Physicists there say they have finally cracked a challenge that stumped Western programmes in the Cold War: turning thorium, a metal long treated as waste, into usable nuclear fuel inside a working molten-salt reactor.
A tiny reactor with a big claim
The experimental device unveiled by the Shanghai Institute of Applied Physics looks nothing like the concrete domes that dominate nuclear skylines. There are no towering cooling towers, no fuel rods, and no roaring turbines. Instead, researchers circulate a glowing, liquid mixture of hot salts through a closed loop, heated to around 750°C.
In that stream of molten salt, they dissolve thorium. Bathed in a controlled flux of neutrons, the thorium atoms capture neutrons and slowly transform into uranium‑233, a fissile isotope capable of sustaining a chain reaction and releasing energy.
Chinese scientists report the first measured, stable conversion from thorium to uranium‑233 inside an operating molten-salt reactor loop.
The set-up does not yet feed a generator. No electricity flows into the Chinese grid from this experiment. Instead, the achievement lies in proving that the thorium–uranium fuel cycle can be driven inside a real machine, not just in simulations or small test loops. For Beijing, it marks a strategic step towards a nuclear programme that no longer depends on traditional uranium mining and enrichment.
How molten-salt reactors break with convention
A nuclear system without steam pressure
Most commercial reactors today rely on water pushed to extremes. Inside a pressurised water reactor, liquid water is kept at about 150 bar and around 300°C. That calls for thick-walled pressure vessels, extensive safety systems, and meticulous maintenance to avoid leaks and corrosion.
The Shanghai prototype works differently. Here, the fuel and coolant are part of the same liquid mixture: hot, fluoride-based salts that stay liquid over a wide temperature range and operate at normal atmospheric pressure.
In a molten-salt reactor, the core runs at near‑ambient pressure, slashing the risk of high‑pressure explosions or steam-driven failures.
If the system overheats or loses power, gravity and basic physics take over. Designs of this type include a freeze plug or safety valve at the bottom of the loop. When triggered, the molten salt drains into a passively cooled tank, where it spreads out and solidifies. The reaction stops as the geometry of the fuel changes and the salt cools.
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No steam, no high-pressure vessel, and no need for emergency water injection systems. Advocates argue that safety is “built in” through the properties of the fuel and coolant rather than imposed by layers of external hardware.
An old American idea, reborn in Asia
The technology itself is not new. In the 1960s, engineers at the Oak Ridge National Laboratory in the United States built and operated a small molten-salt reactor for several years. It worked reliably and demonstrated many of the same principles that fascinate Chinese engineers today: liquid fuel, low pressure, and the potential to use thorium.
Yet the programme lost out in Washington. Uranium-fuelled water reactors could be adapted to produce plutonium for weapons, something a thorium cycle does poorly. During the nuclear arms race, that drawback outweighed any potential civilian benefits. Funding dried up, and molten-salt designs were shelved.
China has retrieved those dusty blueprints and is trying to turn them into a full industrial chain. The aim is not warheads but energy security. The country already runs one of the world’s fastest-growing fleets of conventional reactors, but it remains dependent on imported uranium and global supply chains.
Thorium: from mining waste to strategic asset
A metal China has in vast quantities
Thorium often turns up as an unwanted by-product in rare-earth mines. For decades, these slightly radioactive residues piled up in tailings ponds and waste dumps. Now they look more like a buried reserve.
A 2025 assessment suggested that the Bayan Obo mining complex in Inner Mongolia alone might hold around a million tonnes of thorium in its residues. Geologists estimate that global thorium resources are roughly twice those of uranium, with large deposits in India, Australia, the United States, Brazil and several other states.
| Country | Uranium reserves (t) | Share of global U | Thorium resources (t) | Share of global Th |
|---|---|---|---|---|
| Australia | 1,744,000 | 29.2% | 595,000 | 4.1% |
| India | 200,000 | 3.3% | 846,000 | 5.8% |
| China | 170,000 | 2.8% | 100,000–1,000,000 | 1–7% |
| United States | n/a | n/a | 595,000 | 4.1% |
| Brazil | n/a | n/a | 632,000 | 4.3% |
| Rest of world | 1,067,000 | 17.9% | 8,158,000 | 55.9% |
Thorium itself is not fissile. On its own, it cannot power a reactor. It acts more like fertile soil: it must be “seeded” with neutrons, typically from an initial charge of uranium or another fissile material, to breed uranium‑233.
