Why in News?

Recently, India’s nuclear programme and global debates on advanced reactor technologies are frequently in focus for energy security and climate goals.

• Nuclear Reactor – It is the core component of a nuclear power plant that initiates and controls a sustained nuclear chain reaction.
• In a nuclear power reactor, the energy released is used as heat to make steam to generate electricity.

Pressurised Heavy Water Reactors (PHWRs)

• Fuel – Natural uranium.
• Moderator and Coolant – Heavy water (D₂O).
• Capacity – 220–700 MW.
• Mechanism – Heavy water slows neutrons to thermal speeds, allowing natural uranium to sustain chain reaction.
• India – Backbone of Stage I programme.

Fast Breeder Reactors (FBRs)

• Fuel – U‑238 to Pu‑239, Th‑232 to U‑233.
• Neutrons – Fast neutrons (no moderator).
• Capacity – 500+ MW.
• Mechanism – Uses fast neutrons to convert fertile isotopes into fissile ones, breeding more fuel.
• India – Crucial for Stage II.

Small Modular Reactors (SMRs)

• Fuel – Low‑enriched uranium (3–4% U‑235).
• Capacity – 30–300 Mwe (Megawatt electrical).
• Mechanism – Factory‑built modules with passive cooling; flexible deployment.
• Global – Emerging technology.

Conventional Nuclear Reactors

• Fuel – Enriched uranium (3–4% U‑235).
• Capacity – 500–1000+ MW.
• Mechanism – Thermal neutrons moderated by water in large centralized plants.
• Global – Proven backbone of nuclear power.

Boiling Water Reactors (BWRs)

• Fuel – Enriched uranium (3–4% U‑235).
• Capacity – 600–1000 MW.
• Mechanism – Water boils inside reactor core; steam directly drives turbine.
• Deployment – Common in U.S. and Japan.

Pressurised Water Reactors (PWRs)

• Fuel – Enriched uranium (3–4% U‑235).
• Capacity – 900–1300 MW.
• Mechanism – Water kept under high pressure; heat transferred to secondary loop for steam.
• Deployment – Most widely used globally.

Advanced Heavy Water Reactors (AHWRs)

• Fuel – Thorium + small U‑233/U‑235.
• Capacity – 300–700 MW.
• Mechanism – Heavy water moderates the neutrons to convert fertile Thorium into fissile U-233, while boiling light water (normal water) is used as the coolant to drive the turbine directly.
• India – Stage III of nuclear programme (thorium focus).

References

1. Visual Capitalist | Uranium
2. World Nuclear | Nuclear Reactors