Liquid Fluoride Thorium Reactor

The liquid fluoride thorium reactor (acronym LFTR; spoken as lifter) is a thermal breeder reactor that uses the thorium fuel cycle in a fluoride-based molten (liquid) salt fuel to achieve high operating temperatures at atmospheric pressure.

The LFTR is a type of thorium molten salt reactor (TMSR). Molten-salt-fueled reactors (MSRs) such as LFTR, where the nuclear fuel itself is in the liquid form of molten salt mixture, should not be confused with solid-fueled molten salt-cooled high temperature reactors (Fluoride High-temperature Reactors, FHRs).

Molten salt reactors, as a class, can include both burners and breeders in fast or thermal spectra, using fluoride or chloride salt-based fuels and a range of fissile or fertile consumables. LFTR refers to a particular design subset of MSRs defined by use of fluoride fuel salts and breeding of thorium into uranium-233 in the thermal spectrum.

In a LFTR, thorium and uranium-233 are dissolved in carrier salts, forming a liquid fuel. Typical operation sees the liquid fuel salt being pumped between a critical core and an external heat exchanger, where the heat is transferred to a nonradioactive secondary salt, that then transfers its heat again to a steam turbine or closed-cycle gas turbine.

This technology was first investigated at the Oak Ridge National Laboratory Molten-Salt Reactor Experiment in the 1960s. It has recently been the subject of a renewed interest worldwide. Japan, China, the UK, as well as private US, Czech and Australian companies have expressed intent to develop and commercialize the technology.

LFTRs are a particular class of molten salt reactors that includes several design variations and this article addresses some of these reactor design variations and their advantages and disadvantages, power conversion cycles that could be used to generate electricity with a LFTR, and an important aspect of LFTRs, online removal of fission products. LFTRs differ from other power reactors in almost every aspect: thorium fuel cycle, low operating pressure, liquid fuel, salt coolant, higher operating temperature and online refueling and reprocessing. The unique characteristics of a LFTR give rise to many potential advantages, but also to a number of design challenges.