For China, the attraction lies in turning what used to be a nuisance into a long-term source of domestic fuel. If the technology scales, Beijing could reduce its reliance on imported uranium and lock in supplies for centuries.
A programme slowly taking shape
China’s molten-salt work sits within a broader initiative known as the TMSR (Thorium Molten Salt Reactor) programme, launched in 2011. Since then, engineers have inched through a series of milestones: developing corrosion-resistant alloys, high-temperature pumps, sensors that can survive hot salt, and test loops to validate each component.
In 2021, Beijing announced that it had finished building its first experimental thorium reactor in the Gobi Desert. The latest step in Shanghai adds the key ingredient that was still missing: measured, reproducible breeding of uranium‑233 from thorium under operating conditions.
China now targets a 100‑megawatt demonstration reactor using molten salt and thorium by around 2035, with an eye on future commercial units.
The high temperatures involved open up uses beyond electricity. At roughly 750°C, waste heat from such a reactor could drive hydrogen production, fuel industrial processes like steel or cement making, or feed large-scale thermal storage systems that back up variable renewables.
Could this really sideline uranium?
Why the shift will be slow
No one expects uranium-fuelled reactors to vanish this decade. The thorium cycle is still complex. It creates fewer long-lived actinides than conventional fuel, but it does generate radioactive fission products that need safe handling for decades to centuries. Materials must withstand corrosive salts for years at high temperatures. Regulators will need to adapt to a design that looks very different from current fleets.
Any move away from uranium would also hit established industries and exporting nations. Australia, Kazakhstan, Canada and others currently earn billions from uranium mining. A large-scale shift to thorium would redraw that map and pose questions about stranded assets and long-term contracts.
Yet the Shanghai work sends a message: there is now a live alternative path. For countries with big thorium resources but modest uranium deposits, such as India or Brazil, the technology suddenly looks less like a footnote and more like a card worth keeping in the energy deck.
- Short term: research reactors validate materials, safety systems and fuel chemistry.
- Medium term: 10–100 MW demonstration units serve niche roles, like industrial heat or off‑grid power.
- Long term: full‑scale plants enter the market, competing with advanced uranium reactors and renewables.
Risks, trade‑offs and what could go wrong
Molten-salt reactors avoid the high pressures that haunt traditional designs, but they bring different engineering headaches. The salt mixtures can corrode metal pipes and vessels. If chemistry drifts, the fuel may behave unpredictably. Monitoring a liquid fuel requires different tools and skills than managing solid fuel rods.
Uranium‑233 also poses its own security questions. While it is less suited to classical nuclear weapons programmes than plutonium or highly enriched uranium, it still counts as a direct-use material under non-proliferation rules. Any country running thorium cycles will come under new scrutiny from inspectors and rivals.
There is also a political risk. If molten-salt reactors gain a fashionable reputation as a “fix” for climate and energy, governments may overpromise. Building out a thorium-based fleet takes decades, not years. Overhyping the technology could delay investment in proven decarbonisation tools such as wind, solar and energy efficiency.
Key concepts behind the headlines
For readers trying to make sense of the jargon, a few terms matter. Thorium‑232 is the raw material, a mildly radioactive metal. It is “fertile”, meaning it can absorb a neutron and eventually turn into a fissile isotope, uranium‑233. That uranium‑233 is what actually fissions and releases heat inside the reactor.
Molten salt refers to a chemical mixture, often fluorides of lithium, beryllium or other elements, that melts at several hundred degrees Celsius and stays stable up to nearly 1,000°C. Unlike water, it does not boil at reactor temperatures and carries heat efficiently. In a liquid-fuel design, the fissile material is dissolved in this salt rather than packed into solid pellets.
A simple scenario illustrates the potential: a coastal industrial hub, supplied by wind farms and solar arrays, backs them up with a handful of 100‑MW thorium molten-salt units. When the wind drops at night, operators ramp up the reactors and divert some of the high-temperature heat into hydrogen production. When sunshine returns, reactors shift to steady industrial heat while surplus solar feeds the grid. The mix could cut gas imports, stabilise power prices and slash emissions without relying solely on weather.
China’s small reactor in Shanghai is still only a stepping stone toward that kind of future. Yet by reactivating a technology the West parked 60 years ago, Beijing has signalled that the age of uranium may eventually share the stage with a very different kind of nuclear fuel.
Originally posted 2026-02-21 18:10:44.