RIPE WITH OPPORTUNITY. India enjoys a lead in thorium as well as fast-breeder reactor technology | Photo Credit: RAJESH N

India’s vast thorium resources offer a means for the country to become a global clean energy provider rather than remaining a major energy importer with the attendant vulnerabilities.

The founder of the atomic energy programme in India, Dr Homi Bhabha, recognised this way back in the early 1950s and had, in fact, chalked out a three-stage strategy.

The first stage comprising uranium reactors — essentially the pressurised heavy water reactors (PHWRs) — though delayed, has matured well. It is about to exceed the 10 GWe capacity envisaged for the beginning of the first stage.

Today, there is an unprecedented urgency for nuclear energy globally, driven by economic growth and the need to transition to clean energy. The new nuclear energy development in response, in India as well as globally, is essentially based on uranium. With the ‘once-through’ mode of uranium use that is in practice in most of the world, the known global uranium resources can support only around 500 GWe nuclear capacity, assuming a reactor life of around 60 years.

Against this, nearly three times larger nuclear capacity of 1,400 GWe by 2050, which is only 24 years away, has been projected by the World Nuclear Association. Clearly, resource depletion and supply-chain shocks are imminent within a decade or two. A shift to closed nuclear fuel cycles (reprocessing and recycling) and fast-breeder reactors, which can enhance the energy potential by around two orders of magnitude, is therefore inevitable.

The barrier to this shift are the proliferation concerns around plutonium. The way out of this conundrum is clearly thorium. It’s an opportunity India cannot afford to miss, given its lead in thorium as well as fast-breeder reactor technology, nor can it continue to suffer fuel supply vulnerability despite its vast thorium endowment and global shifts from fossil to nuclear energy.

The successful PHWR technology — the clear choice of investors — is expected to be the workhorse for the mission and may well contribute to at least half of the envisaged capacity. It offers an ideal platform to start irradiating thorium to produce uranium233 and directly connect it to the third-stage thorium reactors. This is necessary since the requisite thorium irradiation capacity through fast-breeder reactors is still decades away.

Thorium-HALEU fuel bundles, which are similar to the natural uranium fuel bundles used in PHWRs and can work with the existing design of PHWRs, can quickly enable thorium irradiation at scale along with significant economic, safety and other dividends. The evolution of the second stage of fast-breeder reactors should continue in the meantime, exactly as per the original plan.

Fast-breeder reactors are needed to continuously augment India’s nuclear energy resource at least until fusion reactors become a reality and deliver energy at the required scale. Accelerator-driven subcritical systems (ADSS) could also supplement fast-breeder reactors in meeting these objectives.

Key challenges

The original three-stage strategy thus remains essentially the same, except for advancing the third stage to immediately follow the first. As a result, we should be able to leverage energy from the uranium233 derived from thorium in time before the challenges in the uranium supply chain start kicking in.

Dealing with the thorium fuel cycle has its challenges. The key issue is with the hard gamma emitting daughter products of uranium232 that invariably accompany uranium233.

While that brings in proliferation resistance in the fuel cycle, it also greatly hinders the manufacture of uranium233-based solid fuel.

Fuel in liquid form, on the other hand, would seem more manageable, particularly since we can draw on our well developed capabilities in reprocessing and high-level radioactive waste immobilisation as well as benefit from insights on the global development of molten salt reactor (MSR) systems.

Unlike traditional nuclear engineering, which is physics-heavy, MSR engineering is chemistry-heavy. Much work is required in materials development, as well as the operational chemistry control of flowing liquid salt to prevent it from dissolving the reactor’s pipes.

Intense co-ordinated work is needed to develop a thorium molten salt reactor (TMSR), which to my mind is a clear choice for the thorium stage.

Since thorium breeds even in the thermal neutron spectrum, TMSR operating in the near thermal spectrum could maximise sustained thorium-based power generation capacity, leveraging the spent thorium-HALEU fuel arising from a given PHWR capacity.

Instead of just jumping on the prevailing small modular reactor (SMR) bandwagon, SMRs based on TMSRs offer a safer and sustainable solution.

An intense R&D mission to advance the third stage and deploy TMSRs within 10-15 years is a critical national necessity.

In the near term, India must accelerate nuclear capacity build-up based on technologies that are already mature and by leveraging all deployment opportunities.

Captive clean electricity supply, leveraging brown field opportunity at retiring coal plant sites, clean hydrogen production — both through thermochemical splitting of water as well as electrolysis, clean base load energy for remote areas, and meeting diverse energy demands through micro-nuclear reactors are but some examples of the diverse opportunities that exist.

Getting the country ready to launch the third stage of thorium reactors in time should be done in parallel to making our energy security import-independent. A conducive ecosystem that can unleash Indian ingenuity to leverage the opportunities opened up by the SHANTI Act has become the need of the hour.

(The writer is a former Chairman, Atomic Energy Commission)

Published on June 15, 2026