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

TokamakA 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 LimitA 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:

  1. Nuclear Fusion involves splitting heavy atomic nuclei to release energy, similar to current commercial nuclear power plants.
  2. The “Greenwald Limit” refers to the maximum density of plasma that can be confined in a Tokamak reactor without instability.
  3. 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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