Relevance: GS III (Science & Tech – Nuclear Energy, Future Fuels) | Source: The Hindu
1. Context
Scientists at China’s EAST (Experimental Advanced Superconducting Tokamak) reactor have achieved a major milestone. They successfully maintained super-hot plasma at a density 65% higher than the theoretical safety ceiling known as the Greenwald Limit.
2. The Science Simplified
To understand the significance, we must break down the mechanics:
Nuclear Fusion: The process that powers the Sun. It involves smashing Hydrogen atoms together to form Helium, releasing massive energy without long-term radioactive waste.
The “Bottle” Problem: Fusion requires millions of degrees. No solid container can hold this. Scientists use Tokamaks (donut-shaped machines) that use powerful magnetic fields to trap the hot gas (Plasma).
The Greenwald Limit: Historically, there was a “density speed limit.” If plasma density pushed past this limit, it would become unstable and crash the reaction.
The Breakthrough: The Chinese team used Tungsten walls coated with Lithium to absorb impurities and stabilize the plasma, effectively breaking this limit without a crash.
3. Why is this Important?
- Efficiency: Higher density means more fusion reactions occur in the same space, leading to higher energy output.
- Implications for ITER: This finding is critical for the ITER project (France). It proves that the massive reactor can operate at higher efficiencies than previously thought, solving a key “density limit” challenge.
UPSC Value Box
Concept / Institution | Relevance for Prelims |
| Tokamak | A device that uses powerful magnetic fields (toroidal shape) to confine plasma. It is the leading design for fusion reactors. |
| ITER (International Thermonuclear Experimental Reactor) | Located in France. A global mega-project to prove fusion feasibility (Net Energy Gain). Members: India, USA, Russia, China, EU, Japan, S. Korea. India’s Role: Providing the Cryostat (world’s largest fridge) and cooling systems. |
| Greenwald Limit | A theoretical operational limit in fusion physics relating to the maximum density of plasma in a tokamak before it becomes unstable. |
Q. With reference to Nuclear Energy, consider the following statements:
- Nuclear Fusion involves splitting heavy atomic nuclei to release energy, similar to current commercial nuclear power plants.
- The “Greenwald Limit” refers to the maximum density of plasma that can be confined in a Tokamak reactor without instability.
- India is a full member country of the ITER project located in France.
Which of the statements given above is/are correct?
(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3
Correct Answer: (c)
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