What is Nuclear Fusion?
The process in which the nuclei of two light atoms combine to form a new nucleus is known as nuclear fusion. It is the process that powers the sun and the stars and is the ultimate energy source for the future of mankind as it is another way of producing nuclear energy like nuclear fission.
The combination of Deuterium and Tritium, the two isotopes of Hydrogen to give Helium and releasing a neutron and giving out around 17 MeV of energy is an example of a nuclear fusion.
Nuclear Fusion reactions occur when two or more nuclei of the atom come close enough up to the extent that the nuclear force pulling them together exceeds the electrostatic force that pushes them apart, fusing them into heavier nuclei. For nuclei lighter than iron-56 the reaction is exothermic, thus releasing energy while for nuclei heavier than iron-56, the reaction is endothermic, thus requiring energy.
Therefore we can say that nuclei smaller than iron-56 are more likely to fuse while those heavier than iron-56 are more likely to break apart.
Nuclear Binding Energy and Nuclear Fusion
When two lighter nuclei undergo a fusion reaction, the combination has a mass that is less than the mass of the initial individual nuclei. This difference in the mass between the reactants and products is compensated by either the release or absorption of energy known as binding energy between the atomic nuclei before and after the reaction.
Einstein’s mass-energy equivalence explains the energy that the reaction gives out energy during Fusion.
Applications of Nuclear Fusion
One of the main uses of nuclear fusion is that of generating electricity. Fusion power makes use of heat that is generated from nuclear fusion reactions to produce electricity with the help of a device called a thermonuclear reactor. In this process, two atomic nuclei that are considerably lighter, are combined to form a heavier nuclear, while releasing energy.
It is a very safe, environmentally friendly, and clean source of energy that creates way less waste than the process of nuclear fission does.
Types of Fusion Reactors
There are several approaches to control and contain a fusion reaction to exist, but the two primary approaches based on confinement are the concept of magnetic confinement and inertial confinement.
Magnetic confinement fusion (MCF) reactors are the more advanced of the two approaches, as and in this they utilise magnetic fields generated by electromagnetic coils to confine a fusion plasma in a donut-shaped (torus) vessel.
Unlike magnetic confinement approaches, inertial confinement fusion (ICF) approaches attempt to externally heat and compress fusion fuel targets to achieve the very high temperatures and even higher densities required to initiate nuclear fusion.
For most ICF concepts and approaches, high power lasers are used to compress and heat the fuel.
Recently, a third approach, which exploits the parameter space between the conditions produced and needed for magnetic and inertial confinement has gained traction in recent years and is receiving much scientific, and even commercial, attention. This is called Magnetised target fusion (MTF), sometimes known as magnetized inertial fusion (MIF), it looks to exploit the use of higher density plasmas than for MCF approaches, but lower power lasers and other drivers than those used in ICF approaches. MTF offers a unique route to fusion, and the accelerated development of several unique concepts has seen significant support.
Components of Magnetic Confinement Reactors
Vacuum vessels are used to hold the plasma and to keep the reaction chamber in a vacuum.
A neutral beam injector is used to inject particle beams from the accelerator into the plasma thus heating the plasma to its critical temperature.
Magnetic field coils are used in magnetic fields, and the plasma is confined in the superconducting magnets.
A central solenoid is used to provide electricity to the magnetic field coils.
Cooling equipment is used to cool down the magnets.
Blanket modules: These are generally used to absorb heat and high-energy neutrons from the fusion reaction.
Diverters: They are used to exhaust helium products.
Advantages of Nuclear Fusion
Fusion is capable of powering the whole world at a very low cost since there is virtually limitless fuel available that can be used to make electricity. There is a lot of energy released in fusion rather than fission, therefore it would be more profitable if it is set up. Also when producing nuclear fusion energy, there is hardly any waste. As a result of this, there would be no money wasted in disposing and clearing of the wastes produced by the reaction.
Thus, Fusion is capable of powering the entire world at a much low cost, as compared to power sources used nowadays. It is a clean energy source that means no greenhouse gases and emitting only helium as exhaust. It is easier to stop nuclear fusion reactions as compared to fission reactions since there is no chain reaction in fusion.
Disadvantages of Nuclear Fusion
It would be very expensive to build a power plant to produce energy because Nuclear fusion can only occur between 14999726.85 degree celsius to 9999726.85 degree Celsius. (Or 10-15 million kelvin) Thus, there are no materials that can cope with 10-15 million K and also since it is a non-renewable energy. There can also be radioactive wastes.
Interesting Facts about Nuclear Energy
Nuclear energy is derived from uranium which is a non-renewable resource that we get from mining.
In the 1930s, a scientist named Hans Bethe discovered the possibility of nuclear fusion and how it was an energy source for the sun.
The energy generated from the process of nuclear fusion is abundant in supply, limitless even.
The largest successful nuclear reactor is at the Culham Science Centre in Oxford.
FAQs on Nuclear Fusion Reactors
1. What is nuclear fusion and how does it generate energy?
Nuclear fusion is a process where two or more light atomic nuclei combine to form a single, heavier nucleus. This reaction releases a massive amount of energy because the total mass of the resulting nucleus is slightly less than the total mass of the original nuclei. This 'missing' mass is converted directly into energy, as described by Einstein’s mass-energy equivalence principle (E=mc²). This is the same process that powers the Sun and other stars.
