Using fusion reactors in place of fission reactors is not a new idea, but the technology has always seemed so far away. However, according to research done by the International Thermonuclear Experimental Reactor (ITER), construction of the world’s largest experimental tokamak nuclear fusion reactor will be completed by 2020. The ITER consists of seven countries: the European Union (EU), Japan, India, China, South Korea, Russia, and the United States. If this reactor is successful, it will pave the way for eventually replacing fission power plants with fusion power plants.
The difference between fusion and fission is that fusion takes heavy atoms (uranium 235 is the most commonly used isotope in industry) and splits them into smaller atoms, producing energy. The heat from this energy is used to generate steam from water to turn a turbine, which powers a generator to produce electricity. Fusion, on the other hand, takes two smaller isotopes (such as deuterium and tritium, which are isotopes of hydrogen) and fuses them together to make a heavier atom (such as helium). Like fusion, the energy from this reaction powers a steam-turbine system to generate electricity.
So what is wrong with our fission power plants that we even have to think about fusion? Fission reactors are usually about 30% to 45% efficient. As Dr. Webber has discussed in class, fission nuclear power plants also generate some very dangerous radioactive waste that we do not really know how to deal with yet. Fusion is a very attractive alternative because it produces no carbon dioxide and is expected to produce 10 times the amount of energy that is required to power the reaction [1]. One of the most attractive aspects of fusion, though, is that it produces a minimal amount of radioactive waste. This is because the deuterium and tritium isotopes chosen for the fusion reaction in the to-be-built reactor do not have a long term legacy of radioactive waste. Not to mention, these hydrogen isotopes are naturally abundant in Earth’s oceans [2]. We would not have to go digging around, looking for fuel for fission anymore.
If fission is so great, why have we not started using it by now? The fusion reaction is extremely hard to contain. Fission is relatively easy to induce compared to fusion. In order to make two atoms fuse together, you need to give the atoms a great amount of potential and kinetic energy to want to even go near each other, let alone fuse. In fact, you would need to heat the gases consisting of the hydrogen isotopes to temperatures greater than 100 million degrees Celsius. That is about 10 times the temperature at the center of the sun! Once fused together, the fuel enters the fourth state of matter: plasma. Needless to say, no material on Earth is able to withstand the high temperatures of plasma [2].
The solution for this is to exploit the physical properties of plasma itself. Plasma consists of charged particles that can be directed and confined by magnetic forces. The particles in the plasma will follow magnetic field lines. Magnetic fields are not affected by heat. ITER’s tokamak reactor will utilize a donut-shaped reactor chamber, called a torus. This torus will use magnetic fields to shape the plasma into a ring-shape, continually spinning the plasma in the torus chamber and preventing the fuel from touching the container walls [3]. When I think of magnetic fields, I automatically imagine refrigerator magnets. So to me, thinking that plasma can be contained by something as small (or should I say as strong?) as a magnetic field is somewhat scary. Of course, the magnetic fields that the torus will have will be much stronger than the refrigerator magnets I am thinking of, but the science is still unfathomable to me, as I am sure it is for many other people as well.
Many people are also concerned about the safety of these fusion reactors. At first I thought that if the fusion reaction somehow escapes from its containment unit that it would just go on to consume everything in its path for the reaction, and the reaction would go out of control. However, Aris Apollonatos, who is the communications leader for the EU branch of the ITER project, says that there is no risk of meltdown or runaway reactions because the plasma will cool itself and stop the process if anything should go wrong [1]. While this makes sense to me, I feel that it would still take a long time for the plasma to cool down from such high temperatures before being safe enough to be around. Though, I am pretty sure that they will have adequate safety measures in place in case anything goes wrong. This reactor is still highly experimental, so they have to be extremely cautious.
Overall, fusion is definitely a promising alternative source of energy to what we have available now. The technology now has made fusion reactors a not-so-distant possibility. I am interested in seeing the result of ITER’s fusion reactor and what it will do for the world’s energy landscape.
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