Experts Clash Over HALEU-Thorium Fuel, A Scientific Debate with High Stakes for India’s Nuclear Future
A seemingly technical report in a scientific journal has ignited a fierce and highly public debate among India’s top nuclear scientists, exposing deep divisions over the country’s future energy path. The January 2026 report, published in the journal Current Science by a team of scientists at the Bhabha Atomic Research Centre (BARC), assessed the viability of using a novel nuclear fuel called HALEU-thorium in India’s existing fleet of reactors. Its conclusion was stark: the fuel was “unsuitable” and far from being a “drop-in” option. This assessment has drawn an incensed reaction from an Indian-origin entrepreneur’s Chicago-based company, a stinging rebuke from a former chairman of India’s Atomic Energy Commission, and a request from an MIT professor to have the paper withdrawn. At the heart of the controversy lies a fundamental question: how should India navigate its ambitious nuclear energy goals, balancing scientific caution with the promise of new technology?
The fuel in question is HALEU-Th, a mix of High-Assay Low-Enriched Uranium (HALEU) and thorium. HALEU is uranium enriched to between 5% and 20% of the fissile isotope U-235, a higher concentration than the 3-5% used in most current reactors. The company at the center of the debate is Clean Core Thorium Energy (CCTE), led by Chicago-based entrepreneur Mehul Shah. CCTE has developed a proprietary HALEU-Th fuel called ‘ANEEL’ (a homage to former Atomic Energy Commission chairman Anil Kakodkar). In August 2025, CCTE reported a significant “burn-up”—a key measure of a fuel’s energy output—during tests at a U.S. Department of Energy reactor. Following this success, the company entered into an agreement with India’s NTPC to “explore” the use of ANEEL in Indian reactors.
The Current Science study, led by BARC scientist K.P. Singh, modelled the performance of India’s workhorse Pressurized Heavy Water Reactors (PHWRs) using three different fuel combinations: natural uranium, slightly enriched uranium, and the HALEU-Th mix. The simulation produced results that, on the surface, seemed to favour the new fuel. The HALEU-Th combination yielded the highest burn-up, a remarkable 50 gigawatts per tonne, while generating the least amount of radioactive waste—only 14% of what current reactors produce. These are significant advantages. Higher burn-up means more energy from less fuel, and less waste is a major environmental and disposal benefit.
However, the study also uncovered a critical safety concern. It found that using HALEU-Th could render the reactor’s shutdown rods—the emergency systems designed to rapidly halt a nuclear chain reaction—around 26% less effective. This is a non-negotiable safety parameter. If the rods cannot quickly stop the reaction, the risk of a runaway event increases. Based on this finding, the study concluded that HALEU-Th is far from being a simple, “drop-in” replacement fuel for India’s current generation of PHWRs and would likely require significant design modifications.
This conclusion has not gone unchallenged. Anil Kakodkar, a towering figure in Indian nuclear science and a former chairman of the Department of Atomic Energy, has been the most prominent and forceful critic. He dismisses the study’s conclusions as “misleading.” According to Dr. Kakodkar, the impact on shutdown rod effectiveness is manageable. He argues that India’s current 700 MWe PHWRs would require “no modification” to use the fuel, while the older 220 MWe variants would need only “negligible” changes. He believes the study authors have fundamentally misunderstood the engineering flexibility of India’s reactors. Given the fuel’s promising performance in U.S. labs and India’s ambitious goal of generating 100 GW of nuclear power by 2047, Dr. Kakodkar has urged the country to move forward with testing the fuel. He points to the existing SHANTI agreement between India and the US as a potential framework for bilateral collaboration on this front. Mehul Shah of CCTE has publicly acknowledged Dr. Kakodkar as a “mentor,” adding a personal dimension to the scientific debate.
The controversy escalated further with an intervention from MIT Professor Koroush Shirvan, who has been involved with CCTE’s fuel design since 2016. Prof. Shirvan wrote a letter to the editor of Current Science requesting the journal to “withdraw” the study, citing “serious and numerous technical flaws.” He argued that the study’s comparison was unfair, as HALEU-Th fuel is not designed for the reprocessing cycle that is central to India’s traditional nuclear strategy, making the comparison “quite misleading.”
