# Explained: How tokamaks hold a star's fire, and where India stands in fusion research

URL: https://upsc.help/current-affairs/2026-11-06/tokamak-fusion-explained-iter/
Date: 6 November 2026 (2026-11-06)
Source: The Hindu, Page 13
UPSC papers: GS3
Publisher: upsc.help (Pratidin), free and open-source UPSC Civil Services current affairs. Not affiliated with UPSC. Every fact was checked against the source reports by a separate review before publishing.

**In one line:** A tokamak uses magnetic fields to hold plasma hot enough for fusion, and ITER, with India as a partner, is the biggest attempt yet to prove the idea at reactor scale.

The Hindu's explainer of 6 November 2026 sets out how tokamaks work and why they are central to the search for fusion power. Fusion joins light nuclei into a heavier one and releases energy. The favoured fuel is deuterium and tritium, two isotopes of hydrogen, which fuse into helium and a fast neutron, releasing 17.6 MeV per reaction, about 80% of it (14.1 MeV) carried by the neutron. The fuel must be heated into a plasma at temperatures of the order of 150 million °C, far hotter than the Sun's core, and no material wall can hold it. A tokamak solves this with magnetism: external coils and an electric current driven through the plasma together create a twisted magnetic field that keeps the plasma inside a ring-shaped vacuum chamber and away from the walls. The name is a Russian acronym for 'toroidal chamber with magnetic coils', and the concept emerged in the Soviet Union in the early 1950s, mainly through Igor Tamm and Andrei Sakharov.

The largest tokamak being built is ITER (International Thermonuclear Experimental Reactor) at Cadarache in southern France. Its seven members are China, the European Union, India, Japan, South Korea, Russia and the United States. India became the seventh full member in December 2005 and supplies about 10% of the components as in-kind contributions, including the 3,850-tonne cryostat built by Larsen & Toubro. ITER aims to produce about 500 MW of fusion power from 50 MW of heating, a gain (Q) of 10, but it is an experiment and will not generate electricity. Under the schedule revised in 2024, operations with deuterium plasma are to begin in 2034 and full deuterium-tritium operation in 2039; the 2016 baseline had planned deuterium-tritium fuel from 2035. In a future power plant, the neutrons would be absorbed in a lithium-bearing blanket, giving heat for steam and breeding new tritium.

India's own programme is based at the Institute for Plasma Research (IPR), Gandhinagar, supported by the Department of Atomic Energy. Its first tokamak, ADITYA, began operating in 1989 and, after an upgrade, resumed as ADITYA-U in 2017; IPR also runs SST-1, a steady-state superconducting tokamak. A Bengaluru start-up, Pranos Fusion, incubated at IPR and JNCASR, has announced PRAGYA, a compact tokamak to test plasma control and superconducting magnets. Elsewhere, China's EAST held a high-confinement plasma for 1,066 seconds in January 2025, and the U.S. National Ignition Facility achieved ignition in December 2022 using lasers, a different route called inertial confinement. The explainer notes that ITER has faced engineering challenges, funding delays and cost escalations, and that it is primarily a physics experiment, not designed to turn heat into electricity.

## Prelims facts

- A tokamak confines plasma in a ring-shaped vacuum chamber using magnetic fields from external coils and a current driven through the plasma.
- Deuterium-tritium fusion releases 17.6 MeV per reaction, about 80% of it carried by the neutron.
- ITER, at Cadarache in France, has seven members including India, which joined in December 2005; it aims for a gain of Q = 10 but will not generate electricity.
- Under ITER's 2024 schedule, deuterium plasma operations start in 2034 and deuterium-tritium operation in 2039.
- India's tokamaks, ADITYA-U and SST-1, are at the Institute for Plasma Research, Gandhinagar.

## Quick recall

- **What does a tokamak use to confine plasma?** Magnetic fields from external coils and a current driven through the plasma, in a ring-shaped vacuum chamber.
- **Energy released by one D-T fusion reaction?** 17.6 MeV, about 80% of it carried by the neutron.
- **Where is ITER being built?** Cadarache, in southern France.
- **When did India become a full member of ITER?** December 2005, as the seventh member.
- **ITER's target fusion gain?** Q = 10: about 500 MW of fusion power from 50 MW of heating.
- **When is ITER to start deuterium-tritium operation under its 2024 schedule?** 2039.
- **Where are India's tokamaks ADITYA-U and SST-1?** At the Institute for Plasma Research, Gandhinagar.
- **Which fusion approach did the U.S. National Ignition Facility use?** Inertial confinement with lasers.

## Prelims practice question

With reference to the International Thermonuclear Experimental Reactor (ITER), consider the following statements:
1. It is being built in France.
2. India is one of its seven members.
3. It is designed to supply electricity to the European grid.
Which of the statements given above are correct?

