Fusion reactors have an image of being the “perfect” energy source. So we can see proponents claiming that once we develop useful commercial fusion reactors, they can produce a boundless amount of energy with just a little radioactive waste.
In the U.S. and Europe, the scientists are trying to gain more energy output from the nuclear fusion power plants than what it initially consumes. If we reach this point, we can practically generate unlimited power (in theory).
Let us start understanding what is nuclear fusion and how a nuclear fusion power plant works.
Nuclear Fusion Process
In 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 huge amount of energy. This is the same reaction that powers hydrogen bombs as well as 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 not possible since it doesn’t offer equally intense pressure and temperature.
Is Nuclear Fusion Possible?
The 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, with the use of some fusion technologies like magnetic confinement, and laser-based inertial confinement, we are getting closer to a solution to this problem.
Nuclear Fusion Technologies
- Magnetic Confinement Fusion (MCF)
In a magnetic confinement fusion, a few hundreds of 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 takes place at a few atmospheres 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. As this 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 upon it. 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
- 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 up the inner layers of material.
The core of the fuel can be compressed to 1000 times its liquid density giving it conditions suitable for fusion to occur. The released energy heats up 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.
How to Make Fusion
- Create plasma
- Apply pressure
How Does Nuclear Fusion Produce Energy?
Here are a few different approaches to fusion.
- Magnetized Target Fusion (MTF)
MTF is also known as magneto-inertial fusion. It is a pulsed approach to fusion. This approach is a combination of the compressional heating of inertial confinement fusion along with the magnetically reduced thermal transport as well as 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 in comparison to what is required for magnetic confinement. It reduces the requirement of stabilizing the plasma for a long time.
- Hybrid Fusion
Hybrid nuclear fusion refers to a process where fusion is combined with fission. In this fusion, the 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)
Benefits and Challenges of Nuclear Fusion
|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 to commercial power|
|Very little radioactive waste that decays quickly|
Other Applications of Nuclear Fusion
- Abundant Fuel Supply
Tritium can be made from lithium in the fusion reactor itself and deuterium can be extracted from seawater.
Since the chances of uncontrolled releases of energy are eliminated, the amount of fuel used in fusion is less compared to fission reactors.
No air pollution since no combustion occurs in nuclear power.
- Less Nuclear Waste
Fusion reactors do not produce any high-level nuclear wastes and the leftover wastes are not weapons-grade nuclear materials.
In the year 1989, two researchers from the U.S. (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 with the use of palladium electrodes on which deuterium nuclei concentrate at high densities.
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 up our planet’s atmosphere. However, fusing two hydrogen nuclei together to form helium isotopes is still a grand scientific challenge.