PFBR at Kalpakkam Attains Criticality

PFBR at Kalpakkam has attained criticality, which is a major milestone for India’s nuclear programme. Read here to understand the significance of this for India’s Nuclear Programme.

India has achieved a major milestone with the indigenously developed Prototype Fast Breeder Reactor (PFBR) at Kalpakkam attaining criticality.

This marks a crucial step in advancing the second stage of India’s nuclear energy programme and strengthens the pathway toward long-term energy security.

PFBR attains Criticality

What is Criticality?

Criticality refers to the stage when a nuclear reactor achieves a self-sustaining chain reaction.

• Each nuclear fission produces enough neutrons to sustain further reactions
• The reactor becomes stable and operationally viable
• Indicates readiness for gradual power generation

What is a Fast Breeder Reactor (FBR)?

A Fast Breeder Reactor is a type of nuclear reactor that:

• Uses fast neutrons (no moderator)
• Produces more fissile material than it consumes

Basic Reaction:

²³⁸U + n —> ²³⁹ Pu

Fertile Uranium-238 absorbs neutrons and converts into Plutonium-239 (fissile fuel).

Key Features of PFBR:

• Capacity: 500 MWe
• Developer/Operator: BHAVINI
• Fuel: MOX (Mixed Oxide: Uranium + Plutonium)
• Coolant: Liquid sodium
• Moderator: None (fast neutron system)

Working Principle:

1. Fission in the core produces energy and fast neutrons
2. Neutrons interact with the U-238 blanket
3. Conversion into Pu-239 (new fuel)
4. The reactor generates more fuel than consumed

This is called the breeding process

India’s Three-Stage Nuclear Programme

India’s nuclear strategy is designed to utilise:

• Limited uranium reserves
• Abundant thorium reserves

Conceptualised by Homi J. Bhabha

Stage 1: Pressurised Heavy Water Reactors (PHWRs)

Features

• Fuel: Natural uranium
• Moderator & Coolant: Heavy water

Role

• Produces electricity
• Generates plutonium (Pu-239) as a by-product

Status

• Backbone of India’s nuclear capacity (~8,180 MWe)
• Expansion through fleet-mode construction

Stage 2: Fast Breeder Reactors (FBRs)

What is a Fast Breeder Reactor?

A Fast Breeder Reactor:

• Uses fast neutrons (no moderator)
• Produces more fuel than it consumes

Working Principle

• Converts fertile U-238 to fissile plutonium (Pu-239)
• Uses MOX (Mixed Oxide) fuel

PFBR at Kalpakkam

• Capacity: 500 MWe
• Developed by BHAVINI
• Uses:
  • MOX fuel
  • Liquid sodium as a coolant

Significance

• Acts as a bridge between Stage 1 and Stage 3
• Generates plutonium for further reactors
• Enables transition to thorium utilisation

Stage 3: Thorium-Based Reactors

Why Thorium?

• India has one of the largest thorium reserves globally

Process

• Thorium (Th-232) gets converted to Uranium-233 (U-233) (fissile)

Future Technologies

• Advanced Heavy Water Reactors (AHWRs)
• Molten Salt Reactors (MSRs)

Strategic Significance of PFBR Criticality

1. Energy Security

• Reduces dependence on imported uranium
• Utilises domestic resources efficiently

2. Fuel Multiplication

• Produces more fissile material than consumed
• Expands nuclear fuel availability

3. Gateway to Thorium Economy

• Generates materials required for third-stage reactors

4. Technological Achievement

• Places India among a select group of nations (e.g., Russia) operating FBRs
• Demonstrates advanced nuclear engineering capability

5. Sustainability

• Supports closed fuel cycle and recycling
• Reduces nuclear waste

Challenges Associated with FBRs

1. Safety Concerns

• Use of liquid sodium coolant (highly reactive)
• Global reluctance due to accident risks

2. High Costs: Expensive construction and maintenance
3. Technological Complexity: Requires advanced materials and fuel reprocessing
4. Delays: The PFBR project faced significant time overruns

Operational Nuclear Power Plants in India

Total Status (as of recent data)

• Total operational reactors: 23
• Installed capacity: ~8,180 MWe
• Reactor types:
  • Pressurised Heavy Water Reactors (PHWRs)
  • Boiling Water Reactors (BWRs)
  • Pressurised Water Reactors (VVER- Russian design)

Way Forward

• Scale up FBR programme (planned 600 MWe reactors)
• Develop thorium-based reactors (AHWR)
• Strengthen fuel recycling infrastructure
• Explore advanced fuels (e.g., HALEU)
• Invest in next-gen reactors like MSRs

Conclusion

The PFBR achieving criticality marks a turning point in India’s nuclear trajectory, accelerating the transition from uranium dependence to a thorium-based sustainable energy system.

By advancing the second stage of the programme, India moves closer to achieving long-term energy independence, technological self-reliance, and low-carbon growth.

Related articles:

• Nuclear waste
• Nuclear energy
• Nuclear terrorism
• Comprehensive Nuclear Test-Ban Treaty (CTBT)
• India’s nuclear weapons programme