On 26 June 2026, the Department of Atomic Energy (DAE) inaugurated the world's first hydrogen-production facility based on the Copper–Chlorine (Cu–Cl) thermochemical cycle, run on nuclear process heat from the Fast Breeder Test Reactor (FBTR) at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam. The Cu–Cl technology itself was developed indigenously by BARC, Mumbai, and demonstrated jointly with IGCAR. For an aspirant, the headline is not really "another nuclear milestone" — it is that nuclear energy has now been used to make clean hydrogen, and that puts the spotlight squarely on the hydrogen economy, one of the freshest and most examinable themes in NDA/CDS science and current affairs. This article keeps the nuclear link brief and focuses on what hydrogen as a fuel is, how it is produced, what the "colour" labels mean, and where the National Green Hydrogen Mission fits.
Hydrogen as a fuel: why the world is excited
Hydrogen is the lightest and most abundant element in the universe, sitting first in the periodic table with atomic number 1. On Earth, though, it almost never occurs free — it is locked up in water (H₂O), in hydrocarbons and in living matter — so it has to be produced by splitting those molecules. That single fact shapes everything about the hydrogen economy: hydrogen is not a primary fuel you dig out of the ground like coal or gas, but an energy carrier you manufacture using some other energy source, much like electricity.
Why bother? Because hydrogen has remarkable fuel properties:
- Very high calorific value — by mass, hydrogen carries about three times the energy of petrol or diesel (roughly 120–142 MJ/kg). Per unit weight, no chemical fuel beats it.
- Clean combustion — when hydrogen burns in oxygen, the only product is water (2H₂ + O₂ → 2H₂O). There is no carbon dioxide, no soot, no sulphur at the point of use. This is the property that makes it central to decarbonisation.
- Versatility — it can be burned directly, or fed to a fuel cell that converts its chemical energy straight into electricity (again, with water as the only emission).
The catch is that hydrogen is only as "clean" as the energy used to make it. Burning hydrogen emits nothing harmful, but if you produced that hydrogen by burning coal or gas, you have simply moved the pollution upstream. That is exactly why the world has developed a colour code for hydrogen — to label how it was made.
The colour code of hydrogen
The colours are not about the gas (hydrogen is colourless and odourless); they are a shorthand for the production route and its carbon footprint. The high-yield ones for NDA:
- Grey hydrogen — made from natural gas by steam methane reforming (SMR). It is the cheapest and most common method today, but it releases CO₂ into the atmosphere. Most of the world's hydrogen is currently grey.
- Blue hydrogen — the same fossil-fuel route as grey, but with carbon capture and storage (CCS) so the CO₂ is trapped rather than released. Lower-carbon, but still based on fossil fuel.
- Green hydrogen — produced by the electrolysis of water using electricity from renewable sources (solar, wind, hydro). No CO₂ at any stage. This is the gold standard and the target of India's flagship mission.
- Pink hydrogen — produced by the electrolysis of water using electricity from a nuclear power plant. Carbon-free, because nuclear electricity is carbon-free. (Closely related labels — purple and red — also denote nuclear routes; red/purple specifically refer to using nuclear heat for high-temperature thermochemical splitting, which is essentially what Kalpakkam's Cu–Cl plant does.)
- Turquoise hydrogen — from methane pyrolysis, which splits natural gas into hydrogen and solid carbon (not CO₂ gas).
The single testable idea: the colour tells you the source of energy and whether carbon was emitted. Grey and blue are fossil-based; green is renewable-electrolysis; pink (and red/purple) is nuclear. The Kalpakkam facility is, in essence, India demonstrating a nuclear (pink/red-family) hydrogen pathway. If you are keeping up with the daily NDA current affairs science set, hydrogen colours are exactly the kind of crisp, factual item examiners love.
How hydrogen is actually produced
Three broad families of methods matter for the exam:
1. Steam Methane Reforming (SMR). Methane (CH₄) is reacted with high-temperature steam over a catalyst: CH₄ + H₂O → CO + 3H₂, followed by a water-gas shift to extract more hydrogen. It is mature and cheap but fossil-fuel based and CO₂-emitting — this is how grey/blue hydrogen is made.
2. Electrolysis of water. An electric current is passed through water, splitting it into hydrogen at the cathode and oxygen at the anode (2H₂O → 2H₂ + O₂). Electrolysis is only as clean as the electricity driving it: powered by renewables it gives green hydrogen; powered by a nuclear plant it gives pink hydrogen. Its drawback is that it is energy-intensive and currently expensive.
3. Thermochemical water-splitting cycles — the family the Kalpakkam plant belongs to. Instead of electricity, these use heat to drive a sequence of chemical reactions that, in net effect, split water into hydrogen and oxygen, with all the chemical reagents recycled. The appeal is efficiency: you skip the electricity-generation step (and its losses) and use the heat directly.
