Super-lasers, cosmic rays and temperatures ten times hotter than our Sun's! What do all of these have in common?
They are all being used or generated on Earth to obtain what we call sustainable energy.
Fusion research aims to reduce or eliminate radioactive and toxic wastes, as well as greenhouse gas emissions. The wastes and gaseous emissions are already significantly lower when compared to other methods of generating energy, such as fission facilities, especially when we include the commissioning and decommissioning of fission power plants. We still need to manufacture the materials required to construct fusion power facilities.
Current fusion research also looks at the metal alloys needed, in order to avoid the need to extract rare earth minerals. Stainless steel, lithium and ceramics are all considered abundant on Earth and easy to mine and are frequently used in fusion power plants.
What is plasma and fusion research?
Plasma research refers to the study of the fourth state of matter. It is a gas, but unlike other gases, plasma consists of ions and electrons that are only "bound" together by electrostatic forces. This makes plasma highly conductive, enabling it to interact strongly with magnetic fields.
As a result, plasma is often used in research on fusion energy.
Fusion research refers to the efforts done by scientists to investigate ways to harness atomic fusion energy for use on Earth. This research is complex because it requires creating a plasma with extremely high temperatures and pressures.
Nuclear fusion represents one of the densest energy sources that we have discovered how to tap into.
Nuclear fusion is a reaction in which two or more atomic nuclei collide and fuse to form a new nucleus. Usually, it's hydrogen fusing into helium.
This process releases a large amount of energy, which can be harnessed to generate electricity.
The atomic nuclei usually used in fusion are two "species" of hydrogen (H), called isotopes, namely deuterium and tritium. They are also called hydrogen-2 and hydrogen-3.
Fusion energy is defined as high-energy density because a lot of power can be produced and measured in the form of:
megajoules per kilogram (MJ/kg);
then be turned into heat or electricity, measured in megawatts - MW.
If we were to rank energy output, fusion comes on top, followed by fission, fossil fuel, hydrogen, biomass such as wood, and renewable energy sources such as tidal, at the end.
Perhaps the most physically unique thing about nuclear power is that the energy density of nuclear fuel is about 2 million times higher than that of any chemical (like fossil fuel, biofuel, or batteries).1
The total energy density of an energy source can be influenced by how it is processed. Our nuclear fission plants cannot harvest 100% of the material they are given, meaning they can't obtain all the energy contained within uranium (U). This is due to current technological restrictions. It might be the same for hydrogen or not!
Cold fusion research
Traditional nuclear fusion requires incredibly high temperatures. In cold fusion, on the other hand, atoms are combined at much lower temperatures. Less high-energy radiation is given off, making this a safer fusion option.
The materials required for cold fusion research include:
A little bit of history now! Cold fusion research and practice were first proposed in the 1930s, but scientific interest in the topic waned after unsuccessful attempts to achieve cold fusion in the 1950s and 1960s. In the early 21st century, however, cold fusion research experienced a resurgence thanks to advances in nanotechnology.
If cold fusion can be harnessed, it could provide a clean and limitless energy source. However, further research is needed to verify its feasibility.2
Cold fusion, as a concept, is not dissimilar to another method which has been scientifically proven but cannot efficiently be maintained for prolonged periods at the moment: muon-catalysed fusion. Muons are injected into a target material, even an atom, where they can then facilitate the fusion of atomic nuclei. This can happen at room temperature or even lower temperatures.
Muons need to be produced artificially for such experiments, which is costly.
A muon is an unstable subatomic (smaller than an atom) particle, usually making up cosmic radiation.3
Unintended consequence? Fusion on Earth can mitigate the helium (He) shortage.
The current state of fusion power research
The current state of fusion power research is influenced by the examples that we were able to obtain from space and nature. What we do on Earth matches the processes we observe inside our Sun, which fuses hydrogen into helium.
Nuclear fusion commonly happens in stars and produces immense amounts of energy, which helps to keep the star burning for billions of years. Nuclear fusion can also be used to create nuclear weapons.
In a nuclear weapon, the energy released by nuclear fusion is used to create an explosion that can cause mass destruction.
Stars start by burning hydrogen, but as they age and hydrogen runs out, they begin to burn helium. Red giants can fuse helium to form beryllium (Be) and obtain its energy. They will "hang in there" until the end using carbon (C) fusion.4
In carbon fusion, carbon (C12) is turned into nitrogen (N), then into oxygen (O2), and then back into carbon (C12). This is also known as the CNO cycle.
Hydrogen fusion lasts billions of years, which is longer than helium fusion. Carbon fusion lasts the least, being maintained in stars, usually for only about 1,000 years.5
Currently, there are two "environments" in which fusion and plasma research can be put into practice:
Inertia chambers: laser beams and x-rays are focused to heat a tiny pellet containing hydrogen fuel mixture (mostly deuterium and tritium) in gaseous, liquid or even solid (ice) forms. Then, the pellet gets ignited.
A National Ignition Facility lab in California carries out inertial fusion experiments. It is so futuristic-looking that parts of Star Trek: Into Darkness were filmed there.6
Magnetic containment chambers: electromagnets are used to generate an electromagnetic field by running a current through them. The hydrogen gas contained in these vacuum chambers is then controlled or suspended by the electromagnetic field. The chamber is also heated by other means, all to allow deuterium and tritium to collide, fuse into helium, and release the energy we want to harvest.
