What is nuclear fusion?

Nuclear fusion is a kind of nuclear reaction, where two more nuclei of different atoms combine to form a single atom or different atoms along with subatomic particles. A nuclear fusion reaction is a method of clean energy production that ensures zero carbon emission and contributes less to greenhouse gas production. Unlike nuclear fusion reaction, nuclear fission reaction splits individual atomic nucleus into several nuclei with the production of heat and a huge amount of energy. Both nuclear fusion and nuclear fission are non-conventional ways of energy generation.

The difference of masses of individual atomic nuclei, which are combined into a single atomic nucleus, results in energy generation, preferably called fusion energy, which is utilized in the generation of electricity known as fusion power.

Nuclear fusion fuel

The primary fuel used in the nuclear fusion plant to initiate a fusion reaction is deuterium and tritium. Both deuterium and tritium are the isotopes of hydrogen, out of which deuterium exists as a small fraction in hydrogen, which is approximately 0.0153%, and are extracted from seawater, and tritium can be extracted from lithium.

Deuterium occurs as a stable isotope of hydrogen, which is non-radioactive and its nucleus consists of a single proton and neutron. The property of deuterium is identical to hydrogen, it has no color and odor, and burns with an invisible pale blue flame. Tritium is a radioactive isotope of hydrogen whose nucleus consists of one proton and two neutrons. Tritium is an extremely rare isotope of hydrogen found in traces in the earth's atmosphere. These are naturally formed by the reaction of hydrogen with cosmic rays. To be used for nuclear fusion reaction, it is majorly produced in the laboratory by irradiating lithium in a nuclear reactor

Ways to perform nuclear fusion reaction

There are several ways to perform nuclear fusion reactions, some of them are outlined below.

Tokamak

A tokamak is a magneto-inertial device, which is primarily a doughnut-shaped device, intended for controlled thermonuclear fusion power production. The term doughnut-shaped comes from its donut-shaped torus. In the torus, the device embeds a powerful magnetic field that stores plasma at high temperatures. In the interior of this device, the energy produced by the fusion reaction is absorbed by the walls, and is stored by appropriate means. A nuclear fusion plant uses this heat energy for electricity generation. The heat from the vessel of the tokamak is transferred to the boilers, which produces steam. This steam is utilized for turning the turbines, which in turn runs the AC generators. At high temperatures, the water content of these boilers begins to form high-pressure steam, which is passed to the turbines, that are coupled to an AC generator. Soviet physicists were the first to conceptualize the tokamak, and the first working tokamak came into existence in 1958.

Inertial confinement fusion

The inertial confinement fusion technique is executed by the inertial confinement systems. These systems replicate the extreme reaction that occurs in stars and gas planets. These systems use an ion beam or a laser beam to compress a small-sized amount of deuterium-deuterium isotope into high densities. Upon reaching a critical point, the fuel is ignited due to shock wave heating and generating a huge nuclear force. This process is generally carried out in fusion reactors several times to generate heat energy.

Aneutronic fusion

The hydrogen-boron reaction primarily falls under this category. This is a new form of energy in which a laser beam is used to fuse hydrogen and boron-11. This fusion results in clean energy generation with the liberation of an adequate amount of heat.

Deuterium-tritium fusion energy

In the deuterium-tritium (D-T) fusion energy process, one deuterium nucleus fuses with one tritium nucleus to give one helium nucleus. The by-product of this reaction results in one free neutron and 17.6 MeV of fusion power. Lithium is placed as a blanket around the walls of the fusion reactor to absorb the neutrons that result in the formation of tritium. The fusion energy thus formed is used to generate high-pressure steam that in turn generates electricity through a generator. This is a general fusion reaction process.

Nuclear reactors

Nuclear reactors are also known as atomic piles. Its primary work is to initiate and control nuclear fission and nuclear fusion reaction. Nuclear fission reactors and nuclear fusion reactors both are the same components of a typical nuclear power plant.

The main component of a reactor is nuclear fuel. A fission reactor popularly uses uranium as the main fuel, where deuterium and tritium from the main fuel for a fusion reactor. The heat energy or the fusion power from the ignition of such fuel is passed to a large assembly of boilers that contain water or other liquids. The liquid is turned into high-pressure steam which exerts forces on the blades of a steam turbine. In the turbine, the pressure energy of the steam is converted to mechanical energy in terms of shaft rotation. This rotation of the shaft turns the armature of an electric generator to produce electricity.

Context and Applications

This topic is extensively taught in various undergraduate and postgraduate degree courses such as:

• Bachelors of Technology in Civil Engineering
• Masters of Technology in Civil Engineering
• Bachelors of Technology in Mechanical Engineering
• Masters of Technology in Mechanical Engineering
• Masters in Science in Energy Systems

Practice Problems

1. Which of the following procedures of creating nuclear fusion uses a torus-shaped device?

1. D-T fusion process
2. Commonwealth fusion
3. Inertial confinement fusion
4. Tokamak

Answer: Option d

Explanation: A tokamak uses a doughnut-shaped torus for initiating the nuclear fusion process.

2. Which country first utilized the working tokamak?

1. Soviet
2. National ignition facility
3. United kingdom
4. None of these

Answer: Option a

Explanation: The Soviet was the first place where the first working tokamak was utilized.

3. Which of the following technologies is used by tokamak?

1. Field-reversed
2. Inertial confinement fusion technology
3. Magneto-inertial technology
4. None of these

Answer: Option c

Explanation: The technology used by most of the tokamaks is magneto-inertial technology.

4. Which of the following nuclear fuel is used by a nuclear fusion plant?

1. Plutonium
2. Uranium
3. Deuterium
4. Polonium

Answer: Option c

Explanation: A nuclear fusion power plant makes use of deuterium and tritium as nuclear fuel.

5. Which of the following is a radioactive isotope of hydrogen?

1. Tritium
2. Deuterium
3. Both a and b
4. None of these

Answer: Option a

Explanation: Tritium is a radioactive isotope of hydrogen, whereas deuterium is a non-radioactive isotope.