- A fusion reactor works when hydrogen atoms come together and form helium atoms, neutrons, and a tremendous amount of energy.
- Experiments related to nuclear fusion have been done several times. But the energy input required to produce the pressures and temperatures that enable fusion reactions in hydrogen isotopes has exceeded the generated fusion energy. So, we don’t have a net gain in energy.
Fusion reactors have an image of being the “perfect” energy source. So we can see proponents claiming that once we develop practical commercial fusion reactors, they can produce unlimited energy with just a little radioactive waste.
In the US and Europe, scientists are trying to gain more energy output from nuclear fusion power plants than it initially consumes. If we reach this point, we can practically generate unlimited power (in theory). Let us start understanding nuclear fusion and how a nuclear fusion power plant works.
Table of Contents
Nuclear Fusion Process
Nuclear fusion energy is generated when two atoms join together to form one. A fusion reactor works when hydrogen atoms come together and form helium atoms, neutrons, and a tremendous amount of energy. This is the same reaction that powers hydrogen bombs and the sun.
The sun we revolve around day in and day out does fusion reactions all the time. It burns ordinary hydrogen at intense densities and temperatures. However, replicating the same process on Earth is impossible since it doesn’t offer equally intense pressure and temperature.
The fusion process applies mainly three steps, Create plasma, Apply pressure, and Repeat.
Is Nuclear Fusion Possible?
Experiments related to nuclear fusion have been done several times. But the energy input required to produce the pressures and temperatures that enable fusion reactions in hydrogen isotopes has exceeded the generated fusion energy. So, we don’t have a net gain in energy.
Nevertheless, we are getting closer to solving this problem with some fusion technologies like magnetic confinement and laser-based inertial confinement.
Nuclear Fusion Technologies
1. Magnetic Confinement Fusion (MCF)
In a magnetic confinement fusion, a few hundred cubic meters of D-T plasma with a density of less than one milligram per cubic meter are confined together by a magnetic field. This occurs at a few atmospheres of pressure and is heated to fusion temperature.
The electrical charges on separated ions and electrons follow the magnetic field lines that make magnetic fields ideal for confining a plasma. The main focus is to prevent these particles from contacting the reactor walls, which can dissipate their heat and slow them down.
The most effective magnetic configuration is known as toroidal. It has a doughnut shape in which the magnetic field is curved to form a closed loop. For better confinement, this toroidal must have a superimposed perpendicular field component. As a result, we obtain a magnetic field with force lines following helical (spiral) paths that confine and control the plasma.
The most important types of toroidal confinement systems are
- Tokamaks
- Stellarators
- Reversed field pinch devices
- Laser-based Inertial Confinement
In an inertial confinement fusion, ion beams or lasers are focused precisely onto the surface of a target. It is a pellet of D-T duel with a diameter of a few millimeters. This is a newer line of research in which the outer layer of the material is heated, making it explode outwards. It generates an inward-moving compression front that compresses and heats the inner layers of material.
The core of the fuel can be compressed to 1000 times its liquid density, making conditions suitable for fusion. The released energy heats the surrounding fuel, which may undergo fusion because of ignition.
A different concept called the Z-pinch (zeta pinch) uses an electrical current in a plasma that is strong enough to generate X-rays. It compresses a tiny D-T fuel cylinder.
2. Magnetized Target Fusion (MTF)
MTF is also known as magneto-inertial fusion. It is a pulsed approach to fusion. This approach combines the compressional heating of inertial confinement fusion and the magnetically reduced thermal transport and magnetically amplified alpha heating of magnetic confinement fusion.
Currently, a range of MTF systems is being experimented with. They use a magnetic field to confine plasma with compressional heating arranged by laser, electromagnetic or mechanical liner implosion.
This combined approach allows you to work with shorter plasma confinement time than what is required for magnetic confinement. It reduces the requirement of stabilizing the plasma for a long time.
3. Hybrid Fusion
Hybrid nuclear fusion refers to a process where fusion is combined with fission. This fusion’s blanket surrounding its core is a subcritical fission reactor. The fusion reaction works as a source of neutrons for the blanket.
Once these neutrons are captured, the fission reaction takes place. The fission reaction produces more neurons, assisting further fission reactions in the surrounding blanket. This concept can also be compared with an accelerator-driven system (ADS).
4. Cold Fusion
In 1989, two researchers from the US (Stanley Pons) and the UK (Martin Fleischman) claimed to have a fusion reactor with simple tabletop apparatus working at room temperature. Cold fusion or N-fusion involves electrolysis of heavy water using palladium electrodes on which deuterium nuclei concentrate at high densities.
Benefits and Challenges of Nuclear Fusion
| Benefits | Challenges |
| Carbon-free | Sustaining plasma for months at a time |
| Abundant fuel | Developing materials to handle extreme temperatures. |
| No chance of a meltdown | Accelerating the pace of commercial power |
| Very little radioactive waste decays quickly |
Benefits of Nuclear Fusion
1. Abundant Fuel Supply
Tritium can be made from lithium in the fusion reactor itself, and deuterium can be extracted from seawater.
2. Safe
Since the chances of uncontrolled energy releases are eliminated, the fuel used in fusion is less than in fission reactors.
3. Clean
No air pollution since no combustion occurs in nuclear power.
4. Less Nuclear Waste
Fusion reactors do not produce any high-level nuclear wastes; the leftover wastes are not weapons-grade nuclear materials.
A nuclear fusion power plant can serve you with the enormous benefits of producing energy without any carbon emissions. It eliminates the chances of heating our planet’s atmosphere. However, fusing two hydrogen nuclei to form helium isotopes is still a grand scientific challenge.
(Last Updated on December 1, 2023 by Sadrish Dabadi)
