When the Prototype Fast Breeder Reactor at Kalpakkam achieved first criticality on 6 April, India did not merely switch on a reactor. It vindicated seven decades of scientific perseverance, strategic foresight, and—at long last—decisive political will. This moment belongs, above all, to the brilliant nuclear scientists and engineers of India, who carried this mission through decades of international sanctions, institutional skepticism, and inadequate political support. But it is also a moment that invites honest reflection on why it took this long, what it truly means, and what must now follow.
The architecture of India’s nuclear programme was drawn by one of the finest scientific minds the country has produced—Dr. Homi Jehangir Bhabha. As early as 1954, Bhabha articulated a three-stage nuclear power programme uniquely suited to India’s resource endowment: abundant thorium reserves, modest uranium deposits, and the civilizational imperative of long-run energy self-reliance. The first stage envisaged Pressurised Heavy Water Reactors fueled by natural uranium, producing electricity while generating plutonium as a byproduct. The second stage—now arrived at Kalpakkam—deploys Fast Breeder Reactors that consume this plutonium while simultaneously breeding more fissile material and, crucially, converting thorium to uranium-233. The third and final stage will deploy Advanced Heavy Water Reactors running on the thorium-uranium-233 cycle, tapping into India’s vast thorium reserves, estimated at over three lakh tonnes, among the largest in the world. This is not merely an energy programme. It is a civilisational insurance policy—a design for a nation that refuses to remain perpetually dependent on imported fossil fuels or foreign nuclear technology.
The achievement of criticality at Kalpakkam must be understood for what it genuinely represents. “Criticality” means the reactor has sustained a controlled, self-sustaining nuclear chain reaction for the first time—the moment a reactor truly comes alive. For a Fast Breeder Reactor, this is particularly significant: unlike conventional reactors, the PFBR uses fast neutrons and liquid sodium as coolant, operating at the absolute frontier of nuclear engineering. The complexity of this technology is reflected in the exclusivity of the club India has now joined. Once the PFBR moves to full commercial operation, India will become only the second country in the world, after Russia, to operate a commercial fast breeder reactor at this scale. This is not a footnote in a technical report; it is a statement of where India now stands in the global hierarchy of nuclear capability. Once the full fleet of Fast Breeder Reactors envisaged under Stage Two is operational, India will produce more fissile fuel than it consumes, creating a self-amplifying cycle of fuel generation that is the very definition of energy sovereignty.
It would be incomplete—and frankly dishonest—to discuss Kalpakkam without acknowledging the political environment that made this acceleration possible. Prime Minister Narendra Modi has approached India’s nuclear future not as a bureaucratic inheritance to be managed, but as a national priority to be driven. His personal presence at Kalpakkam in March 2024 to witness the commencement of core loading was not ceremonial optics; it was a signal of the highest political commitment to a programme that had for too long been treated as a specialist concern of scientists rather than a strategic priority of the government. The Modi government’s Nuclear Energy Mission, announced in the Union Budget 2025-26, set an ambitious target of 100 GW of nuclear capacity by 2047—India’s centenary of independence—backed by budgetary commitment and the newly enacted SHANTI Act, 2025, which modernizes India’s nuclear legal framework. As Prime Minister Modi himself declared upon the achievement of criticality, the PFBR “reflects the depth of our scientific capability and the strength of our engineering enterprise”—and it reflects, equally, the depth of political resolve that his government has brought to bear on this mission.
Equally transformative is the government’s landmark decision to open India’s nuclear sector to private participation. For decades, nuclear power generation was an exclusive preserve of the state—a legacy not merely of ideological instinct but of regulatory inertia and risk-aversion that had calcified into dogma. The amendment enabling private and joint-venture investment in nuclear power plants marks a structural rupture with this past. Private capital, domestic and foreign, brings not just financing but engineering competition, project management discipline, and faster deployment timelines. For a country that must add tens of gigawatts of firm, base-load, zero-carbon power over the next two decades, this opening is not a policy experiment—it is a national necessity.
Intellectual honesty demands we also ask a harder question: why did a reactor whose construction began in 2004 take until 2026 to achieve criticality, missing its original 2010 deadline by 16 years? The delays were not purely technical. The Civil Liability for Nuclear Damage Act passed by the Congressled UPA government in 2010 contained supplier liability provisions so far outside international nuclear commerce norms that global reactor vendors refused to invest, turning the landmark Indo-US civil nuclear deal’s promise into a decade of contractual paralysis. Budgetary allocations remained anaemic, the three-stage programme was treated as ceremonial rhetoric rather than operational priority, and India’s scientists were left to persist with stoicism through years of institutional neglect. The country paid a price in lost time that cannot be recovered.
The contrast with what followed is instructive. After 2014, the Modi government brought to the nuclear programme the combination of political will, institutional reform, and sustained investment it had long deserved. Ten reactors were approved in bulk, streamlining a process that had previously moved at the pace of bureaucratic inertia. The ASHVINI joint venture between NPCIL and NTPC was structured to build four 700 MW reactors in Rajasthan—the first major inter-PSU collaboration in India’s nuclear history. New bilateral agreements with Australia, Canada, Japan, and the United States diversified India’s uranium supply and ended the chronic fuel shortages that had forced reactors to run at barely 40% capacity during the UPA years. Annual nuclear electricity generation rose from approximately 34,000 million units in 2013-14 to nearly 57,000 million units in 2024-25—a 67% increase. The SHANTI Act of 2025 overhauled the entire legal architecture governing atomic energy, while duty exemptions on nuclear plant equipment imports were extended until 2035 to incentivize faster construction. Under the Modi government, installed nuclear capacity has risen from 4,780 MW in 2014 to 8,180 MW in 2024—a growth of over 70% in a decade. Budget 2025-26 committed Rs 20,000 crore specifically for Small Modular Reactor research and development, alongside a roadmap to nearly triple capacity to 22,480 MW by 2031-32.
The road ahead belongs to optimism. India today stands at the threshold of the third stage—the endgame that Bhabha envisaged when he first sketched this programme on a drawing board more than 70 years ago. With thorium-based reactors, India can achieve complete independence from imported nuclear fuel, drawing on reserves sufficient to power the country for centuries. Nuclear energy currently contributes roughly to 3% of India’s electricity. With the 100 GW target, that share could rise to 15-20% by mid-century, providing the firm base-load power that renewables, by their intermittent nature, simply cannot. In a world where climate commitments demand deep decarbonization without sacrificing development, nuclear is not one option among many—it is indispensable.
Kalpakkam is not a finish line. It is the opening of a door that generations of Indian scientists spent their lives building. Under Prime Minister Narendra Modi’s leadership, India has demonstrated that it possesses both the intent and the capacity to translate that vision into reality: through missions, through market reform, and through the quiet, determined empowerment of its scientific establishment. The atom has been India’s faithful servant in waiting. Kalpakkam tells us the wait is over.
- Kartikeya Sharma is Independent Member of Parliament (Rajya Sabha).
