Nuclear fusion

Subject : Science and Technology

Section: Nuclear energy

Context: Three major developments are behind this optimism about nuclear fusion

Concept:

What is a fusion reaction-

In a fusion reaction, two light nuclei merge to form a single heavier nucleus. The process releases energy because the total mass of the resulting single nucleus is less than the mass of the two original nuclei.
Fusion is a different but more powerful way of harnessing the immense energy trapped in the nucleus of an atom.
The nuclear fusion reaction occurs in the sun and other stars, which makes it able to shine and radiate energy.

Nuclear fission process-

In this process, the nucleus of a heavier element is split into those of lighter elements in a controlled manner.
Currently, the nuclear energy in use across the world comes from the fission process.

Energy from nuclear fusion reaction-

A large amount of energy is released in both these processes, but substantially more in fusion than fission reaction.
The fusion of two nuclei of a heavier isotope of hydrogen, called tritium, produces at least four times as much energy as the fission of a uranium atom which is the normal process of generating electricity in a nuclear reactor.
Attempts to master this process begins in the 1950s, but it is incredibly difficult and is still at an experimental stage.
Besides greater energy yield, fusion is also a carbon-free source of energy and has negligible radiation risks.

Challenges in harnessing energy from fusion reaction-

These reactions happen only at very high temperatures, 10 times the temperature that exists at the core of the sun, and creating such an extreme environment in a laboratory requires huge amounts of energy.

What the U.S scientists have achieved-

So, far, the energy released in such experimental fusion reaction has been lower than what is consumed to create the enabling high temperatures.
At best, some of these reactions have produced ‘near-break-even’ energies.
But in the latest experiment conducted at the Lawrence Livermore National Laboratory in California, the scientist has gained the net positive energy i.e. produced more energy from fission reaction than what is consumed to produce that energy.
Scientists use high-energy laser beams to achieve those temperatures, also called ‘inertial fusion’.
But producing it on a commercial scale is still two to three decades away.

Previous achievements-

In december last year, UK-based JET laboratory, which uses magnetic fusion, had improved its previous record for the amount of energy produced from a fusion reaction.
The reaction had run for five seconds and produced 59 megajoules of energy, more than double the previous record.

Experiments in other countries-

The International Thermonuclear Experimental Reactor (ITER) project is going on in southern France, in which France, India and USA are partners. They are using very strong magnetic fields to enable very high temperatures.
India joined the ITER project in The Institute for Plasma Research in Ahmedabad, a laboratory under the Department of Atomic energy, is the lead institution from the Indian side participating in the project.
As a member country, India is building several components of the ITER reactor, while also carrying out a number of experiments and R&D activities related to the project.
ITER, when operational, would become the biggest machine anywhere in the world, more complex than the Large Hadron Collider at CERN or the LIGO project to detect gravitational waves.
Several countries like China, Japan, South Korea and the UK are working on this technology separately.

Joint European Torus and Tokamak

The Joint European Torus (JET – pictured), located at Culham Centre for Fusion Energy, is the largest and most powerful tokamak experiment currently operating. MAST Upgrade, also located at Culham, is a more compact and efficient type of device known as a ‘spherical tokamak’.
The tokamak uses powerful external magnetic fields to confine and control the hot plasma of fusion fuels in a ring-shaped container called a ‘torus’.
It was first developed in the Soviet Union in the 1960s and was soon adopted by researchers around the world due to its enhanced performance compared with other approaches.

US National Ignition Facility

The ‘breakthrough’ announced by the US National Ignition Facility has focused the spotlight on nuclear fusion. NIF reported a net energy gain (more output than input), which is deduced to have come from two nuclei of hydrogen atoms fusing to form a helium nucleus.
Commonwealth Fusion Systems (CFS) is building the world’s first fusion device that produces plasmas which generate more energy than they consume, becoming the world’s first net-energy fusion machine. The device, named SPARC, is for demonstration but a commercial plant is expected to follow.
- Headquartered in Cambridge, Massachusetts, USA, Commonwealth Fusion Systems (CFS) was set up in 2018.
CFS aims to build the demonstration plant, SPARC, by 2025 and the commercial plant by 2030.