China just pulled off a feat no nation has managed before: it kept a nuclear reactor running while swapping out its radioactive fuel. That reactor, quietly humming away in the Gobi Desert, isn’t powered by uranium. It runs on thorium — a silvery metal that offers safer, cleaner, and more abundant nuclear energy with far less waste and no bomb-making potential.

This marks the first time anyone has successfully reloaded fuel in an operational thorium molten salt reactor (MSR) without shutting it down. And it puts China ahead in a race that, until recently, most countries didn’t even know had restarted.

What is a thorium nuclear reactor?

At its core, this reactor works very differently from traditional nuclear plants. Instead of using solid uranium rods submerged in pressurized water, this design dissolves thorium fuel into molten salt. That’s why thorium reactors are often considered a type of “molten salt reactor.”

That salty soup has two jobs: it carries the fuel and cools the system. So, a “meltdown” isn’t really a concern for this type of technology. The fuel is already molten. And if there’s a leak? The liquid fuel would simply cool and solidify, like lava turning back into rock. No pressurized steam, no explosions, and no Chernobyl-style nightmares.

Theoretically, this kind of system is safer, more stable, and can run at atmospheric pressure. That means thinner pipes, smaller containment structures, and far lower risk of catastrophic failure. Also: far less radioactive waste, and no weapons-grade byproducts.

In short, these reactors are the future nuclear advocates have dreamed of — clean, compact, and safe enough to place almost anywhere. But, although they’ve been talked about for decades, no one ever built one — until now.

Why now?

Thorium isn’t new. It’s been waiting in the wings of nuclear research since the mid-20th century. In fact, the U.S. briefly explored MSRs in the 1940s and ‘50s, even pouring hundreds of millions into a nuclear-powered bomber project that was eventually shelved.

But after 1961, thorium reactors were abandoned. Uranium won — largely because it could double as a path to nuclear weapons.

That twist of Cold War logic left a trail of public research behind. According to Xu Hongjie, the project’s chief scientist, that archive gave China a head start. “The US left its research publicly available, waiting for the right successor,” Xu said. “We were that successor.”

His team at the Shanghai Institute of Applied Physics dug into the declassified papers, replicated the old experiments, and then pushed the tech forward. “We mastered every technique in the literature — then pushed further,” he said.

The reactor went critical in October 2023. By June 2024, it reached full power. And in April 2025, they reloaded it—live.

That’s the part that makes this a first. Conventional reactors must power down before refueling. Doing it on-the-fly shows that thorium MSRs can, in principle, be continuous systems — safer, cheaper, and potentially easier to scale.

“We now lead the global frontier”

According to Guangming Daily, the experimental unit is located in the Gobi Desert. The reactor in question is small by power plant standards — just 2 megawatts of thermal output. But it’s also experimental. The point isn’t power, it’s proof of concept.

Xu didn’t mince words. They may have started from what the US left behind, but now that’s all changed. “We now lead the global frontier,” he said at a closed-door meeting at the Chinese Academy of Sciences. He compared the international thorium race to a classic fable. “Rabbits sometimes make mistakes or grow lazy. That’s when the tortoise seizes its chance.”

But this isn’t a China vs US story; this is a clean energy story.

Thorium is more abundant than uranium — by a lot. China has known deposits, including a thorium-rich mine in Inner Mongolia that scientists claim could, in theory, power the country for tens of thousands of years.

The reactor also dodges one of nuclear energy’s biggest headaches: waste. Uranium reactors produce long-lived radioactive byproducts. Thorium produces fewer and shorter-lived ones. Also, it’s lousy for making bombs. That’s a plus for global security.

What’s next?

Xu’s team now plans to go bigger. A 10-megawatt version of the reactor is already under construction and slated for criticality by 2030. Rather ironically, they didn’t really publish their scientific results. We couldn’t find any papers or patents. They went straight for the real-world application. So, while Chinese experts have participated in exchanges with experts from other countries, it’s unclear whether they will share any of their recent findings with anyone else.

The Gobi reactor is experimental. But the tech works, and that’s the big part. A lot of people see small molten salt reactors as an important part of our green energy transition, filling the gaps left by solar and wind energy.

This could, in theory, be scaled globally. And other countries are working on it, too. India, with vast thorium reserves, is advancing its three-stage nuclear program, which includes the development of the Advanced Heavy Water Reactor (AHWR) designed to utilize thorium fuel. Norway, through Thor Energy, is investing in facilities to produce thorium-based products for nuclear power.

In the United States, research institutions like the University of Tennessee are modeling thorium molten salt reactors, supported by private companies such as Flibe Energy. Additionally, the International Atomic Energy Agency (IAEA) is coordinating global research efforts to assess thorium’s potential in various reactor designs IAEA.

These initiatives could be a sign that thorium is finally stepping into the spotlight. This would be good news because in many ways, thorium is better than uranium. But it greatly depends on political will, engineering advances, and public trust.

The thorium tortoise is finally on the move. It remains to be seen how fast it can progress.