For decades India was an outlier in the global nuclear landscape by betting big on thorium as a fuel supplying potentially limitless power to a country short on other sources of energy. Until it wasn’t. On 17 April 2025, the South China Morning Post reported that China has developed the world’s first operational molten salt reactor (MSR) running on thorium fuel with a capacity of 2 MW. Buoyed by the success of the existing reactor, China is already building a larger 10 MW thorium MSR.
India, in contrast, has mastered the first stage of its nuclear programme involving the construction of pressurised heavy water reactors using natural uranium but is nowhere close to the third stage that ultimately uses thorium as a fuel. I argue that China’s initial success with the thorium reactor is a wake-up call for India. The latter should urgently pursue direct thorium utilisation in parallel to the three-stage nuclear power programme.
Dissecting China’s thorium reactor
China’s MSR design is not new. By their own admission, Chinese scientists have borrowed from and built upon publicly accessible troves of research documents from the US’ Oak Ridge National Laboratory’s Molten Salt Reactor Experiment that ran in the 1960s but was closed in 1969. The Chinese 2 MW MSR is located in the Gobi desert and uses molten salt as both the fuel carrier and coolant. China does not just have abundant thorium resources, but thorium is also a byproduct of its massive rare earths industry.
The South China Morning Post (SCMP) article does not clarify how fertile thorium is converted into fissile uranium. There are good reasons to consider science reporting by the SCMP with some caution. As Zichen Wang has argued in his famous Pekingnology newsletter, the SCMP has sometimes exaggerated science reports. But in this case, China’s MSR developments have been covered by other publications such as the IEEE and ABC News as well.
What, why and how of India’s three-stage nuclear plan
India’s three-stage nuclear power programme was first conceptualised by Homi J. Bhabha — often referred to as the father of the Indian nuclear programme — in the 1950s with the ultimate objective of utilising thorium at a big scale.
The first stage involves setting up pressurised heavy water reactors (PHWRs) that run on natural uranium (0.7% fissile U-235 isotope and rest fertile U-238 isotope) as fuel. Plutonium is extracted from the spent fuel from PHWRs after reprocessing.
This plutonium (Pu-239) along with depleted uranium (U-238) is then used as the fuel for fast breeder reactors (FBRs) in the second stage. FBRs breed more fuel than they consume thereby helping setting up more FBRs. At some point a blanket of thorium (Th-232) is introduced in the FBRs.
Thorium is fertile but not fissile. In FBRs, upon being irradiated by neutrons, it transmutes into fissile uranium isotope (U-233). The U-233 then along with Th-232 becomes the fuel for the third stage.
India’s ample thorium reserves can be used to generate about ‘358,000 GWe-yr of electrical energy and can easily meet the energy requirements during the next century and beyond’, according to a study published in the Journal of Nuclear Materials.
It was the domestic abundance of thorium as against scant uranium and hydrocarbon resources that in part motivated the Indian nuclear establishment to conceive of a three-stage plan. Another motivation was to leave the option open to obtain plutonium for weapons purposes.
Moving beyond the three stages
In the last six decades, India has perfected the first stage by establishing and running about 20 PHWRs. As far as the second stage is concerned, India is building a 500 MW prototype fast breeder reactor (PFBR) in Kalpakkam. It is set to become operational only in September 2026. The third stage remains in the R&D phase.
Cognizant of the significant delays in realizing the three stage plan, the Indian nuclear establishment is also pursuing advanced heavy water reactors (AHWR) that ‘will act as a bridge between the first and third stage essentially to advance thorium utilization without undergoing second stage of the three-stage program’, according to a paper by SK Jain, former chairman and managing director of the Nuclear Power Corporation of India. However, for close to a decade now AHWR has remained in the designing phase.
Learning from China’s initial success with the molten salt reactor, India should look beyond heavy water reactors and experiment with different reactor designs. This not just includes molten salt but also accelerator driven system and high-temperature gas-cooled reactor design. As much as the three-stage plan was aimed at securing weapons-grade plutonium for the strategic programme, it has largely served its purpose. But the ultimate objective of the three-stage plan — exploiting thorium for generating potentially limitless power — remains unfulfilled even after six decades. It is time the Indian nuclear establishment adopts realistic direct thorium utilisation plans in parallel to the long-term three-stage plan.
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