construction such as carbon fibre which would reduce the rate of irradiation to the core.

Is the Nuclear Fusion good or bad?

Hard to say.  It does have several advantages over nuclear fission, which is the reaction used today in nuclear plants.  For instance:

• Abundant fuel
• Reaction conditions are so temperamental that a runaway or meltdown situation is not possible, so it is considered intrinsically safe as any problems will just cause the reaction to stop
• No CO2 is produced
• Radioactive materials are mostly constrained to the reactor core itself, with expectations that it would be dangerously radioactive for about 50 years, and lightly radioactive for another 100 making storage and disposal simple when compared to todays radioactive fission waste which can require storage for thousands of years.
• Substantial source of energy capable of replacing all current carbon based electricity for the next 150 billion years based on availability of reactants.

Of course there are some draw backs as well:

• Tritium is bread from liquid Lithium, both of which are radioactive.  During normal operation some Tritium will be released into the atmosphere, and a a leak could result in the release of dangerous amounts of Lithium into the atmosphere.
• Helium is also released, while it is not currently known to impact living organisms, or to act as a green house gas, increasing concentrations of anything in the atmosphere could pose unseen risks.

That’s basically all I know about nuclear fusion, hope you enjoyed.

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