Shanghai, China – November 3, 2025 – China has successfully achieved the world’s first-ever thorium to uranium nuclear fuel conversion in an operational Thorium Molten Salt Reactor (TMSR), marking a significant milestone in advanced nuclear energy technology. The breakthrough, announced by the Chinese Academy of Sciences’ Shanghai Institute of Applied Physics (SINAP), confirms the technical feasibility of utilizing thorium as a nuclear fuel, paving the way for a safer and more sustainable energy future.
This achievement not only solidifies China’s leadership in molten-salt reactor research but also provides crucial technical support for the nation’s ambitious plans for large-scale development and utilization of its abundant thorium resources.
Understanding Thorium Fuel Conversion
Thorium itself is a fertile material, meaning it cannot sustain a nuclear chain reaction on its own. However, when bombarded with neutrons, thorium-232 absorbs a neutron and transmutes into uranium-233, which is a fissile isotope capable of sustaining a chain reaction. The successful “thorium to uranium nuclear fuel conversion” means that China’s TMSR has demonstrated the ability to breed fissile uranium-233 from thorium-232 and then utilize that uranium to produce energy.
This conversion process, confirmed by valid experimental data following thorium fuel loading, is critical for closing the thorium fuel cycle and realizing its potential as a primary energy source. Key physical parameter data of protactinium-233, an intermediate element in the conversion chain, confirmed the establishment of the nuclide conversion chain from thorium-232 to uranium-233 within the reactor.
The Advanced Molten-Salt Reactor (MSR) Technology
The experimental TMSR, built by SINAP in collaboration with other Chinese institutions, is currently the only operational molten-salt reactor in the world loaded with thorium fuel. Located in the Gobi Desert in Gansu province, this 2-megawatt thermal (MWt) liquid-fueled reactor represents a fourth-generation advanced nuclear energy system.
Unlike conventional nuclear reactors that use solid fuel rods and water for cooling, MSRs utilize high-temperature molten salt as both the coolant and the fuel carrier. The fuel, in this case, thorium dissolved in liquid fluoride salts, operates at atmospheric pressure and high temperatures, offering significant safety and efficiency advantages.
Inherent Safety Features
Molten-salt reactors are widely recognized for their inherent safety features. These include:
- Passive Shutdown: If an MSR overheats, a “freeze plug” of solidified salt is designed to melt, allowing the liquid fuel to drain by gravity into a passive cooling tank, safely shutting down the reaction without human intervention.
- Low Pressure Operation: Operating at or near atmospheric pressure significantly reduces the risk of explosions or damage due to pressure buildup, unlike high-pressure water-cooled reactors.
- No Water Requirement: MSRs do not rely on water for cooling, making them suitable for arid regions like the Gobi Desert and eliminating the risk of steam explosions or hydrogen buildup.
Environmental and Resource Benefits
The use of thorium in MSRs offers several environmental and resource advantages:
- Abundant Fuel Source: Thorium is approximately three to four times more abundant in the Earth’s crust than uranium. China, in particular, possesses significant thorium reserves, aligning well with this technological route.
- Reduced Nuclear Waste: Thorium reactors produce significantly less long-lived radioactive waste, particularly problematic transuranic elements like plutonium, compared to conventional uranium reactors. The radioactive waste from thorium reactors also has a much shorter half-life.
- Proliferation Resistance: The uranium-233 bred from thorium is often contaminated with uranium-232, which emits strong gamma radiation, making it less attractive and more difficult to use in nuclear weapons. MSRs can also consume existing plutonium stockpiles.
China’s Thorium MSR Program and Future Outlook
The Thorium-based Molten-Salt Reactor (TMSR) program was launched by the Chinese Academy of Sciences (CAS) in 2011 with a substantial R&D investment. SINAP has been at the forefront of this initiative, making significant progress from laboratory research to the engineering verification of core materials, equipment, and technologies. With domestically developed core equipment and an independent supply chain, China has largely established complete TMSR technology and industrial chains.
This recent success is a crucial step towards China’s long-term energy strategy, which aims for advanced nuclear energy systems to play a vital role in ensuring energy security and achieving large-scale commercialization goals.
Pathway to Commercialization
SINAP plans to collaborate with leading energy companies to further consolidate the TMSR industrial and supply chains, accelerating technology iteration and engineering applications. The ultimate goal is to construct a 100-megawatt demonstration project and achieve its demonstration application by 2035. China has already broken ground on a larger 10 MWe demonstration reactor near Wuwei in Gansu Province, which will generate both electricity and hydrogen and is slated for completion by 2030.
The high temperatures achieved by MSRs also make them ideal for integration with various industrial applications, such as high-temperature hydrogen production, coal chemical engineering, and petrochemical engineering, fostering a complementary, low-carbon, integrated energy system alongside solar and wind power.
Challenges and Global Interest
Despite the promising advantages, challenges remain for the widespread adoption of thorium MSRs, including materials science issues (corrosivity of molten salts), fuel reprocessing complexities, and the need for new regulatory frameworks. Economic viability and the establishment of a robust supply chain for thorium fuel also present hurdles.
However, China’s latest achievement provides strong empirical data supporting the technical viability of the thorium fuel cycle, reinvigorating global interest in this advanced nuclear technology. Several countries, including India and Indonesia, are also exploring similar initiatives, and private companies like Bill Gates’ TerraPower are working on molten salt reactor designs. This milestone could accelerate the global transition towards a more secure, sustainable, and safer nuclear energy landscape.
