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Relevance: GS-III (Science & Technology & Energy) | Source: The Hindu
The Context: Nuclear fusion offers clean, almost endless energy by copying how the Sun shines. Because Earth lacks the Sun’s massive gravity to squeeze atoms together, reactors must heat hydrogen gas to 150 million °C (10 times hotter than the Sun’s core). To hold this superhot gas without melting the machine, scientists use a tokamak—a doughnut-shaped magnetic cage that keeps the fuel floating in mid-air.
1. Fusion vs. Fission & Containment
- Joining vs. Splitting Atoms: Today’s nuclear plants use fission (splitting heavy Uranium atoms), which leaves behind long-lasting radioactive waste. Fusion fuses two light hydrogen twins—Deuterium (from seawater) and Tritium—into harmless Helium, releasing 4 times more energy than fission and 4 million times more than coal, with zero carbon emissions.
- Plasma (The 4th State of Matter): At 150 million °C, electrons break free from atomic nuclei, turning the gas into a glowing, electrically charged soup called plasma.
- Why It Can’t Touch Walls: No solid metal can hold plasma directly. If plasma touches the reactor wall, it scars the metal and cools down in a split second—instantly stopping the reaction (which also makes a runaway nuclear meltdown impossible).
2. Inside a Tokamak: How Magnetic Confinement Work
- The Magnetic Doughnut: Invented by Soviet physicists Igor Tamm and Andrei Sakharov in the 1950s, a tokamak is a doughnut-shaped vacuum chamber. Since plasma is electrically charged, giant superconducting magnets can hold and steer it like an invisible bottle (Magnetic Confinement).
- Twisting the Magnetic Field: A plain ring magnet lets plasma drift out and hit the walls. Tokamaks solve this by running a strong electric current right through the plasma, twisting the magnetic field into a tight spiral (helix) that locks the plasma safely in the middle.
- Making Power & Fresh Fuel: Fast-moving neutrons (which have no charge) escape the magnetic cage and hit the inner walls lined with a Lithium blanket. This produces heat to boil water and spin steam turbines for electricity, while also reacting with Lithium to breed fresh Tritium fuel inside the reactor.
Practice MCQ
Q. Consider the following statements regarding nuclear fusion and tokamak technology:
- A tokamak uses powerful magnetic fields to confine superhot plasma inside a ring-shaped chamber, preventing it from touching physical walls.
- India’s Institute for Plasma Research (IPR) operates domestic experimental tokamaks such as ADITYA-U and SST-1.
Which of the statements given above is/are correct?
(a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2
Answer: (c) Both 1 and 2
Hint: Both statements are correct. Tokamaks use twisted magnetic fields (magnetic confinement) to suspend 150-million-°C plasma away from reactor walls, and IPR Gandhinagar (under DAE) runs India’s indigenous tokamaks ADITYA-U and SST-1 while managing India’s hardware deliverables for ITER in France.
Hint: Both statements are correct. Tokamaks use twisted magnetic fields (magnetic confinement) to suspend 150-million-°C plasma away from reactor walls, and IPR Gandhinagar (under DAE) runs India’s indigenous tokamaks ADITYA-U and SST-1 while managing India’s hardware deliverables for ITER in France.
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