Einstein's equation of energy (released) equals mass (of the released matter) times the speed of light (E=mc2) allows us to calculate how much power is given away from the fusion of two hydrogen nuclei.
The Joint European Torus (JET) in the UK, in 2022, broke the record held for energy produced from a fusion reactor. It produced 59 MJ, or just enough to boil a few kettles.7 However, Brexit means it will only be operational until 2023 and shut down by 2024.
The progress of nuclear fusion research
Fusion and plasma research progress has been made concerning plasma physics, material research and waste disposal, as well as energy containment and generation. Even the metals used for the inner and outer chambers are usually alloys formulated with improved mechanical and thermal properties.
e.g. Oxide Dispersion Strengthened (ODS) steels.
In the future, copper (Cu) coils will be switched for superconducting magnets. The walls of the fusion chambers, made of steel, may also be changed. Moreover, lithium (Li) (a metal) layers mixed with ceramic or beryllium enhance and/or better maintain the (heat of the) fusion processes.
However, the progress of nuclear fusion energy generation has been considered relatively slow over the years. The most recent breakthrough in fusion energy generated was made in 2022 at JET, as mentioned above. The previous record was achieved in 1995, so you can see that progress takes time.
The researchers' main intention is to achieve more energy from the fusion process than we put into running it. We now use more electricity and other resources to create the ideal conditions for fusion to happen than we can catch from the fusion reaction, and use.
We are currently harvesting fusion energy, but it's not sustainable yet!
If successful, it will be the "greenest" energy form our society will have. It might take a while until it becomes commercially viable, even after the breakthrough.
Fusion breakeven is the minimum amount of energy that needs to be injected into a fusion reaction to become self-sustaining.
This condition is necessary because it ensures that plasma can keep on heating itself and thus produce more energy, expressed as Q=1.
For the action to sustain itself, the formula will need to become Q>1.
- Q represents the energy balance/ratio between power input and output into the plasma.
- 1 is the minimum required for the plasma to start heating itself.
ITER project
ITER project is the world's largest fusion facility and fusion and plasma scientific research project. It is located underground in France. Its name stands for International Thermonuclear Experimental Reactor, but the abbreviation also means something in Latin: "the way", to be more specific.
Governments wish to see this reactor operational and capable of producing significant amounts of energy in only a few years, possibly by 2025, but whether that is possible remains to be seen.
This research intends to lead to a commercial reactor in just thirty years.
ITER's type of toroidal reactor is also known as a tokamak.
The tokamak was the first magnetic fusion containment chamber, conceptualised and produced by Soviet Union scientists.
The magnetic fusion chambers are known as toroidal reactors because they maintain hydrogen plasma in a torus shape.
It is important to mention that ITER is still under construction where it is located, in the commune Saint-Paul-lès-Durance. The ITER Tokamak complex consists of ITER itself and several other buildings and facilities necessary for operation, maintenance and safety. ITER will produce 500 MW of power during its 40-second experimental campaign by using < 50 MW of input power to heat up the plasma to fusion conditions. This will be the first time a machine has produced net power from the fusion process.
Now onto a few interesting details!
To compensate for the lack of gravitational forces and pressure, the temperatures inside tokamaks need to be many times higher than the Sun's. One hundred fifty million °C means ten times hotter than our Sun, actually8.
The building of the ITER site started in 2010.
The magnetic vacuum chamber in which the magnets are kept is known as the cryostat - it is made of stainless steel and is supposed to stay at very low temperatures.
JET was ITER's smaller predecessor.
People keep referring to the torus as a doughnut shape.
All the countries contributing to ITER include 27 EU member states, the UK, China, India, Japan, South Korea, Russia, and the US.
Nuclear fusion is a powerful force that can be used for energy generation, and it holds the potential to change the world as we know it. Plasma and fusion processes will continue to be researched for years to come.
Fusion Research - Key takeaways
- The deuterium and tritium isotopes of hydrogen are essential for creating fusion processes on Earth.
- Two leading fusion pathways currently receive much funding: toroidal magnetic containment chambers and laser inertial fusion.
- The energy output is measured in MJ and turned into electricity, and the formula for fusion to become self-sustaining is Q>1.
- Jet and ITER are examples of toroidal fusion reactors that have produced energy from hydrogen fusion.
- Though we wish to imitate stellar processes, we can't nearly replicate the same pressure and gravity conditions on Earth, and thus we need to heat plasma at higher temperatures than inside our Sun.
References
- Dr. Nick Touran, Computing the energy density of nuclear fuel, 2022.
- Michael Greshko, Cold fusion remains elusive—but these scientists may revive the quest, 2019
- Oxford Languages, Muon, 2022
- Georgia State University Department of Physics and Astronomy, Carbon Fusion Cycle, 2005.
- Dr. Christopher Palma, The Evolution of Massive Stars and Type II Supernovae, 2020.
- Chris Lee, Liquid shell gives inertial confinement fusion a smoother burn, 2016
- Reuters, European scientists set nuclear fusion energy record, 2022
- TWI, What is a tokamak and how does it work?, 2022
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