TMSR-LF1

"Project 728" was launched in 1970 to develop nuclear power in China to mitigate an energy crisis caused by industrial fossil fuel demand exceeding domestic supply. Its initial goal was to build a 25 MW_e power plant based on the Molten-Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory in the US; a demonstration MSR was built that achieved criticality in 1971, but was not intended to produce power. Further progress was hampered by the technological, industrial, and economic conditions in 1970s China however, and a pragmatic decision was made develop pressurized light water reactors (PWRs) instead; their first commercial reactor, CNP-300 at Qinshan Nuclear Power Plant, began operations in 1991.^[6][7][8] The interest in MSR technology and Thorium breeding did not disappear however; additionally, the relative lack of water available for cooling PWRs west of the Hu line was seen as a limiting factor for them there (cf. Map of Chinese nuclear power plants).

In January 2011 the Chinese Academy of Sciences (CAS) began the TMSR research and development project to create reactors which, among other advances, would use air cooling.^[9] Its budget was reportedly ¥3 billion ($444 million US).^[10] and is led by Xu Hongjie (徐洪杰), who previously headed the construction of the Shanghai Synchrotron Radiation Facility,^[11] through the Shanghai Institute of Applied Physics (SINAP), which now has MSR research and design facilities in the Jiading District.^[12] The initial project completed there was the TMSR-SF0, an electrically-heated (non-fissioning) simulator to aid development of a proposed "SF" (solid fuel, planned as TRISO,^[13] with molten salt only for cooling) branch of TMSR, as well as to gain operational experience using molten salt more generally. The SF0 has two liquid FLiNaK heat transport loops.^[14]

The "LF" (liquid fuel) design is directly based on the 1960s MSRE.^[15] The site selected for the TMSR-LF1 is part of an industrial park^[16] for the chemical and energy sectors, in a sparsely populated, arid region.^{[location note]} Site construction began in 2018.^[10] At the groundbreaking, a Taoist ceremony was held; after images of it went viral in China (an atheist state), CAS disciplined staff members, and issued a public apology.^[17] A reactor construction permit was issued by the Chinese National Nuclear Safety Administration in January 2020.^[18] Construction was expected to finish in August 2021, with testing to follow.^[19][20] In August 2022, the Chinese Ministry of Ecology and Environment informed SINAP that its commissioning plan for the LF1 had been approved.^[10] A ten-year operating license was issued in June 2023.^[21][22] For the first 5–8 years, it is to be run in batch mode, before converting to continuous mode.^[10]

Criticality was first achieved on 11 October 2023.^[23][24][25] On 17 June 2024, full power (2MW_t) operation was achieved, and on 8 October, it operated at full power for 10 days with thorium in the molten salt; Protactinium-233 was detected, indicating successful nuclear breeding.^[25]

LF1 building 3D model and floor plan published for seismic analysis; below-ground area (pink) holds the reactor.

The TMSR-LF1 is a Generation IV reactor constructed with the following specifications:^[26][27][28]

• Thermal power: 2MW
• Fuel salt: FLiBe (>99.95% Li-7) with fluorides of zirconium, uranium (HALEU: 19.75% U-235), and thorium
  • inlet temperature: 630 °C
  • outlet temperature: 650 °C
  • volume: 1.68 m³
  • flow rate: ~50 kg/s
• Coolant salt: FLiBe
  • inlet temperature: 560 °C
  • outlet temperature: 580 °C
  • flow rate: ~42 kg/s
• Cover gas: Argon (0.05 MPa)
  • volume: 1.6 m³
• Moderator: nuclear graphite
• Structural Material: UNS N10003 superalloy
• Lifetime: 10 years
  • equivalent full power days: 300
  • maximum full power days per year: 60

The reactor is located underground, seated at the bottom of a 14m (46 foot) deep dry well, which is capped at ground level, and above which rises a 20m (66 foot) tall roofed atrium.^[29]

A pilot plant based on the LF1, as well as a fuel salt research facility, is planned for the same site.^{[location note]} New reactor specifications include: core graphite 3 m tall x 2.2 m wide, 700 °C operating temperature, 60 MW thermal output, and an experimental supercritical carbon dioxide-based closed-cycle gas turbine to convert the thermal output to 10 MW of electricity.^[1] Construction is slated to start in 2025, and be completed by 2029. The reactor's output would be used to demonstrate hydrogen production by high-temperature water splitting^[30] ("purple hydrogen").

Following the completion of the 10 MW project, construction of a commercial small modular reactor (SMR) of at least 100 MWe is scheduled to begin in 2030.^[23] A proposal, referring to it as the smTMSR-400, specifies 400 MW_th to generate 168 MW_e.^[31] These are likely to be sited in central and western China, and may also be built outside China in Belt and Road Initiative nations; as low-carbon power plants, they would help to achieve the Chinese government's 2060 goal of carbon neutrality.^[19]