It helps to contrast this with direct thermolysis — simply heating water until it decomposes. That works only at extreme temperatures (well above 2,000°C), which is impractical for any real reactor. A thermochemical cycle is the clever workaround: by routing water-splitting through several intermediate reactions involving a recyclable chemical agent, it achieves the same net result at far lower temperatures.
What the Copper–Chlorine (Cu–Cl) cycle does
The Cu–Cl thermochemical cycle uses compounds of copper and chlorine as the recyclable "go-between." Across a series of coupled reactions — combining steam, copper chloride and the products of earlier steps — water is split into hydrogen and oxygen, and the copper and chlorine compounds are regenerated and reused in a closed loop. No copper or chlorine is consumed overall; only water goes in, and hydrogen plus oxygen come out.
The decisive advantage, and the reason DAE and BARC chose it, is temperature. The Cu–Cl cycle runs at a peak of only about 530°C — far below the thousands of degrees that direct thermolysis or many rival cycles (such as the sulphur–iodine cycle) demand. That comparatively modest temperature is precisely what a reactor's process heat can supply, which is what makes nuclear-assisted hydrogen production realistic. The PIB release highlights the cycle's lower operating temperature and higher thermodynamic efficiency as the reasons it is considered one of the most promising routes worldwide.
Why nuclear heat is a clean source
This is where the brief nuclear link comes in. A nuclear reactor produces enormous quantities of high-temperature heat that are normally used to raise steam and spin turbines for electricity. But that heat can also be tapped directly as process heat for industry — a "non-electric application" of nuclear energy. Crucially, this heat is carbon-free: the fission reaction emits no CO₂.
At Kalpakkam, the heat comes from the Fast Breeder Test Reactor (FBTR) — India's only operating fast reactor, run by IGCAR since the 1980s, which pioneered the sodium-cooled fast-reactor technology that underpins the larger Prototype Fast Breeder Reactor (PFBR), the flagship of Stage 2 of India's three-stage nuclear programme. Feeding the FBTR's clean process heat into the Cu–Cl cycle means the resulting hydrogen carries no greenhouse-gas footprint — a genuine carbon-free hydrogen pathway, and a way of expanding nuclear energy's role beyond electricity into clean fuel. (You do not need to re-learn the whole three-stage programme here; for that backbone, see our NDA general-knowledge study material.)
The National Green Hydrogen Mission
The policy frame for all of this is the National Green Hydrogen Mission, approved by the Union Cabinet on 4 January 2023 with an outlay of ₹19,744 crore. Its headline numbers are prime exam fodder:
- Build a green-hydrogen production capacity of at least 5 MMT (million metric tonnes) per year by 2030.
- Add about 125 GW of associated renewable-energy capacity to power the electrolysers.
- Make India a global hub for the production, use and export of green hydrogen and its derivatives.
- Cut roughly ₹1 lakh crore of fossil-fuel imports and avoid a large slice of annual CO₂ emissions by 2030.
Note the subtlety the examiner can exploit: the Mission targets specifically green hydrogen (renewable electrolysis). The Kalpakkam plant is nuclear hydrogen (pink/red-family), not green — but it serves the same national goal of a clean, carbon-free hydrogen economy and broadens the toolkit by which India can reach it.
What hydrogen is used for
Hydrogen is not a laboratory curiosity — it is already a workhorse industrial chemical, and its clean-energy uses are growing fast:
- Fertilizers (ammonia): Hydrogen is the feedstock for ammonia via the Haber–Bosch process, the basis of nitrogenous fertilizers. This is the single largest current use of hydrogen.
- Petroleum refining: Used to remove sulphur from fuels (hydro-desulphurisation) and upgrade crude fractions.
- Steel making: "Green steel" replaces coking coal with hydrogen as the reducing agent, slashing emissions from one of the hardest-to-decarbonise industries.
- Fuel cells and mobility: Hydrogen fuel-cell vehicles, buses and even trains run clean, emitting only water. India is piloting hydrogen buses and fuel-cell trains.
- Energy storage and grid balancing: Surplus renewable power can be stored as hydrogen and reconverted later, smoothing the intermittency of solar and wind.
Because these uses span agriculture, heavy industry, transport and power, hydrogen is often called the "Swiss-army-knife" of decarbonisation — and a country that masters cheap, clean hydrogen gains both energy security and an export edge. These are the strategic and scientific themes serving-officer faculty unpack in the upcoming Cavalier courses in Delhi.
