Is Nuclear Fusion the Future?

Energy supply for the future is one of the greatest challenges facing humanity today. Simultaneously preventing runaway climate change, providing energy for all, and doing so affordably is no mean feat, especially considering the growing global population, expected to reach 9.7 billion by 2050.

Assuming that reduced CO2 emissions will be a major factor when deciding future energy supply options (it should be – the World Bank has recently warned that expected climate change may put 100 million people in extreme poverty), what is our best option? We have access to a variety of renewable technologies: wind, solar, geothermal, hydroelectric, tidal and more, all of which are rapidly progressing, and the possibility of implementing carbon capture and storage (CCS) to coal or gas power plants.

(The fusion reactor at Tri-Alpha Energy)

There is also an option which doesn’t fit into either the renewables or the fossil fuel families – nuclear power. Nuclear power harnesses the power within atoms. Nuclear energy can be split into two types: fission and fusion. Both use heat released to turn steam turbines which power generators, as has been done traditionally with coal and gas-fired power plants.

Fission is what’s been going on in our nuclear power plants for decades and put simply, is the splitting of heavy elements to release lighter elements, along with neutrons and large amounts of heat. Tiny amounts of fuel produce vast amounts of electricity, but this incredible scale is terrifying as well as promising. The fact that nuclear fission follows a chain reaction, and that it can’t simply be turned off, leads to significant safety fears, as does the long-lasting and highly dangerous radioactive waste it leaves behind. The disasters at Chernobyl and Fukushima, along with a number of smaller accidents, have led to sceptical views of the industry. Furthermore, an increased reliance on fission would of course eventually lead to a pinched fuel supply – there will be a limit to how much Uranium we can get our hands on.

So what about fusion? Fusion can be considered the opposite of fission, where two small nuclei, such as Hydrogen, fuse together to form larger nuclei and release energy, much like what happens in stars. This process is extremely tricky for us to get right – temperatures of a steamy 150,000,000°C are needed to provide the nuclei with enough speed to overcome their repulsive forces. Above this temperature, a superheated plasma is formed, but must be kept in a confined space to maintain the necessary temperature. In reactors known as Stellarators and Tokamaks, this is done using a doughnut-shaped ring of magnets which confine the plasma in the centre of the “doughnut”. There are various experimental fusion reactors following this “magnetic confinement” technique, but these are the most established, and are seeing large European projects: ITER in France and Wendelstein 7-X in Germany investigate their use further. Another method involves imploding a target with laser beams (less excitingly named “inertial confinement fusion”, yawn).

There are a few very promising factors about the fusion process, which interestingly tend to be arguments against fission. The first is fuel abundance. We have enough Hydrogen in the oceans to power fusion reactors for two billion years. Secondly, radioactive waste products would remain dangerous for a period of less than 100 years, whereas fission reactors generate waste which will stick around for thousands of years. Unlike fission, fusion systems could be rapidly shut down, don’t involve a chain reaction and use only a tiny amount of fuel at any one time; all significantly reducing the possibility of serious accidents.

It’s clear, given all the devices that already exist, that fusion is possible. So why aren’t we using it? For now, fusion is just too expensive. The energy output from fusion devices has never yet been more than the input - the best result was a 16 MW output from a 24 MW input in 1997. But no new technology works perfectly straight away, and it’s hoped that with a bit more money, enthusiasm and time, fusion may be the future! ITER is expected to produce 500 MW of fusion power from an input of 50 MW, and if successful it could pave the way for a fusion-filled future. And just when can we expect this? The 2040s seems to be the estimate most commonly cited by those in the business, but at this stage all anyone can really say is that we hope fusion will become practical in the future.

#NuclearFission #EmilyVincent #Physics #Fusion

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