Imagine a World where we could generate electricity, in a carbon-neutral, self-sustaining manor, using the same reactions that take place in the sun? Welcome to Nuclear Fusion. Here we will explore the difference between nuclear fusion and current nuclear power methods, and what the future holds for fusion.
Nuclear power currently provides ~21% of the UK’s electricity supply, using 15 reactors, with plans to increase this to ~25% by 2025. Energy giant EDF say increasing nuclear power will replace the old, polluting power stations (such as coal) which are closing, to provide an affordable, low-carbon energy source to the UK. At the moment, all nuclear power is generated through fission reactions; so what is the difference between fission and fusion? Fission is the process whereby a large atom is hit by a tiny neutron, exciting the larger atom which then splits into two smaller atoms (i.e. radioactive fission products). When the larger atoms split, a huge amount of energy is released as well as additional neutrons, which can initiate a chain reaction, providing more energy. Uranium and plutonium are the most commonly used materials for fission reactions as they are unstable (i.e. it is easy to initiate a reaction) but can be controlled relatively easily with control rods. The energy released by fission reactions usually heats water into steam, which is then used to spin a turbine to generate electricity. To read more about these types of reactors, read the brilliant article by young scientist (and runner up in the 2020 A Short Scientist science writing competition), Daniel.
Fission processes are not ideal though, creating radioactive waste which have a long half-life. The half-life is defined as the time it takes for the number of nuclei of a radioactive element in a sample to halve; for uranium, this is 4.5 billion years. Radioactive waste that is categorised as intermediate is mixed in concrete and kept in stainless steel drums, whilst waste which is considered highly radioactive is stored underwater for 20 years before being kept in purpose-built, underground stores where air is circulated to remove heat the waste produces. High level waste decays to intermediate level waste over thousands of years. The overall process is also not a “zero carbon” option, from uranium mining overseas, to management of radioactive waste, energy production via nuclear fission isn’t the perfect solution (although considered better than fossil fuels such as coal and gas).
What about fusion? Nuclear fusion is the same process which powers the sun. Unlike fission where a large atom is split, fusion occurs when two smaller atoms FUSE (or slam together) to make a heavier atom. For example, the reactions in the sun fuse two hydrogen atoms together to become a larger helium atom and, in the process, generate a massive amount of energy, several times greater than that generated during fission reactions. Alongside a much greater energy output, fusion reactions don’t create radioactive by-products as seen in fission reactions, and use hydrogen which is in plentiful supply. So, why aren’t all nuclear power stations using these cleaner, safer and (almost) eternal fusion reactions already?
Unfortunately, the conditions needed to start a nuclear fusion reaction are very difficult to recreate and maintain. Like the conditions of the sun, to recreate fusion reactions on Earth they require a massive amount of pressure and temperature (at least 100 million°C!) to fuse those first two atoms’ nuclei. However, in recent years, scientists (including those on the SPARC project with MIT) have edged closer to this goal, succeeding in producing controlled fusion reactions, but failing to create a reactor which produces more energy that it uses. There are many approaches to recreating fusion on Earth, here are two that are worth noting: Magnetic Confinement and Inertial Confinement. Magnetic Confinement uses magnets to hold plasma fuel in place before heating it with microwaves, radio waves and particle beams, all in a donut-shaped reactor. Plasma is the fourth state of matter and exists when a gas’s atoms split into positive and negative particles. Plasma is very difficult to hold due to its temperature, and is also difficult to compress. Imagine a squishy toy, if you do not apply equal/even pressure to every side, it will leak out wherever it can; plasma is even more slippery, and miniscule. Inertial Confinement involves 192 lasers which fire at a tiny gold can containing hydrogen fuel, giving off x-rays. These x-rays will hit the hydrogen fuel (which is smaller than a peppercorn), heating and compressing it, turning the fuel to plasma which can then fuse into helium, producing energy and neutrons.
Whilst fusion power is in development, fission processes still generate much more energy than other fuel types (e.g. coal, gas, sun, wind etc.) and in 2020 the UK “government confirmed its commitment to developing [more] nuclear projects“, advancing nuclear technologies to aid the transition to a low carbon economy. Their plan includes working with energy companies, such as EDF, to create smaller nuclear power stations and the use of the next generation of nuclear technologies (i.e. Generation IV, Advanced Modular Reactors (AMRs)), which implement novel cooling systems or fuels. However, “if we could get fusion to work, we [may] never have to worry about energy again“, the major statement of a 2014 article by Susannah Locke, in Vox. Watch this space, we could see a future of fusion.
While You’re Here
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