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| Fig. 1: Map demonstrating that India's Thorium is mostly located in its eastern coastal states. The darker the color, the larger the amount of Thorium reserve estimates. [6] (Source: Wikimedia Commons) |
Recent surveys on the sustainability of nuclear power have no longer simply relied on the amount of Uranium resources globally available but has grown to include the amount of Thorium as well. This is because even though Thorium itself is not fissile, through neutron capture and subsequent β-decay reactions, Th-232 can be transmuted to U-233. [1] In fact, Thorium does have several advantages over Uranium as a nuclear power source. Thorium is three times more abundant in the Earth's crust than Uranium, and many Thorium deposits contain other mineral resources of value (rare earths elements in particular). Significant Thorium deposits exist in the United States, Brazil, India, and Australia; these countries all have estimates of Thorium resources of greater than 600 kt. [1] Additionally, all the Thorium that is mined can be used in a reactor, in comparison to less than 1% of natural Uranium that may be used. [2] Finally, Th-232 possesses a 14 billion year half-life, rendering it safer than Uranium and Plutonium. [2]
Despite all of these factors, the current market for Thorium remains modest: most Thorium production is the by-product of rare-earth recovery. [2] As a result of this small market, little incentive exists to explore new Thorium deposits or to survey known deposits, leaving much uncertainty about the total amount and location of Thorium resources. Most notably, while some countries, such as India, stockpile this excess inventory in the hopes of capitalizing on future nuclear uses, other countries simply dispose of it [3]. In fact, high Thorium disposal costs were been blamed for the decrease in production of rare earths in the United States in 1994 [4]. This provides further evidence for Thorium to garner an increased role in the nuclear power generation, as it would reduce the need for expensive disposal.
All of these factors beg the question: why isn't Thorium being more aggressively pursued as an alternative to Uranium if it has so many benefits? The reality is that the world supply of Uranium has been inexpensive and adequate to meet supply needs, so there has been no real incentive for a new (and largely untested) nuclear energy technology to replace or complement Uranium-based reactors. For some countries with substantial Thorium resources, the Thorium fuel cycle might be a viable option. India, which contains substantial easily exploitable Thorium deposits along its southern coasts and a relatively modest Uranium deposits, has committed much research towards the development of Thorium-based nuclear energy. [5] Its government is currently developing AHWRs that enable a self-sustained Th-232/U-233 based fuel cycle, with hopes of obtaining 65% of its power from thorium. [3] However, full commercialization of these reactors is not expected before 2030. Until the world witnesses the successful use of Thorium reactor technology, it is unlikely that any other countries will dedicate substantial research to such an option themselves. Thus, it is evident that as long as natural Uranium is not scarce and Thorium reactor technology remains commercially unproven, it is unlikely that a Thorium-based fuel cycle will be implemented on a global scale. Right now, the ball is in the court of countries with substantial Thorium deposits, such as India, to make a significant push for Thorium for its future to remain viable.
© Paulette Wolak. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] R. C. Ewing, L. Krall, and M. Englert. "Is Nuclear Fission a Sustainable Source of Energy?" MRS Bull. 37, 417 (2012).
[2] M. R. Srinivasan, R. B. Grover, and S. A. Bhardwaj, "Nuclear Power in India: Winds of Change" Economic and Political Weekly (Mumbai), 3 Dec 05.
[3] B. S. Van Gosen, V. S. Gillerman, and T. J. Armbrustmatcher, "Thorium Deposits of the United States - Energy Resources for the Future?" U.S. Geological Survey, Circular 1336, 2009.
[4] J. B. Hedrick, "Rare Earths," U.S. Geological Survey Minerals Yearbook, 2000.
[5] R. M. Hazen, R. C. Ewing, and D. A. Sverjensky, "Evolution of Uranium and Thorium Minerals," Am. Mineral. 94, 1293 (2009).
[6] "Details of Thorium Reserves," Department of Atomic Energy, Government of India, 10 May 12.
