PFBR Kalpakkam attained first criticality on 6 April 2026
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The indigenously designed Prototype Fast Breeder Reactor at Kalpakkam, Tamil Nadu, attained first criticality on 6 April 2026, the DAE told Lok Sabha on 5 August. It is the forerunner of the second stage of Dr Homi J. Bhabha’s three-stage nuclear programme. Using MOX fuel and a U-238 blanket, it breeds Pu-239 and makes more fuel than it uses.
- Released
- 5 Aug 2026, Lok Sabha reply, DAE
- First criticality
- 6 April 2026
- Reactor
- 500 MW PFBR, Kalpakkam, Tamil Nadu; built by BHAVINI
- Designer
- IGCAR, a DAE unit; nearly 90% domestic manufacturing
- Fuel
- U-Pu Mixed Oxide (MOX), U-238 blanket
- Capacity path
- 8,780 MW now to 22,480 MW by 2031-32
The Prototype Fast Breeder Reactor: what happened?
Criticality means the chain reaction in a reactor has become self-sustaining for the first time. For PFBR it matters more than for an ordinary reactor. It is India’s first commercial fast reactor and the gateway from stage one (uranium) to stage three (thorium) of the nuclear plan.
- IGCAR led design, sodium technology, equipment qualification and safety assessment.
- An under-sodium ultrasonic imaging tool let operators “see” through opaque liquid sodium during fuel loading.
- DISHA, a remote-controlled robotic vehicle, inspects welds between reactor vessels at high temperature.
- Reactor physics estimates closely matched actual performance at first criticality.
- A fleet of 10 indigenous 700 MW PHWRs (7,000 MW) is being built; first pour of concrete done at Kaiga-5 and 6.
What is the three-stage programme?
| Stage | Reactor | Fuel |
|---|---|---|
| 1 | Pressurised Heavy Water Reactors (PHWRs) | natural uranium; spent fuel reprocessed for plutonium |
| 2 | Fast Breeder Reactors (FBRs), such as PFBR | reprocessed Pu-239; U-238 bred into Pu-239 |
| 3 | breeder reactor using thorium | U-233 bred from thorium, initially with Pu-239 as driver fuel |
How does PFBR breed fuel?
- The core is surrounded by a blanket of U-238.
- Fast neutrons turn this fertile U-238 into fissile Pu-239, so the reactor makes more fuel than it consumes.
- It is designed to later use Thorium-232 in the blanket, which turns into U-233, the fuel for stage three.
- The programme is based on a closed fuel cycle to stretch limited uranium and use abundant thorium.
What do the numbers show?
| Item | Figure |
|---|---|
| Installed nuclear capacity now | 8,780 MW |
| Target by 2031-32 | 22,480 MW (incl. 500 MW PFBR) |
| Fleet-mode PHWRs | 10 x 700 MW = 7,000 MW |
| Mahi Banswara 1 to 4 | 4 x 700 MW, by ASHVINI (NPCIL-NTPC JV) |
| Uranium resources (AMD) | 4,42,800 t in situ U3O8, in 11 States |
How does fuel move through the stages?
- Stage 1: natural uranium in PHWRs
- Reprocess spent fuel to recover plutonium
- Stage 2: PFBR burns MOX and breeds Pu-239 from U-238
- Later: thorium blanket breeds U-233
- Stage 3: thorium-based reactors once enough FBR capacity exists
Why does the Prototype Fast Breeder Reactor matter?
| Angle | What to note |
|---|---|
| Energy security | Opens the path to India’s large thorium reserves. |
| Technology | Sodium systems, under-sodium imaging and robotic inspection were developed in India; about 90% of equipment made at home. |
| Industry | Fleet-mode PHWRs build a domestic supply chain. |
| Science | Close match of predicted and actual physics shows design maturity. |
What are the challenges in the Prototype Fast Breeder Reactor?
- Stage three needs adequate FBR capacity first, so thorium use is still far off.
- Liquid sodium is opaque, so fuel loading and inspection need special imaging and robotic tools.
- Nuclear is still a small part of capacity (8,780 MW).
- Fleet projects beyond Kaiga-5 and 6 and Mahi Banswara are at pre-project stage.
What should be done next on the Prototype Fast Breeder Reactor?
- Move PFBR from first criticality to steady power operation.
- Plan more FBRs to build stage-two capacity.
- Keep the fleet-mode PHWRs on schedule to reach 22,480 MW by 2031-32.
- Expand uranium exploration with AI-based mapping, as AMD is doing.
What can Prelims ask on the Prototype Fast Breeder Reactor?
- PFBR: Kalpakkam, Tamil Nadu; first criticality 6 April 2026; 500 MW; BHAVINI.
- Fuel: U-Pu MOX; blanket U-238 breeds Pu-239; later Th-232 breeds U-233.
- IGCAR: principal architect of PFBR.
- DISHA: robotic vehicle for weld inspection.
- ASHVINI: NPCIL-NTPC JV for Mahi Banswara.
How to write about the Prototype Fast Breeder Reactor in Mains
Practice question (15 marks, 250 words): The first criticality of the PFBR is a milestone for India’s three-stage nuclear programme. Explain the significance of fast breeder reactors for India’s long-term energy security.
- Intro: PFBR criticality, 6 April 2026.
- Three stages and closed fuel cycle.
- Breeding: U-238 to Pu-239, Th-232 to U-233.
- Challenges: sodium tech, scale, timelines.
- Way forward: more FBRs, PHWR fleet, 22,480 MW.
What should UPPCS aspirants note?
- AMD lists Uttar Pradesh among the 11 States where in situ uranium resources have been established.
How to use this in Mains
- As per PIB (2026-08-05): the indigenous Prototype Fast Breeder Reactor at Kalpakkam attained first criticality on 6 Apr 2026, a milestone in Bhabha's three-stage programme.
- The fast breeder is the step that leads to using thorium.
Quotable data pointThe indigenous Prototype Fast Breeder Reactor at Kalpakkam attained first criticality on 6 Apr 2026, a milestone in Bhabha's three-stage programme.
PIB: DAE: PFBR criticality, 5 Aug 2026
Exam angle
Prelims: three-stage programme.
Practice MCQs
Original practice questions (not PYQs).
In the PFBR, the fertile material placed in the blanket around the core to breed fissile fuel is
Answer (b) & explanation
PIB (DAE), 5 Aug 2026: U-238 blanket breeds Pu-239.
Consider the following about India's three-stage nuclear programme:
1. Stage one uses natural uranium in PHWRs.
2. Stage two uses fast breeder reactors.
3. Stage three uses U-233 bred from thorium.
Which are correct?
Answer (d) & explanation
PIB (DAE), 5 Aug 2026.
Questions students ask about this
When did PFBR attain first criticality?
On 6 April 2026, at Kalpakkam in Tamil Nadu.
Why is PFBR called a breeder?
Its U-238 blanket is converted into fissile Pu-239 by fast neutrons, so it produces more fuel than it consumes.
Who designed and who built PFBR?
IGCAR, a DAE unit, was the principal architect; BHAVINI is implementing the 500 MW reactor.
What will India's nuclear capacity be by 2031-32?
22,480 MW, up from 8,780 MW, as fleet-mode projects are completed.
Keep studying
Go deeper
Official source: PIB: DAE: PFBR criticality, 5 Aug 2026
facts from cited sources only; faculty review pending