Nuclear fusion fuels our very lifeblood: the Sun.
Humans Invent spoke to Ceri Brenner, from the Central Laser Facility at the Science and Technology Facilities Council (STFC) in Oxford about laser fusion and why it could potentially be a much greener, more efficient and sustainable source of energy than nuclear fission.
Ceri says: "Fusion is currently our best hope for a clean, safe, abundant source of energy for the truly long term."
What is laser fusion?
For fusion to occur the particles have to be in a plasma state of matter, which means all the ions need to be stripped of their electrons as you are trying to squeeze the nuclei together and the electrons get in the way. To achieve fusion, three conditions have to be satisfied in order to get more energy out of a fusion reaction that you put in. First, it has to be hot enough. Second, the density has to be high enough – there has to be enough plasma particles or hydrogen isotopes per square centimeter in order for enough of these fusion reactions to take place. Thirdly, you have to combine the temperature and the density for long enough. Combining all these three together gets you the Lawson criterion: if it exceeds a certain value then you will get more energy out of those fusion reactions than you put in.
There are two approaches to achieving nuclear fusion: either through magnetism or with lasers
There are two approaches to achieving nuclear fusion: either through magnetism or with lasers. ITER, a multi-national worldwide project which is being built in France is using the magnetic approach for example. In order to reach the Lawson criterion by using lasers, you only need to confine it for a few nanoseconds. You can achieve those conditions by having a very small round pellet of fuel and bombarding it with laser beams. If you bombard a spherical pellet with laser beams that has a hard outer shell the effect of the laser shining on the surface will blow off this outer surface.
And that force, because of Newton’s Third Law where every force has an equal opposite force, drives a compression force inwards compressing the inner fuel. That is what the National Ignition Facility (NIF) in the US are currently doing as we speak. They have 192 laser beams. It took about ten years to build and they are currently firing as many shots as they can to try and provide proof that you can get more energy out of the reaction than you put into your laser beam to start with.
How far along have scientists come with nuclear fusion?
The theory has been around for ages but it is only really in the last twenty years that large scale experiments have taken place. It took us a long time to get the engineering together but we are nearly at the point where we can prove the principle experimentally.
The next point of the game is to make the physics work in an engineering sense and transfer it to a commercial scale. When it comes to lasers, instead of firing the laser once every couple of hours which it does at the moment, we need it to be firing ten times a second. We then need to get material scientists, engineers and laser scientists on board to ramp up the repetition of this experiment. There are a couple of projects already set up to tackle this, one of them is a European project called HiPER and that is a European project set up to harness fusion reaction for electricity production and the equivalent in the US is called LIFE and they are doing an analogous thing to HiPER, taking the results of NIF and turning it into an electricity power station by engaging with the industry and trying to get financial support.
Once we have the proof of principle it then becomes really exciting because then we can actually start designing this for real. Designing new technology is never impossible you just need the time and effort to get there.
Ceri believes: "It will take time, but harnessing laser fusion for energy to run power stations is a prize of such immense value for civilisation that it is worth every effort that we can give."
Can you predict how far this is from becoming a reality?
I’ve taking my lead from the LIFE project who are very optimistic and they say once they have proof of principle they’ll have a power station in 10-12 years or at least they will have the first power plant demonstration by then. They could be seen all over the world in another 25 years.
Why is it so much better than existing energy solutions?
Getting energy from fusion seems almost too good to be true when you start writing it up on paper. For example, the fuels you need are Deuterium and Tritium. Deuterium is technically heavy water, it is a hydrogen isotope that can be extracted from sea water which there is plenty of. Tritium is available naturally but the best way to get it is to produce it from Lithium.
Once they have proof of principle they’ll have a power station in 10-12 years
As long as there is plenty of Lithium, then we can get Tritium. So the fuel is abundant and it doesn’t destroy any habitat. When it comes to waste products, you get Helium, which isn’t such a bad thing anyway because people are saying we are running out of natural Helium. When it comes to radioactive waste, it is far better than the waste created from traditional nuclear power stations. They create radioactive waste that can last for thousands and thousands of years whereas the nuclear waste produced from fusion reaction is, comparatively, very short-lived. It has a half life of about 100 years and that is what nuclear energy people call a shallow grave: it does need to be buried but in a 100 years it will be fine and it won’t be damaging the earth forever.
It is basically the perfect alternative and it almost seems too good to be true. It is the most efficient way of producing energy, after all it is what powers the sun. If all the stars and the sun have existed on fusion energy for years and years and it hasn’t blasted the universe or given off a dangerous radioactive glow it’s a good sign.
