SciBar November 2015

Hannah Latham from Rolls-Royce in Derby joins us in The Vat and Fiddle for November’s SciBar to talk about “Fusion Power: A Sunny Prospect or a Stormy Future”

Nuclear fusion is the power behind the sun and due to our dependence on fossil fuels, attempts to recreate fusion on Earth are receiving some quite high priority. To give an idea of how tied to fossil fuels we are, around 68% of the world’s electricity and around 82% of the world’s total energy come from fossil fuels. As at 6pm on the day of SciBar, 64% of the UK’s electricity was being generated through fossil fuels.

While many people would look to renewables to replace fossil fuels but the output of the coal-fired Radcliffe power station is equivalent to 800 wind turbines (assuming 100% utilisation) Meanwhile China built 54 coal power stations last year alone (in the UK, we have just 13) What happens if Indian or another developing nation decides to do the same? What happens when we run out of fossil fuels? Is fusion the answer?

Our current nuclear power stations work through fission – the splitting of the atom. Conversely, fusion is where we join atoms together. Both of these methods produce energy but fusion produces more and produces almost no radiation. However, the only place that we know that fusion occurs it the sun and it looks like you need to be at several million degrees Celsius to make fusion happen (the sun itself is around 15 million degrees C)

Current attempts to create fusion on Earth are focused on using a Tokamak (a series of magnets) to keep some plasma in a doughnut shape (there is a reactor in Oxford called MAST that uses a sphere but the torus is far more popular) As fusion happens, a neutron would be spat out and crash into a blanket outside of this doughnut. This impact would create friction and this heat would then be sent to a regular power station. There the heat is used to boil water and the steam produced spins turbines creating rotational kinetic energy. This is then converted into electrical energy.

So far, we’ve “sort of” managed to create a fusion even here on Earth. At the Joint Energy Torus (JET) in Oxfordshire, they have managed fusion but haven’t managed to get out more energy from the reaction than they have put in. So far they’ve achieved about 73% energy out verses energy in. The longest that they have managed to maintain a reaction for is 6 minutes and 30 seconds but the average is around 1 minute and 20. At that point they have to turn it off or the magnets will melt. In fact no one is sure if JET will actually work (in the sense of creating more energy that it requires) without melting. At its best, JET can produce around 0.8% of the energy that Radcliffe-on-Trent coal fired power station can.

Now the EU have built ITER to try and prove that fusion can produce more energy than you need to put it. ITER is even bigger than JET (which at 11.5m is about 1.3 times the height of an average house) However, to build an actual plant that would generate electricity, it would need to be even bigger.

As a brief aside, this is why Iron Man’s heart doesn’t use nuclear fusion – a device couldn’t be made that small. It was originally going to be fusion powered but due to these real life considerations became electro-magnetic instead.

In 2013 ITER was forecast to cost €15 Billion to build but it’s already over budget. So, even if it works, will it ever be commercially viable. It was due to be fully operational in 2027 but it’s behind schedule too.

Hannah tells us that if we want to want to sound like experts in fusion, then we should confidently state that “it’s 30 years away” (the joke being that this has been the case for a long time) Comparing it to the history of nuclear fission, the neutron was discovered in 1932 and the first commercial nuclear power station opened in Sellafield in 1956 – 24 years (although research was greatly accelerated due to the second world war) On the other hand, the idea of fusion was first suggested in 1920. JET was designed in 1973 and first turned on in 1983. ITER is supposed to come online in 2027 so could we finally have a commercial plant in 2057?

There are still a few issues that need to be solved with nuclear fusion. For example, the next seven years’ supply of helium has already been bought up. Tritium, an isotope of hydrogen that can also be used in fusion is hard to find (although there is a large supply on the moon) Then there are questions about how you actually generate the electricity following fusion because if the steam generated gets too hot (around 700oC) it can melt steel.

However, it does have one huge advantage over fission in that it is self-safe – it cannot go critical. In fact JET goes from being switched on to being stone cold in 25 minutes.

The big question is whether nuclear fusion will be ready in time to start replacing our current coal-fired power plants as they start to age. Although that’s looking unlikely, as it’s still “30 years away”

Author’s notes

Talk from 25/11/2015

Previously unpublished


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