India Examines an Earlier Path to Thorium Through Its Existing PHWR Fleet

India’s long-standing ambition to convert its extensive thorium resources into a major source of nuclear energy is beginning to acquire an additional pathway. Alongside the country’s established three-stage nuclear programme, attention is increasingly turning towards whether thorium-bearing fuels can be introduced much earlier through India’s already mature fleet of Pressurised Heavy Water Reactors.

The idea has been strongly advocated by Dr Anil Kakodkar, former Chairman of the Atomic Energy Commission and one of the principal architects of India’s indigenous nuclear reactor programme. Speaking at the 6th International Climate Summit on 2 September 2026, Kakodkar argued that India should use the expanding PHWR fleet to begin irradiating thorium rather than waiting entirely for large-scale deployment of the third stage of the nuclear programme.

His proposal does not replace India’s three-stage nuclear strategy. Instead, it seeks to create an additional route through which India could begin accumulating experience with thorium fuel, recycling technologies and uranium-233 production while the fast breeder programme continues to mature.

Why Thorium Matters to India

India’s nuclear programme was designed around a fundamental resource imbalance. The country possesses relatively modest uranium resources but very large reserves of thorium-bearing minerals, particularly monazite associated with coastal mineral sands.

Thorium-232, however, is not itself a fissile material capable of sustaining the type of chain reaction used for conventional nuclear power generation. It must first absorb a neutron and eventually transform into uranium-233, which can then serve as nuclear fuel.

This challenge shaped India’s three-stage nuclear programme conceived under Dr Homi Bhabha. The first stage uses indigenous PHWRs primarily fuelled by natural uranium. The second stage employs fast breeder reactors to use plutonium recovered from spent PHWR fuel while producing additional fissile material. The third stage is intended to make extensive use of thorium and uranium-233.

The Department of Atomic Energy continues to describe large-scale thorium utilisation as one of the central objectives of this programme.

PHWRs Could Provide an Earlier Entry Point

Kakodkar’s argument centres on one of India’s strongest nuclear capabilities: the indigenous PHWR.

India has accumulated decades of experience designing, constructing and operating this reactor technology. The country has progressed from 220 MWe units to 540 MWe reactors and subsequently to the indigenous 700 MWe PHWR design now forming an important part of future nuclear capacity expansion.

Instead of treating thorium utilisation exclusively as the final stage of the programme, Kakodkar has proposed using this increasingly large reactor base to irradiate thorium-bearing fuel much earlier.

The approach would allow India to begin developing the supporting fuel-cycle technologies needed for future thorium deployment while continuing conventional nuclear generation from PHWRs.

The reactor itself is particularly suited to such experimentation because PHWRs provide good neutron economy and allow fuel channels to be refuelled while the reactor remains operating.

HALEU-Thorium Fuel Offers Another Possibility

One pathway receiving particular attention combines thorium with High-Assay Low-Enriched Uranium, commonly known as HALEU.

Kakodkar has previously argued that HALEU-thorium fuel could potentially be introduced into PHWRs without requiring fundamental changes to the reactor design. Such fuel configurations could support higher fuel burn-up while simultaneously exposing thorium to neutron irradiation.

The concept has moved beyond academic discussion.

In a Parliamentary reply issued on 11 February 2026, the Department of Atomic Energy confirmed that NTPC and Clean Core Thorium Energy were exploring the development and deployment of ANEEL, a thorium-based fuel intended for PHWRs in India.

Any deployment remains subject to approval by the respective governments and India’s prevailing nuclear laws and regulatory framework.

DAE also made clear that natural uranium oxide fuel will continue to be used in India’s existing PHWR fleet as part of the established three-stage programme.

The exploration of ANEEL therefore represents a potential supplementary fuel pathway rather than a replacement for India’s present PHWR fuel cycle.

India’s Existing Nuclear Strategy Remains Unchanged

The significance of Kakodkar’s proposal lies partly in the distinction between accelerating thorium research and altering India’s nuclear strategy.

The government has not announced the abandonment or restructuring of the three-stage nuclear programme. Official policy continues to regard that programme as the foundation for India’s long-term nuclear fuel security.

Under the existing sequence, spent fuel from PHWRs is reprocessed to recover valuable fissile material. That material supports the fast breeder programme, which in turn is intended to generate the fissile inventory required for eventual large-scale thorium utilisation.

India’s closed fuel cycle is therefore central to the entire strategy.

The Department of Atomic Energy has repeatedly emphasised that spent nuclear fuel is treated as a resource rather than simply as waste because valuable uranium and plutonium can be recovered and reused.

Fast Breeder Reactor Marks a Major Step Towards Thorium

India reached an important milestone in this strategy when the 500 MWe Prototype Fast Breeder Reactor at Kalpakkam achieved first criticality on 6 April 2026.

The PFBR represents the transition towards the second stage of India’s nuclear programme.

The reactor initially uses uranium-plutonium mixed oxide fuel. A surrounding blanket containing uranium-238 allows fast neutrons to produce additional plutonium-239.

Its design also provides for the eventual use of thorium-232 in the blanket. Neutron irradiation can convert thorium into uranium-233, creating the fissile material needed for the third stage.

The Department of Atomic Energy describes the fast breeder programme as the bridge connecting India’s PHWR fleet with future thorium-based reactors.

