Nuclear fusion reactors could become the source of our electricity for the future JULY 29, 2017 By Divya Rajagopal

In a time when our world is getting warmer, it is hoped that fusion technology can provide electricity worldwide by the middle of this century. The challenge to create a source of energy similar to that of the Sun is a challenge in itself.

Fusion is the process by which two lighter nuclei (like hydrogen) under high temperature and pressure combine to form one heavier nucleus with the release of an enormous amount of energy. Gas molecules, in the core of the Sun, are in plasma. Plasma can be described as an ‘electrically-charged gas’ in which the negatively charged electrons in atoms are completely separated from the positively charged atomic nuclei (or ions).

Why isn’t fusion energy here yet?

In order to replicate this process on earth, gases need to be heated to extremely high temperatures of about 150 million degree Celsius. The reaction between the isotopes of hydrogen (deuterium and tritium) is the easiest way to tap fusion energy. Deuterium can be extracted from water and tritium is produced during the fusion reaction through contact with lithium.

Devices are being built which can produce temperatures more than ten times the temperature of the sun. To reach these temperatures, there must be powerful heating devices and minimal thermal loss. The heat dissipation through the walls of the reactor is the primary source of thermal loss. Hence, special arrangements must be made to keep the hot fuel away from the walls.

Doughnut shaped reactor

The ions in the plasma are directed to the magnetic field produced on the walls by an electromagnet and a solenoid at the center. The solenoid acts as the primary winding of a transformer. The resulting magnetic field keeps the particles and their energy away from the reactor wall. The reactor is doughnut-shaped to support this system. For energy production, this plasma has to be confined for a sufficiently long period for fusion to occur.

In Europe, this has been achieved in the Joint European Torus (JET), the world’s largest fusion device which currently holds the world record for fusion power. Nearly 2,000 scientists and engineers are currently working on a broad range of fusion R&D projects in more than 20 laboratories, including JET.

Replacing coal

Fusion energy has the potential to provide a sustainable solution to global energy needs. The basic fusion fuels, from which deuterium and tritium are extracted and generated, are water and lithium. There is enough deuterium for millions of years and easily mined lithium for several hundreds of years. There are around 0.033 grams of deuterium in every litre of water. If used to fuel a fusion power station, the lithium in one laptop battery, complemented with half a bath of water, would produce the same amount of electricity as burning 40 tons of coal.

A 1000-megawatt electric fusion power plant would consume around 100 kg of deuterium and three tons of natural lithium in a year whilst generating 7 billion kilowatt-hours. To generate the same amount of electricity, a coal-fired power plant would need around 1.5 million tons of coal.

An international nuclear fusion project

ITER is an international project with seven members—China, India, Japan, South Korea, the European Union, the Russian Federation and the United States. It is the world’s greatest energy project which aims to demonstrate that fusion can be part of the solution by improving our energy mix to meet the global energy needs.

The construction of the ITER scientific installation in St-Paul-lez-Durance, France, began in 2010 and is expected to last ten years. In parallel, manufacturing is underway in the ITER Members on the components of the ITER machine and shipments of completed components have been arriving since mid-2014. At the heart of the ITER scientific installation is the Tokamak Complex, a 400,000-tonne edifice composed of the Tokamak, Diagnostic and Tritium buildings. The Tokamak Complex is expected to be completed by 2018.

Scientists and policy makers are convinced that we are on the edge of an ‘Age of Fusion’ and the ITER facility and demonstration plants would establish the technology to significantly meet, in the not too distant future, humanity’s energy needs through a virtually inexhaustible, safe, environmentally-friendly and universally-available resource.