The big picture for an aspirant
Tie the threads together and the news writes its own answer key. Hydrogen is the lightest element, an energy carrier (not a primary fuel), with a very high calorific value and water as its only combustion product. It is made by SMR, electrolysis or thermochemical cycles, and labelled by colour according to the energy source — grey/blue (fossil), green (renewable electrolysis), pink/red (nuclear). India's Cu–Cl thermochemical plant at Kalpakkam uses carbon-free nuclear process heat at a modest ~530°C to split water, demonstrating a nuclear route to clean hydrogen, while the National Green Hydrogen Mission (2023; 5 MMT/year by 2030) sets the national ambition. That is a complete, self-reinforcing fact-set — the kind that, once understood, yields easy marks and a strong SSB lecturette.
🎯 Practice MCQs
Q1. Hydrogen is best described as: (a) a primary fuel mined from the earth (b) an energy carrier that must be produced (c) a fossil fuel (d) a radioactive element → (b) — like electricity, hydrogen is manufactured using another energy source, not extracted directly.
Q2. When hydrogen burns in oxygen, the only product formed is: (a) carbon dioxide (b) carbon monoxide (c) water (d) nitrogen oxides → (c) — 2H₂ + O₂ → 2H₂O, which is why it is a clean fuel at the point of use.
Q3. "Green hydrogen" refers to hydrogen produced by: (a) steam methane reforming (b) electrolysis of water using renewable electricity (c) coal gasification (d) methane pyrolysis → (b) — renewable-powered electrolysis emits no CO₂.
Q4. Hydrogen produced by electrolysis of water using nuclear-plant electricity is conventionally called: (a) blue hydrogen (b) grey hydrogen (c) pink hydrogen (d) turquoise hydrogen → (c) — pink hydrogen uses nuclear electricity; nuclear-heat thermochemical routes are termed red/purple.
Q5. The world's first Copper–Chlorine thermochemical hydrogen plant (June 2026) uses nuclear heat from which reactor at Kalpakkam? (a) PFBR (b) Fast Breeder Test Reactor (FBTR) (c) a PHWR (d) KAMINI → (b) — the FBTR, India's only operating fast reactor, supplied the process heat.
Q6. The chief advantage of the Cu–Cl thermochemical cycle over direct thermolysis of water is that it: (a) needs no water (b) operates at a much lower temperature (~530°C) (c) produces no oxygen (d) requires no energy input → (b) — direct thermolysis needs >2,000°C; the cycle achieves splitting at far lower heat.
Q7. Grey hydrogen is produced mainly by which process? (a) electrolysis (b) steam methane reforming of natural gas (c) thermochemical Cu–Cl cycle (d) methane pyrolysis → (b) — SMR is cheap but emits CO₂, hence the "grey" label.
Q8. Under the National Green Hydrogen Mission (2023), India's target green-hydrogen capacity by 2030 is: (a) 0.5 MMT/year (b) 5 MMT/year (c) 50 MMT/year (d) 125 MMT/year → (b) — 5 million tonnes per year, with about 125 GW of associated renewable capacity.
📋 How this gets asked (PYQ pattern)
Hydrogen is a recurring physics-chemistry crossover in NDA/CDS GK: its place as the lightest element (atomic number 1), its high calorific value, and water as the sole combustion product are textbook one-liners that the examiner converts into single-statement MCQs. Production methods (electrolysis vs steam reforming) and the meaning of fuel cells appear in the energy/environment sets. The genuinely fresh 2026 hook is two-fold: the hydrogen colour code (match the colour to its source — grey = SMR, green = renewable electrolysis, pink/red = nuclear) and the National Green Hydrogen Mission numbers (2023; 5 MMT/year and 125 GW RE by 2030; ₹19,744 crore outlay). Layered on top is the current-affairs needle — the Cu–Cl thermochemical plant at Kalpakkam using FBTR heat (BARC + IGCAR) — which lends itself to "where / which reactor / which technology" framings and to a "non-electric use of nuclear energy" angle. We avoid quoting any specific past-paper question number; the pattern above reflects how the topic has consistently surfaced.
Studying for NDA or CDS? The hydrogen economy is fast becoming guaranteed science-and-environment GK and a ready-made SSB lecturette — easy marks once the fuel properties, colour code and Green Hydrogen Mission targets are clear. Track our daily NDA current affairs and prepare with serving-officer faculty in the upcoming Cavalier courses in Delhi.
✍️ Written by Col D.N. Sharma — Veteran, Indian Army; SSB & defence-studies faculty at The Cavalier. Reviewed by the Cavalier Faculty Desk. The Cavalier, founded by ex-Army officers, has trained NDA/CDS/SSB aspirants since 2001 (Facebook · YouTube).
Source: PIB release, 26 June 2026. Facts cross-verified.