Kakodkar’s proposal effectively asks whether another bridge can operate in parallel: using the PHWR fleet itself to begin irradiating thorium before fast breeders are deployed on a much larger scale.

Thorium Research Is Already Continuing Inside BARC

India is also pursuing several reactor and fuel-cycle technologies specifically intended for thorium.

BARC has conducted extensive work on the Advanced Heavy Water Reactor, designed to demonstrate large-scale utilisation of thorium while incorporating passive safety systems.

The AHWR concept was closely associated with Kakodkar’s tenure at BARC and the Atomic Energy Commission. The design is intended to derive a substantial proportion of its energy from thorium.

Research has also expanded into molten salt reactor technology.

In its Republic Day 2026 review, the Department of Atomic Energy reported that BARC’s Critical Facility had been used for specialised criticality experiments involving molten-salt reactor fuel salts at different core locations as part of India’s continuing efforts towards thorium utilisation.

DAE has separately stated that molten salt breeder reactors are being considered as one possible technology for the thorium-based third stage, although the technology still requires considerable development before commercial deployment.

The Importance of Fuel Recycling

Simply placing thorium inside a reactor is not enough to establish a thorium economy.

A complete fuel cycle must be created around it.

Thorium-232 exposed to neutrons eventually produces uranium-233. That fissile material must then be recovered, fabricated into new fuel and returned to reactors.

This requires specialised reprocessing and fuel-manufacturing technologies.

India has therefore placed considerable emphasis on developing a closed nuclear fuel cycle. Kakodkar has also stressed that thorium deployment must be accompanied by improvements in high-burn-up fuels and technologies capable of recovering and recycling material from thorium-bearing fuel.

Without these capabilities, the strategic advantage of India’s thorium resources cannot be fully realised.

Uranium Availability Adds Urgency

Another consideration behind the proposal is the rapid worldwide expansion being planned for nuclear power.

Several countries are extending reactor lifetimes, restarting nuclear programmes or planning new reactors as they seek reliable low-carbon electricity.

This is expected to increase long-term demand for uranium.

India has substantially expanded its domestic uranium resource base and can also import uranium under international civil nuclear cooperation agreements. Nevertheless, the strategic objective of India’s nuclear programme has always been to minimise long-term dependence on external fuel supplies.

Thorium offers a potential route towards that objective because India’s indigenous resources are considerably larger.

Using PHWRs to develop thorium fuel-cycle experience earlier could therefore provide India with greater flexibility if international uranium markets become increasingly constrained.

A Parallel Route Rather Than a Shortcut

The emerging thorium discussion should not be interpreted as India skipping directly from PHWRs to a thorium economy.

Producing electricity from thorium on a large and self-sustaining scale remains technically demanding.

Fast breeder reactors, uranium-233 production, remote fuel fabrication, reprocessing technologies and advanced reactor designs remain essential elements of the programme.

What has changed is the scale of India’s PHWR infrastructure.

With a much larger indigenous reactor fleet planned over the coming decades, those reactors could potentially perform two roles: generating electricity and simultaneously helping develop the fissile inventory and technical experience required for India’s eventual thorium transition.

That possibility did not exist on the same scale when the original three-stage strategy was formulated.

India’s Long Nuclear Road Leads Towards Thorium

India’s pursuit of thorium is one of the longest-running technological programmes in the country’s energy sector.

PHWR development created the indigenous reactor base. Reprocessing established the foundations of the closed fuel cycle. The Prototype Fast Breeder Reactor has now brought India into the second stage of the programme, while BARC continues work on advanced reactors and thorium fuel technologies.

Introducing thorium-bearing fuel into PHWRs could add another dimension to this strategy.

For the moment, it remains an area of technological exploration rather than a government decision to convert India’s reactor fleet to thorium fuel. Yet the official confirmation that thorium-based ANEEL fuel is being examined for Indian PHWRs demonstrates that the concept has progressed beyond theory.

India’s ultimate objective remains unchanged: transforming its large domestic thorium resources into a dependable source of nuclear energy capable of supporting the country for generations.

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References

Department of Atomic Energy / Press Information Bureau — Parliamentary Question: Deployment of ANEEL, 11 February 2026
https://www.pib.gov.in/PressReleasePage.aspx?PRID=2226337

Department of Atomic Energy / PIB — Parliamentary Question: Thorium-Based Power Projects, 11 March 2026
https://www.pib.gov.in/PressReleasePage.aspx?PRID=2238298

Department of Atomic Energy — Prototype Fast Breeder Reactor at Kalpakkam Attains First Criticality, April 2026
https://dae.gov.in/prototype-fast-breeder-reactor-at-kalpakkam-tamil-nadu-attains-first-criticality/

Department of Atomic Energy — Republic Day 2026 Address by Chairman, Atomic Energy Commission and Secretary, DAE
https://dae.gov.in/republic-day-2026-address-by-chairman-aec-secretary-dae/

Bhabha Atomic Research Centre — Profile of Dr Anil Kakodkar
https://barc.gov.in/leaders/

Bhabha Atomic Research Centre Newsletter — Interview with Dr Anil Kakodkar on HALEU-Thorium Fuel and PHWRs
https://www.barc.gov.in/barc_nl/2021/2021010209.pdf

Department of Atomic Energy — Nuclear Power: Myths and Facts / India’s Closed Fuel Cycle
https://dae.gov.in/nuclear-power-myths-and-facts/

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