(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (a) 1 and 2 only. Statements 1 and 2 are correct: ITER is at Cadarache, France, and its seven members are China, the EU, India, Japan, South Korea, Russia and the U.S. Statement 3 is wrong: ITER is an experiment that will not generate electricity.

## UPSC previous-year questions this connects to

- UPSC Mains 2025, GS3: The fusion energy programme in India has steadily evolved over the past few decades. Mention India's contributions to the international fusion energy project - International Thermonuclear Experimental Reactor (ITER). What will be the implications of the success of this project for the future of global energy? (https://upsc.help/pyq/q369-fusion-energy-programme-india-has-steadily-evolved/)
  How to use this story in the answer: Use India's in-kind ITER contributions and its domestic tokamaks for the first part, and ITER's Q = 10 goal and limits for the implications.
- UPSC Prelims 2016, Prelims: India is an important member of the 'International Thermonuclear Experimental Reactor'. If this experiment succeeds, what is the immediate advantage for India?
(a) It can use thorium in place of uranium for power generation
(b) It can attain a global role in satellite navigation
(c) It can drastically improve the efficiency of its fission reactors in power generation
(d) It can build fusion reactors for power generation (https://upsc.help/pyq/prelims/#q370)
- UPSC Mains 2026, GS3: Explain the key challenges for India's energy security. What measures do you suggest for ensuring energy security along with economic growth and sustainability? (https://upsc.help/pyq/q061-key-challenges-india-s-energy-security-measures/)
  How to use this story in the answer: Use fusion research as a long-term, low-carbon option in a forward-looking conclusion on energy security, while noting its distant timeline.

## Mains practice question

Explain the working principle of a tokamak. What are the major scientific and engineering challenges in making fusion a source of commercial electricity? (150 words)

### Model answer

A tokamak is a doughnut-shaped device that uses magnetic fields to confine extremely hot plasma so that light nuclei can fuse and release energy.

## Working principle
- Deuterium and tritium are heated to a plasma of the order of 150 million °C.
- External coils and a current through the plasma create a twisted magnetic field that keeps it off the walls.
- Each D-T fusion releases 17.6 MeV; about 80% goes to the neutron, whose heat a future plant would capture in a lithium blanket.

## Challenges
- **Materials:** walls must survive intense heat and neutron damage.
- **Plasma stability:** instabilities can end a pulse; EAST held a high-confinement plasma for 1,066 seconds only in January 2025.
- **Tritium:** it must be bred from lithium at scale.
- **Cost and time:** ITER's deuterium-tritium operation has slipped to 2039.
- **Net energy is not electricity:** ITER targets Q = 10 but will not generate power.

Fusion is promising, but commercial power remains decades away.

## The basics

## Why this matters
Fusion powers the Sun. If it can be tamed on Earth, it promises large amounts of energy from abundant fuel, with no carbon dioxide from combustion and far less long-lived waste than fission. India is a partner in the biggest fusion experiment ever built and runs its own machines. Tokamaks, the leading design, are a regular Prelims topic.

## Fission and fusion
Nuclear power plants today use fission: a heavy nucleus such as uranium splits. Fusion is the opposite: light nuclei join. See Nuclear fusion. Fusion needs nuclei to collide at enormous speed, which means extreme heat. At such temperatures, matter becomes plasma, a gas of charged particles. The challenge is holding it.

## How a tokamak holds plasma
Charged particles follow magnetic field lines. A Tokamak bends the field into a closed ring, so particles circle forever without touching a wall. Coils outside the chamber make one field; a current driven through the plasma itself makes another. Together they form a twisted field that holds the plasma steady. A related design, the stellarator, makes the twist with complex external coils alone.

## India's place
India joined ITER in December 2005. At home, the Institute for Plasma Research in Gandhinagar runs ADITYA-U and SST-1. Other routes exist: Inertial confinement fusion uses lasers to crush fuel pellets, and achieved ignition at the U.S. National Ignition Facility in December 2022.

## Sources

- https://superkalam.com/current-affairs/06-11-2026/how-do-tokamaks-work-to-make-nuclear-fusion-possible-pg13-2732d912-89bc-45b1-a042-22c0e0cf1c32
- https://WWW.ITER.ORG/mach/tokamak
- https://physicsworld.com/a/iter-fusion-reactor-hit-by-massive-decade-long-delay-and-e5bn-price-hike/
- https://www.neimagazine.com/analysis/indias-activities-in-nuclear-fusion-9640516/
- https://en.wikipedia.org/wiki/Deuterium%E2%80%93tritium_fusion
- https://www.shankariasparliament.com/current-affairs/prelim-bits-5/nuclear-fusion-technology-pranos-fusion