Good day, today's article will be about the progress scientists have made with nuclear fusion and why we should be excited for these developments.
What is Nuclear Fusion?
Unlike the conventional nuclear fission reactions used in power stations, nuclear fusion is the process of fusing two atomic nuclei by overcoming the electromagnetic repulsions between them. By doing this a lot of energy is created.
The first generators that were built for nuclear fusion were made by the USA and the USSR in the 1950’s. The USSR came up with the Tokamak design which is the main design used today. But there are others one of which we’ll be looking into later.
There have been many designs for fusion reactors, some better than others as we’ll see. The two that we’ll look at are; the Tokamak e.g. JET (the Joint European Torus) which is in oxford and is actually the world's largest and currently the most advanced Tokamak, and Helion Energy’s Trenta which uses a new and unique method for nuclear fusion.
Source: UK Atomic Energy Authority
How does it work?
The JET design ionises the inputted materials to form a plasma (a cloud of charge). This Plasma is then spun around the chamber to get the particles to collide due to the high speeds. The reason we can do this is because plasma has a charge, so can be manipulated and confined by a magnetic field made by electromagnets in the walls of the chamber. This also means plasma can’t touch the walls of the chamber and melt it. The temperature begins to gradually rise and becomes hot enough to melt any solid in the universe. Due to the temperature increasing, the ions in the plasma begin to move faster. The ions eventually begin to move so fast they overcome the electromagnetic repulsion between them and collide in the chamber releasing a large amount of energy.
Source: UKAEAofficial, on YouTube
What are the challenges being faced?
We need fuels with low input energy yet a high output energy when they react. So, what are the candidates for this problem? The most common reactants used are Deuterium and Tritium (two Isotopes of hydrogen). They are used for few reasons, for one they have a large probability of forming Helium-4 (the desired product). They also release on average 17.6 Mega electron Volts (MeV) per collision. Which means, by mass, they create over 4 times the energy as Uranium Fission.
Fortunately, 0.02% of the Hydrogen in sea water is Deuterium which means it is relatively abundant. One way to separate the Deuterium is through vacuum distillation. The main issue arises in getting a hold of Tritium, which is mainly found in nuclear fission reactor pools. Unfortunately, these pools only produce roughly 100g of Tritium a year. The Total global reserve of tritium is estimated to be only 20 Kg (not a lot at all). Scientists have worked hard to solve this issue and they have come up with an ingenious solution.
The Proposed solution
When high energy neutrons encounter an atom like Lithium, they split the lithium into Tritium and Helium-4. This is done in a breeder blanket around the fusion chamber. Another atom is need however; the atom must be neutron multiplier I.e. it creates more neutrons after itself reacting with a neutron. The Current best candidate for this is Beryllium - which is the same material used in the James Webb Telescope mirrors. When hit by a Neutron, Beryllium splits into two Neutrons and Two Helium. One Neutron is used to make more tritium and the other is used to generate energy.
The problem with Beryllium is that it is very expensive. Current designs would need anywhere between 216-560 tonnes of Beryllium. The annual global supply in 2021 was 260 tonnes. This is clearly and issue for the JET design as the current global supply would only just about build one generator. The second issue is that Beryllium usually contains some Uranium which is dangerous if used in the generator as the Beryllium will become radioactive, so the generator must be disposed of properly at the end of its lifetime.
Hope In new Innovations
Helion Energy - a company based in Everett, Washington - uses a totally different design. For one, they use much cheaper input materials. The Deuterium that they use is relatively abundant as I mentioned earlier. They also use Helium-3 which they can synthesise themselves through combing two deuterium atoms. You can find out more by visiting their website linked below. However, the fundamental method of fusion is still the same. Like a tokamak, the Trenta design also turns its inputted materials to plasma however instead of spinning the plasma in a ring, a symmetrical chamber is used. Fusion Plasma are made at either ends of the chamber. The two plasmas are then shot towards each other at the exact same time, accelerating at roughly 1 million mph! The two plasmas collide in the middle and stop. They are then further compressed by magnets which raise the temperature to about 100 million degrees Celsius. Each collision produces on average 18.3 MeV.
Source: Helion Energy
How Do We Generate Energy?
You may have figured out that the process of making plasma then getting them to collide requires a lot of energy. So how do we get more energy than we put in? In the conventional Tokamak design the plasma spins around the chamber which causes a shower of neutrons to be sprayed at the walls. These neutrons contain most of kinetic energy created from the collision of the nuclei. The wall of the chamber slows the neutrons given off and thereby convert the kinetic energy to thermal energy. This is then used to heat high pressure water pipes to make steam which spins a turbine. Hence generating energy.
Helion’s design will generates energy by skipping many of the processes in the Tokamak design. Energy is made directly through the resistance of the containing magnetic confinement field. The Plasma contain charged particles which opposes the magnetic field created by the electromagnet rings around the chamber confining it. In the process current is generated by Faraday’s Law. Due to the different materials used, the collision of ions in Trenta results in the charge particles containing most of the energy produced instead of the neutrons given of.
Why is Nuclear Fusion Something to be excited about?
Nuclear Fusion hasn't yet made viable, but if it can be made economically viable it could hypothetically change the face of society. As a Civilisation we could be able to produce clean and safe energy, this would allow the whole world to benefit. We would be able to transition away from fossil fuels. It would also mean less political turmoil as energy will be cheaper due to higher supplies. Lastly, it could open the doors for whole new industries to emerge, previously limited by energy cost for example steal refineries, Desalination and much more.
As you can see the possibilities for Nuclear fusion are endless and many people around the world are working hard to make it a reality. If you want to find out more about Nuclear fusion I would recommend looking into the ITER project, Helion Energy, Tokamak Energy to name a few.
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