Nuclear Energy & Small Modular Reactors (SMRs)

I. Static Foundation – Nuclear Fission

Most nuclear power plants operate on nuclear fission.

Fission is the process in which:

A heavy nucleus (like Uranium-235) splits into smaller nuclei
Releasing large amounts of energy.

This energy is used to produce steam → rotate turbine → generate electricity.

Prelims trap:
Nuclear power plants use fission, not fusion.

II. Uranium vs Plutonium

Uranium-235 is commonly used in reactors.

Plutonium-239 can also be used.

India follows a three-stage nuclear program:

  1. Pressurized Heavy Water Reactors (PHWR)

  2. Fast Breeder Reactors

  3. Thorium-based reactors

UPSC may test which country focuses on thorium — India does.

III. What is a Nuclear Reactor?

A reactor controls nuclear fission chain reaction.

Key components:

Fuel rods
Control rods
Moderator
Coolant

Control rods absorb excess neutrons to prevent runaway reaction.

Prelims trap:
Control rods do not generate energy. They regulate reaction.

IV. What are Small Modular Reactors (SMRs)?

SMRs are:

Smaller nuclear reactors
Factory-built and modular

Advantages:

Lower upfront cost
Scalable
Safer passive cooling systems

They are seen as future of nuclear energy.

UPSC may test what “modular” implies.

V. Nuclear Fusion (Important Distinction)

Fusion is the process where:

Light nuclei combine to form heavier nucleus.

It powers the Sun.

Currently, fusion is experimental for electricity generation.

Prelims trap:
Commercial nuclear plants do not use fusion yet.

VI. Recent Developments (Last 1–1.5 Years)

1️⃣ Global push for SMRs as clean energy alternative.

2️⃣ Renewed focus on nuclear power for climate targets.

3️⃣ India’s interest in expanding nuclear capacity.

4️⃣ International collaboration in nuclear safety.

UPSC may link nuclear power with climate commitments.

VII. Nuclear Waste

Spent fuel remains radioactive.

Requires:

Long-term storage
Shielding

UPSC may test disposal issues.

VIII. Radiation Types (Static Clarity)

Alpha particles
Beta particles
Gamma rays

Gamma rays have highest penetration.

Prelims trap:
Alpha particles can be stopped by paper.

IX. Advantages of Nuclear Energy

Low greenhouse gas emissions
High energy density
Stable baseload power

X. Risks & Concerns

Radioactive waste
Accidents
High initial cost
Security risks

UPSC may frame balanced statement question.

XI. Common Prelims Traps

  • Mixing fusion and fission.

  • Thinking SMRs use different physics.

  • Assuming thorium is widely used commercially.

  • Believing control rods produce energy.

  • Confusing radiation types.

XII. Likely Question Patterns

  • Which of the following statements about nuclear fission are correct?

  • What are Small Modular Reactors?

  • What is India’s three-stage nuclear program based on?

  • Which radiation has highest penetration power?

Nuclear energy links to energy security + climate policy + physics basics.

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