Renewed interest in the use of thorium as a renewable energy has emerged in recent years in light of the need for drastic measures to mitigate the effects of climate change. Thorium-based nuclear power has vast energy potential and its fuel cycle has significant advantages over that of uranium, which has produced nuclear plant disasters over the past half-century that have halted much of the nuclear technology research occurring since World War II. Thorium is a fertile element, possessing great energy capacity. It fuels nuclear reactors through the nuclear fission of uranium-233, which can be easily converted from thorium (1). Thorium is far more abundant on the earth than uranium, lacks weaponization potential, and reduces nuclear waste production. However, thorium has been far less researched than the other primary elements that serve as effective bases for nuclear power, uranium and plutonium, because of the 20th-century emphasis on nuclear weaponry. Now in the wake of the climate change crisis, thorium has been reintroduced into the field of renewable energy research because of its lack of proliferation potential, containment ability in the event of a malfunction or disturbance, and longevity of widespread use.
Despite thorium’s existence in chemical academia for nearly 200 years, the element has experienced only small waves of interest that have been reinvigorated recently by climate change concerns. Named after the Norse god of thunder, Thor, thorium was discovered in 1829 by Swedish chemist JJ Berzelius and was used later that century in the incandescent gas light mantle. Once electricity came around, thorium was essentially forgotten until nuclear physics was put at the forefront of the Allies’ agenda at the beginning of World War II with the Manhattan Project (2). Scientists discovered that uranium salts and thorium rays possessed the penetrating power of X-rays, but contained this energy internally rather than needing external agitation (3). However, researchers concluded that thorium was unsuitable for weaponization and only uranium and plutonium were investigated more extensively. In 1948, former Manhattan Project scientist Alvin Weinberg became director of the Oak Ridge National Laboratory (ORNL), where he continued to research the feasibility of thorium reactors. This led to The Molten Salt Reactor Experiment, which operated at ORNL from 1965 to 1969 before the project fizzled with Washington’s emphasis on expanding its nuclear arsenal amidst Cold War security concerns. Thorium’s relevance has reemerged recently through the dual concerns of eliminating proliferation potential in an increasingly nuclearized world and the need for an abundant source of renewable energy that is efficient and also reduces the biomedical hazards posed in current nuclear plants.
The collective effort for thorium-based nuclear power research has sparked from scientific conferences in recent years, the most prominent and internationally-spanning being the Thorium Energy Conference in 2013. Held at CERN by the International Thorium Energy Committee, the conference was attended by over 200 scientists from 32 countries (4). The conference discussed the feasibility of Liquid Fluoride Thorium Reactors (LFTRs) as a safe, environmentally friendly, and economical alternative to other types of energy plants. Among the content of the lectures presented were a complex and thorough span of the technologies studied for LFTRs including accelerator developments, beam properties, spallation target technology, neutronic analyses, systems reliability, material exposure to strong irradiation sources, and destruction of nuclear waste. The conference addressed possible arguments against thorium technology, such as the concern for breeder reactors in general after the 1986 Chernobyl disaster in the Soviet Union and the more recent radioactive material leakage at a Japanese nuclear power plant following the Great East Earthquake.
However, thorium needs far less initial material to begin energy production than uranium, and does not need continuous transport and feeding of enriched uranium, which increases proliferation risks (5). LFTRs also resist proliferation because thorium cannot be made directly into a weapon; reactors cannot be used to create substantially-sized quantities of pure plutonium, which are needed to make nuclear bombs (6). In addition, thorium is four times more abundant than uranium worldwide, and the element is nearly always found during the mining of rare earth metals, an operation that has recently reopened at Mountain Pass in California and Pea Ridge in Missouri (7). This abundance renders thorium an ideal and reliable new energy source that can last for hundreds of years. According to a 2009 United States Geological Survey, thorium reserves in the U.S. amount to over 44,000 tons, enough to last for hundreds of years. Excluding China, estimated worldwide reserves are around 1.3 million tons, and 1000-Megawatt LFTR plants only use one ton of thorium per year (8). From an economic standpoint, fewer construction materials need to be incorporated in the plants because the large cooling towers and containment structures used in high pressure uranium-based nuclear power plants are unnecessary (9).
