Often when discussing nuclear fuel, our minds jump to common ones such as uranium or even plutonium; yet a new material could significantly improve the safety and sustainability of nuclear energy. The idea of this new form of fuel was rediscovered from a thorium-based nuclear reactor (Vlasov, 2023). Thorium is the 90th element on the periodic table, with its most common isotope being Th232, a fertile material for nuclear fission (RSC, 2023). What makes thorium an exciting new element for nuclear reactors is two key features. Primarily, thorium can be recycled and reused in a way that Uranium fuel simply cannot. This allows far more sustainable nuclear fuel, a crucial property given the scarcity of nuclear resources. Thorium may prove to be a superior long-term energy source, being 3 times more abundant as uranium and having lower production of minor actinides. Some researchers at the Westinghouse Electric Company (IAEA, 2009) have even stated, “It can be argued based on results that the Th breakeven fuel cycle is the only practical way of achieving a reduction in repository radiotoxicity to reference levels within 1000 years.” This remarkable feat may be critical to the long-term sustainability of nuclear energy and its environmental impact in the future.
Large-scale fuel recycling has been a goal of nuclear scientists for decades, but unfortunately many hurdles have been presented. Traditional uranium- and plutonium-based fuels are difficult to recycle due to the unsuitable isotopes that arise during fission. Thorium-based fuels, however, are less prone to absorbing free-floating neutrons and are thus able to continually reproduce significant amounts of U233 to be used in fission (World Nuclear Association, 2020). A brief outline of this revised fuel cycle and recycling is shown below (Figure 1).
Continual reproduction of fissile materials enables greater fuel use of up to 3040% (IAEA, 2009). Greater fuel use only requires recycling the original fuel two to three times. The number of cycles is low due to the increasing isotopic variation of the uranium after continuous recycling. Isotopic variation significantly decreases the abundance of isotopes suited for fission. Despite this constraint, thorium presents a new hope for turning our current, primarily single-use nuclear systems to a closed cycle where materials are employed to their fullest extent.
Sustainability is not the sole appeal of thorium. Minor actinides are produced as a byproduct of nuclear fission and are responsible for the bulk of the radiotoxicity from nuclear waste. Radiotoxicity can result from the decay of minor actinides and can pose a serious hazard due to the required long-term storage of nuclear waste (WHO, 2023). The amount of ionizing radiation resulting from these minor actinides is significantly less with the use of thorium than its other nuclear counterparts. Various studies found that thorium actually produces an order of magnitude fewer minor actinides than traditional uranium fuels (IAEA, 2009).
Thorium has proved itself to be a viable alternative to the status quo of nuclear energy, yet there is still uncertainty as to how it will be deployed. While it is no miracle cure, thorium could lead the way into a new age of atomic energy, and of energy generation as a whole.
REFERENCES
International Atomic Energy Agency (IAEA), 2009, Near Term and Promising Long Term Options For The Deployment Of Thorium Based Nuclear Energy, [online], Available at: https://www-pub.iaea.org/MTCD/Publications/PDF/TE-2009web.pdf [Accessed September 15th, 2023]
Royal Society of Chemistry(RSC), 2023, Thorium – Element Information, [online] Available at: https://www.rsc.org/periodic-table/element/90/thorium [Accessed September 16th, 2023]
Sinha, R. K., Chellapandi, P., Srinivasan, G. I., Dulera, I., Vijayan, P. K., & Chande, S. K. (2023). Generation-IV concepts: India. In I. L. Pioro (Ed.), Handbook of Generation IV Nuclear Reactors: A Guidebook (2nd ed., pp. 485–516). Woodhead Publishing. https://doi.org/10.1016/B978-0-12-820588-4.00015-3
Vlasov, A., 2023, International Agency of Atomic Energy, [online], Available at: https://www.iaea.org/newscenter/news/thoriums-long-term-potential-in-nuclear-energy-new-iaea-analysis [Accessed September 15th, 2023]
World Health Organization (WHO), 2023, Ionizing Radiation and Health Effects, [online] Available at: https://www.who.int/news-room/fact-sheets/detail/ionizing-radiation-and-health-effects [Accessed September 16th, 2023]
World Nuclear Association, 2020, Thorium, [online] Available at: https://world-nuclear.org/information-library/current-and-future-generation/thorium.aspx [Accessed September 16th, 2023]