Chinese Molten Salt Nuclear Reactor Achieves Thorium-to-Uranium Fuel Conversion Milestone

     Researchers at the Chinese Academy of Sciences’ Shanghai Institute of Applied Physics (SINAP) have achieved a first-ever milestone with the successful thorium-to-uranium fuel conversion powering a Thorium Molten Salt Reactor (TMSR). This confirms the technical feasibility of thorium utilization in a molten-salt reactor nuclear energy system. It is currently the only molten salt reactor in the world loaded with thorium. Success with thorium-powered reactors could mean improved safety due to less radioactive waste and more fuel security since China has vast reserves of thorium, as do some other countries, such as Australia.  

     The researchers utilized a fourth-generation advanced nuclear reactor. Construction of the 2 MW TMSR-LF1 reactor began in September 2018. The facility was licensed in June 2023. It achieved first criticality - a sustained reaction - on 11 October 2023. TMSRs use a high-temperature molten salt as a coolant instead of water. Aside from producing less waste and easier-to-process fuel, TMSRs can operate at atmospheric pressure, which reduces mechanical stress on materials and components. TMSRs are the best reactor design for utilizing thorium as a fuel. China’s TMSR program began in 2011 with laboratory experimentation. It can now claim a totally domestically developed TMSR technology. They have a goal to build a 100-megawatt demonstration project and have it operational by 2035. 

     According to Interesting Engineering:

“With this technical feasibility confirmed, SINAP plans to collaborate with leading energy companies to strengthen the supply chain and accelerate the technology’s real-world engineering application.”

     A report earlier this year determined that China has much higher thorium reserves than previously realized. One major new source is iron ore mining waste. It is estimated that the Bayan Obo mining complex alone could yield enough thorium to power China for 60,000 years.

     According to World Nuclear News:

“The TMSR-LF1 uses fuel enriched to under 20% uranium-235, has a thorium inventory of about 50 kg and conversion ratio of about 0.1. A fertile blanket of lithium-beryllium fluoride (FLiBe) with 99.95% Li-7 is used, and fueled with uranium tetrafluoride (UF4).”

“Shanghai Institute of Applied Physics Deputy Director Li Qingnuan said: "Since first reaching criticality on 11 October 2023, the thorium-based molten salt reactor has been continuously generating heat through nuclear fission." She explained that conventional pressurised water reactors require periodic shutdowns and the opening of the pressure vessel top cover to replace the nuclear fuel when refueling is needed. However, the thorium-based molten salt reactor uses liquid fuel, with the nuclear fuel uniformly dissolved in the molten salt coolant and circulating with it, allowing for refueling without shutting down the reactor.”

"This design not only improves fuel utilisation but also significantly reduces the generation of radioactive nuclear waste, which is one of the advantages of thorium-based molten salt reactors."

“Molten salt reactors (MSRs) use molten fluoride salts as primary coolant, at low pressure. They may operate with epithermal or fast neutron spectrums, and with a variety of fuels. Much of the interest today in reviving the MSR concept relates to using thorium (to breed fissile uranium-233), where an initial source of fissile material such as plutonium-239 needs to be provided. There are a number of different MSR design concepts, and a number of interesting challenges in the commercialisation of many, especially with thorium.”

     The project suggests that by the early 2040s, thorium-fueled TMSRs could be seeing significant deployment, at least in China. The Chinese researchers noted that it could facilitate “the construction of a complementary, low-carbon, integrated energy system.”

     The pictures below are from the Chinese Academy of Sciences newsroom.

 

References:

 

Chinese molten salt reactor achieves conversion of thorium-uranium fuel. World Nuclear News. November 4, 2025. Chinese molten salt reactor achieves conversion of thorium-uranium fuel - World Nuclear News

China’s first-ever thorium fuel conversion paves way for 100MW molten-salt reactor. Aman Tripathi, Interesting Engineering. November 1, 2025. China’s first-ever thorium fuel conversion paves way for 100MW molten-salt reactor

China Achieves Thorium-uranium Nuclear Fuel Conversion in Molten-salt Reactor. Chinese Academy of Sciences. November 4, 2025. China Achieves Thorium-uranium Nuclear Fuel Conversion in Molten-salt Reactor----Chinese Academy of Sciences