"An increasingly popular vision of the future sees liquid-fuel reactors playing a central role in the energy economy, utilizing relatively abundant thorium instead of uranium, mass producible, free of carbon emissions, inherently safe and generating a trifling amount of waste." - Robert Hargaves and Ralph Moir, http://www.thoriumenergyalliance.com/downloads/American_Scientist_Hargraves.pdf
Structure and Design of the LFTR
Overview:
The basic idea behind the Generation IV Molten Salt Reactor (MSR) is it utilizes a fuel in a liquid form, rather than the commonly used solid. Given this, the mixture can function both as the fuel and coolant of the reactor. The primary model of the MSR contains thorium and uranium dissolved in a liquid fluoride salt, referred to as the "Liquid Fluoride Thorium Reactor".
The basic idea behind the Generation IV Molten Salt Reactor (MSR) is it utilizes a fuel in a liquid form, rather than the commonly used solid. Given this, the mixture can function both as the fuel and coolant of the reactor. The primary model of the MSR contains thorium and uranium dissolved in a liquid fluoride salt, referred to as the "Liquid Fluoride Thorium Reactor".
Fuel: Thorium, Uranium, Fluoride Chloride Mixture
The fuel is a mixture of thorium and uranium dissolved in fluoride salts of lithium and beryllium. Thorium is a mildly radioactive, relatively abundant element found in natural reserves. The benefit of using thorium within the mixture of the inner-core is it is able to transmute into a fissile element such as uranium-233. With a total of 6,355,000 tons of natural reservoirs available, this is an excellent beneficiary, as thorium is far more abundant and accessible than uranium.
Inner-Core and Moderator
The inner-core of the reactor contains the mixture and fissile element (uranium-233) in liquid fluoride form. A "blanket" of thorium completely envelops the inner-core. The thorium within the outer layering intercepts the residual neutrons from the active fission and transmutes into uranium as diagramed and explained above. In addition, the graphite covering functions as a moderator in order to facilitate induced fission involving the uranium atoms. The immense amount of heat produced as a result of the multitude of fission reactions is transferred out of the inner-core and into the heat exchanger. As the process prolongs, the diminishing uranium and thorium is constantly replaced.
Separation Loops/Energy Production
The reactor consists of two distinct loops that serve different purposes. The first loop transports the irradiated liquid thorium into a decay tank where the uranium-233 can be transported into the inner-core. The second loop transfers the active uranium-233 from the core into the heat exchanger where the heat is derived from. Ultimately, the heat emitted caused by the fission creates steam which drives a turbine and thus produces clean electricity.
Nuclear Waste Management
The fission products, or resulting fragments of the atomic split, slow down the fission reaction and thus reduce the efficiency of the reactor. The LFTR is able to have the fission products be removed during operation, and it fissions virtually all of its fuel, thus fashions a highly efficient process. These remnants are separated by the "Uranium Separator" as diagramed above. The fission products such as xenon and krypton can be reused for medical, industrial, and scientific purposes. If this is not possible, the small amount of waste is safely stored until free of toxic radioactivity.