Is Thorium the Fuel of the Future to Revitalize Nuclear?
Nuclear power produces carbon-free electricity, and the United States has used nuclear power to generate base electricity for decades.
However, nuclear energy carries a dreaded stigma. Following disasters like Chernobyl, Three Mile Island and Fukishima, the public is aware of the potential, albeit misguided, dangers of nuclear energy. The cost of generating nuclear power plants is rising – in stark contrast to the falling cost of alternative forms of energy such as sun and wind, which have gained immense popularity recently.
This trend could continue until market forces make nuclear technology obsolete. In this dynamic comes a resurgence of nuclear technology: liquid fluoride-thorium reactors or LFTRs (“lifters”). An LFTR is a type of molten salt reactor that is much safer than a typical nuclear reactor. LFTRs use a combination of thorium (an element widely found in the earth) and fluoride salts to power a reactor.
A typical arrangement for a modern thorium-based reactor is similar to a conventional reactor, albeit with notable differences. First of all, thorium-232 and uranium-233 are added to fluoride salts in the reactor core. During fission, heat and neutrons are released from the core and absorbed by the surrounding salt. This creates a uranium-233 isotope, since the thorium-232 absorbs an additional neutron. The salt melts to a molten state by operating a heat exchanger and heating an inert gas such as helium, which drives a turbine to generate electricity. The blasted salt flows into a post-processing facility that separates the uranium from the salt. The uranium is then sent back to the core to start the fission process again.
Thorium reactors generate significantly less radioactive waste and can reuse separated uranium, making the reactor self-sufficient after start-up. LFTRs are designed to operate as a low pressure system, unlike traditional high pressure core systems. This creates a safer work environment for workers who operate and maintain these systems. In addition, the fluoride salts have very high boiling points, which means that even a large thermal shock does not cause a massive increase in pressure.
Both of these factors significantly limit the likelihood of a containment explosion. LFTRs do not require massive cooling, meaning they can be placed anywhere and air-cooled. If the core were to become critical, gravity would allow the heated, blasted salt to pass through subterranean fail-safe safety chambers covered by a plug of ice that melts on contact.
LFTRs offer numerous advantages. Remaining radioactive waste cannot be used to manufacture weapons. The fuel costs are considerably lower than with a solid fuel reactor. The salts cost approximately $ 150 / kg and thorium approximately $ 30 / kg.
If thorium becomes popular, that cost will only decrease as thorium is widespread throughout the earth’s crust. Thorium is present in a concentration that is over 500 times higher than that of fissile uranium-235. Historically, thorium was discarded as a by-product of rare earth metal mining. The extraction was able to recover enough thorium to power LFTRs for thousands of years. For a 1 GW installation, the material cost for fuel would be around USD 5 million. Because LFTRs use thorium in its natural state, there is no need for expensive fuel enrichment processes or the manufacture of solid fuel rods, which means that fuel costs are significantly lower than a comparable solid fuel reactor. In an ideally working reactor, post-chemical reprocessing would allow an LFTR to use almost all of the fuel efficiently, with little waste or by-product left behind, unlike a conventional reactor. Ultimately, a thorium plant operates at about 45 percent thermal efficiency, with upcoming turbine cycles potentially improving overall efficiency to 50 percent or more, meaning that a thorium plant can be up to 20 percent more efficient than a traditional light water reactor.
LFTRs pose some challenges. There are significant gaps in the research and materials required for LFTRs. The chemical post-processing plants that would separate uranium from the molten salts for reuse had not yet been built. Each reactor would need some highly enriched uranium (like uranium-235) to start the reactor, which is very expensive. Scientists suggest that a $ 5 billion investment over the next five years could create a viable reactor solution in the US, but with limited funds for thorium, this vision is difficult to achieve. Other countries have made preliminary investments in the construction of thorium reactors.
The public stigma surrounding nuclear power plants is real, and it needs to be overcome before lawmakers can take action, as money must be allocated to research and development to continue the LFTR in the US. It will be difficult to advance this technology without public and scientific support. Education is needed to advance the thorium agenda, disseminate information about thorium-based reactors, and educate the public about their safety. Resources for learning more about thorium and LFTRs include websites like The Independent Global Nuclear News Agency and World Nuclear News, or conferences like the Thorium Energy Conference.
Thorium reactors are another way to generate electricity that could benefit the world. LFTRs are more efficient than their fossil fuel counterparts, safer than a traditional nuclear power plant, and do not cause carbon emissions as a by-product. They are a viable solution for the future of our world’s energy needs.
About the author: Sameer Surampalli is an electrical engineer and transmission & distribution consultant for Burns & McDonnell. He works with customers and stakeholders to conduct feasibility studies for grid connections to wind / solar parks, energy storage and other renewable energies.