India's indigenously developed 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam in Tamil Nadu attained first criticality on April 6, 2026 at 8:25 PM, marking a historic leap for the country's three-stage nuclear power programme envisioned by Dr Homi Bhabha. First criticality is the stage at which a nuclear reactor achieves a self-sustaining fission chain reaction for the first time, and it is a crucial step before power ascension tests and eventual grid connection. The PFBR has been designed and built by Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI) using technology developed by the Indira Gandhi Centre for Atomic Research (IGCAR), an R&D centre under the Department of Atomic Energy. The reactor uses Uranium-Plutonium Mixed Oxide (MOX) fuel and is surrounded by a blanket of Uranium-238, which fast neutrons convert into fissile Plutonium-239, enabling the reactor to breed more fuel than it consumes. In the long run, the blanket will use Thorium-232, which will be transmuted into fissile Uranium-233 to fuel the third stage of India's nuclear power programme based on the country's vast thorium reserves. Construction of the reactor began in 2004 with a planned commissioning in 2010, but the project faced multiple delays due to technological challenges and safety validations. The achievement makes India only the second country after Russia to operate a commercial scale fast breeder reactor, strengthening long term energy security and supporting the Viksit Bharat 2047 vision of achieving 100 GW nuclear capacity.
Kalpakkam PFBR Attains First Criticality, Marks Second Stage of India's Nuclear Power Programme
The 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam attained first criticality on April 6, 2026, marking India's entry into the second stage of its three-stage nuclear programme and taking it closer to thorium based power generation.
Key facts
- PFBR at Kalpakkam attained first criticality on April 6, 2026 at 8:25 PM
- The 500 MWe reactor uses Uranium-Plutonium MOX fuel with a Uranium-238 blanket
- Built by BHAVINI using IGCAR technology under the Department of Atomic Energy
- India becomes only the second country after Russia to operate a commercial scale FBR
- Marks entry into Stage 2 of Dr Homi Bhabha's three stage nuclear programme
- Will eventually use Thorium-232 blanket to fuel Stage 3 of the programme
PYQPrelims/PYQ angle
- RAS 2021 Differentiate between nuclear fission and fusion — Both engage nuclear physics in India's programme; this article details the PFBR's first criticality milestone in Stage-II fission breeding.
- RAS 2024 Nuclear energy roadmap in Union Budget 2025-26 — Both address India's nuclear-energy trajectory; this article documents the PFBR criticality advancing the three-stage programme toward thorium.
Mains angle
Q: Evaluate the strategic significance of the Kalpakkam PFBR's first criticality for India's three-stage nuclear power programme.
Answer (50 words):
India's indigenously built 500 MWe Prototype Fast Breeder Reactor at Kalpakkam, Tamil Nadu attained first criticality on 6 April 2026, advancing the Bhabha three-stage programme. Designed by BHAVINI using IGCAR technology, it uses Uranium-Plutonium mixed oxide fuel and a Uranium-238 blanket paving the thorium-fuelled third stage. Once fully operational, India will become second after Russia.
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Which of the following statements about the Prototype Fast Breeder Reactor (PFBR) at Kalpakkam that attained first criticality in April 2026 is/are correct?\n1. It is a 500 MWe reactor that uses Uranium-Plutonium Mixed Oxide (MOX) fuel.\n2. It was built by Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI) using IGCAR technology.\n3. It marks the beginning of the third stage of India's nuclear power programme.
Statements 1 and 2 are correct. The PFBR is a 500 MWe reactor using Uranium-Plutonium MOX fuel and was built by BHAVINI using technology from IGCAR. Statement 3 is wrong: the PFBR marks the beginning of the SECOND stage, not the third. Stage 3 will use Thorium-232 in the blanket to breed fissile Uranium-233.
Source: Department of Atomic Energy
Frequently asked questions
What is first criticality of a nuclear reactor?
First criticality is the stage at which a nuclear reactor achieves a self-sustaining fission chain reaction for the first time. It is a crucial step before power ascension tests and grid connection.
What are the three stages of India's nuclear programme?
Stage 1 uses Pressurised Heavy Water Reactors with natural uranium. Stage 2 uses Fast Breeder Reactors with Plutonium-239 and Uranium-238. Stage 3 will use Thorium-232 to breed fissile Uranium-233, leveraging India's large thorium reserves.
Which agency built the PFBR?
The PFBR was built by Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI) using technology developed by the Indira Gandhi Centre for Atomic Research (IGCAR), an R&D centre under the Department of Atomic Energy.
Why is this a milestone for energy security?
Fast breeder reactors produce more fissile material than they consume and enable the use of India's vast thorium reserves. They strengthen long term energy security and support the goal of 100 GW nuclear capacity by 2047.
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