In a milestone that slipped past much of the mainstream press, the Department of Atomic Energy has inaugurated the world’s first hydrogen production facility driven by a copper–chlorine thermochemical cycle running on nuclear process heat — recasting the atom as more than a source of electricity.
On June 26, 2026, on the leafy, heavily guarded campus of the Indira Gandhi Centre for Atomic Research (IGCAR) on India’s Coromandel coast, a modest industrial plant quietly rewrote the history of clean energy. Dr. Ajit Kumar Mohanty, Secretary of the Department of Atomic Energy (DAE) and Chairman of the Atomic Energy Commission, inaugurated what no other nation has yet built: a hydrogen production facility based on the copper–chlorine (Cu–Cl) thermochemical cycle, fed directly by nuclear process heat drawn from the Fast Breeder Test Reactor (FBTR).
The event, formally announced by the DAE on June 29, marks the first time anywhere in the world that this particular chemistry — long studied in laboratories from Canada to Japan — has been coupled to an operating nuclear reactor.
IGCAR Director Sreekumar G. Pillai was present at the inauguration, capping a joint development effort between IGCAR and the Bhabha Atomic Research Centre (BARC) in Mumbai, where the Cu–Cl process was developed indigenously over years of research.
“The integration of nuclear energy with emerging clean energy technologies such as hydrogen production represents a strategic pathway towards a sustainable energy future,” Dr. Mohanty said at the ceremony. “Nuclear power, with its unique ability to provide reliable carbon-free electricity as well as high-temperature process heat, is ideally suited to support large-scale hydrogen production while contributing to India’s energy security, decarbonization goals and long-term sustainable development objectives.”
THE THIRD WAY TO MAKE HYDROGEN
To grasp why Kalpakkam matters, consider how the world makes hydrogen today. Roughly 95 million tonnes are produced annually, and the overwhelming bulk is “grey” hydrogen stripped from natural gas by steam-methane reforming — a process that belches out some 9–11 kg of carbon dioxide for every kilogram of hydrogen.
The cleaner alternative, electrolysis, splits water with electricity; when that electricity is renewable the product is “green,” and when it is nuclear the industry calls it “pink.” But electrolysis is power-hungry, and converting reactor heat into electricity only to convert it back into chemical energy wastes a large fraction of the energy along the way.
The Kalpakkam plant takes a third path: thermochemical water splitting, in which high-temperature heat drives a looping chain of chemical reactions that tear water molecules apart directly. Skipping the heat-to-electricity detour saves energy and lifts overall efficiency.
The chemistry works like a molecular relay race. Solid copper(II) chloride meets superheated steam at roughly 400°C, yielding copper oxychloride and hydrogen chloride gas. The oxychloride is then heated to about 500°C — the cycle’s hottest step — where it decomposes, releasing oxygen and leaving molten copper(I) chloride. That copper(I) chloride feeds a low-voltage electrolysis cell, running at just 0.5–1.0 volts compared with the 1.23 volts or more demanded by conventional water electrolysis, which releases hydrogen gas while regenerating copper(II) chloride. A final drying step closes the loop.
The net reaction is elegantly simple: water in, hydrogen and oxygen out. Every other chemical is recycled indefinitely.
The Cu–Cl cycle’s great virtue is its modest appetite for heat. Its maximum temperature of around 500–530°C is far below the 850°C-plus demanded by its chief rival, the sulfur–iodine cycle, and it slots comfortably within the reach of sodium-cooled fast reactors — precisely what Kalpakkam operates.
Estimated overall efficiencies range from about 41 to 49 percent depending on configuration, making it one of the most promising thermochemical routes under study worldwide.
A FORTY-YEAR-OLD REACTOR’S NEW TRICK
The heat source is itself a national treasure. The FBTR, a sodium-cooled fast reactor rated at 40 MW thermal and 13.2 MW electric, achieved first criticality in October 1985 and has served for more than four decades as the workhorse of India’s fast reactor programme — the testbed for fuels, materials and sodium technologies that underpin the 500 MWe Prototype Fast Breeder Reactor now in advanced commissioning nearby. It remains India’s only operating fast reactor, and its coolant temperatures are a natural match for the Cu–Cl cycle’s requirements.
“This achievement builds upon more than four decades of operational experience and technological excellence gained through the Fast Breeder Test Reactor programme at IGCAR,” Dr. Pillai said. “The successful demonstration of hydrogen production using nuclear process heat showcases the versatility of advanced nuclear systems.”
STRATEGY, NOT JUST SCIENCE
The facility is, officials are careful to stress, a technology demonstrator — built to validate the process, gather operating data and pave the way for commercial-scale plants, not to flood the market with hydrogen.
Yet its strategic weight is considerable. It advances India’s three-stage nuclear power programme by giving fast reactors a non-electric, industrial mission for the first time, and it dovetails with the National Green Hydrogen Mission, approved by the Union Cabinet in January 2023 with an outlay of Rs 19,744 crore. That mission targets at least 5 million metric tonnes of annual green hydrogen production capacity by 2030, backed by about 125 GW of new renewable capacity, over Rs 8 lakh crore in investment and nearly 50 million tonnes of avoided CO2 emissions per year.
Nuclear-heat hydrogen — continuous, weather-independent and carbon-free — offers a firm backbone that solar- and wind-powered electrolysers, by their intermittent nature, cannot.
The applications read like a decarbonisation wish-list: green ammonia for fertiliser, hydrogen for steel and refining, fuel for heavy transport and shipping, and storage for a renewables-heavy grid.
INDIA IN THE GLOBAL RACE
India is not alone in chasing nuclear hydrogen, but it has seized a specific crown. Japan’s Atomic Energy Agency has pursued the sulfur–iodine cycle at its High Temperature Engineering Test Reactor, demonstrating 150 hours of continuous hydrogen production in January 2019, and aims for cost-competitive production around 2030 — but at far higher temperatures, and still short of an integrated plant.
Atomic Energy of Canada Limited pioneered the CuCl electrolyser concept at bench scale, and the Generation IV International Forum lists the Cu–Cl cycle among its priority thermochemical routes.
What nobody had done, until now, was bolt the full copper–chlorine loop onto a live reactor. BARC’s published roadmap envisages staged scale-up from bench-scale units producing 10–50 normal litres per hour toward 150 NL/h and 3 Nm³/h demonstration trains — a ladder the Kalpakkam plant will now help climb.
HARD PROBLEMS REMAIN
Scepticism is warranted on one front: the path from demonstrator to factory is littered with engineering thorns. Hot hydrogen chloride and chlorine-bearing vapours are ferociously corrosive; moving solid copper salts between reaction stages is mechanically tricky; and heat must be recovered and recycled between steps with miserly precision to hit the promised efficiencies.
The Kalpakkam plant’s real product, in its first years, will be exactly this knowledge — operational hours, materials performance and process data that no laboratory bench can supply.
Still, the symbolism is hard to miss. Forty years after the FBTR first went critical, the same reactor that taught India how to breed fuel is now teaching it how to make fuel of a different kind. In the global contest to produce clean hydrogen at scale, a 40-megawatt test reactor on the Bay of Bengal has just moved India to the front of one very consequential pack.
– C Natarajan
