# TMSR-LF1

TMSR-LF1 (液态燃料钍基熔盐实验堆; "liquid fuel thorium-based molten salt experimental reactor") is a 2 MW$_t$ molten salt reactor (MSR) pilot plant operating in northwest China.

## History

In January 2011, the Chinese Academy of Sciences (CAS) began the TMSR research and development project to create reactors which, among other advances, will use air cooling. Its budget was reportedly ¥3 billion ($444 million US). and is led by Xu Hongjie (徐洪杰), who previously headed the construction of the Shanghai Synchrotron Radiation Facility, through the Shanghai Institute of Applied Physics (SINAP), which now has MSR research and design facilities in the Jiading District. The initial project completed there was the TMSR-SF0, an electrically-heated (non-fissioning) simulator to aid development of a proposed "SF" (solid fuel, using a molten salt only for cooling) branch of TMSR, as well as to gain operational experience using molten salt more generally. The SF0 has two liquid FLiNaK heat transport loops.
The liquid fuel ("LF") design is based on the 1960s Molten-Salt Reactor Experiment at Oak Ridge National Laboratory in the US. The site selected for the TMSR-LF1 is part of an industrial park in a sparsely populated, arid region. Site construction began in 2018. At the groundbreaking, a Taoist ceremony was held; after images of it went viral in China (an atheist state), CAS disciplined staff members, and issued a public apology. A reactor construction permit was issued by the Chinese National Nuclear Safety Administration in January 2020. Construction was expected to finish in August 2021, with testing to follow. In August 2022, the Chinese Ministry of Ecology and Environment informed SINAP that its commissioning plan for the LF1 had been approved. A ten-year operating license was issued in June 2023. For the first 5–8 years, it is to be run in batch mode, before converting to continuous mode.
Criticality was first achieved on 11 October 2023. On 17 June 2024, full power (2MW$_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.

## Specifications

The TMSR-LF1 is a Generation IV reactor constructed with the following specifications:
* 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 m$^3$
** 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 m$^3$
* 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.

## Future plans

A small modular reactor (SMR) based on the LF1, as well as a fuel salt research facility, is planned for the same site. 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. Construction is slated to start in 2025, and be completed by 2029. The project would also include a high-temperature hydrolysis component, for hydrogen generation. Following the completion of the 10 MW project, in 2030 construction will begin on commercial SMRs of at least 100 MWe. 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.