Few topics get me as excited as nuclear power, especially when it comes to promising future technologies that could help fight the climate crisis. One of my very first articles was about thorium-powered molten salt reactors, but when I wrote that they were little more than a curiosity that hadn’t been seriously looked at since the 1960s. Now I’m hyped all over again, because after a decade of research and development, China is ready to test its first ever thorium-powered molten salt reactor.
China has invested big in nuclear and this particular technology could bring about a huge shift in how nuclear power is generated. 
This reactor, a unit in Wuwei capable of producing just 2 Megawatts of thermal energy, is actually a test bed for two experimental technologies. Those would be the Thorium fuel source and the molten salt coolant. Let’s start with thorium.
Unlike uranium 235, thorium is not fissile, meaning it can’t sustain nuclear fission. Thorium 232, however, is fertile, meaning if it captures a neutron, it will eventually decay into uranium 233, which can then be used to generate power.
Then there’s the molten salt coolant. Molten salt is just what it sounds like; salt that’s been heated to the point it turns from a solid into a liquid. For the salt in the Wuwei reactor, which is a compound of fluorine, lithium, and beryllium, that happens at about 450 degrees Celsius. But a molten salt reactor can use that liquid for more than just coolant. It’s possible to actually dissolve fissile and fertile material into the molten salt.
A molten salt reactor doesn’t necessarily need to use thorium; some nations and private companies are designing molten salt reactors that can use the waste products from the nuclear power plants that exist today. And thorium reactors don’t necessarily need to have their fuel dissolved in a molten salt coolant. But China’s pilot reactor in Wuwei ties both these experimental technologies together. There are a lot of potential upsides to this approach.
Thorium is much more abundant than uranium and is already a waste product of China’s rare earth mineral mining industry. The country is also sorely lacking in uranium deposits within its borders. Though it must be said that in order to use thorium, the whole process needs a jump start from another nuclear technology like uranium 235. Once it’s running though, thorium produces much less long-lived radioactive nuclear waste than uranium, making long-term storage less of a headache.
And while uranium 233 can and has been used in nuclear weapons, it’s always contaminated with isotopes that emit high-energy gamma radiation, so it’s easy to detect and hard to handle, features that make it less suitable for use in weapons.
The molten salt coolant has its own inherent advantages. Water needs to be pressurized to stay in liquid form and effectively cool a reactor, which becomes a safety risk if pressure is lost. Molten salt on the other hand needs no pressurization, it can passively cool itself and quickly solidifies when exposed to air. And finally molten salt reactors are an appealing option for areas where water is scarce, like Wuwei which lies on the edge of the Gobi Desert.
The concept still has a way to go. Newly developed technologies like alloys that resist corrosion, high temperature salt pumps like those used in concentrated solar power plants, and advanced instruments have made it more feasible. But challenges remain and Chinese scientists will have to test the reactor’s stability and safety as well as validate key concepts like the thorium to uranium 233 conversion scheme and how to process the fuel salt. That’s why they’re starting small with a reactor that can power at most 1,000 homes.
If it runs safely and shows potential to be cost effective, China plans to scale up the design and build a plant that could power over a 100,000 homes by 2030. While China pursues this, other countries like France, India, Japan, Norway and the United States are working on their own thorium reactors and I’m sure they’re eager to see China’s results. Thorium molten salt reactors could play a major role in cutting greenhouse gas emissions and fighting the climate crisis. Much of their future now depends on a little 2 megawatt reactor out on the edge of China’s deserts. So, do you think thorium has a future or were we right to stop pursuing it in the 1960s?
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