The journal, however, has stood its ground. Editor S.K. Satheesh stated that the editorial board had considered the comments, consulted with a “senior expert” on the topic, and declined both to publish Prof. Shirvan’s critique and to withdraw the paper. Lead author K.P. Singh also pushed back, stating that Prof. Shirvan’s comments “have no relevance to the main outcome of our study,” implying that the core safety finding about shutdown rods remains valid regardless of the fuel’s intended use.
This scientific dispute has also drawn in other key voices from India’s nuclear establishment, revealing a clear fault line. Ravi Grover, a member of the Atomic Energy Commission and a former BARC scientist, has sided with the study. He argues that the simulations are faithful to real-world conditions, and if they indicate a problem, there is no justification for proceeding with tests at this stage.
On the other side, R. Srikanth, an analyst of India’s nuclear programme at the National Institute of Advanced Studies, Bengaluru, raises a strategic concern. He points out that the HALEU-Th debate comes at a critical juncture, just as India is set to commission its first 500 MWe Prototype Fast Breeder Reactor (PFBR) in Kalpakkam. This reactor marks the start of the crucial second stage of India’s three-stage nuclear programme, which is designed to generate plutonium that will eventually fuel thorium-based reactors in the third stage. The ultimate goal of this decades-long strategy is to free India from its dependence on imported uranium by tapping into its vast domestic thorium reserves.
Srikanth’s question is pointed: HALEU is a commercially limited and expensive fuel that would have to be imported, primarily from the US or Russia. “Why should India replace its current import dependence on uranium with another dependence (on HALEU)?” he asks. He argues that while all technologies should be tested, the country is at a “delicate stage” and must allow its indigenous, three-stage programme to unfold in its “natural course.” To advocate for using thorium in current PHWRs, he suggests, is a “distraction” from the main, long-term strategy.
The debate over HALEU-Th is thus far more than a technical squabble. It encapsulates a fundamental strategic choice. On one hand is the promise of a new, efficient, and potentially game-changing fuel that could boost the performance of existing reactors and reduce waste, with vocal advocates arguing it is safe and ready for testing. On the other is a deeply ingrained scientific caution, a commitment to the indigenous three-stage programme that has guided India’s nuclear ambitions for decades, and a concern about swapping one form of import dependence for another. The outcome of this debate, and the decisions made by policymakers in response to it, will have profound implications for India’s energy security and its long journey towards technological self-reliance.
Questions and Answers
Q1: What is HALEU-Th fuel, and what are its potential advantages according to its proponents?
A1: HALEU-Th is a mix of High-Assay Low-Enriched Uranium (HALEU) and thorium. Proponents, like CCTE, claim it can achieve a much higher “burn-up” (energy output) and generate significantly less radioactive waste (only 14% of current levels) compared to traditional fuels.
Q2: What was the main safety concern raised by the BARC study regarding the use of HALEU-Th in India’s current PHWRs?
A2: The BARC study’s simulation found that using HALEU-Th could render the reactor’s shutdown rods—the emergency system used to rapidly halt a nuclear reaction—around 26% less effective. This critical safety concern led them to conclude the fuel was “unsuitable” for India’s current fleet of reactors without significant design modifications.
Q3: Who is Dr. Anil Kakodkar, and what is his counter-argument to the BARC study?
A3: Dr. Anil Kakodkar is a former chairman of India’s Atomic Energy Commission and a highly respected figure. He called the study’s conclusions “misleading,” arguing that the impact on shutdown rods is manageable. He stated that 700 MWe reactors need “no modification” and 220 MWe reactors only “negligible” changes, and urged India to test the fuel given its promising performance in US labs.
Q4: What is the “three-stage nuclear programme,” and why is its current phase relevant to this debate?
A4: India’s three-stage programme is a long-term strategy to ultimately use its vast domestic thorium reserves for energy, freeing it from reliance on imported uranium. The current, delicate stage involves commissioning the 500 MWe Prototype Fast Breeder Reactor (PFBR) to generate plutonium for future thorium reactors. Critics argue that introducing HALEU-Th now could distract from this indigenous path and create a new import dependence.
Q5: What is the core strategic dilemma at the heart of this scientific debate?
A5: The dilemma is between two paths: embracing a promising new technology (HALEU-Th) that could boost efficiency now, versus staying the course on a decades-old, indigenous strategy designed for long-term self-reliance. The debate pits potential short-term gains against the goal of complete energy independence, and questions whether importing HALEU is any better than importing uranium.
