The Shanghai Institute of Applied Physics (SINAP) of the Chinese Academy of Sciences announced that the experimental TMSR-LF1 thorium-powered molten salt reactor in Wuwei, Gansu Province, has achieved the first successful conversion of thorium-uranium nuclear fuel.
Construction of the two-megawatt thermal TMSR-LF1 reactor began in September 2nd of 018 and was scheduled to be completed in 2024. However, constructed was reportedly completed in August of 2021 after work was accelerated. In August of 2022, SINAP was given approval by the Ministry of Ecology and Environment to commission the reactor. An operating license was granted for the TMSR-LF1 reactor in June of 2023. It achieved a sustained reaction known as “first criticality” on the 11th of October 2023.
The TMSR-LF1 uses fuel enriched to under twenty precent uranium-235, has a thorium inventory of about one hundred and ten pounds and conversion ratio of about one tenth. A fertile blanket of lithium-beryllium fluoride (FLiBe) with ninety-five and ninety-five one hundredth percent Li-7 is used, and fueled with uranium tetrafluoride (UF4).
SINAP said, “In October 2024, the world’s first thorium addition to a molten salt reactor was completed, making it the first in the world to establish a unique molten salt reactor and thorium-uranium fuel cycle research platform.”
On the 1st of November, SINAP announced that TMSR-LF1 achieved the first conversion of thorium and uranium nuclear fuel.
SINAP added, “This marks the first time international experimental data has been obtained after thorium was introduced into a molten salt reactor, making it the only operational molten salt reactor in the world to have successfully incorporated thorium fuel. This milestone breakthrough provides core technological support and feasible solutions for the large-scale development and utilization of thorium resources in China and the development of fourth-generation advanced nuclear energy systems.”
Li Qingnuan is the Deputy Director of the SINAP. She said, “Since first reaching criticality on the 11 of October 2023, the thorium-based molten salt reactor has been continuously generating heat through nuclear fission.” She explained that conventional pressurized water reactors require periodic shutdowns and the opening of the pressure vessel top cover to replace the nuclear fuel when refueling is required. Thorium-based molten salt reactors utilize liquid fuel, with the nuclear fuel uniformly dissolved in the molten salt coolant and circulating with it, allowing for refueling the reactor without shutting down the reactor.
She explained, “This design not only improves fuel utilization but also significantly reduces the generation of radioactive nuclear waste, which is one of the advantages of thorium-based molten salt reactors.”
SINAP’s next step is to accelerate technological iteration and engineering transformation, aiming to complete a one hundred megawatt thermal thorium-based molten salt reactor demonstration project and achieve demonstration applications by 2035, the SINAP Director Dai Zhimin said.
Molten salt reactors (MSRs) use molten fluoride salts as the primary coolant which is kept at low pressure. They may operate with epithermal or fast neutron spectrums, and with a variety of nuclear fuels. Much of the interest today in reviving the MSR concept relates to the use of thorium to breed fissile uranium-233. An initial source of fissile material such as plutonium-239 must be provided. There are a variety of different MSR design concepts, and a number of interesting challenges in the commercialization of many, especially with thorium.