Why India’s thorium reserves could become its biggest strategic energy weapon

How India’s fast breeder reactor programme and thorium reserves together could reshape its long-term energy independence

India’s long-held ambition to break free from uranium dependency is gaining renewed momentum. With between one-quarter and one-third of the world’s known thorium reserves—estimated at 25% to 30%—embedded in monazite sands along its southern and eastern coasts, the country is uniquely positioned to use thorium as a fuel for clean, long-duration nuclear power. These sands, concentrated in states such as Kerala, Tamil Nadu, Odisha, and Andhra Pradesh, have been identified as a strategic mineral resource since the early years of India’s nuclear programme.

Unlike uranium, thorium is not fissile on its own, but when irradiated with neutrons it converts into uranium-233, a fissile isotope capable of sustaining a nuclear chain reaction. This property allows thorium to serve as a fertile material in breeder reactors, offering potentially safer and more efficient nuclear generation with reduced long-lived waste.

Anchoring this vision is the Prototype Fast Breeder Reactor (PFBR) at Kalpakkam in Tamil Nadu. This sodium-cooled, 500 megawatt-electric (MWe) reactor began core loading in March 2024 and is expected to be commissioned by 2026. PFBR is designed to generate more fissile material than it consumes, producing plutonium and uranium-233 for future thorium-fuelled reactors. This breeder capability is central to India’s three-stage nuclear programme, first proposed by physicist Homi Bhabha, which charts a path from natural uranium to a fully closed thorium fuel cycle.

From fast breeder deployment to thorium fuel cycles: can India power itself for centuries?

India’s three-stage nuclear vision begins with pressurised heavy water reactors (PHWRs) running on natural uranium, producing plutonium as a by-product. The second stage—now represented by PFBR—uses this plutonium as fuel in fast breeder reactors to generate more fissile material. The final stage will deploy reactors such as the Advanced Heavy Water Reactor (AHWR) to run on a mix of thorium and uranium-233, completing the shift to an almost entirely indigenous fuel cycle.

If realised, this model could provide India with energy security for centuries. Analysts estimate that its thorium reserves alone could theoretically produce up to 500 gigawatt-electric (GWe) of power over a 400-year period, using only economically recoverable deposits. Thorium-based systems also offer operational and environmental benefits, including reduced quantities of long-lived radioactive waste, higher burn-up efficiency, and lower proliferation risk compared to conventional uranium cycles.

Globally, thorium has attracted periodic interest. Norway’s Thor Energy has tested thorium fuel in light-water reactors, China has invested heavily in molten salt reactor designs, and research in the United States has explored hybrid thorium–uranium cycles. However, no country has yet deployed a full commercial thorium fuel cycle, making India’s programme one of the most advanced attempts to industrialise the concept.

What challenges must India overcome before thorium becomes a mainstream energy source?

While the strategic logic is compelling, technical and operational challenges remain. PFBR’s commissioning has faced multiple delays due to first-of-a-kind integration issues—common for pioneering nuclear projects. Officials from Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI), which is executing the project, say these issues are being addressed through phased testing and safety-focused adjustments.

The AHWR, designed by the Bhabha Atomic Research Centre (BARC), remains in the design and pre-licensing stage, with no industrial-scale deployment yet scheduled. Scaling thorium reactors will require not just proven designs, but also a robust supply chain for thorium mining, processing, and fuel fabrication—areas that currently exist only at pilot scale in India.

Mining itself carries strategic sensitivities. Because monazite sands also contain rare earth elements, extraction requires integrated processing facilities and strict regulatory oversight. India has historically maintained tight control over monazite mining through public-sector enterprises, both to protect its strategic resource and to avoid environmental damage.

Financing is another consideration. While thorium reactors promise long-term fuel cost stability, initial capital requirements are high. Given that no commercial thorium reactor fleet exists anywhere in the world, India’s banks and investors will need strong policy guarantees before committing large-scale funding.

From a long-term energy security perspective, the rewards could be transformational. The ability to generate stable, low-carbon electricity for centuries without relying on volatile global uranium markets would make India one of the most energy-secure nations in the world. In a carbon-constrained future, thorium could also position India as an exporter of nuclear technology, fuel fabrication expertise, and turnkey reactor solutions for other countries with thorium deposits but limited nuclear infrastructure.

If PFBR is commissioned on time and the AHWR or similar thorium-based designs reach commercial readiness, India could leapfrog into a position of global leadership in alternative nuclear fuel cycles. Success would depend not just on engineering breakthroughs, but on policy consistency, public acceptance, and sustained funding. Achieving these milestones could turn India’s vast thorium deposits from a latent resource into the backbone of its clean energy future.