Fusion energy: simplified
This is an introduction to fusion energy and how it affects our world.
Brinda Vijapur
Wait, so what’s nuclear fusion again?
The most efficient fusion reaction in the laboratory setting is the reaction between two hydrogen isotopes deuterium (D) and tritium (T). The fusion of these light hydrogen atoms produces a heavier element, helium, and one neutron. The leftover mass becomes energy. (deuterium and tritium are isotopes of hydrogen)
General characteristics of fusion
- The energy producing mechanism on a fusion reactor is the joining together of two light atomic nuclei
When two nuclei fuse a small amount of mass is converted into a large amount of energy. Energy (E) and Mass (M) are related though Einstein’s relation, E=MC², by the large conversion factor C² where C is the speed of light. Mass can be converted to energy also by nuclear fission, the splitting of heavy nucleus. Fusion reactions are inhibited by the electrical repulsive force, called the coulomb force, that acts between 2 positively charged nuclei.
2. For fusion to occur, the two nuclei must approach each other at high speed in order to overcome their electrical repulsion and attain a sufficiently small separation (less than one-trillionth of a centimeter) so that the short-range strong force dominates
To produce useful amounts of energy, a large number of nuclei must undergo fusion; that is to say a gas of fusing nuclei must be produced. In a gas at extremely high temperatures, the average nucleus contains sufficient kinetic energy to undergo fusion. Such a medium can be produced by heating an ordinary gas beyond the temperature at which electrons are knocked out of their atoms. This is a result in ionized gas consisting of free negative electrons and positive nuclei. This ionized gas in plasma state, the FOURTH state of matter. Most of the matter in the universe is in plasma state.
Fusion, fission, same thing?
Fusion and fission may sound the same however they are no where related to each other. In fission, a large unstable nucleus is split into smaller elements, releasing energy. Fusion by contrast, starts with light atoms. Take 2 hydrogen nuclei for example. Ordinarily, their positive charges repel each other.
Advantages of fusion energy
1.Nuclear fusion doesn’t create harmful waste.
Fusion reactors produce no high activity, long-lived nuclear waste. The activation of components in a fusion reactor is low enough for the materials to be recycled or reused within 100 years. Fusion also does not release carbon dioxide or any green house gas. In comparison, the by-product of fusion is helium, a non-toxic gas.
2. Abundant energy
Fusing atoms together in a controlled way releases nearly four million times more energy than a chemical reaction such as the burning of coal, oil or gas and four times as much as nuclear fission reactions (at equal mass).
3. It is incredibly inexpensive to create.
The power output envisioned for a fusion reactor for the second half of the century is envisioned to be that of a fission reactor. The average cost per kilowatt is expected to be similar or slightly more expensive at the beginning.
4. No risk of meltdown
A Fukushima-type nuclear accident is not possible in a tokamak fusion device. It is difficult enough to reach and maintain the precise conditions necessary for fusion — if any disturbance occurs, the plasma cools within seconds and the reaction stops. The quantity of fuel present in the vessel at any one time is enough for a few seconds only and there is no risk of a chain reaction.
5. Global warming can still be negated without energy loss.
Fusion fuels are widely available and nearly inexhaustible. Deuterium can be distilled from all forms of water, while tritium will be produced during the fusion reaction as fusion neutrons interact with lithium.
Ok so fusion sounds great and everything but why isn’t it everywhere?
Problems with fusion
Our sun constantly does fusion reactions all the time, burning ordinary hydrogen at enormous densities and temperatures. But to replicate that process of fusion on earth- where we don’t have the intense pressure created by the gravity of the sun’s core- we would need a temperature of at least 100 million degrees Celsius, or about 6 times hotter than the sun.
Emerging technology
The few popular upcoming technology working on fusion is the International Thermonuclear Experimental Reactor (ITER), Commonwealth Fusion Systems(CFS) and General Fusion.
ITER is an international nuclear fusion research and engineering project that aims to replicate fusion reactions happening in the sun on the earth. Upon completion of construction of the main reactor and first plasma, planned for late 2025 it will be the world’s largest magnetic confinement plasma physics experiment and the largest experimental tokamak nuclear fusion reactor. ITER’s stated purpose is scientific research, and technology demonstration of a large fusion reactor, without electricity generation. ITERs goals are: to achieve enough fusion to produce 10 times as much thermal output power as thermal power absorbed by the plasma for short time periods. To demonstrate and test technologies that would be needed to operate a fusion power plant including cryogenics, heating, control and diagnostics systems, plus remote maintenance, to achieve and learn from a burning plasma; to test tritium breeding and to demonstrate the safety of a fusion plant.
In my next article, i plan to do a deep dive in Tokamaks, what they do and how they work. Until then, see you!
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