The conference discussed and encouraged more national and international cooperative programs on thorium technologies, with collaboration being the goal to speed up the process in light of the urgency of making fundamental energy shifts for climate change mitigation. One example of such treaty exists between Russia and India, which agreed in December 2008 to set up a new range of reactor units across both countries (10). India has made notable progress towards using thorium-based nuclear power, with specific goals, timelines, and research phases rendering full-scale, government-backed mass implementation possible within the next 50 years. The country’s three-stage nuclear program has the strategic goal to establish a large-scale thorium-based power generator on a sustainable basis, with enough of a fissile inventory to allow for mass conversion of Thorium-232, the isotope occurring in nature (11). Currently, India’s Department of Atomic Energy plans to extensively rely on thorium energy usage by 2070, but the mounting need for fast climate change action and energy to desalinate water makes earlier deployment crucial. In the United States, vested interest in thorium has shifted from the government to the realm of private entrepreneurs, with companies like Flibe Energy marketing the LFTR. Two doctoral students at Massachusetts Institute of Technology have also begun experimenting with Transatomic Power on the Waste Annihilating Molten Salt Reactor they have created (12). On a federal level, United States Senators Harry Reid and Orrin Hatch supported the provision of $250 million in federal research funds to revive the ORNL research from the mid-20th century with the intention to draft specific resolutions as India has done. Other countries are following closely behind, with Canadian scientists studying fast-breeder LFTR design in their Canada Deuterium Uranium (CANDU) research, French researchers including thermal LFTRs as part of their Gen IV research, and China announcing an LFTR program in February 2011. With such a wealth of resources and technology available worldwide, it is crucial for thorium to be considered for climate change mitigation with the same urgency as other nuclear-reactive elements during the security dilemmas of the previous century.
(1) “India doesn’t lag in developing thorium-fuelled nuclear-reactor: MR Srinivasan, former AEC chairman.” India Economic Times. 29 May 2016. Web. 20 June 2016.
(2) Prabhu, Jaideep. “The story of thorium: A $50,000,000,000,000,000 (50 quadrillion) discovery untapped.” Firstpost. 4 June 2016. Web. 20 June 2016.
(4) Cooper, Nicolas, Daisuke Minakata, Miroslav Begovic, and John Crittenden. “Should We Consider Using Liquid Fluoride Thorium Reactors for Power Generation?” Environmental Science & Technology, 2011. 6 July 2011. Web. 20 June 2016.
(5) Engel, J.R., W.R. Grimes, H.F. Bauman, H.E. McCoy, J.F. Dearing, W.A. Rhoades. Conceptual Design Characteristics of Denatured Molten-Salt Breeder Reactor with Once-through Fueling, ORNL/TM-7207. Oak Ridge National Laboratory: Oak Ridge, TN, 1980. Web. 20 June 2016.
(6) Furukawa, K.A. “Road Map for the Realization of Global-Scale Thorium Fuel Cycle by Single Molten-Fluoride Flow.” Energy Conversion Management. 2008, 49, 1832-1848. Web. 21 June 2016.
(9) Moir, R.W., E. Teller. “Thorium-fueled underground power plant based on molten salt technology.” Nuclear Technology, 2005, 151 (Sept.) 334-340. Web. 20 June 2016.
(10) “India doesn’t lag in developing thorium-fuelled nuclear-reactor: MR Srinivasan, former AEC chairman.” India Economic Times. 29 May 2016. Web. 20 June 2016.
(11) Jha, Saurav. “Haten thorium power generation.” Deccan Herald. 30 May 2016. Web. 21 June 2016.
(12) Prabhu, Jaideep. “The story of thorium: A $50,000,000,000,000,000 (50 quadrillion) discovery untapped.” Firstpost. 4 June 2016. Web. 20 June 2016.
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