How do tokamaks work to make nuclear fusion possible?

Source: The post “How do tokamaks work to make nuclear fusion possible?” has been created based on “How do tokamaks work to make nuclear fusion possible?” published in “The Hindu” on 6th November 2026.

UPSC Syllabus: GS 3 – Science and Technology

Context: There is a growing global interest in nuclear fusion as a future source of clean energy and the role of tokamak technology is important in making commercial fusion power possible.

About Tokamak

1. A tokamak is a device that uses powerful magnetic fields to confine extremely hot plasma in a ring-shaped vacuum chamber to achieve controlled nuclear fusion.
2. Nuclear fusion is the process in which two light atomic nuclei combine to form a heavier nucleus, releasing an enormous amount of energy.
3. It is considered a promising technology for developing clean, sustainable and potentially abundant energy.

Working mechanism of Tokamak

1. Creation of Plasma: Plasma, the fourth state of matter, is created by heating gases until electrons separate from atomic nuclei, leaving charged particles.
2. Magnetic Confinement: Powerful magnetic fields confine the extremely hot plasma and prevent it from coming into contact with the reactor walls.
3. Doughnut-shaped Structure: The tokamak uses a toroidal (ring-shaped) chamber to prevent plasma from escaping through the ends of a straight tube.
4. Twisted Magnetic Fields: External magnetic coils and an electric current flowing through the plasma generate two magnetic fields, which combine to produce a helical magnetic field.
5. Stable Confinement: These magnetic fields help keep the plasma confined for sufficient time and at suitable conditions for fusion to occur.

How does Nuclear Fusion generate Energy?

1. Tokamaks primarily use deuterium and tritium, which are isotopes of hydrogen, as fusion fuel.
2. At extremely high temperatures, these nuclei overcome their mutual electrical repulsion and combine to form helium and a high-energy neutron.
3. The reaction releases approximately 17.6 MeV of energy, with about 80% carried by the neutron and 20% by the helium nucleus.
4. A kilogram of deuterium-tritium fuel, if fully fused, could release approximately  joules of energy, roughly ten million times the energy released by the same quantity of coal.
5. The high-energy neutrons transfer their energy to a surrounding layer called the blanket, which absorbs heat to produce steam and drive turbines for electricity generation.
6. The blanket can also contain lithium, which reacts with neutrons to produce tritium, helping the reactor generate its own fuel.

Reason behind the doughnut shape of the Tokamak

1. Charged particles moving in a magnetic field tend to spiral around magnetic field lines.
2. In a straight tube, particles can escape through its ends, whereas a circular chamber eliminates these open ends.
3. However, a simple ring-shaped magnetic field is insufficient because the magnetic field is stronger on the inner side than on the outer side.
4. This variation causes charged particles to drift in opposite directions, creating an electric field that pushes plasma towards the outer wall.
5. To overcome this problem, an electric current is induced through the plasma, creating an additional magnetic field.
6. The combination of these magnetic fields produces a twisted magnetic field that helps maintain stable plasma confinement.

Challenges in Making Tokamak-based Fusion Successful

1. Extreme Temperature: Plasma must be heated to temperatures hotter than the Sun’s core, making containment extremely difficult.
2. Plasma Instability: Maintaining stable plasma confinement without contact with the reactor walls remains a major engineering challenge.
3. High Costs: Large-scale fusion projects require substantial financial investment and advanced engineering capabilities.
4. Fuel Availability: Tritium is rare and radioactive, making its production and management an important challenge.
5. Material Challenges: Reactor components must withstand intense heat, radiation and continuous neutron bombardment.
6. Energy Efficiency: Although fusion reactions have been demonstrated experimentally, no tokamak has yet generated net energy for commercial electricity production.

Major Global Developments

1. ITER (International Thermonuclear Experimental Reactor): ITER is the world’s largest international fusion research project, being developed at Cadarache in France.
   1. It involves seven members: China, the European Union, India, Japan, South Korea, Russia and the United States, representing more than 30 countries.
   2. It aims to demonstrate the scientific and technological feasibility of fusion energy.
   3. Its original cost estimate of €5 billion in 2005 has increased substantially.
   4. ITER has not yet been switched on and is designed to produce 500 MW of fusion power from 50 MW of input heating power once operational.
   5. It is an experimental project and will not convert the generated heat into electricity.
2. China’s EAST Tokamak: China’s Experimental Advanced Superconducting Tokamak (EAST), located in Hefei, achieved a high-confinement plasma duration of 1,066 seconds in January 2025.
   1. In January 2026, it reported operating at plasma densities above a long-standing empirical limit.

India’s Progress in Tokamak Technology

1. ADITYA: India’s first tokamak was developed at the Institute for Plasma Research (IPR), Gandhinagar, and began operating in 1989. It was subsequently rebuilt as ADITYA-U, which resumed operations in 2017.
2. SST-1: The Steady State Superconducting Tokamak produced its first plasma in 2013 and uses superconducting magnets.
3. ITER Participation: India is a member of ITER and contributes important components and technologies for the international project.
4. PRAGYA: Bengaluru-based Pranos Fusion has unveiled PRAGYA, described as India’s first privately developed compact tokamak. It aims to develop capabilities in plasma control and magnetic confinement.

Alternatives to Tokamak-based Fusion

1. Stellarators: These devices use complex external magnetic coils to create twisted magnetic fields without relying on a plasma current. They offer steadier operation but are more difficult to design and construct. Germany’s Wendelstein 7-X is a prominent example.
2. Inertial Confinement: This approach compresses a small fuel pellet using powerful lasers or other beams, causing fusion before the fuel can expand. The US National Ignition Facility demonstrated fusion ignition in 2022.
3. Other Magnetic Configurations: Mirror machines, field-reversed configurations and compact configurations are other approaches being explored for fusion energy.

Conclusion: Tokamak technology represents a promising pathway towards clean, low-carbon and potentially abundant energy. However, overcoming plasma instability, material limitations, high costs and the challenge of achieving sustained net energy remains essential. India’s participation in ITER and its domestic research capabilities provide an opportunity to strengthen its position in the emerging field of fusion energy.

Question: What are tokamaks and how do they facilitate nuclear fusion? Discuss their working principles, potential for energy generation, challenges and India’s progress in this field.

Source: The Hindu