Molten salt reactor

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A molten salt reactor or MSR is a nuclear reactor that uses a molten salt mixture as the primary coolant or as the solvent for the nuclear fuel itself. The concept of a nuclear reactor with liquid fuel was first explored with the Aircraft Reactor Experiment and the Molten-Salt Reactor Experiment at Oak Ridge National Laboratory, but because of poor political support compared to the fast breeder reactor, further research in the United States was terminated in 1969.

MSRs can be designed for thermal or fast spectrum fission depending on the salt used. Lithium and beryllium fluoride salts are well-suited towards thermal spectrum, while chloride salts are theoretically suited for fast spectrum.

In a thermal spectrum design, uranium tetrafluoride is dissolved in a molten mixture of lithium and beryllium fluorides. The fission from fissile isotopes of the uranium generates heat, which is transferred to a heat exchanger. Depending on the design of the reactor, the heat transferred away from the core can be used to boil water for steam turbines, to heat gas for Brayton cycle turbines, or as raw process heat for industrial applications or desalination.

MSRs operate at atmospheric pressure, meaning a heavy reactor vessel and the large containment building are not necessary, as they would be for a light water reactor. If the reactor design dissolves the fuel in the salt, the reactor can utilize a greater percentage of the fissile material than in reactors that use oxide fuel rods because the fuel is impervious to structural damage by the fission product xenon. Additionally, refueling and waste processing can be performed without shutting down the reactor, and greatly reduce the amount of long-lived radioactive waste.

However, because of the lapse in research, many engineering challenges remain, from tritium production to graphite contamination.

Liquid fluoride thorium reactor

A liquid fluoride thorium reactor or LFTR is a variant of the MSR that breeds fissile uranium-233 fuel from thorium in its operation.

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