Experts clash over HALEU-Th fuel for Indian nuclear reactors

Experts clash over HALEU-Th fuel for Indian nuclear reactors Premium

A January report in the journal Current Science authored by scientists at the Bhabha Atomic Research Centre (BARC) has turned radioactive with one of India’s leading nuclear scientists characterising the conclusions of the report as “misleading.”

The study compared the relative merits of different mixes of nuclear-power-grade uranium and concluded that a mix of concentrated uranium-235 and thorium, called HALEU-Th, was “unsuitable” for India’s current fleet of reactors and “undesirable” for how India’s three-stage nuclear programme is envisioned.

The assessment drew an incensed reaction from the Chicago-based company Clean Core Thorium Energy (CCTE). Led by Indian-origin entrepreneur Mehul Shah, the company has prepared a HaALEU-Th mix called ‘ANEEL’, short for “Advanced Nuclear Energy for Enriched Life”.

In August 2025, CCTE reported a significant burn-up – a marker of the energy output of nuclear fuel – at the Advanced Test Reactor at the U.S. Department of Energy’s Idaho National Laboratory. The test was timed with the passage of the SHANTI Act 2025 in India’s Parliament, which opened the country’s nuclear power sector to foreign and private sector participation. CCTE then entered an agreement with India’s NTPC to “explore” the use of ANEEL in reactors in India. (NTPC and the Nuclear Power Corporation of India have a prior agreement to jointly operate nuclear power plants.)

Mr. Shah told The Hindu that despite an authorisation from the U.S. Department of Energy to transfer ANEEL fuel technology to India and an agreement following” assurances” provided by India’s nuclear authorities, the “next steps” haven’t taken off. This means testing it in India.

The study in Current Science involved modelling the fuel core of the pressurised heavy water reactor (PHWR) with three fuel combinations:

(i) Natural uranium: 7 kg of uranium-235 and 993 kg U-238);

(ii) HALEU-Th: 32 kg of U-235, 129 kg of U-239, and 839 kg of thorium; and

(iii) Slightly enriched uranium: 11 kg of U-235 and 989 kg of U-238.

U-235 can sustain a chain reaction; U-238 and thorium mainly act as fertile materials that breed fissile fuel. For instance, thorium-232 can absorb a neutron to become U-233, which then undergoes fission.

Nuclear reactors around the world use uranium enriched, i.e. processed to contain a higher concentration of U-235, to a maximum of 4%. Anything higher (5%-20%) is called HALEU, short for “high assay low enriched uranium”. For the purpose of producing energy, no country can enrich uranium beyond 20% as that will render the fuel weapons-grade, which is restricted by non-proliferation agreements.

While India has limited reserves of U-238 and imports nearly all its requirements, it has since the 1950s planned its nuclear programme on being able to eventually harness its vast reserves of thorium.

In their simulation, the BARC scientists found the HALEU-Th combination yielded the highest burn-up of 50 gigawatt-days per tonne (GWd/t) while generating the least amount of spent fuel, a.k.a. radioactive waste: only 14% of what current reactors produce.

While the U.S. considers spent fuel to be radioactive waste and carefully stows it away, India reprocesses its spent fuel to extract plutonium and uranium to prepare mixed oxide fuels.

The study also said, however, that using HALEU-Th could require significantly changing the design of India’s reactors because it also rendered the shutdown rods — a system used to rapidly stop nuclear reactions during an emergency — around 26% less effective. So, it concluded, “HALEU-Th fuel is far from a ‘drop-in’ option for the present generation of PHWRs.”

To Anil Kakodkar, former chairman of the Department of Atomic Energy and member of the Atomic Energy Commission (AEC), such a conclusion doesn’t follow from the results.

“The HALEU-Th actually gives you an advantage. Spent fuel will come down, meaning fewer storage needs and reduced recycling costs,” he told The Hindu. He holds the view that India’s current PHWRs, of 700 MWe capacity, require “no modification” and the 220-MWe reactors require “negligible” modification. “They [the study authors] are not understanding this... The conclusions are misleading ” he added.

His reaction was milder than a letter from Prof. Koroush Shirvan, of the Department of Nuclear Science and Engineering, Massachusetts Institute of Technology (MIT), to Current Science S.K. Satheesh asking that the journal “withdraw” the study due to “serious and numerous technical flaws present in the article.”

The nub of his argument was that the paper lacked “even a methods section” on how the authors analysed the reactor core. He also said the numbers that the authors presented didn’t match the values obtained by the authors, were not available anywhere online, and were not based on core-level analysis.

“I have been supporting Clean Core since 2016 as the head of their fuel design through my consulting privileges at MIT,” Prof. Shirvan wrote in an email to The Hindu. After Mr. Shah asked for his opinion on the paper, he said he found the article to be a bit out of context, since HALEU-thorium fuel is not meant for reprocessing, so to compare it to more reprocessing friendly fuel forms is quite misleading.”

Mr. Satheesh, the editor, told The Hindu that the journal had considered Prof. Shirvan’s comments, had co-consulted with a “senior expert” on the topic, and decided to not publish his comments nor withdraw the paper. Dr Singh, the lead author of the study, also said Prof. Shirvan’s comments had “no relevance to the main outcome of our study” and that he and his co-authors “stood firm” on the scientific findings.

Dr. Kakodkar however said that given the performance of the HALEU-Th mix in U.S. labs and India’s ambition to have 100 GW of nuclear energy by 2047, the country should move to “test” the fuel: “Now that we have the SHANTI agreement, why can’t we use it for a bilateral collaboration?”

“A time will come when Indian demand for uranium will become a significant fraction of global uranium demand. The CCTE group has … reached a target burnup of 60GWd/t MW,” he added. “It took only 20 months. There is no irradiation facility here in India. Our burnup tests are small. … In the U.S. they have used a reactor which is designed in that way for higher power. This development needs collaboration. … What is the harm in trying it out?”

Mr. Shah said he considered Dr. Kakodkar “a mentor”; the name ‘ANEEL’ is an homage. Dr. Kakodkar also said he had no ‘stake’ in CCTE: “I’m retired but I consider it my mission that India should use thorium soon.”

However, AEC member and former BARC scientist Ravi Grover supported the study’s conclusions, saying the computer simulations it used were standard practice and that the group comprised experts in computing various optimal scenarios regarding the use of thorium.

“We already use thorium in our experimental reactors. These simulations are faithful to real world situations, so if the results say one thing, why should we at this stage conduct these (thorium) tests?” Dr. Grover told The Hindu. “India has a well thought-out plan that involves using thorium once enough fissile plutonium had been produced from its fast breeder reactors.”

R. Srikanth, an analyst of India’s nuclear programme at the National Institute of Advanced Studies, Bengaluru, said HALEU-Th has emerged just as India is set to commission its first 500-MWe sodium-cooled fast breeder reactor, in Kalpakkam, marking the start of the second stage of its nuclear power programme. The plutonium generated in such reactors will finally open the door to the third stage, where advanced heavy water reactors will use plutonium alongside thorium, thus freeing India from using imported uranium.

“This has been the plan all along. HALEU is commercially limited and expensive. Why should India replace its current import dependence on uranium with another dependence (HALEU)?,” Dr. Srikanth added, “Everything should be tested but we are at a delicate stage today and must allow our programme to unfold in its natural course. To advocate for the use of thorium in our current PHWR, seems like a distraction.”

jacob.koshy@thehindu.co.in

Published - March 13, 2026 09:00 am IST

Source: TheHindu
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