2. What are the key differences between nuclear fusion and nuclear fission?
The primary difference lies in the process itself. Nuclear fission involves splitting a heavy, unstable nucleus (like Uranium-235) into two smaller nuclei. In contrast, nuclear fusion involves combining, or fusing, two light nuclei (like hydrogen isotopes) into a heavier one. Furthermore:
- Fuel: Fission uses heavy elements like uranium, which are rare. Fusion uses light elements like hydrogen (Deuterium and Tritium), which are abundant.
- Waste: Fission produces long-lived radioactive waste. Fusion's main byproduct is helium, an inert gas, with some short-lived radioactive components within the reactor structure.
- Safety: Fission reactions can lead to chain reactions that are difficult to stop. Fusion reactions are not chain reactions and require precise conditions; any disruption causes the reaction to stop immediately.
3. How does the process of nuclear fusion in the Sun differ from that in a man-made reactor?
While both rely on the same fundamental principle, the conditions and reactions differ. In the Sun's core, immense gravitational pressure naturally creates the high temperatures and densities needed for fusion. The primary reaction is the proton-proton chain, which fuses hydrogen nuclei into helium over millions of years. In a man-made reactor, like a Tokamak, we cannot replicate the Sun's gravity. Instead, we use powerful magnetic fields or lasers to achieve even higher temperatures (over 150 million °C) to initiate a much faster fusion reaction, typically between deuterium and tritium.
4. What are the main types of nuclear fusion reactors currently under development?
There are two primary approaches to achieving controlled nuclear fusion:
- Magnetic Confinement Fusion (MCF): This method uses powerful magnetic fields to contain the superheated fuel, called plasma, in a donut-shaped vessel (a Tokamak or stellarator). The magnetic fields prevent the plasma from touching the reactor walls, which would otherwise vaporise.
- Inertial Confinement Fusion (ICF): This approach uses high-powered lasers or ion beams to rapidly heat and compress a tiny pellet of fusion fuel. The immense pressure and temperature cause the fuel to implode, initiating fusion for a fraction of a second before it expands.
5. What are the major advantages of pursuing nuclear fusion for energy production?
Nuclear fusion offers several significant advantages as a potential energy source:
- Abundant Fuel: The primary fuels, deuterium and lithium (to breed tritium), are widely available in seawater and the Earth's crust, offering a virtually limitless supply.
- Clean Energy: The process does not produce CO₂ or other greenhouse gases. The main byproduct is helium, which is a non-toxic, inert gas.
- Inherent Safety: Fusion reactors cannot have a runaway chain reaction or meltdown. The reaction requires precise conditions, and any malfunction causes the plasma to cool and the reaction to stop safely.
- Less Radioactive Waste: Fusion does not produce high-level, long-lived nuclear waste like fission. While some reactor components become radioactive, they have a much shorter half-life.
6. Why is it so challenging to build a practical and sustainable nuclear fusion reactor?
The difficulty lies in recreating and sustaining the extreme conditions necessary for fusion. The main challenges are:
- Achieving Extreme Temperatures: Fusion requires temperatures exceeding 150 million degrees Celsius, which is ten times hotter than the core of the Sun.
- Plasma Confinement: Containing this superheated plasma without it touching the reactor walls is a major engineering feat, requiring incredibly strong and stable magnetic fields or precisely aimed lasers.
- Energy Sustainability: A fusion reactor must produce significantly more energy than it consumes to heat the plasma and run its systems. Achieving this 'net energy gain' has been a long-standing scientific goal.
- Material Durability: The inner walls of the reactor are bombarded with high-energy neutrons, which can degrade the materials over time. Developing materials that can withstand this for long periods is crucial.
7. What is a Tokamak and what is its specific function in a fusion reactor?
A Tokamak is a device used in magnetic confinement fusion. Its name is a Russian acronym that translates to 'toroidal chamber with magnetic coils'. Its primary function is to use a powerful combination of magnetic fields to contain and shape the hot plasma into a stable, donut-like (toroidal) ring. This prevents the extremely hot plasma from touching and destroying the reactor's inner walls, allowing it to reach the temperatures required for fusion to occur.
8. Could a nuclear fusion reactor cause a nuclear accident similar to Chernobyl or Fukushima?
No, a nuclear fusion reactor is considered inherently safe and cannot cause a nuclear accident like those seen with fission reactors. This is because the process is not based on a chain reaction. A fusion reaction requires a continuous and precise input of external energy and fuel. If there is any disruption, such as a loss of power or a breach in containment, the plasma immediately cools down and the reaction stops within seconds, without any risk of a meltdown or a large-scale release of radioactive material.
9. What is the typical nuclear reaction equation used in experimental fusion reactors?
The most efficient and widely studied fusion reaction for terrestrial power plants involves two isotopes of hydrogen: deuterium (D) and tritium (T). The reaction equation is:
D + T → ⁴He + n + 17.6 MeV
This means one Deuterium nucleus (²H) fuses with one Tritium nucleus (³H) to produce one Helium nucleus (⁴He), a free neutron (n), and 17.6 million electron volts of energy.
